Cargo Systems and Operating Manual MANUAL CONTENTS
PART 2: CARGO SYSTEM DESCRIPTION 2.1 Containment System
LIST OF CONTENTS GENERAL ARRANGEMENT INTRODUCTION (INCLUDING SNAM SAFETY PROCEDURES AND INSTRUCTIONS) SYMBOLS AND COLOUR SCHEME ISSUE AND UPDATE CONTROL PART 1: LNG, NITROGEN AND INERT GAS 1.1 Physics of Gases 1.1.1 1.1.2
2.2
2.3
Gas Laws Definitions
2.1.1
Gas Transport System Construction
2.1.2
Deterioration or Failure
LNG LERICI 2.12 Deck Salt Water Cooling System 2.13 Air Systems 2.13.1
Cargo Piping System 2.2.1
Description
2.2.2
Pipeline Identification System
2.2.3 2.2.4
Pressure Control Anti-Surge Operation
Cargo Pumps 2.3.1
Main Cargo Pumps
2.3.2
Stripping/Spray Pumps
2.3.3
Emergency Cargo Pumps
1.2.1 1.2.2 1.2.3
1.3
2.4
Properties of LNG Physical Properties, Composition, and Characteristics of LNG Flammability of Methane, Oxygen and Nitrogen Mixtures Supplementary Characteristics
Properties of Nitrogen and Inert Gas 1.3.1 1.3.2
Compressor House 2.4.1
2.5
2.6
Nitrogen Inert Gas
Description
Gas Heaters 2.5.1
Boil-Off / Warm-Up Gas Heaters
2.5.2
Vent Gas Heater
Vaporisers 2.6.1
General Description
2.6.2
Main Vaporiser
2.6.3
Forcing Vaporiser and Demister
ILLUSTRATIONS AND TABLES 1.1.1a 1.1.1b 1.2.1a 1.2.1b 1.2.1c 1.2.1d 1.2.1e 1.2.2a 1.2.3a 1.2.3b 1.3.1a
Graph - Boyle’s Law Graph - Charles’ Law Table - Physical Properties of LNG Components Table - Composition of North African LNG Table - Properties of Methane Graph - Methane Saturated Vapour: Pressure - Temperature Equilibrium Graph - Relative Density of Methane and Air Graph - Flammability of Methane, Oxygen, and Nitrogen Mixtures Double Hull and Compartments Temperatures Structural Steel Grades Plan Structural Steel Ductile to Brittle Transition Curve
2.7
2.8
Gas Compressors 2.7.1
HD Compressors
2.7.2
LD Compressors
Vacuum Pumps 2.8.1
2.9
Vacuum Pumps
Inert Gas and Dry Air Systems 2.9.1
Inert Gas and Dry Air Plant
2.10 Nitrogen Production Systems 2.10.1
Nitrogen Production Plant
2.11 Ballast System 2.11.1
Ballast System Description
2.11.2
Cargo and Ballast Valves Hydraulic System
2.14.1
Cargo Control Room, Cargo Console and Panels
Deck Steam Description
3.3
Custody Transfer System 3.3.1 3.3.2
ILLUSTRATIONS AND TABLES 2.1.1a 2.1.1b 2.1.1c
2.1.1e 2.1.1f 2.1.1g 2.1.2a 2.2.1a 2.2.4a 2.3.1a 2.3.2a 2.3.3a 2.5.1a 2.5.2a 2.6.2a 2.6.3a 2.7.1a 2.7.1b 2.7.2a 2.7.2b 2.8.1a 2.9.1a 2.10.1a 2.11.1a 2.11.2a 2.11.2b 2.11.2c 2.12 2.13.1a 2.14.1a
Issue: 1
3.2
2.14 Deck Steam System
2.1.1d
1.2
General Service and Control Air System
PART 3: CONTROLS AND INSTRUMENTATION 3.1 Integrated Monitoring System
Cargo Tank Lining Reinforcement Construction of Containment System - Flat Area Construction of Containment System - Securing of Insulation Boxes Construction of Containment System - Longitudinal Dihedral Construction of Containment System - Corner Part Man Hole Arrangement Man Hole Cover Arrangement Hull Steel Grades Cargo Piping System Gas Compressors Surge Control System Main Cargo Pump Spray Pump Emergency Pump Boil-Off/ Warm-Up Gas Heater Vent Gas Heater Main Vaporiser Forcing Vaporiser and Demister HD Gas Compressors Table - HD Alarm and Trip Settings LD Gas Compressors Table - LD Alarm and Trip Settings Vacuum Pumps Inert Gas and Dry Air Systems Nitrogen Production Systems Ballast System Cargo Valves Hydraulic System Ballast Valve Hydraulic System Cargo and Ballast Valve Control Deck Salt Water Cooling System Deck Instrument and General Service Air Systems Deck Steam System
3.3.3
Custody Transfer System Independent Very High Level Alarm System Failure of CTS Computer
ILLUSTRATIONS 3.1.1a 3.1.1b 3.1.1c 3.2.1a 3.3.2a 3.3.2b 3.3.3a
IMS System Overview Typical System Screen Shots Typical System Screen Shots Control Room Layout CTS Measurement Cargo Tank Temperature Measurement Cargo Record Sheet
PART 4: CARGO OPERATIONS 4.1 Overview Operating Procedures 4.2
Normal In-Service Operations 4.2.1 4.2.2
4.2.3
4.2.4
4.2.5 4.2.6 4.2.7 4.2.8
Loading Gas Freeing with Other Tanks In Service Cargo Tank Stripping with Other Tanks In Service Gas Freeing with Other Tanks In Service Cargo Tank Warming with Other Tanks In Service Gas Freeing with Other Tanks In Service Cargo Tank Gas Freeing (Version 1 & 2) Initial Insulation Space Inerting (Steps 1 & 2) Insulation Space Inerting During Normal Service Loaded Voyage with (Normal & Forced) Boil-Off Gas Burning Discharging with Gas Return from Shore Ballast Voyage
List of Contents - Page 1
Index
Print
Exit
Cargo Systems and Operating Manual 4.3
Out of Service Operations 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6
4.4
Drying and Inerting Tanks Displacing Inert Gas with LNG Vapour Tank Cool Down Tank Warm Up Gas Freeing Aerating
Emergency Operations and Procedures 4.4.1 4.4.3 4.4.4 4.4.5 4.4.6 4.4.7 4.4.8 4.4.9 4.4.10 4.4.11 4.4.12 4.4.13 4.4.14 4.4.15 4.4.16
Cargo Discharging without Gas Return from Shore Use of Emergency Cargo Pump In Service Repairs to Tanks Jettisoning of Cargo Cargo Spillage on Deck and Piping Leakage Over-filling of Cargo Tanks Structural Failure of Inner Hull Ship Shore Operations in Event of Fire or Emergency Personnel Contact with LNG Fire Control Procedure for Main Vent Mast (Nitrogen Injection) Cargo Piping Valve Freeze-up Procedure Cargo and Ballast Valve Failure Procedure Primary Membrane Failure Punching Device Loaded Voyage without Gas Burning
ILLUSTRATIONS 4.1 4.2.1a 4.2.1b 4.2.1c 4.2.1d 4.2.2a 4.2.3a 4.2.4a 4.2.4b
Issue: 1
Basic Cargo Operations Sequence Chart Cargo Lines Cool down Loading with Vapour Return to Shore Via Ship HD Compressor Loading with Vapour Return to Shore Via Shore Compressor Nitrogen Setting Up During Loading Cargo Tank Stripping with Other Tanks In Service Cargo Tank Warm Up with Other Tanks In Service Cargo Tank Freeing with Other Tanks In Service (Version 1) Cargo Tank Freeing with Other Tanks In Service (Version 2)
Initial Insulation Space Inerting Evacuation of Insulation Spaces (First Step) 4.2.4d Filling from Liquid Nitrogen (Second Step) 4.2.5a Insulation Space Inerting During Normal Service 4.2.6a Loaded Voyage with Normal Boil-Off Gas Burning 4.2.6b Loaded Voyage with Forced Boil-Off Gas Burning 4.2.7a(i) Discharging with Gas Return from Shore 4.2.7a(ii) Stripping Cargo Tanks with Gas Return from Shore 4.2.8a Ballast Voyage with Normal Boil-Off Gas Burning 4.3.1a Drying Cargo Tanks 4.3.1b Inerting Tanks Prior to Gas Filing 4.3.1c Drying and Inerting Cargo Tanks using Nitrogen from Shore 4.3.2a Displacing Inert Gas (Gassing Up) with LNG Vapour 4.3.3a(i) Tank Cool Down With Return Through LNG Header 4.3.3a(ii) Tank Cool Down With Return Through Vapour Header 4.3.4a Tank Warm Up 4.3.4b One Tank Warm Up 4.3.5a Gas Freeing 4.3.6a Aerating 4.4.1a Cargo Discharge without Gas Return from Shore 4.4.3a Emergency Cargo Pump Fitting Sequence 4.4.5a Jettisoning of Cargo 4.4.7a Over-filling of Cargo Tanks 4.4.8a Secondary Barrier Space De-Watering 4.4.15a Barrier Punch 4.4.16a Loaded Voyage without Gas Burning
LNG LERICI
4.2.4c
PART 5: SAFETY SYSTEMS 5.1 Deck Salt Water Systems 5.1.1 5.1.2 5.1.3 5.1.4 5.1.5
Spray System Firemain System Air Locks Dry Powder System Ship Side Water Curtain Spray
5.1.6 5.1.7
5.2
Infrared Gas Analyser System Catalytic Gas Analyser Hand Held Gas Analyser (O 2, CO 2, CO, Dew point, CH 4)
Fire Detection System
5.6
Gas-Dangerous Spaces and Zones
5.7
Glycol Heating System 5.7.1 5.7.2
Description Glycol Heating for LNG Dual Purpose Heaters
Insulation and Barrier Systems 5.8.1 5.8.2 5.8.3 5.8.4
5.9
5.8.4 5.9.1a 5.9.2a
Leakage Detection
Fire Detection System 5.5.1
5.8
5.8.2a
Inner Hull Failure 5.4.1
5.5
ESD System
Gas Detection System 5.3.1 5.3.2 5.3.3
5.4
5.3.1a 5.4.1a 5.5.1a 5.5.1b 5.6.1a 5.7.1a 5.7.2a 5.8.1a
Emergency Shut Down System 5.2.1
5.3
CO2 Protection in Cargo and Motor Compressor Rooms Vent Mast Extinguishing
Leakage Detection Damage to Primary Insulation Space Gas in Interbarrier Space Damage to Primary Insulation Space Emergency Discharge of LNG Primary Insulation Space Drainage Barrier Punch Systems
Ventilation of Ballast and Trunk Void 5.9.1 5.9.2 5.9.3
Ventilating a Double Hull Ballast Tank Ventilating the Trunk Deck Void Space IMO Code for Existing Ships Carrying Liquefied Gases in Bulk
ILLUSTRATIONS 5.1.1a 5.1.2a 5.2.1a
Deck Water Spray System Deck Fire Main System Emergency Shut-down System
Gas Detection Systems De-Watering Pump Arrangement Fire Detection System Fire Sensor Control Panel Gas-Dangerous Zones Glycol Heating System Cofferdam Heating System Nitrogen Sweeping with Gas Concentration Below Alarm Point Evacuation of Damaged Insulation Spaces Primary Insulation Space Drainage - Barrier Punch Systems Ventilating the Ballast Tanks Ventilating the Trunk Void Spaces
PART 6: INNER HULL AND COLD SPOT INSPECTION PROCEDURES 6.1
Introduction
ILLUSTRATIONS 6.1a 6.1b 6.1c 6.1d 6.1e 6.1f 6.1g 6.1h 6.1i 6.1j 6.1k 6.1l 6.1m 6.1n 6.1o 6.1p 6.1q 6.1r 6.1s
No 1 Cofferdam Perspective No 1 Port Ballast Tank Perspective No 1 Stb’d Ballast Tank Perspective No 1 Above Tank Void Space Perspective No 2 Cofferdam Perspective No 2 Port Ballast Tank Perspective No 2 Stb’d Ballast Tank Perspective No 2 Above Tank Void Space Perspective No 3 Cofferdam Perspective No 3 Port Ballast Tank Perspective No 3 Stb’d Ballast Tank Perspective No 3 Above Tank Void Space Perspective No 4 Cofferdam Perspective No 4 Port Ballast Tank Perspective No 4 Stb’d Ballast Tank Perspective No 4 Above Tank Void Space Perspective No 5 Cofferdam Perspective Fore Peak Ballast Tank (Port Side Perspective View) Fore Peak Ballast Tank (Stb’d Side Perspective View)
List of Contents - Page 2
Cargo Systems and Operating Manual
LNG LERICI
PART 7: STRESS AND DAMAGE STABILITY CASES 7.1
Introduction 7.1.1
7.2
Loading Stability Computer
Cases 7.2.1
Case 1
Damaged Compartments 41 and 214
7.2.2
Case 2
Damaged Compartments 41, 214, 213, 49, 34, 400 and 500
7.2.3
Case 3
Damaged Compartments 34, 35, 49, 51, 401 and 500
7.2.4
Case 4
Damaged Compartments 35, 36, 51, 53, 402 and 500
7.2.5
Case 5
Damaged Compartments 36, 37, 53, 55, 403 and 500
7.2.6
Case 6
Damaged Compartments 36, 37, 54, 56, 403 and 500
7.2.7
Case 7
Damaged Compartments 37, 55, 201, 404 and 500
7.2.8
Case 8
Damaged Compartments 37, 56, 202, 404 and 500
7.2.9
Case 9
Damaged Compartments 200, 201 and 207
7.2.10
Case 10
Damaged Compartments 200, 202 and 207
7.2.11
Case 11
Damaged Compartments 200, 208 and 1
7.2.12
Case 12
Damaged Compartments 206 and 1
7.2.13
Case 13
Damaged Compartments 208 and 1
7.2.14
Case 14
Damaged Compartments 41, 215, 49, 50 and 500
7.2.15
Case 15
Damaged Compartments 41, 215 and 49
7.2.16
Case 16
Damaged Compartments 49, 50, 51, 52 and 500
7.2.17
Case 17
Damaged Compartments 49 and 51
7.2.18
Case 18
Damaged Compartments 51, 52, 53, 54 and 500
7.2.19
Case 19
Damaged Compartments 51 and 53
7.2.20
Case 20
Damaged Compartments 53, 54, 55, 56 and 500
7.2.21
Case 21
Damaged Compartments 53 and 55
7.2.22
Case 22
Damaged Compartments 55, 56, 12 and 500
7.2.23
Case 23
Damaged Compartments 200, 16, 207 and 55
7.2.24
Case 24
Damaged Compartments 200, 204 and 207
7.2.25
Case 25
Damaged Compartments 200, 203 and 207
7.2.26
Case 26
Damaged Compartments 200, 207, 9 and 5
Issue: 1
List of Contents - Page 3
Cargo Systems and Operating Manual
LNG LERICI
General Arrangement of LNG Lerici
Length Overall 216.14m Length Between Perpendiculars 205.00m Extreme Breadth 33.90m Extreme Depth 21.26m Summer Draught 9.52m Corresponding Deadweight 35761.00 tonnes Light Displacement 17099.00 tonnes Loaded Displacement (Summer) 52860.00 tonnes Cargo Tank Cubic Capacity (100% Full) 65299.00 m3 Distance From Keel To Highest Point 53.25m Air Draught 44.10m
Issue: 1
General Arrangement of LNG Lerici - Page 1
Cargo Systems and Operating Manual INTRODUCTION General Although the ship is supplied with Shipbuilder’s plans and manufacturer’s instruction books, there is no single handbook which gives guidance on operating complete systems, as distinct from individual items of machinery. The purpose of this manual is to fill some of the gaps and to provide the ship’s officers with additional information not otherwise available on board. It is intended to be used in conjunction with the other plans and instruction books already on board and in no way replaces or supersedes them. In addition to containing detailed information of the Cargo and related systems, the CARGO OPERATING MANUAL contains safety procedures, and procedures to be observed in emergencies and after accidents. Used in conjunction with the SNAM SMS MANUAL, this information is designed to ensure the safety and efficient operation of the ships. Quick reference to the relevant information is assisted by division of the manual into Parts and Sections, detailed in the general list of contents on the preceding pages. Reference is made in this book to appropriate plans or instruction books. For other information refer to: 1) Books and Publications contained in the SMS Directory
1
2
3
4 5
Never continue to operate any machine or equipment which appears to be potentially unsafe or dangerous and always report such a condition immediately. Make a point of testing all safety equipment and devices regularly. Always test safety trips before starting any equipment. In particular, over-speed trips on auxiliary turbines must be tested before putting the unit into operation. Never ignore any unusual or suspicious circumstances, no matter how trivial. Small symptoms often appear before a major failure occurs. Never underestimate the fire hazard of petroleum products, whether fuel oil or cargo vapour. Never start a machine remotely from the control room without checking visually if the machine is operating satisfactorily.
In the design of equipment and machinery, devices are included to ensure that, as far as possible, in the event of a fault occurring, whether on the part of the equipment or the operator, the equipment concerned will cease to function without danger to personnel or damage to the machine. If these safety devices are neglected, the operation of any machine is potentially dangerous.
Description The concept of this Cargo Operating Manual is based on the presentation of operating procedures in the form of one general sequential chart (algorithm) which gives a step-by-step procedure for performing operations required for the carriage of LNG.
LNG LERICI Each cargo handling operation consists of a detailed introductory section which describes the objectives and methods of performing the operation related to the appropriate flow sheet which shows pipelines in use and directions of flow within the pipelines. Details of valves which are OPEN during the different operations are provided in-text for reference. The ‘valves’ and ‘fittings’ identifications used in this manual are the same as those used by Snam.
Illustrations All illustrations are referred to in the text and are located either in-text where sufficiently small or above the text, so that both the text and illustration are accessible when the manual is laid face down. When text concerning an illustration covers several pages the illustration is duplicated above each page of text. Where flows are detailed in an illustration these are shown in colour. A key of all colours and line styles used in an illustration is provided on the illustration. Details of colour coding used in the illustrations are given in the colour scheme. Symbols given in the manual adhere to international standards and keys to the symbols used throughout the manual are given on the following pages.
Notices The following notices occur throughout this manual:
2) SMS MANUAL In many cases the best operating practice can only be learned by experience. Where the information in this manual is found to be inadequate or incorrect, details should be sent to the Snam LNG Operations Office so that revisions may be made to manuals of other ships of the same class.
Safe Operation The safety of the ship depends on the care and attention of all on board. Most safety precautions are a matter of common sense and good housekeeping and are detailed in the various manuals available on board. However, records show that even experienced operators sometimes neglect safety precautions through over-familiarity and the following basic rules must be remembered at all times.
Issue: 1
The manual consists of introductory sections which describe the systems and equipment fitted and their method of operation related to a schematic diagram where applicable. This is then followed where required by detailed operating procedures for the system or equipment involved. The overview of cargo operations, as detailed in 4.1, consists of a basic operating algorithm which sets out the procedure for cargo handling operations from dry dock to first loading and from first loading through the normal cargo operating cycle. The relevant illustration and operation Section number is located on the right hand side of each box.
! WARNING Warnings are given to draw reader’s attention to operation where DANGER TO LIFE OR LIMB MAY OCCUR.
! CAUTION Cautions are given to draw reader’s attention to operations where DAMAGE TO EQUIPMENT MAY OCCUR. NOTE: Notes are given to draw reader’s attention to points of interest or to supply supplementary information.
Introduction - Page 1
Cargo Systems and Operating Manual ELECTRICAL SYMBOLS KEY Circuit breaker
INSTRUMENTATION IDENTIFIERS & SYMBOLS KEY
&
Moulded case air current breaker Fuse Fused switch Switch
1
AND Gate (both inputs must be present in order for there to be an Output). OR Gate (any one input will result in an output)
A
Ammeter
V
Voltmeter
Hz
Frequency meter
Normally closed contact Normally open contact kW
Kilowatt
Syn
Synchroscope
Contact with pushbutton Single contact pushbutton normally closed Changeover switch/contact
Latching device
Two-way switch with ÔoffÕ position
Battery
Limit switch normally open
Double junction of conductors vertically in line
Pressure switch (closed by pressure) Temperature switch (closed)
Conductors crossing but not joining
ÒOff loadÓ disconnect links Connection for portable cables
Junction of conductors
Relay coil Capacitor Rectifier Transformer M
Motor A C generator 3 phase generator Signal lamp Overload release (thermal)
S
Motor starter
LNG LERICI
Overload release (magnetic)
AI AT FC FI FIC FS HY HIC HSS HS HTS LA LC LG LIA LS LT LPS OdA OC PA PC PCV PdA PdI PdS PdC PdT PI PS PT QA QI QT SA SI ST TA TC TCS TdA TE TI TIC TR TRC TS TT VA VS VIC HS XA YT ZS ZI ZT ZA
Analyser indicator Analyser transmitter Flow controller Flow indicator Flow indicator control Flow switch High adjust High indicator control High switch selector High selector High temperature selector Level alarm Level controller Level glass Level indicator Level switch Level transmitter Low pressure selector Oil detection alarm Oxygen content Pressure alarm Pressure controller Pressure control valve Pressure differential alarm Pressure differential indicator Pressure differential switch Pressure differential control Pressure differential transmitter Pressure indicator Pressure switch Pressure transmitter Quality alarm Quality indicator Quality transmitter Salinity alarm Speed indicator Speed transmitter Temperature alarm Temperature controller Temperature control sensor Temperature differential alarm Temperature element Temperature indicator Temperature indicating controller Temperature recorder Temperature recording controller Temperature switch Temperature transmitter Vacuum alarm Vacuum Switch Viscosity indicating controller High selector Group alarm Vibration transmitter Movement switch Position indicator Movement transmitter Position alarm
COLOUR SCHEME Locally Mounted Instrument
Glycol Cold Water Sanitary FW
Remotely Mounted Instruments L
Trip
Letters outside the circle of an instrument symbol indicate whether high (H), high-high (HH), low (L) or low-low (LL) function is involved O = Open C = Closed
Automatic Trip
LNG Liquid LNG Vapour Combustion Air Warm LNG Vapour Gas Burning Supply Glycol Hot Water Fire Main Sea Water
I
Interlock
Electrical Distribution Diesel Oil Liquid Nitrogen Primary Space Nitrogen Gaseous Nitrogen Ballast Water SW Lub - Oil Freon Secondary Space Nitrogen Inert Gas DSH Steam 8 Bar Condensate Dry Air Deck Spray Water Instrument Air Hydraulic Oil FW Cooling Wet Air Electrical Instrumentation
Issue: 1
Symbol and Illustration Colour Scheme
Cargo Systems and Operating Manual
LNG LERICI
MECHANICAL SYMBOLS KEY Bursting disc Flexible hose
Emergency remote quick closing valve
Alarm Klaxon
Self-closing test valve
Flame Trap
Relief or safety valve
Removable pipe Length (Spoolpiece)
P Pressure Relief Valve
Screw Lift Valve Chest Screw Down NR Valve Chest
Two-way cock T L
Three-way cock (T or L signifies plug form)
L. C.
Locked Closed Valve
Lever operated cock
L. O.
Locked Open Valve
Trip valve
Trace Heating And Insulated Pipe
Ball float valve Valve with hose connection
Insulated Pipe Pump
Piston operated valve
Butterfly valve
Diaphragm operated valve (indicates close or open in the event of air supply failure)
T branch pipe
Diaphragm valve
Cross branch pipe
Straight safety valve
Crossing pipe
Angle safety valve
Straight globe valve
Cock
Angle globe valve
Bib cock
Suction bell mouth
Angle NR valve
Gate valve
Strainer
Flow control valve
Filter
Globe valve Needle valve Ball valve Quick closing valve
Automatic drain Orifice or restriction Globe valve (screw lift) Vent Pipe
Straight swing type NR valve
P
Issue: 1
E
Pneumatic electrical Convertor
Diaphragm Adjustable flow rotary displacement pump
Sieve strainer
Water trap
Remote manual control Remotely controlled valve (2 or 3 way) P
Pneumatic control
H
Hydraulic control
E
Electric control
M
Motorized control
Air moisture eliminator Straight venting check valve with flame arrestor Angle venting check valve
T
Turbine
C
Centrifugal compressor
C
Reciprocating compressor
M
A C motor
M
D C motor
Angle venting check valve with flame arrestor
Sounding and filling cap Condenser Sight glass Vaporiser
Vacuum breaker
Angle automatic shut off valve
Spectacle flange Open Closed
Angle anti-siphon vacuum breaker
Strainer Straight sludge box
Motor
Cooler
Tee
Bleeding plug
M
Heater
Venting box with flame arrestor
Straight automatic shut off valve
Funnel with sieve
Gutterway or Drip-pan
Angle sludge box
Straight anti-siphon vacuum breaker
Needle valve
Pressure reciever
Pressure reducing valve
Bend
Quick closing valve
Air fan heater
Lubricator
Blind flange
De superheater Pneumatic or Hydraulic Switch
Ignitor
3 way Ð plug valve 3 plug ports
Quick opening valve
Hydraulic Check Valve
Basket strainer
Manual control
Spring loaded NR valve
Valve with limit switch
Duplex filter
Manifold with lift check valves
Angle swing type check valve
Straight NR valve
Solenoid operated valve
Manifold with screw down swing valves
Valve of any type
Valve with gland sealing
Non-return valve (N R)
Angle fire type valve
Sea water chest with grid
3 way Ð plug valve 2 plug ports
Electric heater
Straight fire type valve
Sea water chest
Diaphragm operated valve with built-on positioner
Screw down N R valve
Ball or plug valve
Jack
3 way globe valve
3 way Ð plug valve 2 plug port 1 per bottom
Hydraulic Oil Filter
Air eliminator
Suction bellmouth
Automatic shut off sounding cap
Back flow preventer for continuous pressure P
Reciprocating pump Rotary pump
Ejector/ Eductor
Constant flow rotary displacement pump
Straight tube exchanger
U tube exchanger
Funnel
Earth
List of Symbols
Cargo Systems and Operating Manual ISSUE AND UPDATE CONTROL This manual is provided with a system of issue and update control. Controlling documents ensures that:
This manual was produced by:
•
documents conform to a standard format;
For any new issue or update contact:
•
amendments are carried out by relevant personnel;
•
each document or update to a document is approved before issue;
•
a history of updates is maintained;
•
updates are issued to all registered holders of documents;
•
sections are removed from circulation when obsolete.
WRIGHT MARINE TECHNOLOGY LTD.
The Technical Director WMT Technical Office The Court House 15 Glynne Way Hawarden Deeside, Flintshire CH5 3NS, UK E-Mail:
[email protected]
Document control is achieved by the use of the footer provided on every page and the issue and update table below. In the right hand corner of each footer or header are details of the page’s section number and title followed by the page number of the section. In the left hand corner of each footer is the issue number. Details of each section are given in the first column of the issue and update control table. The table thus forms a matrix into which the dates of issue of the original document and any subsequent updated sections are located. The information and guidance contained herein is produced for the assistance of certificated officers who by virtue of such certification are deemed competent to operate the vessel to which such information and guidance refers. Any conflict arising between the information and guidance provided herein and the professional judgement of such competent officers must be immediately resolved by reference to SNAM, Head Office, Milan.
Issue: 1
LNG LERICI
List of Contents General Arrangement Introduction (Including SNAM Safety Procedures and Instructions) Symbols and Colour Scheme
Issue 1 November 98 November 98 November 98
Issue 2
Issue 3
Issue 4
November 98
Text 1.1 1.1.1 1.1.2 1.2 1.2.1 1.2.2 1.2.3 1.3 1.3.1 1.3.2
November November November November November November November November November November November
98 98 98 98 98 98 98 98 98 98 98
Illustrations 1.1.1a 1.1.1b 1.2.1a 1.2.1b 1.2.1c 1.2.1d 1.2.1e 1.2.2a 1.2.3a 1.2.3b 1.3.1a
November November November November November November November November November November November
98 98 98 98 98 98 98 98 98 98 98
Text 2.1 2.1.1 2.1.2 2.2 2.2.1
November November November November November
98 98 98 98 98
Issue and Update Control - Page 1
Issue: 1
Issue and Update Control - Page 2
Cargo Systems and Operating Manual
Issue 1
Issue 2
Text 3.1 3.2 3.3 3.3.1 3.3.2 3.3.3
November November November November November November
98 98 98 98 98 98
Illustrations 3.1.1a 3.1.1b 3.1.1c 3.2.1a 3.3.2a 3.3.2b 3.3.3a
November November November November November November November
98 98 98 98 98 98 98
Text 4.1 4.2 4.2.1 4.2.2 4.2.3 4.2.4 4.2.5 4.2.6 4.2.7 4.2.8 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.4
Issue: 1
November November November November November November November November November November November November November November November November November November
98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98 98
Issue 3
LNG LERICI
Issue 1
Issue 4
Issue 2
Text 4.4.1 4.4.3 4.4.4 4.4.5 4.4.6 4.4.7 4.4.8 4.4.9 4.4.10 4.4.11 4.4.12 4.4.13 4.4.14 4.4.15 4,4.16
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Illustrations 4.1 4.2.1a 4.2.1b 4.2.1c 4.2.1d 4.2.2a 4.2.3a 4.2.4a 4.2.4b 4.2.4c 4.2.4d 4.2.5a 4.2.6a 4.2.6b 4.2.7a(i) 4.2.7a(ii) 4.2.8a
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Issue 1 Illustrations 4.3.1a 4.3.1b 4.3.1c 4.3.2a 4.3.3a(i) 4.3.3a(ii) 4.3.4a 4.3.4b 4.3.5a 4.3.6a 4.4.1a 4.4.3a 4.4.5a 4.4.7a 4.4.8a 4.4.15a 4.4.16a Text 5.1 5.1.1 5.1.2 5.1.3 5.1.4 5.1.5 5.1.6 5.1.7 5.2 5.2.1 5.3 5.3.1 5.3.2 5.3.3 5.4
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LNG LERICI
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Text 5.4.1 5.5 5.5.1 5.6 5.7 5.7.1 5.7.2 5.8 5.8.1 5.8.2 5.8.3 5.8.4 5.9 5.9.1 5.9.2 5.9.3
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Illustrations 5.1.1a 5.1.2a 5.2.1a 5.3.1a 5.4.1a 5.5.1a 5.5.1b 5.6.1a 5.7.1a 5.7.2a 5.8.1a 5.8.2a 5.8.4 5.9.1a 5.9.2a
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Issue 1 Text 6.1 Illustrations 6.1a 6.1b 6.1c 6.1d 6.1e 6.1f 6.1g 6.1h 6.1i 6.1j 6.1k 6.1l 6.1m 6.1n 6.1o 6.1p 6.1q 6.1r 6.1s
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Text 7.1 7.1.1
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Illustrations 7.2.1 7.2.2 7.2.3 7.2.4 7.2.5 7.2.6
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Issue 1 Illustrations 7.2.7 7.2.8 7.2.9 7.2.10 7.2.11 7.2.12 7.2.13 7.2.14 7.2.15 7.2.16 7.2.17 7.2.18 7.2.19 7.2.20 7.2.21 7.2.22 7.2.23 7.2.24 7.2.25 7.2.26
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Part 1 LNG, Nitrogen and Inert Gas
Cargo Systems and Operating Manual PART 1: LNG, NITROGEN AND INERT GAS 1.1 Physics of Gases This chapter provides some basic information on chemistry of gases in general. It is expected to give an outline of the important physical and chemical properties of liquid gases.
Charles’ Law (Gay Lussac’s Law) Provided the pressure P of a given mass of gas remains constant, then the volume V of the gas will be directly proportional to the absolute temperature T of the gas, ie.
This result may be expressed thus: The product of the pressure and volume of a quantity of gas divided by its absolute temperature is a constant and this may be written as
V = constant x T.
PV where C is a constant. = C or PV = CT T Dalton’s Law of Partial Pressures The sum of the partial pressure of the constituent gases of a mixture of gases is equal to the total pressure of the gas mixture. P = P1 + P2 + Pn
Therefore
1.1.1 Gas Laws Although strictly speaking a perfect gas is an ideal which can never be realised in practice, the behaviour of many real gases is very similar to the behaviour of a perfect gas. Two of the laws describing the behaviour of perfect gases are Boyle’s Law and Charles’ Law. Boyle’s Law This law may be stated as follows: Provided the temperature T of a perfect gas remains constant, then the volume V of the gas is inversely proportional to its pressure P, ie. P x V = constant if the temperature remains constant.
LNG LERICI
V = constant for constant pressure P. T
P 1
2
1.1.2 Definitions Absolute Pressure The total pressure of a gas called Absolute Pressure is the sum of gauge pressure plus the barometric or atmospheric pressure.
V
0 1.1.1b Charles Law
P P1
If a gas changes from state 1 to 2 during a constant pressure process, then
1
V1 V2 = = constant T1 T2 If the process is represented on a P - V diagram, the result will be as shown in the figure above.
P2
2 V1
V2
V
Combination of the Laws of Boyle and Charles The pressure, volume and temperature of a gas may all change at once from P1 V1 and T1 to P2 V2 and T2. In this case, because pressure changes, Charles’ Law will not apply and because the temperature changes, Boyle’s Law will also not apply.
1.1.1a Boyle's Law If a gas changes from a state 1 to a state 2 during a constant temperature process (isothermal), then P1 x V1 = P2 x V2 = constant If the process is represented on a graph having axes of pressure P and volume V, the result will be as shown in the figure above. The curve is known as a rectangular hyperbola, having the mathematical equation xy = constant
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This change of state may therefore be regarded as taking place in two stages: a) By a change according to Boyle’s Law; b) A change according to Charles’ Law. By doing this it will be found that the following will apply PV P1V1 = 2 2 T2 T1
Absolute Temperature The fundamental temperature scale with its zero at absolute zero and expressed in degrees Kelvin. One degree Kelvin is equal to one degree Celsius or one degree Centigrade. For the purpose of practical calculations in order to convert Celsius to Kelvin add 273. It is normal for the degree Kelvin to be abbreviated in mathematical formulae to ‘K’ with the degree symbol being omitted.
Approved Equipment Equipment of a design that has been type-tested and approved by an appropriate authority such as a governmental agency or classification society. Such an authority will have certified the particular equipment as safe for use in a specified hazardous atmosphere. Auto-Ignition Temperature The lowest temperature at which a solid, liquid or gas combusts spontaneously without initiation by spark or flame. Avogadro’s Law Avogadro’s Hypothesis states that equal volumes of all gases contain equal numbers of molecules under the same conditions of temperature and pressure. Avogadro’s Law Avogadro’s Hypothesis states that equal volumes of all gases contain equal numbers of molecules under the same conditions of temperature and pressure.. BLEVE This is the abbreviation for a Boiling Liquid Expanding Vapour Explosion. It is associated with the rupture, under fire conditions, of a pressure vessel containing liquefied gas.
Absolute Zero The temperature at which the volume of a gas theoretically becomes zero and all thermal motion ceases. It is generally accepted as being -273.16°C.
Boil-off Boil-off is the vapour produced above the surface of a boiling cargo due to evaporation. It is caused by heat ingress or a drop in pressure.
Activated Alumina A desiccant (or drying) medium which operates by adsorption of water molecules.
Boiling Point The temperature at which the vapour pressure of a liquid is equal to the pressure on its surface (the boiling point varies with pressure).
Adiabatic Describes an ideal process undergone by a gas in which no gain or loss of heat occurs. Aerating Aerating means the introduction of fresh air into a tank with the object of removing toxic, flammable and inert gases and increasing the oxygen content to 21% by volume. Airlock A separation area used to maintain adjacent areas at a pressure differential. For example, the airlock to an electric motor room on a gas carrier is used to maintain pressure segregation between a gas-dangerous zone on the open deck and the gas-safe motor room which is pressurised.
Booster Pump A pump used to increase the discharge pressure from another pump (such as a cargo pump). British Thermal Unit The quantity of heat required to raise 1 pound of water through one degree Fahrenheit, expressed in Btu. Bulk Cargo Cargo carried as a liquid in cargo tanks and not shipped in drums, containers or packages.
1.1 Physics of Gases - Page 1
Cargo Systems and Operating Manual Calorie The quantity of heat required to raise 1 gramme (1g) of water through 1°C. A kilo calorie is equal to 1000 calories. In the ISO system, the unit used is the JOULE (J). 1 calorie (cal) 4.185J 1 thermie (th) = 106 cal Calorific Value The calorific value or heat of combustion is defined as the amount of heat released when a unit quantity of gas is burned at atmospheric pressure and at ambient temperature (25°C). The gross value is obtained when the contribution from the latent heat of condensation of the water vapour formed is recovered; the net calorific value is a more realistic parameter pertaining to practical conditions when flue gases are usually maintained above 100°C. However, the gross heating value is the standard adopted almost universally for the calculation of thermal efficiencies of fuel burning appliances. Canister Filter Respirator A respirator consisting of mask and replaceable canister filter through which air mixed with toxic vapour is drawn by the breathing of the wearer and in which the toxic elements are absorbed by activated charcoal or other material. A filter dedicated to the specific toxic gas must be used. Sometimes this equipment may be referred to as cartridge respirator. It should be noted that a canister filter respirator is not suitable for use in an oxygen deficient atmosphere. Carcinogen A substance capable of causing cancer. Cargo Area That part of the ship which contains the cargo containment system, cargo pumps and compressor rooms, and includes the deck area above the cargo containment system. Where fitted, cofferdams, ballast tanks and void spaces at the after end of the aftermost hold space or the forward end of the forwardmost hold space are excluded from the cargo area. (Refer to the Gas Codes for a more detailed definition). Cargo Containment System The arrangement for containment of cargo including, where fitted, primary and secondary barriers, associated insulations, interbarrier spaces and the structure required for the support of these elements. (Refer to the Gas Codes for a more detailed definition).
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Cascade Reliquefaction Cycle A process in which vapour boil-off from cargo tanks is condensed in a cargo condenser in which the coolant is a refrigerant gas such as R 22. The refrigerant gas is then compressed and passed through a conventional sea water-cooled condenser. Cavitation A process occurring within the impeller of a centrifugal pump when pressure at the inlet to the impeller falls below that of the vapour pressure of the liquid being pumped. The bubbles of vapour which are formed collapse with impulsive force in the higher pressure regions of the impeller. This effect can cause significant damage to the impeller surfaces and, furthermore, pumps may loose suction. Certificate of Fitness A certificate issued by a flag administration confirming that the structure, equipment, fittings, arrangements and materials used in the construction of a gas carrier are in compliance with the relevant Gas Code. Such certification may be issued on behalf of the administration by an approved classification society. Certified Gas Free A tank or compartment is certified to be gas-free when its atmosphere has been tested with an approved instrument and found in a suitable condition by an independent chemist. This means it is not deficient in oxygen and sufficiently free of toxic or flammable gas for a specified purpose. Cofferdam The isolating space on a ship between two adjacent steel bulkheads or decks. This space may be a void space or ballast space. Compression Ratio The ratio of the absolute pressure at the discharge from a compressor divided by the absolute pressure at the suction. Condensate Reliquefied gases which collect in the condenser and which are then returned to the cargo tanks. Critical Density Density at critical temperature and pressure. Critical Pressure The pressure at which a substance exists in the liquid state at its critical temperature. (In other words it is the saturation pressure at the critical temperature).
LNG LERICI Critical Temperature and Pressure The critical temperature of a gas is the temperature above which the substance cannot be liquid however great the pressure. The critical pressure of a gas is the pressure required to compress a gas to its liquid state at its critical temperature. Cryogenics The study of the behaviour of matter at very low temperatures. Dalton’s Law of Partial Pressures This states that the pressure exerted by a mixture of gases is equal to the sum of the separate pressures which each gas would exert if it alone occupied the whole volume. Dangerous Cargo Endorsement Endorsement issued by a flag state administration to a certificate of competency of a ship’s officer allowing service on dangerous cargo carriers such as oil tankers, chemical carriers, or gas carriers. Density The density of a substance is the weight per unit volume at standard temperature of 15°C. This is usually quoted in kg/m3 or g/cm3 or kg/dm3. Deepwell Pump A type of centrifugal cargo pump commonly found on gas carriers. The prime mover is usually an electric or hydraulic motor. The motor is usually mounted on top of the cargo tank and drives, via a long transmission shaft, through a double seal arrangement, the pump assembly located in the bottom of the tank. The cargo discharge pipeline surrounds the drive shaft and the shaft bearings are cooled and lubricated by the liquid being pumped. Dewpoint The temperature at which condensation will take place within a gas if further cooling occurs. Endothermic A process which is accompanied by the absorption of heat
Enthalpy The enthalpy of a mass of a substance is a measure of its thermodynamic heat content whether the substance is liquid or vapour or a combination of the two. Enthalpy (H) is defined as: H = U + PV where and
U is the internal energy P is the absolute pressure V is the total volume of the system (liquid + vapour)
Entropy The entropy of a liquid or vapour is its enthalpy divided by the absolute temperature. It is expressed as kilocalories per kilogramme per degree Celsius (kcal/kg/°C) and remains constant while the liquid or vapour volume changes without absorption or release of heat. However, entropy increases or decreases if the material receives or surrenders heat from or to its surroundings. Over an infinitely small change in temperature, the increase or decrease of entropy, when multiplied by the absolute temperature, gives the heat absorbed or lost by the fluid Explosive Limits The limits of the explosive range, that is, the range between the minimum and maximum concentrations of hydrocarbon vapour in air which form explosive (flammable) mixtures: usually abbreviated to LEL (Lower Explosive Limit) and UEL (Upper Explosive Limit). Sometimes referred to as LFL (Lower Flammable Limit) and UFL (Upper Flammable Limit). Explosion-Proof/Flameproof Enclosure An enclosure which will withstand an internal ignition of a flammable gas and which will prevent the transmission of any flame able to ignite a flammable gas which may be present in the surrounding atmosphere. Flame Arrestor A device fitted in gas vent pipelines to arrest the passage of flame into enclosed spaces. Flame Screen A device incorporating corrosion resistant wire meshes. It is used for preventing the inward passage of sparks (or, for a short period of time, the passage of flame), yet permitting the outward passage of gas.
1.1 Physics of Gases - Page 2
Cargo Systems and Operating Manual Flash Point The lowest temperature at which a liquid gives off sufficient vapour to form a flammable mixture with air near the surface of the liquid or within the apparatus used. This is determined by laboratory testing in a prescribed apparatus. Gas-Safe Space A space on a ship not designated as a gas-dangerous space. Hard Arm An articulated metal arm used at terminal jetties to connect shore pipelines to the ship’s manifold. Heel The amount of liquid cargo retained in a cargo tank at the end of discharge. It is used to maintain the cargo tanks cooled down during ballast voyages by recirculating through the sprayers. On LPG ships such cooling down is carried out through the reliquefaction plant and on LNG ships by using the spray pumps. Hold Space The space enclosed by the ship’s structure in which a cargo containment system is situated. Hydrates The compounds formed by the interaction of water and hydrocarbons at certain pressures and temperatures. They are crystalline substances. Hydrate Inhibitors An additive to certain liquefied gases capable of reducing the temperature at which hydrates begin to form. Typical hydrate inhibitors are methanol, ethanol and isopropyl alcohol.
Incendive Spark A spark of sufficient temperature and energy to ignite a flammable gas mixed with air. Inert Gas A gas, such as nitrogen, or a mixture of gases containing insufficient oxygen to support combustion. Inerting Inerting means: (i) the introduction of inert gas into an aerated tank with the object of attaining an inert condition suited to a safe gassing-up operation. (ii) the introduction of inert gas into a tank after cargo discharge and warming-up with the object of: (a)
reducing existing vapour content to a level below which combustion cannot be supported if aeration takes place
(b)
reducing existing vapour content to a level suited to gassing-up prior to the next cargo
(c)
reducing existing vapour content to a level stipulated by local authorities if a special gasfree certificate for hot work is required.
Insulation Flange An insulating device inserted between metallic flanges, bolts and washers to prevent electrical continuity between pipelines, sections of pipelines, hose strings and loading arms or other equipment. Interbarrier Space The space between a primary and a secondary barrier of a cargo containment system, whether or not completely or partially occupied by insulation or other material.
IAPH International Association of Ports and Harbours.
Intrinsically Safe Equipment, instrumentation or wiring is deemed to be intrinsically safe if it is incapable of releasing sufficient electrical or thermal energy under normal conditions or specified fault conditions to cause ignition of a specific hazardous atmosphere in its most easily ignited concentration.
lCS International Chamber of Shipping.
ISGOTT International Safety Guide for Oil Tankers and Terminals
IMO International Maritime Organization. This is the United Nations specialised agency dealing with maritime affairs.
Isothermal Descriptive of a process undergone by an ideal gas when it passes through pressure or volume variations without a change of temperature.
IACS International Association of Classification Societies.
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LNG LERICI Latent Heat The latent heat of a liquid is the quantity of heat absorbed on vapourisation at normal boiling point, or conversely, it is the amount of heat given out when the vapour is condensed at atmospheric pressure. As the heat content of the liquid increases with temperature, the latent heat decreases.The value of latent heat data lies in calculating the quantity of gas that will be vapourised at a given liquid temperature by a specific heat input. Latent Heat of Vaporisation Quantity of heat to change the state of a substance from liquid to vapour (or vice versa) without change of temperature. Liquefied Gas A liquid which has a saturated vapour pressure exceeding 2.8 bar absolute at 37.8°C and certain other substances specified in the Gas Codes. Liquefied Natural Gas (LNG) Liquefied Methane and mixtures of other hydrocarbon gases in which Methane predominates. Lower Flammable Limit (LFL) The concentration of a hydrocarbon gas in air below which there is insufficient hydrocarbon to support combustion .
Mole The mass that is numerically equal to the molecular mass. It is most frequently expressed as the gram molecular mass (g mole) but may also be expressed in other mass units, such as the kg mole. At the same pressure and temperature the volume of one mole is the same for all ideal gases. It is practical to assume that petroleum gases are ideal gases. Mole Fraction The number of moles of any component in a mixture divided by the total number of moles in the mixture. Mollier Diagram A graphic method of representing the heat quantities contained in, and the condition of, a liquefied gas (or refrigerant) at different temperatures. NGLs This is the abbreviation for Natural Gas Liquids. These are the liquid components found in association with natural gas. Ethane, propane, butane, pentane and pentanesplus are typical NGLs. NPSH This is the abbreviation for Net Positive Suction Head. This is an expression used in cargo pumping calculations. It is the pressure at the pump inlet and is the combination of the liquid head plus the pressure in the vapour space.
LPG This is the abbreviation for Liquefied Petroleum Gas. This group of products includes propane and butane which can be shipped separately or as a mixture. LPGs may be refinery by-products or may be produced in conjunction with crude oil or natural gas.
OCIMF Oil Companies International Marine Forum.
MARVS This is the abbreviation for the Maximum Allowable Relief Valve Setting on a ship’s cargo tank as stated on the ship’s Certificate of Fitness.
Oxygen-Deficient Atmosphere An atmosphere containing less than 21% oxygen by volume.
mlc This is the abbreviation for metres liquid column and is a unit of pressure used in some cargo pumping operations . Molar Volume The volume occupied by one molecular mass in grams (g mole) under specific conditions.For an ideal gas at standard temperature and pressure it is 0.0224 m3/g mole.
Oxygen Analyser Instrument used to measure oxygen concentrations in percentage by volume.
Partial Pressure The individual pressure exerted by a gaseous constituent in a vapour mixture as if the other constituents were not present. This pressure cannot be measured directly but is obtained firstly by analysis of the vapour and then by calculation using Dalton’s Law. Peroxide A compound formed by the chemical combination of cargo liquid or vapour with atmospheric oxygen or oxygen from another source. In some cases these compounds may be highly reactive or unstable and a potential hazard.
1.1 Physics of Gases - Page 3
Cargo Systems and Operating Manual Polymerisation The chemical union of two or more molecules of the same compound to form a larger molecule of a new compound called a polymer. By this mechanism the reaction can become self-propagating causing liquids to become more viscous and the end result may even be a solid substance. Such chemical reactions usually give off a great deal of heat. Primary Barrier This is the inner surface designed to contain the cargo when the cargo containment system includes a secondary barrier.
Saturation Temperature The saturation temperature is that at which boiling occurs. At this temperature bubbles of vapour form in the liquid and break through the surface to occupy the space above it as a vapour. Supply of heat at this temperature causes further generation of vapour but does not increase the temperature until all the liquid has been converted into a vapour. Another definition of saturation temperature is that it is the temperature at which the two phases, liquid and vapour, can exist in equilibrium with each other. As the pressure is increased so is the saturation temperature, until the critical point is reached.
Other refrigerant gases listed in the IGC Code are shown in Appendix 2 although many are now controlled with a view to being phased out under the Montreal Protocol (1987).
Saturated Vapour Pressure The pressure at which a vapour is in equilibrium with its liquid at a specified temperature.
Relative Liquid Density The mass of a liquid at a given temperature compared with the mass of an equal volume of fresh water at the same temperature or at a different given temperature.
Secondary Barrier The liquid-resisting outer element of a cargo containment system designed to provide temporary containment of a leakage of liquid cargo through the primary barrier and to prevent the lowering of the temperature of the ship’s structure to an unsafe level.
Relative Vapour Density This is the relative weight of vapour compared with the weight of an equal volume of dry air at standard conditions of temperature and pressure, ie 15°C and atmospheric pressure of 760mm Hg. Restricted Gauging A system employing a device which penetrates the tank and which, when in use, permits a small quantity of cargo vapour or liquid to be expelled to the atmosphere. When not in use, the device is kept completely closed. Rollover The phenomenon where the stability of two stratified layers of liquid of differing relative density is disturbed resulting in a spontaneous rapid mixing of the layers accompanied in the case of liquefied gases, by violent vapour evolution.
Sensible Heat Heat energy given to or taken from a substance which raises or lowers its temperature. Shell and Tube Condenser A heat exchanger where one fluid circulates through tubes enclosed between two end-plates in cylindrical shell and where the other fluid circulates inside the shell. Silica Gel A chemical used in driers to absorb moisture. Sl (Systeme International) Units An internationally accepted system of units modelled on the metric system consisting of units of length (metre), mass (kilogram), time (second), electric current (ampere), temperature (degrees Kelvin), and amount of substance (mole). SIGTTO Society of International Gas Tanker and Terminal Operators Limited.
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LNG LERICI Slip Tube A device used to determine the liquid-vapour interface during the ullaging of semi and fully pressurised tanks.
Superheated Vapour Vapour removed from contact with its liquid and heated beyond its boiling temperature.
SOLAS International Convention for the Safety of Life at Sea, 1974; as amended.
Surge Pressure A phenomenon generated in a pipeline system when there is a change in the rate of flow of liquid in the line. Surge pressures can be dangerously high if the change of flow rate is too. rapid and the resultant shock waves can damage pumping equipment and cause rupture of pipelines and associated equipment
Span Gas A vapour sample of known composition and concentration used to calibrate gas detection equipment. Specific Gravity SG The specific gravity of a gas is normally defined as the ratio of its density to that of air at the same temperature and pressure (taken as unity). Specific gravity of liquids expresses the relative weight of these hydrocarbon liquids at their boiling point as compared to water at 4°C. Specific Heat This is the quantity of energy in kilo Joules required to change the temperature of 1kg mass of a substance by 1°C. For a gas the specific heat at constant pressure is greater than that at constant volume. Specific Volume This is the volume occupied by one kg of the substance at 15°C and 760mm Hg pressure. Spontaneous Combustion The ignition of material brought about by a heat-producing chemical reaction within the material itself without exposure to an external source of ignition. Static Electricity Static electricity is the electrical charge produced on dissimilar materials caused by relative motion between each when in contact. Submerged Pump A type of centrifugal cargo pump commonly installed on gas carriers and in terminals in the bottom of a cargo tank. It comprises a drive motor, impeller and bearings totally submerged by the cargo when the tank contains bulk liquid.
Therm The therm is equal to 100,000 Btu. Toxicity Detector An instrument used for the detection of gases or vapours. It works on the principle of a reaction occurring between the gas being sampled and a chemical agent in the apparatus. TLV This is the abbreviation for Threshold Limit Value. It is the concentration of gases in air to which personnel may be exposed 8 hours per day or 40 hours per week throughout their working life without adverse effects. The basic TLV is a Time-Weighted Average (TWA). This may be supplemented by a TLV-STEL (Short-Term Exposure Limit) or TLV-C (Ceiling exposure limit) which should not be exceeded even instantaneously. Viscosity (Kinematic) The property of a liquid which determines its resistance to flow. The usefulness of viscosity data lies in specifying pumps for liquid transfer and in predicting pressure losses in pipe systems. The unit used is the stoke (St) or centistoke (cSt). Vapour Density The density of a gas or vapour under specified conditions of temperature and pressure. Void Space An enclosed space in the cargo area external to a cargo containment system, other than a hold space, ballast space, fuel oil tank, cargo pump or compressor room or any space in normal use by personnel.
1.1 Physics of Gases - Page 4
Cargo Systems and Operating Manual 1.2
Properties of LNG
1.2.1 Physical Properties, Composition and Characteristics of LNG Natural gas is a mixture of hydrocarbon which, when liquefied, forms a clear colourless and odourless liquid; this LNG is usually transported and stored at a temperature very close to its boiling point at atmospheric pressure (approximately –160°C). The actual composition of North African LNG will vary depending on its source and on the liquefaction process, but the main constituent will always be methane; other constituents will be small percentages of heavier hydrocarbons, e.g. ethane, propane, butane, pentane, and possibly a small percentage of nitrogen. A typical composition of LNG is given in Table 1.2.1b, and the physical properties of the major constituent gases are given in Table 1.2.1a. For most engineering calculations (eg. piping pressure losses) it can be assumed that the physical properties of pure methane represent those of LNG. However for custody transfer purposes when accurate calculation of the heating value and density is required, the specific properties based on actual component analysis must be used. During a normal sea voyage, heat is transferred to the LNG cargo through the cargo tank insulation causing vapourisation of part of the cargo, ie. boil-off. The composition of the LNG is changed by this boil-off because the lighter components having lower boiling
LNG LERICI
points at atmospheric pressure vapourise first; therefore the discharged LNG has a lower percentage content of nitrogen and methane than the LNG as loaded, and a slightly higher percentage of ethane, propane and butane, due to methane and nitrogen boiling off in preference to the heavier gases. The flammability range of methane in air (21% oxygen) is approximately 5.3 to 14% (by volume). To reduce this range the air is diluted with nitrogen until the oxygen content is reduced to 5% prior to loading after dry dock. In theory, an explosion cannot occur if the O2 content of the mixture is below 13% regardless of the percentage of methane, but for practical safety reasons, purging is continued until the O2 content is below 5%. This safety aspect is explained in detail later in this section. The boil-off vapour from LNG is lighter than air at vapour temperatures above -110°C or higher depending on LNG composition (see graph 1.2.2a), therefore when vapour is vented to atmosphere, the vapour will tend to rise above the vent outlet and will be rapidly dispersed. When cold vapour is mixed with ambient air the vapour-air mixture will appear as a readily visible white cloud due to the condensation of the moisture in the air. It is normally safe to assume that the flammable range of vapour-air mixture does not extend significantly beyond the perimeter of the white cloud. The auto-ignition temperature of methane, ie. the lowest temperature to which the gas needs to be heated to cause self-sustained combustion without ignition by a spark or flame, is 595°C.
Methane
Ethane
Propane
Butane
Pentane
Nitrogen
Formula
CH4
C 2H6
C3H 8
C4H10
C5H12
N2
Molecular Weight
16.042
30.068
44.094
58.120
72.150
28.016
Boiling Point at 1 bar absolute
-161.5°C
-88.6°C
-42.5°C
-5°C
36.1°C
-196°C
Liquid Density at Boiling Point (kg/m3)
426.0
544.1
580.7
601.8
610.2
808.6
Vapour SG at 15°C and 1 bar absolute
0.554
1.046
1.54
2.07
2.49
0.97 kg/m3
Gas volume/liquid volume Ratio at Boiling Point and 1 bar absolute
619
431
311
311
205
694
Flammable Limits % in air by Volume
5.3 to 14
3 to 12.5
2.1 to 9.5
2 to 9.5
3 to 12.4
Non flammable
Auto - Ignition Temperature
595°C
510°C
510/583°C
510/583°C
?
-
Gross Heating Value at 15°C (kJ/kg)
55500
51870
50360
50360
49010
0
Vaporisation Heat at Boiling Point (kJ/kg)
510.4
489.9
426.2
385.2
357.5
199.3
Table 1.2.1b
Composition of North African LNG Formula
Arzew
Skikda
Libya
Methane
CH4
88.00
92.55
71.40
Ethane
C 2H 6
7.95
5.37
16.00
Propane
C 3H 8
2.37
0.59
7.90
Butane
C4H10
1.05
0.24
3.40
Pentane
C5H12
0.03
Nitrogen
N2
0.60
1.25
Average molecular weight
18.35
17.21
22.66
Temperature at atm press (°C)
-162.04
-164
-159
464.34
456
531
Density
(kg/m3)
Table 1.2.1c
1.30
Properties of Methane -161.5°C
Boiling point 1 bar absolute Liquid density at boiling point (kg/m )
426.0
Vapour SG at 15°C and 1 bar absolute
0.554 kg/m3
Gas volume/liquid volume ratio at -161.5°C at 1 bar absolute
619
Flammable limits % in air by volume
5.3to 14
Auto-ignition temperature
595°C
Gross Heating Value kJ at 15°C
55500
Critical temperature
-82.5°C
Critical pressure
43 bar a
3
Table 1.2.1a Physical Properties of LNG Components
Issue: 1
1.2 Properties of LNG - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Variation of Boiling Point of Methane with Pressure See Fig 1.2.1d Variation of Boiling Point of Methane with Pressure. The boiling point of methane increases with pressure, and this variation is shown in the diagram for pure methane over the normal range of pressures on board the vessel. The presence of the heavier components in LNG increases the boiling point of the cargo for a given pressure. The relationship between boiling point and pressure of LNG will approximately follow a line parallel to that shown for 100% methane.
+20 0 – 20
Lighter than air
– 40
Pressure (mbar abs)
Methane vapour – 60 temperature °C – 80
1,300
–100 –120 Heavier than air –140
1,200
–160 Cargo Tank Pressure Set Point Range
1,100 1,060
1.5 1.4 1.3 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5
Usual Cargo Tanks Pressure Set-Point
1,050 Ratio =
Atmospheric Pressure Range
1,000
Density of Methane vapour Density of Air
(Density of air assumed to be 1.27 kg/m3 @ 15°C)
950
1.2.1e Relative Densitiy of Methane and Air
900
800
700 -165
-164
-163
-161.3 -162 -161 0 Temperature C
-160
-159
1.2.1d Methane Saturated Vapour: Pressure - Temperature Equilibrium Issue: 1
1.2 Properties of LNG - Page 2
Cargo Systems and Operating Manual 1.2.2 Flammability of Methane, Oxygen and Nitrogen Mixtures The ship must be operated in such a way that flammable mixture of methane and air are avoided at all times. The relationship between gas/air composition and flammability for all possible mixtures of methane, air and nitrogen is shown on the diagram above. The vertical axis A-B represents oxygen-nitrogen mixtures with no methane present, ranging from 0% oxygen (100% nitrogen) at point A, to 21% oxygen (79% nitrogen) at point B. The latter point represents the composition of atmospheric air. The horizontal axis A-C represents methane-nitrogen mixtures with no oxygen present, ranging from 0% methane (100% nitrogen) at point A, to 100% methane (0% nitrogen) at point C. Any single point on the diagram within the triangle ABC represents a mixture of all three components, methane, oxygen and nitrogen, each present in specific proportion of the total volume. The proportions of the three components represented by a single point can be read off the diagram. For example, at point D : Methane : Oxygen : Nitrogen :
6.0% (read on axis A-C) 12.2% (read on axis A-B) 81.8% (remainder)
The diagram consists of three major sectors: a) The Flammable Zone Area EDF. Any mixture whose composition is represented by a point which lies within this area is flammable. b) Area HDFC. Any mixture whose composition is represented by a point which lies within this area is capable of forming a flammable mixture when mixed with air, but contains too much methane to ignite. c) Area ABEDH. Any mixture whose composition is represented by a point which lies within this area is not capable of forming a flammable mixture when mixed with air.
Using the Diagram Assume that point Y on the oxygen-nitrogen axis is joined by a straight line to point Z on the methane-nitrogen axis. If an oxygen-nitrogen mixture of composition Y is mixed with a methane-nitrogen mixture of composition Z, the composition of the resulting mixture will at all times be represented by point X, which will move from Y to Z as increasing quantities of mixture Z are added. Note that in this example point X, representing changing composition, passes through the flammable zone EDF, that is, when the methane content of the mixture is between 5.5% at point M, and 9.0% at point N.
LNG LERICI a) Tanks and piping containing air are to be inerted with nitrogen before admitting methane until all sampling points indicate 5% or less oxygen content; b) Tanks and piping containing methane are to be inerted with nitrogen before admitting air until all sampling points indicate 5% methane. It should be noted that some portable instruments for measuring methane content are based on oxidising the sample over a heated platinum wire and measuring the increased temperature from this combustion. This type of
Applying this to the process of inerting a cargo tank prior to cooldown, assume that the tank is initially full of air at point B. Nitrogen is added until the oxygen content is reduced to 13% at point G. The addition of methane will cause the mixture composition to change along the line GDC which, it will be noted, does not pass through the flammable zone, but is tangential to it at point D. If the oxygen content is reduced further, before the addition of methane, to any point between 0% and 13%, that is, between points A and G, the change in composition with the addition of methane will not pass through the flammable zone. Theoretically, therefore, it is only necessary to add nitrogen to air when inerting until the oxygen content is reduced to 13%. However, the oxygen content is reduced to 5% during inerting because, in practice, complete mixing of air and nitrogen may not occur. When a tank full of methane gas is to be inerted with nitrogen prior to aeration, a similar procedure is followed. Assume that nitrogen is added to the tank containing methane at point C until the methane content is reduced to about 14% at point H. As air is added, the mixture composition will change along line HDB, which, as before, is tangential at D to the flammable zone, but does not pass through it. For the same reasons as when inerting from a tank containing air, when inerting a tank full of methane it is necessary to go well below the theoretical figure to a methane content of 5% because complete mixing of methane and nitrogen may not occur in practice. The procedures for avoiding flammable mixtures in cargo tanks and piping are summarised as follows:
analyser will not work with methane-nitrogen mixtures that do not contain oxygen. For this reason, special portable instruments of the infrared type have been developed and supplied to the ship for this purpose.
Area EDFE flammable
B
21
E
20
!
19 F
18
CAUTION
This diagram assumes complete mixing which, in practice, may not occur
17 Y 16 M 15 N
14 G 13
Mixtures of air and methane cannot be produced above line BEFC
X D
12 11 Oxygen % 10 9 8 7 6 5 Area HDFC capable of forming flammable mixtures with air, but containing too much methane to explode
4 3 Area ABEDH not capable of forming flammable mixture with air
2 1 Z A 0
10
H
20
30
40
50
60
70
80
C 90
100
Methane %
1.2.2a Flammability of Methane, Oxygen and Nitrogen Mixtures
Issue: 1
1.2 Properties of LNG - Page 3
Cargo Systems and Operating Manual
LNG LERICI METHANE
REACTIVITY DATA
Emergency Procedures - Methane
METHANE FORMULA
CH4
U.N. NUMBER
2043
FAMILY
Hydrocarbon
APPEARANCE
Colourless
ODOUR
Odourless
“fire damp” “marsh gas” LNG
THE MAIN HAZARD FLAMMABLE.
EMERGENCY PROCEDURES FIRE
Stop gas supply. Extinguish with dry powder, Halon or CO2. Cool surrounding area with water spray.
LIQUID IN EYE
DO NOT DELAY. Flood eye gently with clean fresh/sea water. Force eye open if necessary. Continue washing for 15 minutes. Obtain medical advice/assistance.
LIQUID ON SKIN
DO NOT DELAY. Treat patient gently. Remove contaminated clothing. Immerse frostbitten area in warm water until thawed (see Chapter 9). Obtain medical advice/assistance.
VAPOUR INHALED
Remove victim to fresh air. If breathing has stopped, or is weak/irregular, give mouth-to-mouth/nose resuscitation.
SPILLAGE
Stop the flow. Avoid contact with liquid or vapour. Flood with large amounts of water to disperse spill and prevent brittle fracture. Inform Port Authorities of any major spill.
AIR
No reaction.
WATER (Fresh/Salt)
No reaction. Insoluble. May freeze to form ice or hydrates.
OTHER LIQUIDS/ GASES
Dangerous reaction possible with chlorine..
CONDITIONS OF CARRIAGE NORMAL CARRIAGE CONDITIONS
Fully refrigerated.
GAUGING
Closed, indirect.
SHIP TYPE
2G.
VAPOUR DETECTION
Flammable.
MATERIALS OF CONSTRUCTION UNSUITABLE
SUITABLE
Mild steel.
Stainless steel, aluminium, 9 or 36% nickel steel, copper.
PHYSICAL DATA BOILING POINT @ ATMOSPHERIC PRESSURE VAPOUR PRESSURE kg/cm2 (A)
-161.5˚C
RELATIVE VAPOUR DENSITY
0.554
See graphs
MOLECULAR WEIGHT
16.04
SPECIFIC GRAVITY
0.42
ENTHALPY (kcal/kg)
7.0 68.2
COEFFICIENT OF CUBIC EXPANSION
0.0026 per ˚C @ -165˚C
LATENT HEAT OF VAPOURISATION (kcal/kg)
See graphs
SPECIAL REQUIREMENTS
Liquid @ -165˚C @ -100˚C
Vapour 130.2 @ -165˚C 140.5 @ -100˚C
FIRE AND EXPLOSION DATA FLASH POINT -175˚C (approx) FLAMMABLE LIMITS 5.3 -14% AUTO-IGNITION TEMPERATURE 595˚C
HEALTH DATE TVL
Issue: 1
1000 ppm
ODOUR THRESHOLD
Odourless
EFFECT OF LIQUID
Frostbite to skin or eyes. Not absorbed through skin.
EFFECT OF VAPOUR
Asphyxiation - headache, dizziness, drowsiness. Possible low temperature damage to lungs, skin. No chronic effect known.
1.2 Properties of LNG - Page 4
Cargo Systems and Operating Manual
LNG LERICI
Emergency Procedures - Nitrogen N2
U.N. NUMBER
2040
FAMILY
Noble Gas
APPEARANCE
Colourless
ODOUR
Odourless
THE MAIN HAZARD FROSTBITE.
NITROGEN
REACTIVITY DATA
NITROGEN FORMULA
AIR
No reaction.
WATER (Fresh/Salt)
No reaction. Insoluble.
OTHER LIQUIDS/ GASES
No reactions.
EMERGENCY PROCEDURES FIRE
Non-flammable. Cool area near cargo tanks with water spray in the event of fire near to them.
LIQUID IN EYE
DO NOT DELAY. Flood eye gently with clean sea/fresh water. Force eye open if necessary. Continue washing for 15 minutes. Seek medical advice/assistance.
LIQUID ON SKIN
DO NOT DELAY. Handle patient gently. Remove contaminated clothing. Immerse frostbitten area in warm water until thawed (see Chapter 9). Obtain medical advice/assistance.
VAPOUR INHALED
Remove victim to fresh air. If breathing has stopped, or is weak/irregular, give mouth-to-mouth/nose resuscitation.
SPILLAGE
Stop the flow. Avoid contact with liquid or vapour. Flood with large amounts of water to disperse spill and prevent brittle fracture. Inform Port Authorities of any major spillage.
PHYSICAL DATA BOILING POINT @ ATMOSPHERIC PRESSURE VAPOUR PRESSURE kg/cm2 (A)
-195.8˚C 2 @ -190˚C 10 @ -170˚C
RELATIVE VAPOUR DENSITY
0.967
MOLECULAR WEIGHT
28.01
SPECIFIC GRAVITY
0.9
ENTHALPY (kcal/kg)
Liquid 7.33 @ -196˚C 34.7 @ -150˚C
COEFFICIENT OF CUBIC EXPANSION
0.005 @ -198˚C
LATENT HEAT OF VAPOURISATION (kcal/kg)
47.5 @ -196˚C 17.3 @ -150˚C
CONDITIONS OF CARRIAGE NORMAL CARRIAGE CONDITIONS
Fully refrigerated.
GAUGING
Closed, indirect.
SHIP TYPE
3G.
VAPOUR DETECTION
Oxygen analyser required.
MATERIALS OF CONSTRUCTION UNSUITABLE
SUITABLE
Mild steel.
Stainless steel, copper, aluminium.
SPECIAL REQUIREMENTS Vapour 54.7 @ -195˚C 52.0 @ -150˚C
High oxygen concentrations can be caused by condensation and enrichment of the atmosphere in way of equipment at the low temperatures attained in parts of the liquid nitrogen system; materials of construction and ancillary equipment (e.g. insulation) should be resistant tot he effects of this. Due consideration should be given to ventilation in areas where condensation might occur to avoid the stratification of oxygen-enriched atmosphere.
FIRE AND EXPLOSION DATA FLASH POINT Non-flammable FLAMMABLE LIMITS Non-flammable AUTO-IGNITION TEMPERATURE Non-flammable
HEALTH DATE TVL
Issue: 1
ODOUR THRESHOLD
1,000 ppm
EFFECT OF LIQUID
Frostbite to skin or eyes.
EFFECT OF VAPOUR
Asphyxiation. Cold vapour could cause damage.
Odourless
1.2 Properties of LNG - Page 5
Cargo Systems and Operating Manual 1.2.3 Supplementary Characteristics
5
When Spilled on Water: 1 2
Boiling of LNG is rapid due to the large temperature difference between the product and water, LNG continuously spreads over an indefinitely large area, it results in a magnification of its rate of evaporation until vapourisation is complete,
3
No coherent ice layer forms on the water,
4
Under particular circumstances, with a methane concentration below 40%, flameless explosions are possible when the LNG strikes the water. It results from an interfacial phenomenon in which LNG becomes locally superheated at a maximum limit until a rapid boiling occurs. However, commercial LNG is far richer in methane than 40% and would require Iengthy storage before ageing to that concentration.
5
The flammable cloud of LNG and air may extend for large distances downward (only methane when warmer than -100°C is lighter than air) because of the absence of topographic features which normally promote turbulent mixing.
Vapour Clouds 1
2
If there is no immediate ignition of an LNG spill, a vapour cloud may form. The vapour cloud is long, thin, cigar shaped, and under certain meteorological conditions, may travel a considerable distance before its concentration falls below the lower flammable limit. This concentration is important, for the cloud could ignite and burn, with the flame travelling back towards the originating pool. The cold vapour is denser than air and thus, at least initially, hugs the surface. Weather conditions largely determine the cloud dilution rate, with a thermal inversion greatly lengthening the distance travelled before the cloud becomes nonflammable. The major danger from an LNG vapour cloud occurs when it is ignited. The heat from such a fire is a major problem. A deflagrating (simple burning) is probably fatal to those within the cloud and outside buildings but is not a major threat to those beyond the cloud, though there will be burns from thermal radiations .
3
When loaded in the cargo tanks, the pressure of the vapour phase is maintained as substantially constant, slightly above atmospheric pressure.
4
The external heat passing through the tank insulation generates convecting currents within the bulk cargo, heated LNG rises to the surface and boils.
Issue: 1
6
The heat necessary for the vapourisation comes from the LNG, and as long as the vapour is continuously removed by maintaining the pressure as substantially constant, the LNG remains at its boiling temperature. If the vapour pressure is reduced by removing more vapour than generated, the LNG temperature will decrease. In order to make up the equilibrium pressure corresponding to its temperature, the vapourisation of LNG is accelerated resulting in an increased heat transfer from LNG to vapour.
Reactivity Methane is an asphyxiant in high concentrations because it dilutes the amount of oxygen in the air below that necessary to maintain life. Due to its inactivity, methane is not a significant air pollutant, and due to its insolubility, inactivity, and volatility it is not considered a water pollutant.
LNG LERICI Insulation Thickness Secondary = 0.300m + Primary = 0.250m --------------0.550m
LNG Within Secondary Barrier -23
Air Temperature = -180C Wind = 5 knots -28
-21
Air Temperature = -180C Wind = 5 knots -23
-21
-20 -22
-25
LNG Cargo Temperature = -1630C -43 Cofferdam (Without Heating)
-59
Cofferdam (Without Heating) -63
-15
TYPICAL 65,000 MID SECTION
-18
-13
-45
m3
-5
-15
-3
-4
-7
Cryogenic Temperatures Contact with LNG or with materials chilled to its temperature of about -160°C will damage living tissue. Most metals lose their ductility at these temperatures; LNG may cause the brittle fracture of many materials. In case of LNG spillage on the ship’s deck, the high thermal stresses generated from the restricted possibilities of contraction of the plating result in the fracture of the steel. The figure 1.2.3b shows a typical ship section with the minimum acceptable temperatures of the steel grades selected for the various parts of the structure.
LNG Within Primary Barrier
-2
-1 -3
-2
Sea Water Temperature = 0oC
Sea Water Temperature = 0oC No. Air Temperature Inside Compartment No. Steel Plating Temperature
Illustration 1.2.3a Double Hull & Compartments Temperatures o D (-20 C)
E (-30oC)
o E (-30 C)
E (-30oC) o E (-30 C)
E (-30oC)
E (-30oC) D (-20oC)
D (-20oC)
E (-30oC)
B (-10oC)
D (-20oC)
o D (-20 C)
D (-20oC)
D (-20oC) o
B (-10 C)
D (-20oC)
Illustration 1.2.3b Structural Steel Grades Plan
1.2 Properties of LNG - Page 6
Cargo Systems and Operating Manual
LNG LERICI
Behaviour of LNG in the Cargo Tanks When loaded in the cargo tanks, the pressure of the vapour phase is maintained substantially constant, slightly above atmospheric pressure. The external heat passing through the tank insulation generates convecting currents within the bulk cargo, heated LNG rises to the surface and is boiled-off. The heat necessary to the vapourisation comes from the LNG, and as long as the vapour is continuously removed by maintaining the pressure as substantially constant, the LNG remains at its boiling temperature. If the vapour pressure is reduced by removing more vapour than generated, the LNG temperature will decrease. In order to make up the equilibrium pressure corresponding to its temperature, the vapourisation of LNG is accelerated, resulting in an increased heat transfer from LNG to vapour. If the vapour pressure is increased by removing less vapour than generated, the LNG temperature will increase. In order to reduce the pressure to a level corresponding to the equilibrium with its temperature, the vapourisation of LNG is slowed down and the heat transfer from LNG to vapour, reduced. LNG is a mixture of several components with different physical properties, particularly the vapourisation heat: the more volatile fraction of the cargo vapourises at a greater rate than the less volatile fraction. The vapour generated by the boiling of the cargo contains a higher concentration of the more volatile fraction than the LNG. The properties of the LNG ie. the boiling point, density and heating value, have a tendency to increase during the voyage.
Issue: 1
1.2 Properties of LNG - Page 7
Cargo Systems and Operating Manual 1.3
Properties of Nitrogen and Inert Gas
1.3.1 Nitrogen Nitrogen is used for the pressurisation of the inter barrier spaces, for purging of cargo pipe lines, fire extinguishing in the vent mast risers and for the sealing of the gas compressors. It is produced either by the vapourisation of liquid nitrogen supplied from shore or by generators whose principle is based on hollow fibre membranes to separate air into nitrogen and oxygen. Physical Properties of Nitrogen Nitrogen is the most common gas in nature since it represents 79% in volume of the atmospheric air. At room temperature, nitrogen is a colourless and odourless gas. Its density is near that of air: 1.25 kg/m3 under the standard conditions. When liquefied, the temperature is -196°C under atmospheric pressure, density of 810 kg/m3 and vapourisation heat of 199 kJ/kg. Properties of Nitrogen Molecular weight Boiling point at 1 bar absolute Liquid SG at boiling point Vapour SG at 15°C and 1 bar absolute Gas volume/liquid volume ratio at –196°C Flammable limits Dew point of 100% pure N2
28.016 –196°C 1.81 0.97 695 Non Below –80°C
LNG LERICI
1.3.2 Inert Gas Inert gas is used to reduce the oxygen content in the cargo system, tanks, piping and compressors to prevent an air/CH4 mixture prior to aeration post warm up before refit or repairs and prior to gassing up operation post refit before cooling down. Inert gas is produced on board using an inert gas generator supplied by Navalimpianti, which produces inert gas at 6000m3/h with a -45°C dew point burning low sulphur content gas oil. This plant can also produce dry air at 6250m3/h and -45°C dew point (see section 2.9 for more details). The inert gas composition is as follows: • oxygen -50mbar)
Key LNG Liquid Warm LNG Vapour Steam
TT
Condensate Liquid Nitrogen Gaseous Nitrogen Electrical Instrument Air
Issue: 1
2.6.2a Main Vaporiser
Cargo Systems and Operating Manual 2.6
2.6.1 General Description The main vaporiser (YA/5151) is used for vaporising LNG liquid, to provide gas when displacing inert gas from the cargo tanks with LNG vapour, and for maintaining the pressure in the tanks when LNG is being discharged and vapour is not supplied from shore. This vaporiser can be arranged for vaporising liquid nitrogen for the initial filling of the insulation spaces. The forcing vaporiser (YA/5152) is used for vaporising LNG liquid to provide gas for burning in the boilers to supplement the natural boil off. Both main and forcing vaporisers are situated in the compressor room. 2.6.2 Main Vaporiser (See Illustration 2.6.2a) Manufacturer
Cryostar
Model
75-UT-25/21 - 3.6.
Heating medium
Saturated steam.
Inlet temp of the medium (°C)
170 / 190
Maximum gas flow (kg/h)
12800
Inlet LNG temperature (°C)
-163
Outlet gas temp (°C)
-140 to 20.
Alarms are provided on the outlet gas temperature, high level and low temperature of the condensate water.
The main vaporiser is used for the following operations: 1
Discharging cargo at the design rate without the availability of a vapour return from the shore. If the shore is unable to supply vapour return, liquid LNG is fed to the vaporiser by using one stripping pump or by bleeding from the main liquid line. The vapour produced leaves the vaporiser at approximately -140°C and is then supplied to cargo tanks through the main vapour header. Vapour pressure in the cargo tanks will normally be maintained at 1100 mbar abs (minimum 1040 mbar) during the whole discharge operation. Additional vapour is generated by the tank sprayer rings, the LNG being supplied by the stripping/spray pump.
Issue: 1
2
Purging of cargo tanks with GNG after inerting with inert gas and prior to cooldown. LNG is supplied from the shore to the vaporiser via the stripping/ spray line. The vapour produced at the required temperature +10°C is then passed to the cargo tanks;
9
Fill up the vaporiser with liquid using manual control. Check all flanges and joints for any signs of leakage.
5
AF AF AF AF
! WARNING
6
582.01
Thorough checks around the main vaporiser and associated flange connections must be conducted during operation.
- High high condensate level trip and alarm
7
AF 557.01
- Low low condensate temperature trip and alarm Set point: < +70°C
8
AF AF AF AF
518.01 518.02 518.03 518.04
- High high tank pressure trip and alarm Set point: 190 mbar
9
AF AF AF AF
519.01 519.02 519.03 519.04
- High high primary space pressure trip and alarm Set point: -50 mbar
10 When vapour is produced switch the control for liquid valve to remote and automatic.
519.01 519.02 519.03 519.04
On Completion of Operation Note: This operation is the normal procedure if the cargo tanks have been inerted with inert gas containing carbon dioxide. 3 Inerting could be carried out by evaporation of liquid nitrogen supplied from shore but the cost is very expensive. The vapour produced at the required temperature +10°C is then passed to the cargo tanks. 4
Shell and U tube design
•
If the back pressure in the discharge piping to shore is not sufficient to have a minimum of 4 bar at the inlet to the vaporiser, a stripping/spray pump will be used to supply liquid to the vaporiser;
Vaporisers
LNG LERICI
Evaporation of liquid nitrogen from shore for insulation spaces inerting, after membranes in service tests.
Operating Procedures Set the LNG or nitrogen pipelines as detailed for the operation about to be undertaken. For vaporising liquid nitrogen a removable bend must be fitted at the inlet to the vaporiser. A Main Vaporiser To prepare the main vaporiser for use 1
Open the shell side vent valve.
2
Crack open the shell side drain valve.
3
Crack open steam supply manual valve (making sure steam to deck is available).
4
When all air is expelled from shell, shut the vent valve.
5
When the correct level in condensate outlet is obtained, the drain valve is put on automatic control.
After about 30 minutes when pressures and temperatures have stabilised on the vaporiser. 6
Slowly open fully the steam inlet manual valve.
7
Open the instrument air supply to the vaporiser controls.
8
In the Cargo Control Room, set the controls for the main vaporiser on the Bailey IMS Mimic and select the control loop required, ie for gas header or insulation spaces header.
1
Shut liquid valve 456.
2
Shut the steam supply valve when no LNG remains.
3
Open steam side vent and then open the drain when all steam has been vented.
4
Keep vapour side valve open to system until vaporiser reaches ambient temperature.
Control Process control is on outlet temperature from vaporiser with high and low temperature alarms. This is controlled on the TCV (temperature control valve).
- High primary space pressure alarm Set point: 10 mbar
Points 6, 7, 8, 9 activate closing of valve FCV01, TCV and steam supply, thus tripping main vaporiser.
The steam condensate from the vaporiser is returned to the drains system through the condensate drains cooler and observation tank on deck on the aft bulkhead of the motor room. The LNG inlet (valve FCV01) to vaporiser is controlled by signals from the primary space pressure and gas header pressure controllers or manually. The control loop for FCV01 is arranged with a selector switch for selection of the control parameter. The following alarms and trips are available: 1
AF 557.01
- Low condensate temperature alarm Set point: + 80°C
2
AF AF AF AF
- High tank pressure alarm Set point: 180 mbar
3
AF 582.01
- High condensate level alarm contact switch
4
AF 580.01
- High gas outlet temperature alarm Set point: + 20°C
517.01 517.02 517.03 517.04
2.6 Vaporisers - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.6.3a Forcing Vaporiser and Demister
KBD
Compressors Suction
Set
Vapour Header
Key
FI
FT PI xxxx
TIC LNG Liquid
Forcing Vapouriser Control Feed-back
TA H
LNG Vapour
HS Open Close
Steam
Forcing Vapouriser Control Feed-back
xxxx
H LA xxxx
Condensate Electrical
To No.4 Vapour Dome
Steam Supply (See 2.14.1a)
Re-evaporation TT
TI
Trip
Demister YA / 5153
Instrumentation PT
LD Compressor Trip
Trip Vent
TI
PI
LS
LA H
HC
Forcing Vaporiser YA / 5252
LC
Trip
HC
TCV
LS
LG
Line Strainer
To Tank No.4 Vapour Dome
KBD HIC
PI
To Tank No.4 Vapour Dome
TI
PIC
Set
To No.4 Vapour Dome Boilers Combustion Demand
Trip
Stripping/Spray Header FCV063
455
Drain LA
H
xxxx
High Vapour Header Pressure
HC Condensate To Gas Exchangers Drain Cooler
1
TT TI xxxx
TA xxxx L
Issue: 1
2.6.3a Forcing Vaporiser and Demister
Cargo Systems and Operating Manual 2.6.3 Forcing Vaporiser and Demister The forcing vaporiser (YA/5152) it is used for vaporising LNG liquid to provide gas for burning in the boilers to supplement the natural boil off. Both the main and forcing vaporisers are situated in the compressor room. Forcing Vaporiser (See Illustration 2.6.3a) The forcing vaporiser is used to supplement boil-off gas for fuel gas burning up to 105% MCR. The LNG is supplied by a stripping/spray pump. LNG flow is controlled by an automatic inlet feed valve which receives its signal from the Boilers Combustion Control system and an independent spill/return line with a discharge valve to the cargo tank. Specification Manufacturer
Cryostar
Model
15-UT-25/21 - 4.2.
This is made possible by: a) Two knitted mesh filters inserted in the gas flow path to fractionate the droplets and create the necessary turbulence to transform the small droplets injected into a fine fog of liquid gas and also to moisten the mesh wires acting as vaporising surface;
7
Open the instrument air supply to the vaporiser controls.
8
In the Cargo Control Room, set the controls for the forcing vaporiser on the Bailey IMS Mimic.
9
Start the spray pump.
b) Two conical baffles installed in the tube to allow eventually accumulated liquid to be directed into the gas stream on the pipe bottom.
10 Fill up the vaporiser with liquid manually.
Demister A demister is used downstream of the forcing vaporiser to serve as a moisture separator and prevent any carry over of liquid to the LD compressors. Both vaporiser tubes are fitted with spiral wires to promote turbulence ensuring efficient heat transfer and production of superheated LNG vapour at the exit of the tube nests. A level controller is fitted on the steam condensate side of both the vaporisers. The controller ensures that a correct level of condensate is maintained at all times during its operation by regulating the drain valve.
Shell and U tube design
•
Manufacturer
Cryostar
Model
VMS-1 0/1 2-700 Shell with in / out nozzles and drain.
Heating medium
Saturated steam.
Inlet temp of the medium (°C)
174 / 190
Maximum gas flow (kg/h)
3500
Inlet LNG temperature (°C)
-163
Gas flow (kg/h) =
3500
Outlet gas temp (°C)
-40.
Service temperature (°C)
-40
Alarms are provided on the outlet gas temperature, high level and low temperature of the condensate water.
Each vaporiser is equipped with a temperature control system to obtain a constant and stable discharge temperature for various ranges of operation. The temperature of the gas produced is adjusted by injecting a certain amount of by-passed liquid into the outlet side of the vaporiser through a temperature control valve and liquid injection nozzles. A re-evaporator is also used to ensure that accumulation of non-vaporised liquid at the vaporiser discharge is avoided and that the output is at a stable temperature.
•
An alarm is provided on the level of the drained LNG.
To prepare Forcing Vaporiser for use 1
Open shell side vent valve.
2
Crack open shell side drain valve.
3
Crack open steam supply manual valve.
4
When all air has been expelled from shell, close the vent valve.
5
When the correct level in condensate outlet is obtained, the drain valve is put on automatic.
After about 30 minutes when pressures and temperatures have stabilised on the vaporiser. 6
Issue: 1
LNG LERICI
Check all flanges and joints for any signs of leakage.
4
AF 582.01
- High high condensate level trip and alarm Set point: 292 mm
5
AF 589.01
- Low low condensate temperature trip and alarm Set point: < +50°C
6
AF AF AF AF
- High high tank pressure trip and alarm Set point: + 190 mbar
7
High level alarm for demister trips the low duty compressor.
11 When vapour is produced, switch the control for liquid valves TCV and FCV to remote.
! WARNING Thorough checks around the forcing vaporiser and the associated flange connections must be conducted during operation. On Completion of Operation 1
Shut liquid valve 455 which automatically shuts down the vaporiser.
2
Shut the steam supply valve when no LNG remains.
3
Open steam side vent and then open the drain when all steam has been vented.
4
Keep vapour side valve open to system until vaporiser reaches ambient temperature.
518.01 518.02 518.03 518.04
Points 4,5 and 6 activate automatic closing of valve FCV, TCV and steam supply, thus tripping the forcing vaporiser.
Controls and Settings The forcing vaporiser is basically started and stopped by the opening or closing of liquid valve 455. The vapour outlet temperature is controlled by valve TCV 3713 on the vaporiser by-pass. This valve closes without air. The LNG inlet flow is controlled by control valve 063 which receives the signals from the Boilers Combustion Control System. The following alarms and trips are available: 1 AF 582.01 - High condensate level alarm Set point: 240 mm 2
AF 589.01
3
AF 592.01
- Low condensate temperature alarm Set point: + 70°C - High gas outlet temperature alarm Set point: - 40°C
Slowly open fully the steam inlet manual valve.
2.6 Vaporisers - Page 2
Cargo Systems and Operating Manual
LNG LERICI Illustration 2.7.1a HD Gas Compressors
Electric Motors Room Control Panel
TT
TA
FIC
Cargo Compressor Room Surge Line
TI TI
Gas Tight Bulkhead
H
Vapour Out HH
H
Trip
PS
TT
PdI
PI L
Nitrogen Seal Gas
TT
FT TT HHX Surge Controller
YT
FIC PT1
TI TA
HH
PT2
T Electric Motor
TI
Gear Box
Vapour In
Trip XA
Alarms in CCR
ZI
PS
XA
Main Oil Pump (Drive from Gear Box)
LL
HIC HHY
Common Alarms
Common Trip Alarms XA
Trip
Sea Water Cooling
PS
Oil Cooler
L Start Lock Out for Low Pressure
Single in ECR
ZS
YT
Thermostatic Control Valve
TT
HY
L
ZT
Inlet Guide Vanes Actuator
H
PI
HH
TT
H Cargo Tanks Pressure
PdS
T3
Standby Oil Pump (Electric Drive)
Self Regulating Valve set at 7 bar
Trip Low Differential Pressure Between Gas Main and Primary Insulation Pressure
Trip
Key PI
Lub Oil
Lock To Start For Lower Level. No Trip T3
TI
L.O.E/P Start Lock for L Level T3
Start Lock for L Pressure
Instrument Air LG
HH Temperature Trip
Instrument Air Steam Supply
Thermostatic Control Valve
LL Pressure T3
Trip
SW Cooling
LS
Lubrication Oil Sump Tank
Trip T3
Gaseous Nitrogen
L
T3
Issue: 1
TT
LNG Vapour
- Lube Oil Level - Bearings - Gearbox Oil - Blkd Penetration - Vibrations - Diff. Seal Gas Emergency Stop from LCP - Supply Cabinet in Engine Room CCR
HH
H
TT E.S.D.S Activated
Condensate
Steam
Electric
Condensate
Instrumentation
2.7.1a HD Gas Compressors
Cargo Systems and Operating Manual 2.7
Gas Compressors
•
Differential pressure: vapour header / primary pressure header = 0 mbar
•
Tank No.1, 2, 3 or 4 - very high liquid level
•
Safeties on local control system (oil temperature, oil pressure, discharge gas temperature, seal gas pressure)
•
Electric power failure
•
Ventilation flow failure in the electric motor room
2.7.1 HD Compressors Gas Compressors (YA/5121 A I B -YA/5122 A I B) Two high duty (HD) compressors, installed in the compressor room on deck, are provided for handling gaseous fluids: LNG vapour and various mixtures of LNG vapour, inert gas or air during the cooling down, cargo operation and tank treatments. Two low duty (LD) compressors, installed in the compressor room on deck, are provided for handling the LNG vapour for the boiler produced by the natural boil off and forced vaporisation, which is used as fuel. The HD and LD compressors are driven by electric motors, installed in an electric motor room segregated from the compressor room by a gas tight bulkhead; the shaft penetrates the bulkhead with a gas tight shaft seal. HD Compressors Manufacturer
Cryostar
Model
CM 400/55
Type
• •
Centrifugal. Single stage. Fixed speed with adjustable guide vanes.
Volume flow (m3/h)
15000
Inlet pressure (mbar)
1060
Outlet pressure (mbar)
1800
Minimum inlet temperature (°C)
-140
Shaft speed (rpm)
10000
Motor speed (rpm)
3580
Rated motor power (kW) 400 The compressors are operated locally or from the CCR.
Compressor Systems Seal Gas System The seal gas system is provided to prevent lub-oil mist from entering the process stream (compressed LNG vapour) and to avoid cold gas flow into the gearbox and into the lub-oil system. Seal gas is nitrogen produced by the nitrogen generators onboard. The seal gas is injected into the labyrinth type seals between the gearbox shaft bearing and the compressor wheel. The system is maintained by a pressure control valve where seal gas pressure is always higher than the suction pressure (usually adjusted at 0.3 bar) Seal gas entering the gearbox from the shaft seals is returned to the lub-oil sump, separated from the oil and vented to atmosphere. After a period of more than 8 days of non-operation, the unit must be purged with dry and warm nitrogen. Lub-oil System Lub-oil in the system is stored in a vented 400 litres luboil sump. An integrated steam immersion heater with thermostatic switch is fitted in the sump to maintain a constant positive temperature and avoid condensation when the compressors are stopped.
The following conditions trip the compressors:
•
Safeties in ESDS
•
Tank No.1, 2, 3 or 4 - differential pressure: tank / primary space = 5 mbar
•
Tank No.1, 2, 3 or 4 - differential pressure: tank / secondary space = 0 mbar
•
Differential pressure: vapour header / atmospheric pressure = 3 mbar
Issue: 1
Lub-oil is supplied from the sump through separate suction strainer screens and one of the 2 lub-oil pumps. The discharge from the pumps is through check valves to a common lub-oil supply line feeding the gearbox, bearings and bulkhead seal. The main operational pump is driven by the high speed shaft gear. Upon failure of the driven pump, the stand-by electric motor driven auxiliary pump is energised immediately and a remote alarm is initiated to indicate abnormal conditions. The stand-by electric motor driven auxiliary pump is also used to start the compressors.
LNG LERICI The lub-oil passes through a sea water cooled oil cooler and a thermal bypass temperature control valve, to maintain the lub-oil inlet temperature at approximately 35°C. The oil supply to the bearings is fed via a 25 micron duplex filter with an automatic continuous flow switch change over valve.
Inlet Guide Vanes To achieve the required gas flow, the compressors have inlet guide vanes fitted at the suction end.
A pressure control valve regulates the oil flow to the bearings. Excess oil is bypassed and discharged to the sump. Pump relief valves act as back up and are set at 7 bar.
Rotation of the vanes is possible through its full range of travel of -30° to +80°. The position is indicated both locally and at the Centralised Control Room. (Range 0 to 100%)
The lub-oil system feeds the following: - Journal bearing on both sides of the high speed shaft; - Journal bearing on the driven end of the low speed shaft; - Integral thrust and journal bearing on the non driven end of low speed shaft; - Sprayers for the gear wheels; - Gas compressors’ bulkhead seals Surge Control System An automatic surge control system is provided to ensure that the compressor flow rate does not fall below the designed minimum. Below this rate, the gas flow will not be stable and the compressor will be liable to surge, causing shaft vibration which may result in damage to the compressor. All the gas compressors are equipped with an automatic surge control system which consists of: - A flow transmitter; - Suction and delivery pressure transmitter; - A ratio station; - An anti-surge controller; - A bypass valve on the gas stream. On the basis of a preset ratio between the gas flow and compressor differential pressure signals, the anti-surge controller produces a signal which modulates a compressor bypass valve.
The vanes are operated by pneumatic actuators which receive control signals from the flow controller.
Bulkhead Shaft Seals Each compressor shaft is equipped with a forced lubricated bulkhead shaft seal preventing any combustible gas from entering the electric motors room. The seals are of flexibox supply. They are fixed on the bulkhead and float on the shafts, supported by two ball bearings. The lub-oil seal ensures tightness between the two bearings. The lubrication comes from the main lub-oil circuit. Operating Procedures To prepare for running of HD Compressors Check the lub-oil level in the sump tank. 1 Start lub-oil heater about 30 minutes (depending on ambient temperature) prior to expected compressor start up. 2
Open compressor suction and discharge valves.
3
Open seal gas supply manual valve.
4
Run auxiliary lub-oil pump to warm up gearbox and bearings.
Check the lub-oil system for leaks. 5
Open cooling water inlet and outlet for the lub-oil cooler.
6
Open instrument air supply to control panel.
7
Switch ON power to the control cabinet.
8
At least two alternators should be coupled to the main switchboard to have sufficient power available at the cargo switchboards.
9. When stopping compressor, leave auxiliary lub-oil and seal gas until compressor is warm (approx. 1 hour)
2.7 Gas Compressors - Page 1
Cargo Systems and Operating Manual 9
Set up the cargo piping system for the right operation to be carried out.
LNG LERICI
2.7.1b HD Alarm and Trip Settings
In the Cargo Control Room
No.:
10 Select the appropriate mimic on HD compressor for the correct operation.
1
Suction Gas Press PT 1 PSL 1
2
Discharge Gas Press.
PT 2
3
Discharge Gas Temp. TE 2A
TSHH 2A
-112°C
4
Discharge Gas Temp. TE 2B
TSH 2B
5
Oil Tank Level
LSL 5
6
Vibration YE 9
YSH 9
7
Temp. Oil System TE 8B
8
11 IGV (inlet guide vanes) must be shut and surge valve open before starting.
Tag Nr.
Normal Operation Condition
Instr. Range Action /adjustment H;HH Alarm Trip L;LL Interlock
Set Point
Signal
1.06 bar a -25÷200mbarg
L
A
0.95 bar a
contact
1.80 bar a 0 ÷ 1100 mbarg
-
-
-
4-20mA
-150... + 100°C
HH
T
+80°C
contact
-112°C
-150... + 100°C
H
A
+70°C
contact
±4 mm
±6 mm
L
A; I1
-5mm
contact
H
A
40µm
contact
15...20µm 0...100µm
YSHH 9 TSH 8B
~42°C
0...100°C
HH H
T A
50µm 55°C
contact contact PT100
Temp. Oil System TE 8A
TSHH 8A
~42°C
0...100°C
HH
T
60°C
contact PT100
9
Temp. Oil Bulkhead Seal TE 9B
TSH 9B
~60°C
0...100°C
H
A
70°C
contact PT100
10
Bearing Temp. TE 9A
TSL 9A
~65°C
0...100°C
L
A; I2
15°C
contact
11
Lube Oil Press.
PSL 8
~2 bar
0.1...10.3 bar
L
A; I2
1.0 bar
contact
12
Lube Oil Press.
PSLL 8
~2 bar
0.1...10.3 bar
LL
T
0.8 bar
contact
13
Seal Gas Press.
PDSL 11
0.3 bar
4...bar
L
A; I1; I2
0.2 bar
contact
14
Seal Gas Press.
PDSLL 11
0.3 bar
4...bar
LL
T
0.15 bar
contact
15
Flow Transmitter
FT 1
different
0...74.6/ 0...45 mbar
-
-
-
4-20 mA
16
Issue: 1
Item
T: A: I1: I2:
Trip Alarm Start-up Interlock L.O. Pump Start-up Interlock Machine
2.7 Gas Compressors - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.7.2a LD Gas Compressors Electric Motors Room Control Panel in Switchboard Room
TT
Cargo Compressor Room Surge Line
TI
H TA
Vapour Out HH
H
TI
Gas Tight Bulkhead
Trip
PS
TT
FIC
PdI
PI L
Nitrogen Seal Gas
TT
FT TT HHX Ratio Controller
YT
PT1
FIC
TI TA
HH
PT2
T Electric Motor
TI
Gear Box
Vapour In
Trip XA
Alarms in CCR
ZI
PS
XA
Main Oil Pump (Drive from Gear Box)
LL
HIC HHY
Common Alarms
Common Trip Alarms XA
Trip
Sea Water Cooling
PS
Oil Cooler
L Start Lock Out for Low Pressure
Single in ECR
ZS
YT
Thermostatic Control Valve
TT
HY
L
ZT
Inlet Guide Vanes Actuator
H
PI
HH H
TT E.S.D.S Activated
TT
H PdS
Cargo Tanks Pressure
HH TT
Trip
T3
Key
Trip
- Lube Oil Level - Bearings - Gearbox Oil - Blkd Penetration - Vibrations - Diff. Seal Gas
T3
T3 Emergency Stop from LCP - Supply Cabinet in Engine Room CCR
Issue: 1
SW Cooling Instrument Air LG
Instrument Air Steam Supply
Thermostatic Control Valve
Condensate
LL Pressure T3
Trip
Gaseous Nitrogen
LS
Lubrication Oil Sump Tank
Trip T3
LNG Vapour
L
Start Lock for L Pressure
Lub Oil
Lock To Start For Lower Level. No Trip TI
L.O.E/P Start Lock for L Level T3
PI
Standby Oil Pump (Electric Drive)
Self Regulating Valve set at 7 bar
Low Differential Pressure Between Gas Main and Primary Insulation Pressure
HH Temperature Trip
Steam
Electric
Condensate
Instrumentation
2.7.2a LD Gas Compressors
Cargo Systems and Operating Manual Compressor Sub-systems
2.7.2 LD Compressors Manufacturer
Cryostar
Model
CM 300/45
Type
Centrifugal. Single stage. Variable speed with adjustable guide vanes.
Volume flow (m3/h)
4000
Inlet pressure (mbar)
1060
Outlet pressure (mbar)
1800
Minimum inlet temperature (°C) -140 Maximum shaft speed (rpm)
24000
Motor speed (rpm)
1775 to 3550
Rated motor power (kW) 150 • The compressors are operated locally or from the Cargo Control Room. •
The following conditions trip the compressors:
•
Safeties in ESDS
•
Tank No. 1, 2, 3 or 4 - differential pressure: tank/ primary space = 5 mbar
•
Tank No. 1, 2, 3 or 4 - differential pressure: tank/ secondary space = 0 mbar
•
Differential pressure: vapour header/atmospheric pressure = 3 mbar
•
Differential pressure: vapour header/primary pressure header = 0 mbar
•
Safeties in combustion control system.
•
Safeties on local control system (oil temperature, oil pressure, discharge gas temperature, seal gas pressure)
•
Electric power failure
Seal Gas System The seal gas system is provided to prevent lub-oil mist from entering the process stream (compressed LNG vapour) and to avoid cold gas flow into the gearbox and into the lub-oil system. Seal gas is nitrogen produced by the nitrogen generators onboard. The seal gas is injected into the labyrinth type seals between the gearbox shaft bearing and the compressor wheel. The system is maintained by a pressure control valve where seal gas pressure is always higher than the suction pressure (usually adjusted at 0.3 bar) Seal gas entering the gearbox from the shaft seals is returned to the lub-oil sump, separated from the oil and vented to atmosphere. Lub-oil System Lub-oil in the system is stored in a vented 400 litres luboil sump. An integrated steam immersion heater with thermostatic switch is fitted in the sump to maintain a constant positive temperature and avoid condensation when the compressors are stopped. Lub-oil is supplied from the sump through separate suction strainer screens and one of the 2 lub-oil pumps. The discharge from the pumps is through check valves to a common lub-oil supply line feeding the gearbox, bearings and bulkhead seal. The main operational pump is driven by the high speed shaft gear. Upon failure of the driven pump, the stand-by electric motor driven auxiliary pump is energised immediately and a remote alarm is initiated to indicate abnormal conditions. The stand-by electric motor driven auxiliary pump is also used to start the compressors. The lub-oil passes through a sea water cooled oil cooler and a thermal bypass temperature control valve, to maintain the lub-oil inlet temperature at approximately 35°C. The oil supply to the bearings is fed via a 25 micron duplex filter with an automatic continuous flow switch over valve. A pressure control valve regulates the oil flow to the bearings. Excess oil is bypassed and discharged to the sump. Pump relief valves act as back up and are set at 7 bar.
Issue: 1
LNG LERICI The lub-oil system feeds the following: - Journal bearing on both sides of the high speed shaft; - Journal bearing on the driven end of the low speed shaft; - Integral thrust and journal bearing on the nondriven end of low speed shaft; - Sprayers for the gear wheels; - Gas compressors’ bulkhead seals Surge Control System An automatic surge control system is provided to ensure that the compressor flow rate does not fall below the designed minimum. Below this rate, the gas flow will not be stable and the compressor will be liable to surge, causing shaft vibration which may result in damage to the compressor. All the gas compressors are equipped with an automatic surge control system which consists of: - A flow transmitter; - A compressor differential pressure transmitter; - A ratio station; - An anti-surge controller; - A bypass valve on the gas stream. On the basis of a preset ratio between the gas flow and compressor differential pressure signals, the anti-surge controller produces a signal which modulates a compressor bypass valve.
The seals are of flexibox supply. They are fixed on the bulkhead and float on the shafts, supported by two ball bearings. The lub-oil seal ensures tightness between the two bearings. The lubrication comes from the main lub-oil circuit. Operating Procedures To prepare for running of LD Compressors Check the lub-oil level in the sump tank. 1 Start lub-oil heater about 30 minutes (depending on ambient temperature) prior to expected compressor start up. 2
Open compressor suction and discharge valves.
3
Open seal gas supply manual valve.
4
Run auxiliary lub-oil pump to warm up gearbox and bearings.
Check the lub-oil system for leaks. 5
Open cooling water inlet and outlet lub-oil cooler (usually left open).
6
Open instrument air supply to control panel.
7
Switch ON power to the control cabinet.
8
Switch ON power to the variable speed controller. (Each LD compressor is supplied from a separate cargo switchboard ie Port and Stbd).
In the Centralised Control Room. 9
Inlet Guide Vanes To achieve the required gas flow, the compressors have inlet guide vanes fitted at the suction end. The vanes are operated by pneumatic actuators which receive control signals from the flow controller. Rotation of the vanes is possible through an angle of 100°. The position is indicated both locally and at the Centralised Control Room on the DCS. Bulkhead Shaft Seals Each compressor shaft is equipped with a forced lubricated bulkhead shaft seal preventing any combustible gas from entering the electric motors room.
Set up the cargo piping system for the correct operation to be carried out.
10 Select the appropriate mimic on LD compressor for the correct operation. 11 IGV (inlet guide vanes) must be shut and motor speed adjusted to 50% before compressor can start. 12 Message “Ready to start” appears on the mimic display below the compressors when the safeties are clear. 13 Start the compressor motor. 14 Switch compressor control to automatic mode.
2.7 Gas Compressors - Page 3
Cargo Systems and Operating Manual
LNG LERICI
2.7.2b LD Alarm and Trip Settings No.:
Item
Tag Nr.
Normal Instr. Range / Action Operation adjustment H;HH Alarm Trip Condition L;LL Interlock
Set Point
Signal
1.06 bar a -25÷200mbarg
L
A
0.95 bar a
contact
1.80 bar a 0+ 1100 mbarg
-
-
-
4-20mA
-150... + 100°C
HH
T
+80°C
contact
-150... + 100°C
H
A
+70°C
contact
±6 mm
L
A;I1
-5mm
contact
H
A
40µm
contact
T A
50µm 55°C
contact contact PT100
1
Suction Gas Press. PT 1 PSL 1
2
Discharge Gas Press.
PT 2
3
Discharge Gas Temp. TE 2A
TSHH 2A
-9°C
4
Discharge Gas Temp. TE 2B
TSH 2B
-9°C
5
Oil Tank Level
LSL 5
6
Vibration YE 9
YSH 9
±4 mm
15...20µm 0...100µm
YSHH 9 TSH 8B
~42°C
0...100°C
HH H
7
Temp. Oil System TE 8B
8
Temp. Oil System TE 8A
TSHH 8A
~42°C
0...100°C
HH
T
60°C
contact PT100
9
Temp. Oil Bulkhead Seal TE 9B
TSH 9B
~60°C
0...100°C
H
A
70°C
contact PT100
10
Bearing Temp. TE 9A
TSL 9A
~65°C
0...100°C
L
A;I2
15°C
contact
11
Lube Oil Press.
PSL 8
~2 bar
0.1...10.3 bar
L
A;I2
1.0 bar
contact
12
Lube Oil Press.
PSLL 8
~2 bar
0.1...10.3 bar
LL
T
0.8 bar
contact
13
Seal Gas Press.
PDSL 11
0.3 bar
0...4 bar
L
A;I1;I2
0.2 bar
contact
14
Seal Gas Press.
PDSLL 11
0.3 bar
0...4 bar
LL
T
0.15 bar
contact
15
Flow Transmitter
FT 1
different
0...74.6/ 0...25 mbar
-
-
-
4-20 mA
16
T: A: I1: I2:
Issue: 1
Trip Alarm Start-up Interlock L.O. Pump Start-up Interlock Machine
2.7 Gas Compressors - Page 4
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.8.1a Vacuum Pumps Secondary Insulation Spaces Main Primary Insulation Spaces Main
No 3. Mast Riser 569
568 -60¡C TA
TS
L Trip VA
VS
PI
AW 072VX
TI
FA
FS
L
571 Trip
Lub Oil Vacuum Pump (Inboard)
LA
LS Motor
TI
Vacuum Pump YA/5201A
FA
FS
L Trip
L
100¡C H TA
TS AW 826VX
Cooling Water Inlet -60¡C TA
TS
L Trip PI
VA
VS TI
Cooling Water Outlet
AW 072VX
FA
FS
L
572
SW Cooling
Vacuum Pump (Outboard)
LA
LS Motor
Vacuum Pump YA/5201B
TI
FS
FA L
TS
Electric Motors Room
Key
Trip
Lub Oil
AW 827VX
Cargo Compressor Room
Trip
L
Secondary Space Nitrogen
H
Primary Space Nitrogen
100¡C TA
Lub Oil Electrical Instrumentation
Issue: 1
2.8.1a Vacuum Pumps
Cargo Systems and Operating Manual 2.8
Vacuum Pumps
2.8.1 Vacuum pumps (See Illustration 2.8.1a) Two vacuum pumps located in the cargo compressor room are used to evacuate the primary and secondary spaces atmosphere in the following cases: 1
To replace air with nitrogen for inerting;
2
To replace methane with nitrogen for gas freeing before dry docking after there has been leakage of cargo;
3
To test tightness of the membranes at regular intervals or after membrane repairs.
4
When the associated tank is opened up.
Control and Alarm Settings Each vacuum pump will stop if the lubrication oil tank level, or flow is low, the discharge temperature is high or the suction temperature is low.
AF 622.01 AF 622.02
High discharge temperature alarm Set point: +170°C Trip the pumps
AF 619.01 AF 619.02
High vacuum alarm Set point: 200 mbar a Trip the pumps
Low lubrication oil level alarm Set point: 5 cm Trip the pumps
AF 623.01 AF 623.02
Low cooling water flow alarm Normal flow rate 1500l/h
The pumps are sea water cooled from the deck cooling sea water system (refer to 2.12). The pumps are started and stopped from the starter panel in the CCR. Auto from the CCR and local from the ECR.
Specification
! CAUTION If there is a computer control failure, the vacuum pumps can only be stopped from the ECR and not from the compressor room or CCR.
! CAUTION If the primary space pressure were to be reduced below the secondary space pressure there is a danger of distorting the secondary barrier by lifting it off its supporting insulation. A maximum pressure difference of 30 mbar is allowed. Discharge from the pumps is led to No. 3 mast riser.
Issue: 1
Ensure free rotation of pump. Operate manual lub-oil pump and ensure oil drips are evident at each sight glass. If the pump has been stopped for more than 24 hours it is essential to turn the rotor by hand 2 or 3 turns before starting the pump to ensure that the blades are not stuck on the cylinder.
3
The vacuum pumps can now be started.
AF 624.01 Low lubrication oil flow alarm AF 624.02 6/10 drops per 10 seconds Trip the pumps AF 624.03 AF 624.04
! CAUTION
2
AF 621.01 Low suction temperature alarm AF 621.02 Set point: -60°C Trip the pumps
The pumps are driven by electric motors situated in the electric motors room through a gas tight bulkhead seal. The two pumps are used in parallel to evacuate the primary and secondary spaces in order to reduce the time taken to achieve the vacuum of 200 mbar a.
If there is a failure or stoppage and the vacuum pump is hot and the cooling water has stopped, await for room temperature before restarting in order to avoid shock due to cold water.
LNG LERICI
Vacuum pumps: Two horizontal rotary dry vacuum pumps, single staged type P8O manufactured by MPR industries, capable of creating a vacuum of 200 mbar a in the primary and secondary insulation spaces and driven at 875 rpm by 27 kW increased safety electric motors through a gas tight bulkhead seal (817 m3/h). Suction temperature -50°C to +45°C Operating Procedures 1
Open the sea water cooling water inlet and outlet at the vacuum pump. Check through the pump drain valve that there is no water in the pump. A sample intake is fitted on the drain valve in order to permit sampling during operation. Then vent the pump cooling water lines. When evacuating the insulation spaces, the secondary barrier space is evacuated to 950 mbar a before the primary barrier space suction isolating valve is opened. Both spaces are taken down to 200 mbar a. This process ensures that it is not possible to lower the pressure in the primary barrier insulation space without having the same pressure in the secondary barrier insulation. Check pump lub-oil tank level.
2.8 Vacuum Pumps - Page 1
Cargo Systems and Operating Manual
LNG LERICI
2.9.1a Inert Gas and Dry Air System
Chiller Unit Pump
Vent to Funnel
Refrigeration Compressor and Evaporator
Combustion Air Fans Demister
Intermediate Dryer Unit
Demister
Scrubber O2 Analyser
Ignitor
Sprayer Bar
Combustion Chamber
Fuel Inlet
Chiller Unit
Steam Atomizing
Burner Unit and Combustion Chamber CI0 01VF
Effluent Seal
Effluent Pipe Not Lined
Electric 80 kW Heater
206
From Ballast Pump Key
Light Ship Draught
B1 Desiccant Vessel Unit No.1
Min.2m
Fan Filter and Drain
B2 Desiccant Vessel Unit No.2
Vent to Funnel
Combustion Air Steam Diesel Fuel Oil
Cooler
Effluent Discharge Overboard
Reactivation Dryer System
Chilled Water Sea Water Inert Gas Sea Water Fiber Glass Lined Effluent Pipe Final Dryer Unit
Issue: 1
Inert Gas to Deck
2.9.1a Inert Gas and Dry Air Systems
Cargo Systems and Operating Manual 2.9
Inert Gas and Dry Air Systems
2.9.1 Inert Gas and Dry Air Plant (XAI5321 and XD/5321 A through F) The dry air / inert gas plant, installed in the engine room, produces dry air or inert gas which is used for the tank and piping treatments prior and after a dry docking or an inspection period. The operating principle is based on the combustion of a low sulphur content fuel and the cleaning and drying of the exhaust gases. The inert gas plant includes an inert gas generator, a scrubbing tower unit, two centrifugal fans, an effluent water seal, a fuel injection unit, an intermediate dryer unit (refrigeration type), a final dryer unit (adsorption type) and an instrumentation / control system. Manufacturer
Navalimpianti.
Inert gas delivery rate (Normal m3/h) 6500 Dry air delivery rate (Normal m3/h)
6500
Delivery pressure (bars)
0.3
Inert gas/dry air dew point (°C)
-45
Inert gas composition (% vol) Oxygen
1
Carbon dioxide < 15 Carbon monoxide < 100 ppm Hydrogen < 100 ppm Sulphur oxide < 2 ppm Nitrogen oxide < 65 ppm Nitrogen balance to 100% •
Soot complete absence. The dry air/inert gas plant is locally operated.
The connection to the cargo piping system (refer to 2.2.1a) is made through two non-return valves and a spool piece which is in the normally closed position and the connection to the gas header is made through a removable bend (not normally connected). Working Principle Inert gas is produced by combustion of Gas Oil supplied by the Gas Oil Pump with air provided by blowers, in the combustion chamber of the Inert Gas Generator. A good combustion is essential for the production of a good quality, soot free, low oxygen inert gas.
Issue: 1
The products of the combustion are mainly carbon dioxide, water and small quantities of oxygen, carbon monoxide, sulphur oxides and hydrogen. The nitrogen content is generally unchanged during the combustion process and the inert gas produced consists mainly of 85% nitrogen and 15% carbon dioxide. Initially, the hot combustion gases produced are cooled indirectly in the combustion chamber by a sea water jacket. Thereafter cooling of the gases mainly occurs in the scrubber section of the generator where the sulphur oxides are washed out. The sea water for the Inert Gas Generator is supplied by one of the ballast pumps via ballast main isolating valve 206. Before delivery out of the generator, water droplets and trapped moisture are separated from the inert gases by a demister. Further removal of water occurs in the intermediate dryer stage, where the refrigeration unit cools the gas to a temperature of about 5°C. The bulk of the water in the gas condenses and is drained away with the gas leaving this stage via a demister. In the final stage, the water is removed by absorption process in a dual vessel desiccant dryer. The desiccant dryer units work on an automatic change over cycle, where the out of line desiccant unit is first reactivated with warm dry air which has gone through the reactivation dryer system. A Pressure Control valve located at the outlet of the Dryer Unit maintains a constant pressure throughout the system, thus ensuring a stable flame at the generator. Dewpoint and oxygen content of the Inert Gas produced are permanently monitored. The oxygen level controls the ratio of the air/fuel mixture supplied to the burner. The oxygen content must be below 1% by volume and the dewpoint up to a maximum of - 65°C with a minimum of -55°C. Both parameters are displayed locally and remotely through the Bailey IMS. For delivery of Inert Gas to the cargo system, two combined remote air-operated control valves operated through solenoid valves are fitted on the distribution system, ie the Purge valve and the Delivery valve. Dry-Air Production The Inert Gas Generator can produce Dry-Air instead of Inert Gas with the same capacity. However, for the production of Dry-Air: a There is no combustion in generator;
LNG LERICI b There is no measure of oxygen content. The oxygen signal is overridden when the mode selector is on Dry-Air production. After the processes of cooling and drying, and if the dewpoint is correct, the dry air is supplied to the cargo system through the delivery valve (with the purge valve closed). Burner Description The combustion air is supplied to the main burner by two ‘roots’ type blowers of 50% capacity each. The quantity of combustion air to the burner can be manually adjusted by a regulating valve in the excess air discharge line. Fuel (Gas oil) is supplied at a constant pressure by the Gas oil electric pump which has a built-in pressure overflow valve. Before ignition or start up of the unit, and with the pump running, all the fuel is pumped back via this fuel oil overflow valve which also serves to regulate the delivery pressure of the pump. The fuel oil flows to the nozzle of the main burner via two solenoid valves and two fuel oil regulating valves. A programme switch in the local control panel regulates one of the solenoid valves which also operates the pilot burner and initial firing. The main burner is ignited by a pilot burner. The fuel oil is atomised in 2 steps. Firstly, the fuel oil is dispersed by a spray nozzle. Then it is subjected to a tangential impulse flow of steam which when it comes into contact with the axially orientated impulse flow of fuel, causes the ultrafine dispersion of the fuel oil. Atomising steam for the ultramiser burner is fed via a special steam superheater. A pressure reducer stabilises the incoming steam pressure and the correct atomising pressure for the main burner can be adjusted. The pneumatic valve in the steam line is opened a few seconds after ignition of the pilot burner. The steam superheater is fitted in the combustion chamber. The steam is further heated in the steam superheater, located in the combustion chamber to produce dry steam for efficient atomisation of fuel in the burner. •
For alarms and operating indications, refer to the manufacturer’s P & I diagrams.
2.9 Inert Gas and Dry Air Systems - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.10.1a Nitrogen Producton System 130m3/h Screw Compressor To Funnel PI 40 Buffer Tank 7.5m3 8 bar
M
TS 15
DPS 5 PI
PT AO2 H>5% 25
H
PI
Drain
DPA 1-2
DPS H
PI
N2 57.5m3/h Membrane
DPA
O2 25
H
L
PI 35
L PS 20
PI 35 PCV 35
Drain
PT
PS
PT 35
130m3/h Screw Compressor Drain
N2 57.5m3/h Membrane
R12. COOLER Cooler UNIT Unit Freon Dryer Unit
M
Drain Drain
Drain Key Key DPA
Issue: 1
Gaseous Nitrogen
H.T. Dew Point
PS 20
L.P. Accumulator
PT 35
H.P. Delivery
AO2 25
O2 >5%
Air
PT 35
L.P. Delivery
TS 15
H.T. Air
Chilled Water
DPS 5
Filter Blocked
DPA
Oxygen Enriched Air
H.T. Dew Point
Electrical
2.10.1a Nitrogen Production System
Cargo Systems and Operating Manual 2.10 Nitrogen Production System 2.10.1 Nitrogen Production Plant (XA/5221) Two nitrogen generators, installed in the engine room, produce gaseous nitrogen which is used for the pressurisation of the barrier insulation spaces, as seal gas for the HD and LD compressors, fire extinguishing in the vent mast risers and for purging of various parts of the cargo piping. The two high capacity units (45m3/h each), will operate in parallel when high nitrogen demand is detected and will start automatically, i.e. during initial cooling down. When loading only one unit will need to be run - the other unit being kept on standby. The operating principle is based on the hollow fibre membranes through which compressed air flows and is separated into oxygen and nitrogen. The oxygen is vented to the atmosphere via the engine funnel and the nitrogen stored in a 7.5m3 buffer tank ready for use. The high capacity unit consists of two AS 36 - 12 bar screw compressors, two air dryers, 3+3 stage filters arranged in series, before passing into the membrane units. An oxygen analyser, after the membrane, monitors the oxygen content, and if out of range, above 3% O2.
The nitrogen is stored in a 7.5m3 buffer tank, where high and low service pressure set points actuate the start and stopping of the generators. It is filled at a pressure of 7-8 bar abs and delivery pressure og 3 bar abs. High Capacity Unit Manufacturer Nominal flow rate (N m3/h) Nitrogen purity Dew point (°C) Outlet gas composition (%vol)
Screw compressor: Kaeser type AS 36 Compressed air at membrane inlet Maximum back pressure O2 enriched air Nominal power Nitrogen temperature Feed temperature
Issue: 1
Tecnoco 57.5 + 57.5 97% -55 at 8 bar (g) Oxygen < 3 Carbon dioxide < 30 ppm Nitrogen balance to 100% 160 Nm3/h
Nitrogen dryers: Zander - 99% at 1 micron oil retention down to 0.5 mg/m3 at 7 bar and 20°C Dew point (with drying capability of membranes, final dew point will be < -55°C) -26°C A three way pneumatic operated valve is installed on the membrane outlet. This valve is controlled by the O2 concentration analyser, redirecting the flow to the funnel if O2 above 5%. •
The gaseous nitrogen generators are operated automatically, locally or from the CCR.
Control Systems and Instrumentation The control panel permits fully automated unmanned operation of the units. The following alarms and controls are mounted on the control panels.
LNG LERICI Audible and visual alarms for the following: N2 Pressure to users: < 2.9 bar (g) locally & CCR remote panel N2 Pressure to users: > 3.1 bar (g) locally & CCR remote panel N2 Pressure in buffer tank: > 9 bar (g) locally & CCR remote panel N2 Pressure in buffer tank: < 4 bar locally & CCR remote panel O2 Percentage: > 5% after 5 minutes Dew point: > 65% after 5 minutes Filter dirty: > 1 bar Feed air temperature: < 55°C locally & CCR remote panel Compressor failure: locally & CCR remote panel Process shut-down: locally & CCR remote panel Shut down applies in the following situations: O2 percentage: > 5% after 5 minutes Dew point: > 65% after 5 minutes Feed air temperature: < 55°C N2 Buffer tank N2 pressure: > 9 bar (g)
Push Buttons for Start/Stop Operation Selection for N2 delivery valve close/open/auto Push button for audible alarm acknowledgement Continuous N2 delivery pressure Continuous O2 content reading Oxygen Analyser A fixed O2 content analyser is installed on the package units, which is connected before the remotely operated three way valve. The analyser has the following characteristics, O2 range 0 to 25%, with an output signal of 4 to 20 mA for the remote indicator, alarm panel and three way valve actuation. Remote Control Panel The following instruments, signals and controls are installed on the panel: Oxygen content indicator 0 to 25% O2 N2 delivery pressure indicator 0 to 4 bar Start/stop push buttons Alarm acknowledgement push button
12 bar 0.5 bar 23kW 5 ÷ 45°C 5 ÷ 45°C
2.10 Nitrogen Production System - Page 1
Cargo Systems and Operating Manual
LNG LERICI Key
Illustration 2.11.1a Ballast System
Sea Water Ballast Sea Water Ballast Stripping D
Draught Level Sensor
Overboard Discharge Port Sea Chest
355
Ballast Tank No. 4 Port
Ballast Tank No. 3 Port
Cross Over
PI xxxx
PT
xxxx
PI
H
LI
LT
LT
xxxx
H
LI
LT
xxxx
L
H
LI
LT
xxxx
L
LI xxxx
L
L
280
PT
PI
Ballast Tank No. 1 Port
Cofferdam No.3
255
H
PI
Ballast Tank No. 2 Port
D
Stripping Eductor
xxxx
PI PT
FORE PEAK
301
330
205
AFT PEAK
341
241
221
231
PORT BALLAST PUMP NO. 1
340
D
270
206
230
202
203
242
332
232
250
D
265
260
285
H xxxx
L
PI
275
LI
H LT
xxxx
291
H
LI
LT
xxxx
LI
H LT
xxxx
L
L
LI xxxx
L
L
Cofferdam No.3
High Sea Chest Main Direct Bilge Suction To ER Central Water Cooling
Issue: 1
LT
LI
LT 295
Stb'd Side Above Fore Dry Double Bottom
212
312
222
322
H
290
200
VOID SPACE
310
305
240
STARBOARD BALLAST PUMP NO. 2
204
210
220
342
Pipe Tunnel Bilge Suction
211
320
201
207
To Inert Gas Scrubber
311
321
331
350
Cross Over
In E.R Under Shaft
To Cargo System Water Cooling
Starboard Sea Chest
Ballast Tank No. 4 Stbd
Ballast Tank No. 3 Stbd
D
Ballast Tank No. 2 Stbd
Ballast Tank No. 1 Stbd
2.11.1a Ballast System
Cargo Systems and Operating Manual 2.11 Ballast System 2.11.1 Ballast System Description (See Illustration 2.11.1a) The ballast spaces beneath and around the out board side of the cargo tanks are utilised as ballast tanks to optimise draft, trim and heel during the various load conditions of the vessel. Ballast will be carried during the return passage to the loading port, when only sufficient gas is carried to maintain the tanks and their insulation at cryogenic temperatures. The ballast spaces are divided into 8 tanks, that is port and starboard under each of the 4 cargo tanks. In addition, the fore and aft peak tanks are also used to carry ballast when required. This gives a total ballast capacity of 26081m3, approximately 26733 tonnes when filled with sea water. Two, 1200m3/h, vertical centrifugal pumps are fitted, which enable the total ballast capacity to be discharged or loaded in approximately 24 hours using 1 pump, or 12 hours using both pumps. The pumps are driven by electric motors and are located on the engine room floor, starboard side forward. The 600 mm fore and aft ballast main runs through the duct keel with tank valves mounted on tank bulkheads. This main reduces to 500mm at tank No. 3 and to 300 at tank No. 1. The 200mm stripping main also runs though the duct keel on the port side, this is connected to the stripping eductor. Both ballast pumps fill and empty the tanks via the port side 600mm main. Stripping and final educting is done using 1 pump as the driving water for the eductor on the 200mm stripping main. The fore peak ballast space can also be filled and emptied using the ballast mains. The cross over between the 2 mains being at No. 1 ballast tank. All ballast pipes are of GRP. with galvanised steel bulkhead pieces. All valves are AMRI butterfly valves hydraulically operated, fail safe type, except cross-over and masters. 2 Ballast pumps, electric motor driven XA/404A & B Make: - Kvaerner Singapore Type: - Double suction, single stage axially split centrifugal Issue: 1
Rated output: 1200m3/h at 30m head, are mounted at the forward end bottom platform of the E.R. These pumps take their suction from the sea/sea cross over or from the high sea chest, the latter being the normal operation when loading ballast and from tanks via port side header when discharging. Ballast Eductor 180m3/h at 30m head. The ballast pumps are used to supply sea water to the inert gas system. System Control The ballast system is controlled entirely from the control room using the keyboard in conjunction with mimic ELSAG BAILEY Ballast. The ballast pumps are started and stopped using the mimic board, provided that the switches on the local control panel are set to remote. When on local control, the pumps can be started and stopped from the local control panel, and can be stopped from this panel regardless of the position of the local/remote switch. The local control panels always take priority and can wrest control from the control room at any time. All hydraulically operated valves in the system are also operated using the keyboard in conjunction with mimic ELSAG BAILEY Ballast. Two basic types of valve are fitted, those which can be positioned at the fully closed position or fully open, and those which can be positioned at any point between fully open and fully closed. The position of all valves is shown on the mimic. Provision is made for a portable hand pump to be used to operate each valve in the event of hydraulic accumulator failure. The pump discharge valves and the overboard discharge tank valves are multi-positional. All other valves are either open or closed. In addition to being operable from the control room, the valves can also be operated from the hydraulic power station, using the push buttons on the individual solenoids. Mimic ELSAG BAILEY Ballast also shows when the pumps are switched to remote, the pumps suction and discharge pressure, the position of the manually operated valves and the level in each tank, in terms of inage. System Capacities and Ratings Ballast pumps: Kvaerner Singapore Model: CAD 350-12V48AAN, each rated at 1200m3/h against a head of 30 mlc at 1188rpm.
LNG LERICI Control and Alarm Settings Point No. AF 452.01 AF 452.02 AF 452.03 AF 452.04 AF 452.05 AF 452.06 AF 452.07 AF 452.08 AF 452.09
Setting 16m 20m 20m 20m 20m 20m 20m 20m 20m
Description Fore peak tank level high No.1 port ballast tank level high No.1 stbd ballast tank level high No.2 port ballast tank level high No.2 stbd ballast tank level high No.3 port ballast tank level high No.3 stbd ballast tank level high No.4 port ballast tank level high No.4 stbd ballast tank level high
3
Open the gravity filling valve from sea 265. When a flow has been established the fore peak valve 200 and forward isolation 210 can be shut.
4
Open the valve(s) on the tank(s) to be filled as required by the ballast plan. No.1 Port
No.1 Stb’d 212 No.2 Port
A)
Maloperation of the ballast system will cause damage to the GRP pipework. Damage is generally caused by pressure surge due to sudden changes in the flow and the presence of air pockets. During the ballasting operation great care must be taken to ensure that flow rates are adjusted smoothly and progressively. In particular, the pumping rate should be reduced to one pump when filling only one tank and use made of the discharge to sea to further reduce the rate before shutting of the final tank valve.
231
No.3 Stb’d 232 No.4 Port
241
No.4 Stb’d 242 5
As the level in each tank reaches that required, open the valve of the next tank before closing the valve of the full tank.
6
When all the tanks are at their correct level shut the tank valves, ballast main valves 220, 205 and gravity filling valve 265
To ballast the ship
! CAUTION
221
No.2 Stb’d 222 No.3 Port
Operating Procedures It is assumed that the main sea water cross-over pipe is already in use, supplying other sea water systems, eg. main circulating system, sea water service system, and that the cargo and ballast valve hydraulic system is also in use.
211
Note The speed when filling by gravity will sharply decrease as the level of the water line is approached. The tanks will require to be filled to their capacity with the ballast pump.
It is necessary to eliminate air pockets that may be present in the piping before proceeding with normal ballasting operations. This is achieved by running ballast by gravity into either the fore peak or No. 1 tank. It is important not to compress any air in the system. To achieve this, the valve admitting water to the system should be opened last. i) Fill by gravity All operations are carried out from the control room using the keyboard in conjunction with the mimic board ELSAG BAILEY Ballast. 1
Open the valve 200 to the fore peak tank.
2
Open ballast main valves 210, 220, 205 this will enable initial line filling to expel air trapped in the lines.
2.11 Ballast System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Key
Illustration 2.11.1a Ballast System
Sea Water Ballast Sea Water Ballast Stripping D
Draught Level Sensor
Overboard Discharge Port Sea Chest
355
Ballast Tank No. 4 Port
Ballast Tank No. 3 Port
Cross Over
PI xxxx
PT
xxxx
PI
H
LI
LT
xxxx
H
LI
LT
LT
xxxx
L
H
LI xxxx
L
LI
LT
xxxx
L
L
280
PT
PI
Ballast Tank No. 1 Port
Cofferdam No.3
255
H
PI
Ballast Tank No. 2 Port
D
Stripping Eductor
xxxx
PI FORE PEAK
301
330
PT
205
AFT PEAK
341
241
221
231
PORT BALLAST PUMP NO. 1
340
D
270
206
230
202
203
242
332
232
250
D
265
260
285
H xxxx
L
PI
275
LI
H LT
xxxx
291
H
LI
LT
xxxx
LI
H LT
xxxx
L
L
LI xxxx
L
L
Cofferdam No.3
High Sea Chest Main Direct Bilge Suction To ER Central Water Cooling
Issue: 1
LT
LI
LT 295
Stb'd Side Above Fore Dry Double Bottom
212
312
222
322
H
290
200
VOID SPACE
310
305
240
STARBOARD BALLAST PUMP NO. 2
204
210
220
342
Pipe Tunnel Bilge Suction
211
320
201
207
To Inert Gas Scrubber
311
321
331
350
Cross Over
In E.R Under Shaft
To Cargo System Water Cooling
Starboard Sea Chest
Ballast Tank No. 4 Stbd
Ballast Tank No. 3 Stbd
D
Ballast Tank No. 2 Stbd
Ballast Tank No. 1 Stbd
2.11.1a Ballast System
Cargo Systems and Operating Manual ii) 1
10 Open ballast eductor suction valve 340 (automatic).
Close the pump discharge valve 204 and stop the pump.
When it becomes necessary to start the ballast pumps, 5 Open valves 230, 201 (port pump) 250, 202, 270 (stb’d pump).
Close all other valves.
6
Close valve 280.
7
Check that a ballast tank valve is open.
12 When all tanks have been stripped close eductor suction valve 340.
8
Start ballast pump.
9
Open pump discharge valve 207 (port), 204 (stb’d).
To ballast the ship using the port ballast pump
6
Follow operations 6 to 8 inclusive above.
Confirm the manual operated valves on the sea water suction are open. Open the valve(s) on the tank(s) to be filled as required by the ballast plan.
7 8
Fore peak 200 No.1 Port
211
B) To deballast the ship
No.1 Stb’d 212 No.2 Port
No.4 Stb’d 242 Aft peak ballast operations are performed by engine room general service pumps
Under no circumstances should a vacuum be drawn on a closed ballast main.
13 Strip the ballast tanks as required (see below).
Before starting the deballasting operations, the main lines must be purged of any air pockets in the following manner.
C)
1
Open overboard discharge valve 255.
2
Open ballast main valve 280 and isolation main valves 205, 220 and 210 (if the fore peak is to be deballasted)
Using the port ballast pump. 1 Open sea water valve 291. 2
Open ballast pump inlet valves 290, 295.
3
Open fore peak valve 200.
3
Open ballast eductor driving water supply valve 330.
A flow will now be established
4
Open ballast eductor overboard discharge valve 355.
5
Open main ballast pump overboard discharge valve 255. (to regulate driving water throughput to eductor).
6
Open ballast stripping main isolating valves 310 (if stripping the fore peak), 320, 305.
211
7
Start ballast pump.
No.1 Stb’d 212
8
Open ballast pump discharge valve 207.
No.2 Port
9
Open valve on first ballast tank to be stripped
231
No.3 Stb’d 232 No.4 Port
241
Open ballast isolating valves 210 (if required to fill the Fore Peak) 220, 205, 280 Open sea water inlet valves to the pump 290, 295, 240, 201
4
Start the port ballast pump
5
Open the pump discharge valve 207.
6
As the level in each tank reaches that required, open the valve for the next tank before closing the valve to that tank which is full.
7
When all tanks are near to the required level, reduce the flow rate progressively by discharging to sea via overboard discharge valve 255.
8
Close the final tank valve when it reaches the required level.
9
Close the pump discharge valve 207 and stop the pump.
10 Close all other valves iii)
10 As the level reaches that required, open the valve on the next tank before closing the valve on that tank.
Maloperation of the ballast system will cause damage to the pipework. Damage is generally caused by pressure surge due to sudden changes in the flow rate. During the deballasting operation this can be caused by the opening of a full, or partly full tank into the ring main when it is under vacuum. This is a particular risk when eductors are in use.
No.3 Port
3
! CAUTION
221
No.2 Stb’d 222
2
LNG LERICI
To ballast the ship using the stb’d ballast pump
4
Open the valve(s) on the tank(s) to be emptied as required by the deballast plan.
11 When suction has been lost on all tanks that are required, close the pump discharge valve 207 (port), 204 (stb’d) and stop the pump(s). 12 Close tank valves, isolating main valves 210, 220, 205, pump inlet valves 230, 201 (port), 250, 202 (stb’d), 270 and overboard discharge valve 255.
Fore peak 200 No.1 Port
221
To strip the ballast tanks using the ballast eductor
No.2 Stb’d 222
Fore peak 200
No.3 Port
No.1 Port
231
No.1 Stb’d 312
No.4 Port
No.2 Port
Follow operations 1 to 2 inclusive above.
2
Open the valves 290, 295, 260, 202.
3
Open valve 270 stb’d pump isolating valve to ballast main.
4
Start the pump.
No.4 Port
5
Open pump discharge valve 204.
No.4 Stb’d 342
Issue: 1
14 Close all other valves opened in operations 1 to 6. D)
To supply sea water to the inert gas scrubber system via the ballast pump.
Using the stb’d ballast pump. 1 Open sea water valve 291. 2
Open pump suction valves 290, 295.
3
Ensure inert gas system is ready to receive ballast pump supply. Open inlet valve to inert gas scrubber system 206.
4
Start ballast pump.
5
Open ballast pump discharge valve 204.
321
1
No.4 Stb’d 242
13 Close ballast pump discharge valve 207 and stop pump.
311
No.3 Stb’d 232 241
11 When one tank has been stripped, open the next tank valve before closing the previous tank.
No.2 Stb’d 322 No.3 Port
331
No.3 Stb’d 332 341
2.11 Ballast System - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.11.2a Cargo Valves Hydraulic System Control Blocks for ESDS Manifold Valve Numbers 001 002 003 004 005 006 007 008 401 408
Control Blocks for Liquid Dome Valves Valve Numbers 010, 011, 012, 013, 110 020, 021, 022, 023, 120, 030, 031, 032, 033, 130, 040, 041, 042, 043, 140
Distribution Control Rack No. 2 Low Pressure High Flow
Control Blocks
Control Blocks
Valve Numbers 114 124 134 144 431 441 501 502
Valve Numbers 400 403 404 406 410 411 420 421 430 440 451 452
5 Litre Accumulator for each ESDS Valve
To Individual ESDS Manifold Valves (see Illustration 2.11.2c)
Drain
115 bar
Pneumatic Pilot Control Valves
Distribution Control Rack No. 2 High Pressure Low Flow
To Other ESDS Control Blocks
P4
To ESDS Port Accumulators
P5
PdA
PdA
PdA
To ESDS Starboard Accumulators
PdA
Cooler To Starboard ESDS Control Block Deck Sea Water Cooling
115 bar 10 bar PT 115 bar
PA Trip
LL PT
Trip
PA H
LL
TA
HH TA
LA
Hydraulic Cooling Circulating Pump
L TT
M
M
LA
TT
LS
LL LS
M Key 700 Litre Hydraulic Oil Tank
Control Air Hydraulic Oil System Deck Sea Water Cooling Drain
Issue: 1
Instrumentation
2.11.2a Cargo Valves Hydraulic System
Cargo Systems and Operating Manual 2.11.2 Cargo and Ballast Valves Hydraulic System General Description All valves necessary for the normal operation of the cargo and ballast system are hydraulically operated by two separate hydraulic power packs situated on Upper Deck cross alleyway. Control of the power pack units and the valve operation is via the IMS Elsag Bailey mimic and key board in the cargo control room. All remotely operated valves are piston operated except for the liquid dome valves which have vain type actuators. The supply of oil is controlled by solenoid valves arranged in two racks in the hydraulic room on Upper Deck. Rack No.1 which is on the starboard side as you enter the hydraulic room, controls the ballast, bilge and bunkering valves. Rack No.2, situated on the port side controls the cargo valve operation. The following valves:- the ballast pump discharge valves, ballast pump overboard discharge to sea, main, auxiliary and stripping/spray pump discharge valves can be throttled in and stopped at any intermediate position between fully open and fully shut. All other valves remotely operated are arranged to be either fully open or fully shut. The ESDS cargo manifold valves each have their own hydraulic accumulators to ensure there is always sufficient pressure for their operation. Cargo Operations, System Capacity and Rating. (illustration 2.11.2a) There are three electric motor driven hydraulic pump units with this power pack, a small 0.75kw motor is used to drive an oil circulating cooling pump and two main motors (26 kW), each driving a hydraulic tandem pump rated at 80 l/min and 5 l/min, with a normal working pressure 110/115 bar. Pressure filter: type 10/20 micron, with a pressure differential alarm, visual indicator for blockages and a manual change over to a standby filter. Return filter: 125 micron, with a pressure differential alarm and visual indication for blockage. Hydraulic oil tank: 700 litres
Hydraulic Power Pack No. 2 (Cargo) The hydraulic power pack consists of a 700 litre oil tank with two sets of hydraulic tandem pumps situated under the tank. This is best described as a high pressure low flow and a low pressure high flow system, the valves concerned as indicated. Suction for each of the pumps is through 125 micron filters, before passing into the main pressure rail through individual non return valves. The normal operating pressure is up to 110 bar, with pressure relief valves set to 115 bar. The flow now passes through pressure line filters 10/20 micron, fitted with a differential pressure alarm switch with a manual change over to the standby filter.
LNG LERICI Emergency Hand Pump Operation All the hydraulic valves apart from the liquid dome valves have an emergency hand pump connection. There are two portable emergency hand pump units, one available on deck and one in the duct keel space for use on the ballast valves. The isolating valves on the distribution block are first shut off and the flexible hoses from the emergency hand pump fitted to the snap on connectors, the control of direction is via a hand operated change over control block.
The return oil passes through a 125 micron filter before returning to the storage tank. A control panel with alarm indication is fitted to the front of the power pack tank, which has the selection control for the pumps in lead / lag configuration. Pressure switches control the pump cut in/out, with low low pressure alarm and pump failure alarm transmitted to the IMS Elsag Bailey. The oil level in the tank is monitored with a low level alarm switch and a low low alarm which will trip the pumps. The temperature of the oil is also monitored, with a high temperature trip switch protecting the system. A small oil circulation pump draws from the service tank via a 125 micron suction filter, the discharge from the pump passes via a 10/20 micron filter fitted with an differential pressure alarm and manual by-pass, to a tube cooler which is cooled from the deck sea water system (see section 2.12) There is no accumulator fitted directly to this system, apart from the individual accumulators fitted to the manifold ESDS valves.The accumulators are pressurised by hydraulic lines P4 & P5 up to a working pressure of 110 bar, where it will be maintained by the inlet check valve and by the pneumatic pilot valve which controls the outlet to the manifold ESDS valves. In the event of the ESDS being activated, the pilot air line is vented, enabling the accumulator control block to change over, allowing the high pressure hydraulic oil to be directed onto the closing side of the manifold valve actuating piston. The emergency hand pump opening and closing connections for these valves are over ridden by the flow from the accumulator system.
Cooling pump; flow rate 20 l/h at 5 bar ESDS hydraulic accumulators, fitted in proximity to the ESDS manifold valves with a capacity of 5 litres per accumulator.
Issue: 1
2.11 Ballast System - Page 3
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.11.2b Ballast Valve Hydraulic System
Control Blocks for Ballast Valves MR001VR MR002VR
To Bilge System Valves
To Bunker System Valves
CE001VR CE002VR CE003VR CE004VR
SE158VR SE160VR SE168VR SE175VR
200, 201, 202, 204, 207, 220, 230, 240, 250, 255, 260, 270, 280, 290, 291, 320
Distribution Control Rack No. 1
Accumulator
32 Litre
115 bar
115 bar PdA
PdA
PdA
PT
Trip
Trip PS
Pump Cut In
HH TA
LA
PS Pump Cut Out LL
TT
PA
LS M
M
LL
Key
400 Litre Hydraulic Oil Tank
Hydraulic Oil System
Drain
Issue: 1
2.11.2b Ballast Valve Hydraulic System
Cargo Systems and Operating Manual Ballast Operations, System Capacity and Rating (illustration 2.11.2b) There are two electrically driven hydraulic pumps in the power pack, which are used for the control of the ballast, bilge and bunkering valves. Each pump is rated at 80l/min with a normal working pressure of 110 bar. Pressure filter: 10/20 micron, with a pressure differential alarm, visual indicator for blockages and a manual change over to a standby filter. Return filter: type 125 with a pressure differential alarm and visual indication for blockage
LNG LERICI
operate the ballast system. The rack also contains 28 further valves for the operation of the bilge and bunkering systems. Emergency Hand Pump Operation All the hydraulic valves apart from the liquid dome valves have an emergency hand pump connection. There are two portable emergency hand pump units, one available on deck and one in the duct keel space for use on the ballast valves. The isolating valves on the distribution block are first shut off and the flexible hoses from the emergency hand pump fitted to the snap on connectors.
Hydraulic oil tank: 400 litres System accumulator: 32 litres Hydraulic Power Pack No.1 (Ballast) The hydraulic power pack consists of a 400 litre oil tank in which two hydraulic pumps are submerged. Suction for each pump is through a 125 micron filter, the discharge from each pump passing into the main high pressure rail through individual non return valves. The normal operation pressure is up to 110 bar, with pressure relief valves set at 115 bar. A 32 litre accumulator acts as a buffer for the storage of pressurised oil for the period that the pumps are not running, the accumulator is itself pre pressurised with nitrogen in a bladder located in the top of the accumulator which acts to dampen out pressure pulsations. The discharge is led into a common line before passing through a 10/20 micron filter, which is fitted with a differential pressure alarm switch with a manual change over to the standby filter. The return oil passes through a 125 micron filter before returning to the service tank. A control panel with alarms indication is fitted to the front of the power pack tank, which has the selection control for the pumps in lead / lag configuration. Pressure switches control the pump cut in/out, with low low pressure alarm and pump failure alarm transmitted to the IMS Elsag Bailey alarm mimic. The oil level in the tank is monitored with a low level alarm switch and a low low alarm which will trip the pumps. The temperature of the oil is also monitored, with a high temperature trip switch protecting the system. The high pressure discharge from the pumps is led via the accumulator and pressure filter to the distribution solenoid rack which contain the 26 valves that are required to
Issue: 1
2.11 Ballast System - Page 4
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.11.2c Cargo and Ballast Valve Control Typical for each ESDS Valve
ESDS Valve Group A
Key Emergency Hand Pump Connection
P4
To Port ESDS Accumulators
P4
To Starboard ESDS Accumulators
Emergency Hand Pump Connection
Control Air
To other ESDS Control Blocks
Pneumatic Pilot Control Valves
Liquid Dome Valve Group
Low Pressure High Flow
Hydraulic Oil
Ballast Valve Group
Emergency Hand Pump Connection
Valve Group B
Emergency Hand Pump Connection
Emergency Hand Pump Connection
Emergency Hand Pump Connection
Valve Group C
Return Direct to Service Tank
Issue: 1
2.11.2c Cargo and Ballast Valve Control
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.12 Deck Salt Water Cooling System
Cargo Compressor Room Key Sea Water Condensate Cooler Outlet
Cargo Heaters Observation Tank / Drains Cooler
Anti Siphon Loop
Vacuum Pumps
Cargo Hydraulic System Cooler
To Engine Room
Hydraulic Room HD Compressors
From General Service Pumps
To Ballast Pumps
O.6m Above Load Water Line
285 To Engine Room SW Cooling System
LD Compressors
275 Low Suction Chest Suction from Ballast Tanks
Issue: 1
H
H
265
291
Engine Room
Cargo Compressor Room
2.12 Deck Salt Water Cooling System
Cargo Systems and Operating Manual
LNG LERICI
2.12 Deck Salt Water Cooling System The cargo compressor room is supplied with sea water for cooling the HD and LD gas compressors lub oil system, and for the vacuum pump jackets. A supply is also led to the cargo heaters condensate drains cooler, which is mounted on the aft bulkhead of the motor room. The deck salt water cooling system is supplied from 2 engine room mounted sea water pumps XA/1496A & B. Normally the pumps will take their suction from either the high or low sea water chests. In the situation where the ship is in dry dock, the pumps can draw from the ballast tank system via hydraulic valve 265. The compressor room and cargo heater drains cooler sea water discharge line is led via an anti-syphon loop overboard through No. 4 starboard ballast tank, the discharge being 600mm above the loaded water line. The anti-syphon loop has its vent situated above the compressor room deck. The deck sea water system also supplies the cargo hydraulic system oil cooler which is situated in the hydraulic room on the upper deck.
Issue: 1
2.12 Deck Salt Water Cooling System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.13.1a Deck Instrument and General Service Air Systems
Manifold Main Deck Ladder Hoist Port Bunker Crane Weed Blow for Emergency Fire Pump Sea Water Box
To Forecastle Deck
Hydraulic Room Spraying Nozzles
Spraying Nozzles
Spraying Nozzles
Spraying Nozzles Vent Mast No.2
Supply from Engine Room
De-watering Pump No.2 Secondary Barrier
To Suez Canal Search Light
De-watering Pump No.1 Secondary Barrier
Gas Heaters
Main Vaporiser
Forcinging Vaporiser
H.D. Compressor
Main Deck Ladder Hoist
L.D. Compressor
Stbd. Bunker Crane
De-watering Pump No.3 Secondary Barrier Glycol Heaters
De-watering Pump No.4 Secondary Barrier
Hydraulic Station
Barrier Connection
Manifold Water Trap and Drain
Key General Service Air Instrument Air
Issue: 1
2.13.1a Deck Instrument and General Service Air Systems
Cargo Systems and Operating Manual
LNG LERICI
2.13 Air Systems 2.13.1 General Service and Control Air System The general service air is supplied by a single 240m3/h at 8.5bar compressor XA/226 mounted in the engine room with a 3m3 receiver X/A237 in line. The control instrumentation air is supplied by 2 x 290m3/h at 8.5bar compressors XA/224A & B mounted in the engine room. The compressors discharge into a 5m3 receiver, before passing into the distribution line via an automatic refrigeration and absorption dryer unit. Instrumentation compressors are arranged for one to be in the duty run mode and the other to be in a standby condition. For emergency use there is a cross over connection between the general service and instrumentation before and after the air receivers. The operation and control of both the general service and instrumentation air compressors and the dryer unit is from the engine room. The general service air supplies the following deck equipment: bunker crane port and starboard, accommodation ladder hoists port and starboard and secondary space dewatering pumps mounted in secondary barrier well. A number of outlets are arranged around the deck of the ship to facilitate the use of pneumatic power tools etc. At the forecastle there is a facility for connection of the Suez canal searchlight, there is also a line leading down to the emergency fire pump sea chest for weed blowing. At the starboard aft corner of the accommodation there is a water trap to enable all water to be drained from the system. The control and instrumentation air supplies the following equipment on deck: stripping excess flow regulating valve nozzles at each cargo tank, the supply of air into the compressor room for the control of the HD and LD compressors, vaporisers and heater systems, for the glycol heaters in the motor room and all glycol system regulating valves for the cofferdam heating. The system also operates the No. 2 vent mast riser fire smothering system with the release of nitrogen.
Issue: 1
2.13 Air Systems - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2.14.1a Deck Steam System Vent Gas Heater YA/5142
Return to Observation Drain Tank via Drains Cooler in Engine Room
Electric Motors Room
VAG 52
Compressor Room T
VA/ 031VD
SP/ 013SC
HC
VA/ 040VD
PIC
VA/ 040VD
YA/5151
SP/ 015SC SP/ 016VD
VAO 24
T
YA/ 5500B VA/ 041VD
SP/ 001VD
VA/ 041VD
VA/ 032VD
SP/ 014SC
SP/ 012VD
Forcing Vaporiser
LC
From Engine Room Steam Supply
Drip Tray Heating for Manifold
SP/ 001VD
Cofferdam Heater VAO 25
SP/ 011VD
Main Vaporiser
VA/ 060VR
YA/5152
VA/ 061VR
SP/ 001VD
VA/ 060VR HC
PIC
VA/ 033VD
VA/ 042VD
VA/ 042VD
SP/ 015SC SP/ 017VD Boil Off Heater
L.D. Compressor Oil Sump
SP/ 021SC
SP/ 002VD
YA/5122A SP/ 001VD
YA/ 5500A VA/ 043VD
SP/ 001VD
VA/ 043VD LC
VA/ 034VD
VA/ 061VR ICARE Gas Sample Analyser
SP/ 002VD
SP 001VD
VA/ 035VD
Steam
Control Air
SP/ 021SC
YA/ 5122B
Key
Condensate Drains Cooler
Condensate
L.D. Compressor Oil Sump
H.D. Compressor Oil Sump
SP/ 021SC
SP/ 002VD
YA/ 5121A SP/ 001VD
Observation Tank
SP/002VD SP/021SC
Drip Tray Heating for Manifold
OdA
VA/ 036VD
Sea Water Instrument
Deck Sea Water Cooling To Engine Room Atmospheric Drains Tank
Issue: 1
Drain
H.D. Compressor Oil Sump
SP/ 021SC
SP/ 002VD
VA/ 052VD
YA/ 5121B SP/ 001VD
Drain
2.14.1a Deck Steam System
Cargo Systems and Operating Manual 2.14 Deck Steam System 2.14.1 Deck Steam Description (See Illustration 2.14.1a) Deck steam is distributed to the cargo compressor room, electric motor room and main deck. The cargo steam is used for heating of the following heat exchangers. a) b) c) d) e)
Main vaporiser Forcing vaporiser Gas compressor sump heating Vent Gas heater Glycoled water heaters
CRYOSTAR
The steam to inert gas plant is for the inert gas generator burner gas oil atomiser system. Heating steam at 8 bar, 175°C is supplied from the LP heating steam range via water separators. The heating drains from the cargo heat exchangers are led to a condensate drains cooler (located outside the compressor and motor room on the aft bulkhead), which is cooled from the deck sea water cooling system (see section 2.12). The drains having passed through the condensate cooler flow into an observation tank, where any oil contamination will be spotted, before returning via the atmospheric drains tank to the engine room. The observation tank on deck is fitted with a gas analyser for the indication of a possible tube failure in any of the cargo heat exchangers. The degassing tank has its vent led on deck to a safe position above the cargo compressor room. The heating drains from the inert gas plant are led to the contaminated drains cooler in the engine room, before passing on to the observation tank and atmospheric drains tank. Steam to Cargo Compressor Room The steam supply to the cargo compressor room is via isolating manual valves VA025 and VA024 located in the engine room.
Issue: 1
Glycoled Water Heaters The use of these 2 heaters is to ensure heating of the cofferdams and liquid dome of each tank, boil off heating and tank warm up.
LNG LERICI 3
Warm through lines until steam is seen blowing out from the water separator drain lines.
4
Open fully manual valves VA025 and VA024.
5
Set up the gas heat exchangers’ drains cooler for use and opening sea water inlet and outlet cooling water valves.
6
The fuel gas heater, main heater, forcing vaporiser and main vaporiser are then set up and operated as described under operating procedures for gas heaters and vaporisers 2.5 and 2.6.
Steam is fed to the heaters by means of two control valves ie high flow steam controller and low flow steam controller.
7
The high flow and low flow steam controllers operate at 5 bar and 3 bar steam pressure respectively depending on the load conditions (refer to 2.5.x for more information on glycoled heaters).
For the glycol cofferdam steam heater, the drains are led to the observation tank in the engine room via a manual valve which has to be opened.
8
The glycol boil off steam heater, main and forcing vaporiser, vent gas, HD and LD compressor sump heater drains are led to the condensate drains cooler and observation tank on deck, before passing to the atmospheric drains tank in the engine room.
The heating system maintains a permanent ambient temperature above +5°C. The heat exchangers are of shell and tube design with the glycol water passing through the tubes in 2 passes.
Vaporisers Two steam heated vaporisers are located in the cargo compressor room. They are both of shell and tube type design. One is the main vaporiser and the other is designed as the forcing vaporiser. The steam supply to these vaporisers is by means of a pneumatic control valve on each unit. Inert Gas Generator Atomising Steam The atomising steam is dried in a superheater fitted in the combustion chamber envelope, before being fed to the main burner. Prior to starting the unit, water in the steam supply can be drained through the manual bypass valve on the drain trap. In service, the drains discharged from the main burner can be adjusted through a pressure reducer. An ON-OFF pneumatic operated valve in the steam line opens a few seconds after ignition of the pilot burner and closes if the pilot and main burners are out of operation. Operating procedures Supplying Steam to Cargo Auxiliaries Room and Electric Motors Room 1
Open drain valves on water separators on the deck steam line.
2
Crack open manual valve VA025 and VA024 to supply steam on deck.
Supplying Steam to Inert Gas Generator 1
Open isolating valves on dryer unit steam drains trap.
2
Open isolating valves on inert gas generator steam drains trap.
3
Open heating drains return valve to drains cooler in engine room.
4
Crack open manual valve in engine room for steam supply to inert gas generator.
5
Drain water from steam lines for inert gas generator by opening the bypass on the drains trap for inert gas generator unit.
6
Open up manual valve fully when lines are fully warmed through.
Number 2 Riser Gas Heater This unit is also supplied with steam from the deck steam system, raising the temperature of vented gas from -140 to 0°C. A high temperature alarm is provided on the gas outlet from the heater and alarm inlet temperature low (-116°). The condensate outlet has a low temperature alarm with trip, a high level alarm with trip and a level switch fitted.
2.14 Deck Steam System - Page 1
Part 3 Controls and Instrumentation
Cargo Systems and Operating Manual
LNG LERICI SHIPS OFFICE
Illustration 3.1.1a IMS System Overview
WHEELHOUSE
ACCOMMODATION OfficerÕs Cabins, Mess Cargo Alarm
Cargo System Alarm Wheelhouse Alarm Back-up
Machinery System Alarm and Engineer Calling
Operator Interface Station
Ship Administrative LAN
Operator Interface Station
Gate-Way OfficerÕs Cabins, Mess Engine Room Alarms LAN
Engine Control Room
Operator Interface Station
Operator Interface Station
Cargo Control Room
Operator Interface Station
Gate-Way
INFINET to INFINET Bridge
Engine Room Redundant INFINET
MSWB
Gate-Way
EGP (with redundancy)
Boiler 1 Control
Operator Interface Station
ER + Auxiliary (with redundancy)
Boiler 2 Control
MCC
Cargo Redundant INFINET
Cargo (with redundancy)
Torque Meter System
Ballast (with redundancy)
Gate-Way
CTS
Alarm Back-up
Key
Alarm Back-up
RS 422 Cable
T/G1
Issue: 1
T/G2
T/G3
ER Sensors
Cargo Plants
Ballast & Fuel Oil Valves
3.1.1a IMS System Overview
Cargo Systems and Operating Manual PART 3: CONTROLS AND INSTRUMENTATION 3.1 Integrated Monitoring System System Overview Maker: Elsag Bailey Type: INFI-90 Control and monitoring facilities for the cargo systems are provided by the Integrated Monitoring System (IMS) INFI 90. The IMS functions can be classified as follows: alarms and alarm management; process control; trending; saving and retrieving files; alarm / log printer. The Mulitifunctional Processor Module (MFP) is the heart of the INFI 90 system, which accepts both digital and analogue input/output signals. The MFP modules operate on a local area network called the Control Way, which allows complete process data to be shared to the operator consoles called Operator Interface Stations (OIS). Operator interface stations are located in the cargo control room and engine control room. The bridge and the C.E.O's cabin OIS, offer only an overview of alarm, control and monitoring information. Operator Station The CCR is the main location of the IMS, with the CPU cabinets which are fed via an UPS system located on the after bulkhead of the CCR. The main console in the cargo control room contains two operator stations, which can perform the cargo operation supervision, control, configuration, alarm acceptance and log printout functions. Each monitor is linked to a trackball which sits on the console desk top and a command keyboard, which is located in a draw to the side. Access is gained to the cargo operating system by placing the trackball on the SNAM Master Menu grey key on the operator screen marked Ballast and Cargo Systems and left clicking. A pop up menu will appear called Cargo Operation Monitoring, which is used to gain access to the relevant process, again with the positioning of the trackball and left clicking. The keyboards are used for entering alphanumerical data and issuing commands, having first selected the process target with the trackball. Apart from the information log print out, it is also possible for a screen shot (dump) being sent for hard copy to a printer.
Issue: 1
Alarms An alarm condition is indicated on the operator screen and also sent to the designated alarm printer with the time and date. The alarms are divided into 6 groups according to their priority status; Group S; forms the diagnostic (internal) system Group 1; forms the alarms designated critical Group 2; forms the alarms designated non-critical Group 3; forms the alarms of the fire detection system Group 10; forms the alarms for the boiler port side Group 11; forms the alarms for the boiler starboard side Command Control Command of the electric pumps is via the MSDD (MultiState Device Driver) pop up display, which is initiated from the trackball selection of a pump. The visual image on the screen allows the operation of the pumps via the command keyboard, with the selection option of either automatic or manual operation. The display shows the last state selection, indication state, feed back, auto/manual selection and keyboard command state. When selected to the run state, the image of the pump (triangle in a circle) will change from blue (Stopped) to green (Run). A yellow indicator will appear in the bottom left hand corner of the dialog box if it is in an alarm condition. Command function of the valves that are either Open or Closed is from the RCM (Remote Control Memory) pop up display, which is initiated from the trackball selection of a valve. The visual image shows the current position and state of the valve. The keyboard is used to give the command order. When selected and the command to open is given, the visual image of the valve will change from red (Closed) to green (Open). A yellow indicator will appear in the bottom left hand corner of the dialog box if it is in an alarm condition.
Logging Data is collected by the log over a period of time. The collection period depends on the type of log: either on a regular schedule or only under certain conditions. When the log ends, the data can be printed automatically to a printer. The log data is retained on the hard disk, so that it is possible to reprint the log. Only a limited number of retained historical log data files can be kept on the computer's hard disk; as new logs are collected, the oldest are deleted. To keep log data files as permanent records, it maybe copied to floppy disks. Reprints of log files can be done directly from floppy disk if required.
LNG LERICI Six types of logs are available: periodic, trigger, system events/operator action, trend, trip, and SOE logs. Periodic logs collect and print data at regular intervals or as the events occur. Periodic logs are suited for logs required on a regular schedule, such as an end-of-shift log. The system can configure up to 64 periodic logs. Trigger logs collect and print data according to trigger conditions. Using trigger tags, it is possible to define four types of trigger conditions: collect, print, hold, and resume. Data collection begins when a collect trigger condition is detected. Data collection stops and the log printed when a print trigger condition is detected. Trigger logs are suited for batch logging where a batch can start and end at any time. The system can be configured for up to 64 trigger logs. System Event/Operator Action logs record all tag alarms and are printed at regular intervals. The system can include in the log returned-to-normal alarms and digital changes of state. The system can also create a log of operator actions, such as control actions, logins, and alarm acknowledgments. The printed logs list events line by line, in which specific information can be shown on each line. There are only the two system event logs: alarm log and operator action log. Trend logs print out collected trend data.. Trend logs are configured to print at regular intervals. The printed format of a trend log is fixed; with the specific the trend tags included in each log. The system can configure up to 64 trend logs.
Trending Trend displays may be obtained for the display elements in which a variable has been configured to be logged, such as a level or a temperature. Trend displays are provided in either one of two forms ie, either current trend displays or historical trend displays Trend logs present trend data in columns. The source for the trend log data is the actual trend data file. The resolution is independent of the actual trend sample. Trend graphic displays and trend logs show the same data because both sample the trend data file in the same manner. Up to 64 trend logs can be configured, and each can have one of four periods: hour, shift, day, and week. Up to 20 trend tag names can be configured on a single log, and up to 240 values can be reported for each trend index. Trend logs can be configured to print automatically or manually (on demand). A more detailed account is given in the Lan 90 Operation Instruction Manual.
Illustrations 3.1.1b and 3.1.1c give an over view of the screen displays
Trip logs collect data before and after a trip. A trip occurs when values or states of tags that are specified meet conditions that have been set (e.g.. when an analogue tag's value exceeds 100).The specific tags are arranged to collect data for the amount of data collected before and after the trip. When a trip condition occurs, a trip log containing the pre-trip and post-trip data is printed. The printed format of a trip log is fixed; with only the specific tags to include and the amount of pre-trip and post-trip data. Trip log data can also be plotted onto a graphic display. The system can configure up to 20 trip logs. SOE (Sequence of Events) logs collect data for selected critical digital points where the given situation requires that the sequence of changes of state for these points or group of points be known in the most exacting ways possible. SOE logs meet this requirement by listing all digital state transitions in time order and in onemillisecond resolution.
3.1 Integrated Monitoring System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
3.1.1b Typical System Screen Shots LP PORT STBD AIR
CARGO ESD STATUS
TEMPERATURE SENSORS
SHIP/SHORE ELECTR ESD SYSTEM A C >1
INHIBIT
TEST
&
SHIP/SHORE PNEUM FORE COMPR DECK ROOM
MANIFOLD PT SD
TEST
CCR WH
ESD SIGNALS TO SHORE (ELECT)
>1
STOP MAIN CARGO PUMPS
OFF
ESD SYSTEM B AFT DECK PT SD
>1
OFF
STOP SPRAY PUMPS
>1 >1 COMP. ROOM 1 2
CARGO TK LIQ. DOME 1 2 3 4
MANUAL RELEASE
CARGO TK GAS DOME 1 2 3 4
PORT 1 2 3 4
1
MANIF. PORT 1 2 3
MANIF. STBD 1 2 3
>1
3
4 TANKS
RESET R
STOP L.D. COPMRESSORS CLOSING MASTER FUEL GAS VALVE
&
B DISAB.
NORMAL ESD A STATUS
VERY HIGH LEV (>99%)
2
>1
3
4 TANKS
TRIM
CLOSING MANIF. VALVES
COMPR. ROOM VENTIL. OFF OVERR. AT SEA A DISAB.
1
2
STOP H. D. COMPRESSORS
>1
S
HYDR. POWER PACK L.P.
1 2 3 4 STARBOARD 1
>1 FUSE PLUGS
HIGH PRESS MANIFOLD
>1 >1
STOP EMERG. PUMP
>1
MAIN SWB POWER FAILURE >1
>1
TANK PRESSURE
0 . 00
>1
HEADER PRESSURE
m
LIST
NORMAL ESD B STATUS
S
0 . 00
DEG
R
WIND SPEED
0 . 00
kn
SECONDARY BARRIER TEMPERATURE ( Co) TANK 4 TANK 3 TANK 2 1 TANK TOP-CENTER -30 -33 -28 2 AFT BLKD-CENTER -50 -36 -35 3 BOTTOM-AFT STBD -41 -63 -83 4 BOTTOM-AFT PORT -58 -55 -42 5 WALL-AFT STBD (UP) -40 -31 -32 6 WALL-AFT PORT (DW) -47 -43 -48 7 BOTTOM-AFT CENTER -103 -101 -94 8 BOTTOM-CENTER -57 -60 -79 9 FORE BLKD-UP -53 -48 -42 10 FORE BLKD-DOWN -44 -52 -50
TANK 2 -117.72 -117.63 -117.64 -117.56
ESD SYSTEM B
21.1
BALLAST-PUMPS
DENS
0 . 00
5
9 2 10
12
8 4
7
3
SECONDARY SPACE
TANK 1 -117.12 -131.69 -162.65 -162.70 -162.59
22.3
TRIM
11
DOUBLE HULL
CARGO TEMPERATURE ( C) TANK 4 TANK 3 TOP -113.19 -115.01 75% -125.20 -127.00 50% -162.73 -162.75 25% -162.71 -162.77 BOT -162.68 -162.71
SEA TEMPERATURE ( C)
DEG
STBD
1
15 . 7 14 . 8 15 . 7 16 . 4 16 . 0 14 . 0
14 . 4 13 . 7 14 . 7 15 . 0 14 . 5 14 . 9
14 . 8 13 . 4 14 . 6 15 . 0 14 . 7 10 . 7
AMBIENT AIR TEMPERATURE ( C)
0.0
PORT
6
DOUBLE HULL TEMPERATURE ( Co) 1 TANK TOP-CENTER 15 . 5 2 AFT BLKD-CENTER 12 . 2 7 BOTTOM-AFT CENTER 15 . 4 8 BOTTOM-CENTER 14 . 8 11 TANK TOP-FORE 15 . 9 12 WALL-CENTRE STBD 16 . 1
ESD SYSTEM A
WIND DIRECTION
TANK 1 -32 -39 -81 -50 -20 -42 -106 -72 -42 -37
m
LIST
0 . 00
WATER PRESENCE INSIDE SECONDARY INSULATION TANK 4 TANK 3 TANK 2 TANK 1 ALARM VERY HIGH ALARM HIGH
T
WATER BARRIER DETECTOR TEST
DEG
WIND SPEED
0 . 00
kn
WIND DIRECTION
0.0
DEG
BALLAST-TANKS
1.025 kg/Cm3
OUT BOARD H
355 H
OUT BOARD
PORT 6.846 m
H
0.0 %
255
0.0 Bar 330
INERT GAS SCRUBBER
4.7%
8.3 %
270
204
H
0.8 A
BALL . P1
BALL . P2
- 0 Bar
REMOTE
REMOTE
AFT PEAK 2.161 m 271.4 m3
TUNNEL SUCTION
0.2 Bar
- 0. Bar
H
340
H H
TK 3 PORT 19.868 m 2835 m3
341
241
H
331
H
H
230
C
CONTROL ACQUIST.
265
H
H
H
240
260
7.410 m 0.1 Bar
DIRECT BILGE SUCTION
Issue: 1
m
LIST
285
295
DEG
WIND SPEED
*****
H
H
320
310
H
H
H
210
200
kn
WIND DIRECTION
118.4 Bar ***
DEG
312
H
232
TK 3 STBD 19.967 m 2849 m3
H
SEA CHEST
322 H
290 HYDRAULIC OIL PRESSURE
0 . 59
311
H
FORE PEAK 13.496 m 976.3 m3
211
H
H
242
TK 4 STBD 1.938 m 844.7 Cm3
H
BALL. TANKS 0 . 25
332
H
H
250
H
TRIM
H
220
202 342
275
221
FWD
H
13%
291 CONTROLS SEL. ECR ****** CROSS OVER
H
321
AFT
H
H
TK 1 PORT 20.175 m 2401 m3
305
0.6 A
H H
231
H
205 201
TK 2 PORT 4.063 m 1525 m3
- 0.1 Bar 350
H
207
TK 4 PORT 2.004 m 874.8 m3
0.0 Bar EDUCTOR
280
H
222
TK 2 STBD 4.118 m 1531 m3
0 . 10
H
H
212
TK 1 STBD 19.634 m 2303 m3
STBD 6.918 m HYDRAULIC OIL PRESSURE
BALL. PMPS. TRIM
m
LIST
0 . 00
6.590 m3
DEG
WIND SPEED
0 . 00
kn
WIND DIRECTION
117.9 Bar 0.0
DEG
Typical System Screen Shots - Page 1
Cargo Systems and Operating Manual
LNG LERICI 3.1.1c Typical System Screen Shots
WU/BO HEATERS
LOW DUTY COMPRESSORS
GLYC. OUTL.
450
MANUAL TRIP H
451
LDC1 ALARMS TRIP EMERG. STOP COMMON ALARM HIGH VIBR.
0 17.1 C 411 mbar
T
-5 %
AUTO
MAN
0.000 RPM
REMOTE 453
FCV
H
LDC 1
LDC1 STATUS READY TO START
GLYC.INL.
CO 105 REMOTE
TAL PAL
C
PAL PALL TAH TAHH
BOILERS AUX LO P
460
GLYC.IN.
REMOTE
PDAL PDALL
063
452
0
16.8 C 62.4 mbar
T 28 %
V. MAIN 454
FVC MANUAL CO
L. MAIN 405
LO SUMP TANK LAL
OIL SUPPLY
GLYC. OUTL. LDC2 ALARMS TRIP EMERG. STOP COMMON ALARM HIGH VIBR.
IGV MANUAL
SEAL GAS
MAN
0.000 RPM
441 TAH -25.0 C TAL
PAL
GLYC.IN.
PAL PALL TAH TAHH
AUX LO P
TVC
REMOTE
PDAL PDALL
HYDRAULIC OIL PRESSURE LIST
0 . 45
DEG
WIND SPEED
0 . 00
kn
WIND DIRECTION
0.7 Bar 5.8 Bar 0.1
DEG
IGV
HDC1 ALARMS TRIP EMERG. STOP COMMON ALARM HIGH VIBR.
MAN
0.00 A
REMOTE HDC1 STATUS
SURGE VALVE
PAL PAL PALL TAH TAHH
REMOTE
PDAL PDALL LO SUMP TANK LAL
OIL SUPPLY HDC2 ALARMS TRIP EMERG. STOP COMMON ALARM HIGH VIBR.
H
1.44 mBar
410
X VIBRATION 0.4 mmE-3
108 DEG
DEG
0 . 00
WIND SPEED
WIND DIRECTION
0.0
DEG
DP PR/MAIN HEADER: 10.5 mBar
NITROGEN SYSTEM
mBar
kn
STOR. TANK
VENT RISER TK3
PORT
TAH L.O.FAL L.O.FAL C.W.FAL TAL VAHH
IN PR.
IN SEC
SPARE
AUTO
AUTO
MANUAL
CO 6.9
CO -4
CO 0.0
SEAL GAS
CO
6.02
0.0
3.04
P
mBar
P
P
mBar
H
501
H
502
M. TRIP TRIP VAC. P1
VAC. P2
REMOTE
REMOTE
NotAv1
NotAv1
TRIPRST
TRIPRST
TAH L.O.FAL L.O.FAL C.W.FAL TAL 1018 mBar 17 0C VAHH
STBD
IGV
OUT PR.
SPARE
IN SEC
AUTO
MANUAL
AUTO
CO -5
CO 0.0
6.00 mBar
SECONDARY HEADER PRIMARY HEADER
REMOTE
mBar 3.21
P
CO -5 P 3.16 mBar
TRIPRST
mBar 5.79 P
MAN
0.00 A
444 mBar 25 . 1 C TAHH TAH
440 TAH 27 C
SURGE VALVE
TAL PAL PAL PALL TAH TAHH
AUX LO P REMOTE
PDAL PDALL
0 . 00
DEG
113 mBar
113 mBar
112 mBar
TK4
TK3
TK2
TK1
80 DEG IGV MANUAL
SEAL GAS
WIND SPEED
CO
0 . 00
kn
Y VIBRATION -0.5 mmE-3
PDALL
PDALL
6.08 mBar 3.44 mBar
0.0
REMOTE
LOADING LIST
112 mBar H
212 mBar
420
LO SUMP TANK LAL
OIL SUPPLY
Issue: 1
0 . 00
HYDRAULIC 107 Bar OIL PRESSURE 121 Bar
LOCAL
H
HDC2 STATUS
0 . 00
LIST
24.0
0.0
MANUAL
HDC 2
LOCAL
TRIM
0 . 00
TAL
AUX LO P
CO
MAIN VAP.
1.10 mBar 24.4 C TAHH TAH
430 TAH 26 C
TRIM
N2 PROD. PLANTS FAIL 1 FAIL 2 COMM.ALARM 1-2
H
HDC 1
OIL SUPPLY
SEAL GAS
421
SET TIME
MANUAL
LOADING
ATM.PF 1017
HIGH DUTY COMPRESSORS
LO SUMP TANK LAL
H
0 . 61 mBar X VIBRATION - 0 . 2 mmE-3
107 DEG
REMOTE
0 . 25 m
CO 58 ********
GLYC.INL.
GLYC. SYS.
MANUAL
1 . 10 mBar SURGE 25 . 5 C VALVE TAHH TAH
72
72 %
GAS ONLY
12.0
0.0
REMOTE
LDC 2
LDC2 STATUS
REMOTE
TRIM
CO
H
REMOTE
WU/BO HEATER 2
411
X VIBRATION 16 . 2 mmE-3
108 DEG
SET TIME
TVC
MANUAL TRIP
H
98 . 7 mBar
0
105 %
H
SURGE VALVE
19.5
WU/BO HEATER 1
REMOTE
461 mBar 16.4 C TAHH TAH
431 TAH 0.0 C
HYDRAULIC OIL PRESSURE WIND DIRECTION
107 Bar 121 Bar 0.0
DEG
TEMP.NON.
TRIM
0.24 m
5.78 mBar 3.65 mBar
PDALL
PDALL
6.14 mBar 3.42 mBar
5.89 mBar 2.67 mBar HYDRAULIC OIL PRESSURE
MAIN VAP..
LIST
0.32
0
SB
WIND SPEED
0.00
kn
WIND DIRECTION
0.87 Bar 4.38 Bar 0.1
DEG
Typical System Screen Shots - Page 2
Cargo Systems and Operating Manual
Illustration 3.2.1a Control Room Layout
LNG LERICI
Forward
Fans Shut Down
Tecnoco Nitrogen Generator Control Panel
ESDS Panel
Load Master Monitor
Overhead Schematic Cargo/Ballast Status Board
Elsag Bailey I.O.s
Foxboro Custody Transfer System
Mooring Control Printer
LD No 1 Surge Control
Load Master Printer Foxboro CTS Monitor
Automatic Winch Control
Elsag Bailey Screen Shot Printer LD No 2 Surge Control
Log Printers
Elsag Bailey IMS Monitors Ship Net Computer
CCTV
Elsag Bailey IMS Monitors
U.P.S
Foxboro CTS Printer
HD No 1 Surge Control
Cargo Control Console
99% and 98.5% Cargo Tank Level Alarm
Foxboro CTS Backup Computer Fire Push Button
Electric Motor and Compressor Room Fire Mimic
Inert Gas Indicator
Winch Monitoring System
HD No 2 Surge Control
CCR Air Conditioning
ICARE Primary and Secondary Insulation Space Gas Detection System
Issue: 1
3.2.1 Control Room Layout
Cargo Systems and Operating Manual 3.2
Cargo Control Room, Cargo Console and Panels
(See Illustration 3.2.1a) Supervision of all cargo handling operations is carried out from the Cargo Control Room (CCR): located on deck B of the accommodation block with a forward looking view. The CCR houses the Cargo Console and the control cabinets for the ELSAG Bailey (IMS) (see 3.1) a printer desk, control cabinets for the Emergency Shut Down System (ESDS), and the analyser cabinet for the ICARE Gas Detection system.
Analogue Gauges For Cargo Pumps
LNG LERICI
The Cargo Console is situated on the starboard forward side of the CCR and contains the following: 1 Two IMS operator stations; 2
One operator station for the Custody Transfer System (CTS) (see 3.3);
3
A CCTV monitor showing the port and stbd manifold areas and trunk deck area.
4
Master fuel gas and nitrogen injection valve control.
5
Automatic winch control.
6
CETENA Loadmaster station
7
ESDS panel
Distributed Control System
Alarm Indication Panel
Track ball
Manual trip button
9
Analogue gauges for the main cargo pumps, stripping/spray pumps and auxiliary cargo pump, a wind speed and direction indicator, and analogue cargo tank level indicators.
Printing facilities for 1 and 2 are located on a desk on the starboard bulkhead.
CCTV
Distributed Control System
Load Master
Keyboard
8
ESDS Panel
Telephone Ship to Shore Communication (Hot Line)
Custody Transfer System
Automatic Winch Control
Master Fuel Gas and Nitrogen Injection Valve Controls
Track ball
Selection Switch For Emergency Cargo Pump Manual Trip Buttons
Issue: 1
3.2 Cargo Control Room, Cargo Console and Panels - Page 1
Cargo Systems and Operating Manual 3.3
Custody Transfer System
Introduction (See Illustration 3.3.2a) LNG is bought and sold on its calorific content, normally expressed in Btu’s rather than on a volume or weight basis. However, at the present time there are no practical instruments available to determine the net calorific content transferred during loading and discharge so that for the moment this value is determined partly by measurement and partly by analysis of cargo calculation by means of the following formula: Total energy transferred Q
=
Vd HL
-
VTsPvHv TvPs
3.3.1 Custody Transfer Measurements The Foxboro Custody Transfer CT-IV System provides the high accuracy measurements and data logging of levels, temperatures and pressures required for the calculation of total LNG Cargo loaded or discharged. All Custody Transfer Measurements can be displayed on a video monitor and in addition liquid level measurements of each tank can be individually displayed on the remote 4-Digit. LED-Type digital indicators. The system automatically scans and prints the values of the selected measurement. In addition, the data is converted to volumetric and mass measure, corrected for the ship’s list and trim based on manual and automatic inputs from a software configured to handle various functions.
where : The software configuration includes : V = the apparent volume of cargo loaded or discharged at an average temperature Tl (m3) d = density of cargo at temperature Tl (kg/m3) HL = the gross calorific value of the cargo calculated from the component analysis of the cargo (Btu/kg) from mean value of loading and discharge sample (MLNG uses MJ/kg) Ts = standard temperature (°K) Tv = average temperature of gas in the cargo tanks either before loading or after discharge (°K) TL = average temperature of liquid in cargo tanks either before loading or after discharge Pv = the absolute pressure of the gas in the cargo tanks, that is, gauge pressure of gas + barometric pressure (mbar) Pv = standard atmospheric pressure (1013mbar) Hv = the gross heating value of gas vapour at 15.6°C and 1013mbar (Btu/m3). This value is assumed to be a constant 36,000 Btu/m3 based on pure methane (MLNG uses Btu/scf) In establishing the value of the cargo transferred to and from the ship, the vessels responsibility is limited to measurement/calculation of the following values: V, Tv, Pv. These measurements/calculations are made by ship and shore representatives and are normally verified by an independent surveyor. The values HL and d are determined ashore at the loading and discharge ports and the calculations are completed by the buyers and sellers. The quantity of cargo delivery is expressed in MMBtu or tonnes.
Issue: 1
1
2 3 4
manually input density data representative of the total cargo from a cargo composition library stored in memory (up to 10 composition and density values is available). 2 analog inputs for list and trim. volume expression in cubic metres mass expression in tonnes.
Custody transfer measurement takes place before and after loading and discharging. During gauging, all cargo systems on the ship should be closed and the shore connections isolated or disconnected. No ballast operations should take place during measurement and the vessel should, if possible, be on even keel and upright. However, the operation can be conducted with a slight trim if the corrections included in the tank calibration tables are applied. Custody Transfer Documents are produced detailing the volumes of cargo and vapour transferred during both loading and discharge operations. Level measurement The level measurement system consists of a long coaxial sensor installed in the tank and extends over the full depth in which the level is to be measured. The liquid level is determined by measuring the electrical capacitance of the sensor segment intersecting the liquid level. The capacitance of this segment is compared with the capacitance of a reference segment located below the liquid surface. The ratio of these two measurements results in the accurate determination of liquid level that is
LNG LERICI independent of liquid properties such as dielectric constant, temperature and density. This ratiometric method of cargo level measurement includes an innovative calibration assurance feature incorporated to maintain the accuracy of the level measuring sub system; this system is called the ON-LINE Validation System. The level measurement accomplished provides an accuracy of ± 7.5mm over the entire gauging height. The display resolution is 1mm at the system workstation and printer. In the event of failure of the level sensing devices, the HSH 806 float gauges may be used for level measurement providing that approval is given by the shore representatives. The accuracy of the float gauge is the same as the capacitance gauge.
! CAUTION To avoid failure the float of the float gauge must be maintained blocked at the top position except when during the actual measurement. The total gross number of cubic metres of cargo in the tanks before and after loading or discharging is calculated using the average level reading determined. This volume is corrected for heel, trim, volume, vapour pressure and cargo and vapour temperatures. The difference in these volumes at the start and end of the operation will be taken as the apparent volume (m3) of cargo delivered.
Although the temperature variation over the depth of liquid should be no more than a fraction of a degree, the variation of vapour temperature, particularly at the end of discharge, will be more pronounced. Pressure measurement Absolute pressure measurement in each of the cargo tank is determined by intelligent pressure transmitters. The accuracy of the measurement is ± 0.1% of span to a resolution of 1mb at system workstation and printer. Range of measurement is 800 to 1400mb. Ambient temperature effect on the transmitter is ± 0.2% per 55°C change between limits of -30°C and +60°C. 3.3.2 Independent Very High Level Alarm System Two very high level alarms per tank are provided by independent point sensing elements. Fixed sensors inside the cargo tanks detect the cargo at predetermined levels and system accuracy is ± 6mm. The very high alarm adjusted at 98.6% of the tank height, when activated will close the corresponding tank filling valve. The very very high alarm adjusted at 98.5% of the tank height, when activated will initiate an Emergency Shut Down Alarm (ESD) (refer to Section 5.2). This involves the shutting of manifold and tank loading valve of the tank in question. DCS has facilities to inhibit at 98.5 and 99 to allow opening of tank valve during the level alarm testing. In addition, a blocking function is provided to allow all cargo tank level alarms to be overridden when at sea.
Temperature Measurement Temperature measurement is accomplished by means of Platinum Resistance transducers (500ohms) providing an accuracy of ± 0.2°C from -165°C to 145°C, ± 0.3°C up to - 120°C and ± 1 - 5°C up to + 80°C. Data is displayed at the system workstation and printer with a resolution of 0.01°C. There are five active and five spare temperature sensors in each tank and each reading is recorded. The determination of whether the temperature point is in vapour or liquid will be made from the liquid level indication. It is safe to assume that any point that indicates a temperature of more than 3° above the LNG temperature must be in the vapour space.
3.3 Custody Transfer System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 3.3.2a CTS Measurement Feed Through Local Level Indicator Coaxial Cables to Control Unit via Zener Barriers
Level Gauge
Liquid Dome
100% High Sensing Range
99% High Segment 98.5% 6" Full Bore Ball Valve
75%
Middle Segment 4 Per Tank Weather Deck 50%
Insulated Support Brackets
Mid Sensing Range
Tank Ceiling
Primary Barrier
25% Low Segment
HSH 806 Level Indicator Tank Bottom
Issue: 1
Low Sensing Range
Column Support 0%
3.3.2a CTS Measurement
Cargo Systems and Operating Manual
LNG LERICI
Illustration 3.3.2b Cargo Tank Temperature Measurement
Port
Starboard Key
1
Secondary Space Double Hull
11
5
9 2 12 10
Secondary Barrier Temperature °C 1 Tank Top Centre 2 Aft. Bulkhead Centre 3 Bottom Aft. Stboard 4 Bottom Aft.Port 5 Wall Aft. Starboard (Up) 6 Wall Aft. Starboard (Down) 7 Bottom Aft. Centre 8 Bottom Centre 9 Forward Bulkhead Up 10 Forward Bulkhead Down Double Hull Temperature °C 1 Tank Top Centre 2 Aft. Bulkhead Centre 7 Bottom Aft. Centre 8 Bottom Centre 9 Forward Bulkhead Up 11 Tank Top Forward 12 Wall Centre Stboard
6 8 7 4
Issue: 1
3
3.3.2b Cargo Tank Temperature Measurement
Cargo Systems and Operating Manual
LNG LERICI 3.3.3a Cargo Record Sheet
CARGO RECORD
TRANSPORTI MARITTIMI LNG/C ...................................................
PORT ................................................
N˚ .....................
DATE.................................................
CARGO VOLUMES WHEN VESSEL IS LOADED VESSEL LIST ......
VESSEL TRIM ................
Cist. N˚
LIQUID LEVEL IN METRES
Tank N˚
Gauge Reading a
Trim Correction b
List Correction c
Tape Correction d
Liquid Average Temperature -˚C
Correct Level e
LIQUID VOLUME IN CUBIC METRES Volume At -160˚C
Multi Temperature
Correct Volume f
VAPOUR SPACE Average Vapour Temperature ˚C
Pressure mm H2O
Tank Capacity m3
Vapour Volume m3
1-S 1-D 2-S 2-D 3-S 3-D 4-S 4-D
CARGO VOLUMES WHEN VESSEL IS EMPTY VESSEL LIST ......
VESSEL TRIM ................
Cist. N˚
LIQUID LEVEL IN METRES
Tank N˚
Gauge Reading a
Trim Correction b
List Correction c
Tape Correction d
Correct Level e
Liquid Average Temperature -˚C
TOTAL .................................
AVG ...............
AVG ...............
DATE ...................................
FACT ..........................
LIQUID VOLUME IN CUBIC METRES Volume At -160˚C
Multi Temperature
Correct Volume f
TOTAL ..........................
CORRECTED TOTAL ....................... VAPOUR SPACE
Average Vapour Temperature ˚C
Pressure mm H2O
Tank Capacity m3
Vapour Volume m3
1-D 1-S 2-D 2-S 3-D 3-S 4-D 4-S
TOTAL .................................
AVG ...............
AVG ...............
FACT .......................... SPECIFIC GRAVITY Tank N˚
Reading g
NET LIQUID CARGO VOLUME
VAPOUR DISPLACEMENT
(Difference between loaded vessel and empty vessel corrected liquid volumes)
(Difference between empty vessel and loaded vessel corrected vapour volumes)
TOTAL ..........................
CORRECTED TOTAL .......................
1-D 1-S
CUBIC METRES
h
THERMIES
i
BTU
j
METRIC TONS
k
2-D 2-S
CUBIC METRES
3-D 3-S 4-D 4-S Avg.
Issue: 1
Cargo Record Sheet - Page 1
Cargo Systems and Operating Manual 3.3.3 Failure of CTS Computer If the computer should fail during custody transfer, it is usually still possible to read and record the individual level, temperature and signal readings from the local digital read-out panels otherwise the levels have to be measured using the HSH 806 float gauges. The volume calculations and corrections have to be made by hand using the hard copy of the tank gauge tables.
The sum total of column [f] will give the total contents of the tanks.
The Cargo Record report sheet is used in conjunction with the gauging tables, which contain the correction figures for Trim, List, Bottom Fine Gauging and Thermal (level gauge) of each individual tank, to give the accurate values of the cargo C.V, Btu, m3 and metric tons.
The loading terminal will give the ship the specific gravity valve of the LNG cargo, filled in column [g] and the PCS value.
The ships trim, list, local tank gauge readings, average tank temperature, vapour space temperature, cargo specific gravity figures are required. With these figures proceed as follows.
The Thermie of the cargo is calculated as follows:-
Under trim correction table (for relevant tank): The gauge reading is read from the right hand side (interpolate gauge figure), the actual gauge figure is filled in column [a]. Move across the page until below the trim value of the ship (interpolate trim figure). The correction value in mm will also require interpolation (a +ve value is by the head and a -ve value is by the stern). Insert correction value in column [b]. Under list correction table (for relevant tank): The gauge reading is read from the right hand side (interpolate gauge figure). Move across the page until below the actual list value of the ship (interpolate list figure). The correction value in mm will also require interpolation (a +ve or -ve value correction value is given). Insert this value in column [c].
LNG LERICI
The net liquid cargo volume, value [h], is the subtraction of the remaining volume after discharge, from the loaded volume. [f]
net
= [f]
loaded
-[f]
discharged
Ship’s Figures
Specific gravity [g] x PCS x net liquid cargo volume [h] = Thermies The Btu of the cargo is calculated as follows:Thermie ÷ 0.252 =Btu This figure inserted in [J]. The metric tons of the cargo is calculated as follows:m3 [h] x specific gravity [g] = metric tons This figure is inserted in [k]. When the computer is back on line it can be used in the manual mode to perform the level calculations.
Under thermal correction table (for relevant tank): The gauge reading is read from the right hand side (interpolate gauge figure). Move across the page until below the vapour temperature (interpolate temperature figure), the actual vapour temperature figure is given in column [v]. The mm correction figure is +ve and filled in column [d]. The correct tank level value to be inserted into column [e] can now be calculated as follows:e = a+b+c+d From this gauge corrected figure [e], using the Bottom Fine Gauging Table, an accurate volume (m3º) of each tank is established, which is inserted in column [f].
Issue: 1
3.3 Custody Transfer System - Page 2
Part 4 Cargo Operations
Cargo Systems and Operating Manual
LNG LERICI Illustration 4.1 Basic Cargo Operations Sequence Chart
PART 4: CARGO OPERATIONS 4.1 Overview Operating Procedures Introduction In normal service, each operating procedure will be followed by a subsequent procedure (See Illustration 4.1 Basic Cargo Operations Sequence Chart) necessitating that some valves will be left open. For ease of explanation, it is assumed that, although unlikely, all valves are closed at the beginning of each operating procedure, unless otherwise stated. Note: Before commencing any operation it is important to check that reversible bends are in the correct positions so that all tanks are in communication with the appropriate vapour and liquid headers.
Heating Cargo Tanks
Ballast
Discharging with Gas Return from Shore
4.2.3a
Gas Freeing Cargo Tanks 4.3.7a Discharging without Gas Return from Shore
4.4.1a
! CAUTION Before removing any reversible bend it is imperative to ensure that the pipeline and bend is inerted to prevent the pipeline being opened in a gaseous condition. After changing the bend it is again necessary to inert the section of pipeline in order to prevent the possibility of an air/gas mixture and ice being formed.
Return Voyage in Ballast with Gas Burning
see Note!
In the following procedures, the principal cargo lines, headers, pumps, heat exchangers and compressors are shown in a simplified perspective view with colours designated to represent specific flows. The valves involved in the operation are coloured in accordance with the process flow and it should be recognised that while liquid, vapour and other fluids may be present in other parts of the lines, only the main flows associated with an operation are shown.
Issue: 1
Deballast
Loaded Voyage Without Gas Burning
4.4.16a
Loading with/without Ship Compressors
Loaded Voyage with Gas Burning
Aerating Cargo Tanks
4.3.8a
Evacuating Insulation Spaces
4.3.1
4.2.4
All valves involved in an operation are annotated with valve designation in the colour of the process flow.
Note: This is if the trade route is through the Suez Canal, were charges would be made if gas were held in the tanks.
4.3.6a
DRYDOCK
4.2.1b 4.2.1c
Drying Cargo Tanks
4.3.3a
Inerting Cargo Tanks
4.3.3b
Purging Cargo Tanks with Cargo Vapour
4.3.4a
Cooling Down Cargo Tanks
4.3.5a
4.2.2a 4.2.2b
4.1 Overview Operating Procedures - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.1a Cargo Lines Cooldown 101 117
161 003
103 105
001
163
489
053
051
401 007
107
005
167
114
481
491 119
171 012
173
116
011 112
166 057
118
115
164
501
165
113
482
162
062
055
487
168
124
177 129 022
127
111
486 Vent Gas Heater
128
126
484
485
Vapour Dome
Liquid Dome
021
170
403
483
492
125
013 010
110
175
122 123
023 020
120
Vapour Dome
Liquid Dome 121
2
160
1
137 134 493 139
138
135
032
190
1
033 030
130
063
1
T
2
132 133
k an
136
031
Vapour Dome
Liquid Dome 404
180
131
090
172
000
494
061
152
574
405
144
Jettison
147
149 145
041
148
2
176 156
043 040
140
102
Vapour Dome
1
400
056
178 058
Liquid Dome
Dual Purpose Heaters
453
141
406
460
502
002
006
104
488
155
158
402
2 nk a T
004 004
153
142
143
151
054 154
146
042
052 052
174
106
008 157
TCV 454
108 FCV 451
FCV
To Insulation Spaces
2
450
TCV
470
k an
410 452
HD Compressor No. 1 (Inboard)
Degassing line into Main Cargo Pump Cable Penetration
455 FCV
430 FCV
To Engine Room
Forcing Vaporiser
TCV
440
Key
T
420
1
3
411
FCV FCV
Demister
Inert Gas from Engine Room
AW/912
LNG
456 TCV 421
HD Compressor No. 2 (Outboard)
k an
T
4 LD Compressor No. 1 (Inboard)
480
431 FCV
LNG Vapour Main Vaporiser
441 FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.2.1a Cargo Lines Cooldown
Cargo Systems and Operating Manual 4.2
4.2.1 Loading It is assumed that all preparatory tests and trials have been carried out as per section 4.2.10 on the ballast voyage prior to arrival at the loading terminal • All operations for the loading of cargo are controlled and monitored from the ship’s Cargo Control Room. The loading of LNG cargo and simultaneous deballasting are carried out in a sequence to satisfy the following:
•
•
•
•
header is maintained by adjusting the compressor flow.
Normal In-Service Operations
• The Cargo tanks are filled at a uniform rate. • List and trim are controlled by the ballast tanks. • The cargo tanks are to be topped off at the fill heights given by the loading tables. • During topping off, the ship should have a trim limited 1m by the stern, but if possible kept on an even keel. • During the loading, the ship may be trimmed according with terminal maximum draught, in order to assist in emptying the ballast tanks. • The structural loading and stability, as determined by the loading computer, must remain within safe limits. An officer responsible for the operation must be present in the Cargo Control Room when cargo is being transferred. A deck watch is required for routine checking and/or any emergency procedures that must be carried out on deck during the operation.
•
The cargo tanks must be maintained in communication with the vapour header on deck, with the vapour valve on each tank dome open.
•
The vent mast No. 2 is maintained ready during the loading operation, for automatic venting, as a back up, with the vent heater in service.
•
If the tanks have not been previously cooled down, LNG spraying is carried out.
Alongside Terminal •
Connect and bolt up the shore ground cable.
•
Connect and test the shore communication cable.
•
•
During the loading operations, communications must be maintained between the ship’s Cargo Control Room and the terminal: telephone and signals for the automatic actuation of the Emergency Shutdown from or to the ship. At all times when the ship is in service with LNG and mainly during loading, the following are required: • The pressurisation system of the interbarrier spaces must be in operation with its automatic pressure controls. • The secondary Level Indicating system should be maintained ready for operation . • The temperature recording system and alarms for the cargo tank barriers and double hull structure should be in continuous operation. • The gas detection system and alarms must be in continuous operation. Normally when loading cargo, vapour is returned to the terminal by means of the HD compressors or shore compressor. The pressure in the ship’s vapour
•
• Test the telephone for normal communication with the terminal. • Test the back up communication arrangements with the terminal. • Change over the blocking switch for the shutdown signal from the terminal, from the blocked to the terminal position. Connect the terminal loading arms to the four LNG crossovers and one vapour crossover. This operation is done by the terminal personnel. • Check that the coupling bolts are lubricated and correctly torqued. In the cargo control room (Cargo Control Room), switch on the cargo tank level alarms and level shutdowns which are blocked at sea: • Switch the Very High Level alarm from blocked to normal on each tank. • Switch the High and Low Level alarms from blocked to normal on each tank. • Verify that alarms for Level Shutdowns blocked are cleared. • Connect the nitrogen purge hoses to the crossover connections 108, 106, 104, 102 (or 107, 105, 103, 101) and 488 (or 489), then purge the air from each loading arm. • Pressurise each loading arm with full nitrogen pressure through the purge valve, and soap test each coupling for tightness. Bring the ship to a condition of no list and trim, and record the arrival conditions for custody transfer documentation. Official representatives of buyer and seller are present when the printouts are run.
LNG LERICI Cargo lines cool down: • Assuming the ship is starboard side alongside.
•
•
• Open valves, 180,170,160. • On each vapour dome open the following valves to allow the supply of LNG to the spray rings:-114, 117, 118, 124, 127, 128, 134, 137, 138, 144, 147 and 148. • Open the vapour manifold valve 402. • Open manifold valves, 157, 158, 155, 156, 153, 154, 151 and 152, which will allow liquid into the stripping/spray main via cross over valve 160. Assuming that the aft loading arm is the first to be cooled down • Open liquid manifold valve 058. • Crack open the liquid filling valves 010 and 040 for tanks No.1 and 4. Inform the terminal that the ship is ready to receive LNG.
Open valve 052
•
Slowly increase the terminal pumping rate until the liquid main and spray headers have cooled down (approximately 15/20 minutes).
Note: In order to avoid the possibility of pipe sections hogging, the liquid header and crossovers must be cooled down and filled as quickly as possible. • Open the filling valves to the tanks 040, 030, 020 and 010 fully. • On completion of the loading arms cooldown •
Open liquid manifold valves 056, 054, 052 and the LNG manifold quick closing valves 006, 004 and 002.
•
Inform the terminal to increase the loading rate to the ships maximum capacity.
•
• Close valves 152, 154, 156 and 158. On each tank keep open the stripping/spray valves to the spray rings in order to avoid over pressure due to line warm up.
• Open the LNG quick closing valve 008 on the liquid manifold. • •
The terminal should be instructed to begin pumping at a slow rate for approximately 15 minutes, in order to gradually cool down the terminal piping and the ships headers.
Start one HD compressor and adjust the flow rate to maintain the tank vapour pressure at 20/25 mbar g.
+ 40
TYPICAL COOLING-DOWN CURVES (INVAR MEMBRANE NO-96 SYSTEM)
+ 30 + 20 + 10 0
Main Assumptions :
- 10
Cooling-Down performed in 10 hours and requiring about 500 - 800 m3of LNG Primary membrane temperature = average temperature given by sensors on tripod mast (uppermost + lowest)/2
- 20 - 30 - 40 o
C
- 50 Legend :
- 60
Previous cooling-down curves observed on 'Methania' and MISC 'Tiga' series ships
- 70 - 80
Cooling-down curve observed on 'Hanjin Pyeong Taek' (gas trials, tank No. 3)
- 90
Selected cooling-down curve for new 130,000 - 138,000 m 3 class LNG carriers
- 100 - 110 - 120 - 130 - 140 0
Issue: 1
•
1
2
3
4
5
6 Hours
7
8
9
10
11
12
4.2 Normal In-Service Operations - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.1b Loading With Vapour Return To Shore Via Ship HD Compressor 161 003
001 491 051
401 164 007 167
005
165
057
055
Vapour Dome
010 Liquid Dome
492
Vent Gas Heater
403
Vapour Dome
020 Liquid Dome
2 1 493
k an
T
2 030
1
1 Vapour Dome
Liquid Dome 404
k2 n a
152
494 052
Jettison
151
054 102 154 004
153
2 156 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1
502
T
002
402
104
056 058
406
488
155 106
158
006 008 157 108
To Insulation Spaces
2
k an
410
HD Compressor No. 1 (Inboard)
420
1 430 FCV
To Engine Room
Forcing Vaporiser
T
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
440 FCV
LNG
Demister
Inert Gas from Engine Room
Anti-Surge Control
LNG Vapour
HD Compressor No. 2 (Outboard)
k an
T
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.2.1b Loading With Vapour Return To Shore Via Ship HD Compressor
Cargo Systems and Operating Manual To Load Cargo with Vapour Return to Shore Via HD Compressor It is assumed for clarity of the description that all valves are closed prior to use and that the ship is stb’d side alongside. 1 Checks to be made before cargo operation: Test remote operation of all tank valves and manifold crossover valves. Test remote operation of ballast valves. Test HD Compressors, ballast pumps, safety systems and bulkhead heating systems.
9
2
Safety precautions: Ensure hull water curtain is in operation on stb’d side. Prepare fire fighting equipment, water hoses and protective clothing for use. In particular the manifold dry powder monitors should be correctly aligned ready for remote operation. Ensure the water spray system on deck is ready for operation, filters installed and off shore blanks removed.
11 Increase loading rate.
Prepare both HD Compressors YA/5121 A&B for use with seal gas and lub oil system in operation. (See 2.7)
14 Monitor tank pressures in order to achieve a pressure of about 80mbar.g. Open valve 404 vapour header to compressors and valve 406 on the compressors discharge side. Start one or both HD compressors as necessary. Close valve 403 vapour header to crossover.
3
4
5
6
Nitrogen system: Ensure that nitrogen storage tank is at maximum pressure and that the two nitrogen production plants are ready for use. • Arrange nitrogen piping to preferentially feed the primary insulation spaces. • Open the additional supply valves 561, 564. • Adjust set point of the nitrogen supply regulating valves 530, 510 at 6mbar.g and 520 at 3mbar.g. • Adjust set point of the nitrogen regulating relief valves, primary insulation space, 540 at 8mbar.g and secondary insulation space, 560 at 5mbar.g.(see illustration 4.2.1b) Switch on unblocking level alarms in the Custody Transfer System and run custody transfer print-out for official tank gauging. Open gas outlet valves on tank gas domes (normally these valves are left open).
8
- communications with shore. - ship/shore electrical and pneumatic connection and safety devices ESDS. - carry out safety inspections. Complete the relevant ship/shore safety checklist. 10 Open filling valve of tank No.4 and tank No. 1 fully, 040 and 010. Open filling valves of tank No. 2: 020, and tank No. 3: 030: (see cargo line cooldown)
12 Start deballasting programme. Keep draught, trim and hull stresses within permissible limits by controlling deballasting. Refer to trim and stability data provided. 13 Start bulkhead heating in cofferdams. This should already be running in automatic.
15 Adjust opening of tank filling valves to maintain even distribution. 16 Ease in the filling valve of each tank as the tank approaches full capacity. Arrange to terminate tanks at 15 minutes intervals. 17 Level alarms. When any tank approaches 95% capacity inform shore.
The high and very high level alarms and shut downs are emergency devices only and should on no account be used as part of the normal topping-off operation 18 Before topping-off the first tank, request shore to reduce loading rate and continue reducing when topping off each following tank. When a tank is at its required level, close the corresponding loading valve
Issue: 1
21 On completion of draining loading arms, close the liquid manifold ESDS valves. The shore lines are now pressurised at 2 to 3 bar with nitrogen. Open the manifold ESDS by pass valve 151, 153, 155, 157 to allow the nitrogen to flush the liquid into No. 4 tank. Close the by pass valves when the nitrogen pressure has fallen to 0 bar. Repeat the operation 3 times, or until no liquid remains in the manifold lines. The purging of the liquid lines should be carried out one at a time. When gas readings obtained from an explosimeter are less than 50% LEL at the vent cocks, all valves are closed and the loading arms are ready to be disconnected. Leave loading valve of tank No. 4 (040) open until the piping has returned to ambient temperature.
22 Tank level alarms.
Tank No. 2: 492
On high duty gas compressors open valves 410, 420, 430, 440.
20 Liquid lines including the horizontal part of the manifolds will automatically drain to tank No. 4. The inclined parts of the manifold are purged inboard with nitrogen.
Close valve at correct filling limit capacity (see filling diagram). High level alarm will sound at 98.5% capacity and filling valve concerned will automatically close. Very high level alarm will operate at 99% capacity and will initiate the Emergency Shut Down System.
27 Open valves necessary to allow warming up. These are normally the loading valves, pump discharge valves and spray valves on the tank domes.
19 Stop loading when the final tank reaches a capacity according to the filling chart, minus an allowance for line draining and leave the tank loading valve open (040).
In Cargo Control Room:
! WARNING
Tank No. 4: 494 Open vapour crossover valve 403.
tank No. 1: 010, tank No. 2: 020, tank No. 3: 030. It is convenient to finish loading by tank No. 4 for ease of line draining, leave a capacity of 50m3.
Standby valve before level approaches about 97%.
Tank No. 1: 491
Tank No. 3: 493 7
Check - connection of liquid and vapour arms.
LNG LERICI
Inhibit independent level alarms prior to proceed to sea. 23 Complete deballasting operation to obtain an even keel situation for final measurement. When measurement is completed adjust ballast tank levels for sailing condition. 24 Stop the HD compressors just prior to sailing, before closing vapour manifold ESDS valve 402 for nitrogen purging and disconnection of loading arms, If departure is delayed, the vapour return to shore should be continued. 25 Disconnect vapour arms. 26 Prepare cargo system for gas burning at sea.
4.2 Normal In-Service Operations - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.1c Loading With Vapour Return To Shore Via Shore Compressor 003
001 491 053
007
501
005
057
051
055
Vapour Dome
010 Liquid Dome
492
Vent Gas Heater
403
020
Vapour Dome
Liquid Dome
2 1 493
k an
T
2 030
1
1 Vapour Dome
Liquid Dome 404
k2
n Ta
494
Jettison
2 502 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1
402
056 058 006 008
k3
To Insulation Spaces
2
n Ta
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
LNG Vapour
HD Compressor No. 2 (Outboard)
k an
T
Degassing Line Into Main Cargo Pump Cable Penetration LNG
Demister
Inert Gas from Engine Room
Key
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.2.1c Loading With Vapour Return To Shore Via Shore Compressor
Cargo Systems and Operating Manual
LNG LERICI
Loading with Vapour Return To Shore Via Shore Compressor The loading with vapour return via shore compressor is the same as normal loading except that the ships H.D. compressors are not used. Instead the vapour header cross over valve 403 is opened and vapour supply to the ships H.D. compressors isolating valve 404, is closed. The vapour now returns directly from the vapour header to the manifold line. The pressure in the tanks is maintained at a safe level by shore control of the terminal compressor, which draws the vapour directly from the ship.
Issue: 1
4.2 Normal In-Service Operations - Page 3
Cargo Systems and Operating Manual
LNG LERICI Excess Nitrogen Is Vented To Mast 1
Illustration 4.2.1d Nitrogen Setting Up During Loading
No 1 Cofferdam Insulation Spaces Exhaust Control No 2 Cofferdam
552 554
540
557 550
560 556 512
551 553
555 511
501
No 3 Cofferdam
522
No 4 Cofferdam 521
To No 1 Tank Secondary Space 532 No 5 Cofferdam
1 k n Ta
531 Primary Space 542 574
541
To No 2 Tank Secondary Space
Supply from Nitrogen Storage Tank
Secondary Space
563 Vacuum Pump (Inboard)
562 572
567
530
566
AW/827VX AW/826VX
510
561 520
571
564
Vacuum Pump (Outboard)
502
565 568
569
Main Vaporiser
T
k an
3 Liquid Nitrogen Shore Supply
Key Nitrogen To Secondary Insulation Spaces
To No 4 Tank Secondary Space
4 nk a T
Issue: 1
k2
n Ta
To No 3 Tank Secondary Space
Nitrogen To Primary Insulation Spaces
4.2.1d Nitrogen Setting up During Loading
Cargo Systems and Operating Manual Nitrogen Setting Up During Loading The operating procedure for the normal inerting is as follows (see illustration 4.2.1d). 1
Start one nitrogen generator to pressurise the buffer tank. The pressure drop in the buffer tank actuates the starting of the generator. In the case of a large nitrogen demand, the stand-by generator will automatically start.
2
Adjust the set point of the nitrogen supply regulating valves 520 to the secondary header at 2 mbar and 510 to the primary header at 4mbar.
3
At the forward part of the trunk deck, ensure that the valves 551, 552, 556, and 557 are open.
LNG LERICI
In this respect, it should be recalled that this membrane is subjected to a -800mbar gauge vacuum pressure - both during global testing at the construction stage and also for the insulation spaces cycles purging.
4
Adjust the set point of the nitrogen exhaust regulating valves 540 (primary) at 6mbar and 540 (secondary) at 4mbar. If either the supply or exhaust regulating valves fail, the the stand-by regulating valve can be brought into operation, 530 (supply) and 550 (exhaust). Under normal operations these valves are left isolated. In cases where other consumers reduce the availability of nitrogen for the insulation spaces, the pressure may temporarily fall below the atmospheric pressure.
This condition is NOT CRITICAL insofar as the differential pressure (Ps - Pp) between the secondary spaces pressure (Ps) and the primary space pressure (Pp) does not exceed 30mbar: (Ps - Pp) < 30mbar
! WARNING When the depression in the primary insulation spaces relative to the secondary insulation spaces reaches 30mbar, the two insulation spaces shall be immediately inter-connected - which will involve a manual operation. When put in communication and therefore subjected to the same nitrogen pressure, the primary and secondary insulation spaces can withstand a large depressurisation without any damage. It should be noted that, even with the tanks fully loaded, a pressure lower than atmospheric pressure in the primary insulation spaces is not harmful to the primary membrane.
Issue: 1
4.2 Nitrogen Setting Up During Loading - page 4
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.2a Cargo Tank Stripping With Other Tanks In Service 101 117
161 003
103 105
001 162
163
489
053
051
401 007
107
005
167
114
481
491 119
171 012
173
116
011 112
166 057
118
115
164
501
165
113
482
062
055
487
168
124
177 129 022
485
111
486 Vent Gas Heater
128
126
Vapour Dome
Liquid Dome
484
021
170
403
483
492 127
125
013 010
110
175
122 123
023 020
120
Vapour Dome
Liquid Dome 121
2
160
1
137 134 493 139
138
135
032 031
190
1
033 030
130
063
1
T
2
132 133
k an
136
Vapour Dome
Liquid Dome 404
180
131
090
k2 n a
172
000
494
061
152
480
405
144
Jettison
147
149 145
102 154
148 176 156
043 040
140
Vapour Dome
1
400
004
Dual Purpose Heaters
453
141
406
460
402
104
056
178 058
Liquid Dome
502
T
002 153
2
142
143
151
054
146
042 041
052
174
488
155 106
158
006 008 157
TCV 454
108 FCV
k3
451
FCV
To Insulation Spaces
2
450
TCV
470
410
n Ta
452
HD Compressor No. 1 (Inboard)
420
1
455 FCV
430 FCV
To Engine Room
Forcing Vaporiser
TCV
440
Key Degassing line into Main Cargo Pump Cable Penetration
411
FCV FCV
Demister
Inert Gas from Engine Room
AW/912
LNG
456 TCV 421
HD Compressor No. 2 (Outboard)
480
431 FCV
LNG Vapour
k4 n Ta
LD Compressor No. 1 (Inboard)
Main Vaporiser
441 FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.2.2a Cargo Tank Stripping With Other Tanks In Service
Cargo Systems and Operating Manual
LNG LERICI
4.2.2 Gas Freeing With Other Tanks In Service Cargo Tank Stripping With Other Tanks In Service (see illustration 4.2.2a) It may become necessary to displace LNG vapour with inert gas in a cargo tank with other tanks still in service in order to prepare a tank for inspection. There are two possibilities when this can be carried out i.e During the first laden voyage. During the ballast voyage. These two possibilities use the same procedures. Tank No.1 will be demonstrated for this example. This vessel is assumed to in gas burning mode. (Only the valves concerned with the gas burning operation are open, all other valves are closed.) 1
Strip all possible LNG from tank No.1. During the laden or ballast voyage, remove the maximum LNG with the stripping pump and transfer to the other tanks via the stripping/spray main, liquid header and the filling pipes.
2
Open valves 170, 090 and 190.
3
Open the filling valves on the other tanks, 020, 030 and 040.
4
Ensure the filling valve on tank No.1 is shut.
5
Start the stripping pump in tank No.1 and open the discharge valve 110.
! Caution Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
Issue: 1
4.2 Cargo Tank Stripping With Other Tanks In Service
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.3a Cargo Tank Warm Up With Other Tanks In Service 101 117
161 003
103 105
001 162
163
489
053
051
401 007
107
005
167
114
481
491 119
171 012
173
116
011 112
166 057
118
115
164
501
165
113
482
062
055
487
168
124
177 129 022
485
111
486 Vent Gas Heater
128
126
Vapour Dome
Liquid Dome
484
021
170
403
483
492 127
125
013 010
110
175
122 123
023 020
120
Vapour Dome
Liquid Dome 121
2
160
1
137 134 493 139
138
135
032
190
1
033 030
130
063
1
T
2
132 133
k an
136
031
Vapour Dome
Liquid Dome 404
180
131
090
k2
172
000
494
061
152
480
405
144
Jettison
054 154
148
2
140
002
176 156
043 040
Vapour Dome
1
400
Dual Purpose Heaters
453
141
406
460
402
104
056
178 058
Liquid Dome
502
n Ta
004
153
142
143
151 102
146
042 041
CL045FO
147
149 145
052
174
488
155 106
158
006 008 157
TCV 454
108 FCV
k3
451
FCV
To Insulation Spaces
2
450
TCV
470
410
n Ta
452
HD Compressor No. 1 (Inboard)
420
1
Key
455 FCV
430 FCV
To Engine Room
TCV
440
Degassing line into Main Cargo Pump Cable Penetration
Forcing Vaporiser
411
FCV FCV
Demister
Inert Gas from Engine Room
AW/912
456 TCV 421
HD Compressor No. 2 (Outboard)
k an
T
4 LD Compressor No. 1 (Inboard)
480
431 FCV
Main Vaporiser
441 FCV
LNG Warm Vapour
LNG Vapour
LD Compressor No. 2 (Outboard)
Issue: 1
4.2.3a Cargo Tank Warm Up With Other Tanks In Service
Cargo Systems and Operating Manual Gas Freeing With Other Tanks In Service Cargo Tank Warming Up With Other Tanks In Service (see illustration 4.2.3a) Warming up tank No.1 During the laden or ballast voyage, tank No.1 is warmed by re-circulating heated LNG vapour. This warm vapour is re-circulated by one L.D. compressor and heated via the cargo heaters to 50°C. The hot vapour is introduced through the filling pipe at the bottom of the tank to evaporate any remaining LNG liquid that was unable to be removed via the stripping out process. Excess vapour generated during the warming-up operation of the tank is burned in the main boilers or vented to atmosphere.
LNG LERICI
13 Close the tank vapour.valve 491. ! Caution Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
The warm-up procedure is as follows; 1
Stop the L.D. compressor in use for gas burning and close gas heater valve outlet 453.
2
Install spool piece CL.045FO and open valve 063 to discharge heated vapour to the LNG header.
3
Prepare gas heaters YA/5141B for use. The temperature set point is adjusted to 50°C (corresponding to gas burning case).
4
Start the L.D. compressor YA/5122B.
5
At the vent mast No.2 open valves 481, 483, 484 and 486. The set point of regulating valve 487 is adjusted to 1080mbar a. Vent heater YA/5142 is now prepared for use.
6
Open the compressor suction valve 404 from the vapour header.
7
Open the inlet and outlet valves from the compressor 411 and 431.
8
Open the heater inlet and outlet valves 451 and 453.
9
Open the vapour valves on each tank 491, 492, 493 and 494.
10 Open the filling valve 010 on tank No.1. 11 Monitor the pressure in tank No.1 and adjust the compressor flow in order to maintain the pressure in the tank at 1060 mbar a. 12 At the end of the operation, when the coldest temperature of the secondary barrier is at least +5°C stop and shut down the gas burning system, stop the L.D. compressor and shut the tank filling valve 010.
Issue: 1
4.2 Cargo Tank Warm Up With Other Tanks In Service
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.4a Cargo Tank Gas Freeing With Other Tanks In Service 101 117
161 003
103 105
001
163
489
053
051
401 007
107
005
167
114
481
491 119
171 012
173
116
011 112
166 057
118
115
164
501
165
113
482
162
062
055
487
168
124
177 129
Vent Gas Heater
021
170
403
111
486 128
126
Liquid Dome
484
485
127
125
022
483
492
Vapour Dome
013 010
110
175
122 123
023 020
120
Vapour Dome
Liquid Dome 121
2
160
1
137 134 493 139
138
135
032
190
1
033 030
130
063
1
T
2
132 133
k an
136
031
Vapour Dome
Liquid Dome 404
180
131
090
172
000
494
061
152
480
405
144
Jettison
147
149 145
041
102 154
148
2
140
Vapour Dome
1
400
Dual Purpose Heaters
453
141
406
460
402
104
056
178 058
Liquid Dome
502
2
002
176 156
043 040
nk Ta
004
153
142
143
151
054
146
042
052
174
488
155 106
158
006 008 157
TCV 454
108 FCV 451
FCV
To Insulation Spaces
2
450
TCV
470
k an
410 452
HD Compressor No. 1 (Inboard)
T
420
1
Key
455 FCV
430 FCV
To Engine Room
Forcing Vaporiser
TCV
440
Degassing line into Main Cargo Pump Cable Penetration
411
FCV FCV
Demister
Inert Gas from Engine Room
AW/912
3
456 TCV 421
HD Compressor No. 2 (Outboard)
n Ta
k4 LD Compressor No. 1 (Inboard)
480
431 FCV
Inert Gas
Main Vaporiser
441 FCV
LNG Vapour
LD Compressor No. 2 (Outboard)
Issue: 1
4.2.4a Cargo Tank Gas Freeing With Other Tanks In Service
Cargo Systems and Operating Manual Gas Freeing With Other Tanks In Service Cargo Tank Gas Freeing (Version 1) (see illustration 4.2.4a) This following procedure is not undertaken whist the vessel is in gas burning mode on either laden or ballast voyage. After the cargo tank has been warmed up (see Cargo Tank Warming Up With Other Tanks In Service), the LNG vapour is displaced with inert gas. The inert gas from the inert gas generating plant is introduced into the bottom of the cargo tank via the LNG filling pipe. The gas from the tank is vented from the top of the tank through the gas dome safety valves to the vent mast.
LNG LERICI
! Caution Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
The gas freeing procedure is as follows; 1
Prepare the inert gas generating plant for use in inert gas mode.
2
Open the vapour valves on the tanks that are not being gas freed 492, 493, 494. Ensure the vapour valve on tank No.1 remains shut.
3
At vent mast No.2 open valves 481, 483, 484 and 486. Adjust the set point of regulating valve 487 to 150mbar gauge.
4
Prepare vent heater YA/5142 for use.
5
Install spool piece CL.045FO and open valves 460 and 063 to supply the inert gas to the LNG header.
6
Open the filling valve 010 on tank No.1.
7
Remove the plug on the gas dome safety valves on tank No.1. This is in order to evacuate the inert gas in tank No.1 to the vent mast.
8
Start the inert gas plant delivering to No.1 tank. Monitor the methane content inside the tank until it has reached the acceptable level.
9
Open valve XH/5321G upstream of the two non return valves on the dry air /inert gas discharge line.
10 Monitor tank No.1 pressure and check that tank No.1 pressure is always higher than the insulation space pressure, taking into account the pipe losses between the gas dome safety valves and vent mast. 11 When the hydrocarbon content from tank No.1 has fallen below 2.5%, isolate and shut off the tank. Stop the inert gas supply and shut down the plant.
Issue: 1
4.2 Gas Freeing With Other Tanks In Service - Version 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.4b Cargo Gas Tank Freeing With Other Tanks In Service (Second Version)
101 117
161 003
103 105
001 162
163
489
053
051
401 007
107
005
167
114
481
491 119
171 012
173
116
011 112
166 057
118
115
164
501
165
113
482
062
055
487
168
124
177 129 022
485
111
486 Vent Gas Heater
128
126
Vapour Dome
Liquid Dome
484
021
170
403
483
492 127
125
013 010
110
175
122 123
023 020
120
Vapour Dome
Liquid Dome 121
2
160
1
137 134 493 139
138
135
032 031
2
132 190
133
Ta
136
1
033 030
130
063
1 k n
Vapour Dome
Liquid Dome 404
180
131
090
172
000
494
061
144
Jettison
102 154
148 176 156
043 040
140
Vapour Dome
1
400
Dual Purpose Heaters
453
141
406
460
T
004
402
104
056
178 058
Liquid Dome
502
2
002 153
2
142
143
151
054
146
042 041
052
174
147
149 145
k an
152
480
405
488
155 106
158
006 008 157
TCV 454
108 FCV 451
FCV
To Insulation Spaces
2
450
TCV
470
HD Compressor No. 1 (Inboard)
T
420
1 Flexible Hose
k an
410 452
3 Key
455 FCV
430 FCV
To Engine Room
TCV
440
Degassing line into Main Cargo Pump Cable Penetration
Forcing Vaporiser
411
FCV FCV
Demister
Inert Gas from Engine Room
AW/912
456 TCV 421
HD Compressor No. 2 (Outboard)
n Ta
k4 LD Compressor No. 1 (Inboard)
480
431 FCV
Main Vaporiser
441 FCV
Inert Gas
LNG Vapour
LD Compressor No. 2 (Outboard)
Issue: 1
4.2.4b Cargo Tank Gas Freeing With Other Tanks In Service
Cargo Systems and Operating Manual Gas Freeing With Other Tanks In Service Cargo Tank Gas Freeing (Version 2) (see illustration 4.2.4b) It is not possible to use gas burning and the gas freeing procedure at the same time. Due to the fact that the gas freeing operation of a cargo tank will take approximately 20 hours, a significant amount of LNG vapour from boiloff, will have to be vented to atmosphere. In order to avoid this the following procedure can be adopted. The following procedure calls for the separation of the fuel gas line from the inert gas line by installing additional pipe elements.
LNG LERICI
! Caution Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
The gas freeing procedure is as follows; The vessel is in gas burning mode. 1
Prepare the inert gas generating plant for use in inert gas mode.
2
Open the vapour valves on the tanks that are not being gas freed 492, 493, 494. Ensure the vapour valve on tank No.1 remains shut.
3
At vent mast No.2 open valves 481, 483, 484 and 486. Adjust the set point of regulating valve 487 to 150mbar gauge.
4
Prepare vent heater YA/5142 for use.
5
Connect the flexible hose between the inert gas line and liquid line.
6
Ensure the jettison discharge valve 000 is shut.
7
Open the inert gas supply valve 061 to the LNG header.
8
Open the filling valve 010 on tank No.1.
8
Remove the plug on the gas dome safety valves on tank No.1. This is in order to evacuate the inert gas in tank No.1 to the vent mast.
8
Start the inert gas plant delivering to No.1 tank. Monitor the methane content inside the tank until it has reached the acceptable level.
9
Open valve XH/5321G upstream of the two non return valves on the dry air /inert gas discharge line.
10 Monitor tank No.1 pressure and check that tank No.1 pressure is always higher than the insulation space pressure, taking into account the pipe losses between the gas dome safety valves and vent mast. 11 When the hydrocarbon content from tank No.1 has fallen below 2.5%, isolate and shut off the tank. Stop the inert gas supply and shut down the plant.
Issue: 1
4.2 Gas Freeing With Other tanks In Service - Version 2 - page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.4c Initial Insulation Space Inerting No 1 Cofferdam
Insulation Spaces Exhaust Control
Evacuation Of Insulation Spaces (First Step) No 2 Cofferdam
511
512 No 3 Cofferdam
522
No 4 Cofferdam 521
From No 1 Tank Secondary Space 532 No 5 Cofferdam
1 k n Ta
531 Primary Space 542 480
541 Supply from Nitrogen Storage Tank
From No 2 Tank Secondary Space From No 3 Tank Secondary Space
Secondary Space
nk Ta
2
Vacuum Pump (Inboard) 572 AW/827VX AW/826VX
571 Vacuum Pump (Outboard) 568 569
Main Vaporiser
k an
3
T
Key From No 4 Tank Secondary Space
Nitrogen From Secondary Insulation Spaces
k4 n Ta
Issue: 1
Nitrogen From Primary Insulation Spaces
4.2.4c Initial Insulation Space Inerting
Cargo Systems and Operating Manual Initial Insulation Space Inerting First Step: Evacuation of Insulation Space
!
CAUTION To avoid major damage to the secondary barrier, never evacuate a primary insulation space whilst leaving the associated secondary space under pressure, and never fill a secondary space whilst the primary space is under a vacuum. Prior to putting a cargo tank into service initially, or after dry docking, it is necessary to replace the ambient humid air in the insulation space with dry nitrogen. This is done by evacuating the insulation spaces with the vacuum pumps and refilling them with nitrogen. The procedure is repeated until the oxygen content is reduced to less than 3%. Evacuation of all the insulation spaces takes approximately 8 hours. Refilling nitrogen takes approximately 4 hours using the main vaporiser. Three cycles are usually necessary to reduce the oxygen to less than three per cent by volume.
! CAUTION Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes. Before refilling with nitrogen, the insulation spaces are evacuated to 200mbar absolute pressure. The evacuation of the insulation spaces is also used in order to check the integrity of the barriers during periodical test. To avoid possible damage to the secondary membrane, the secondary insulation spaces must be evacuated before the primary insulation spaces. The pipe work at the vacuum pumps suction has been designed to ensure that the evacuation of the primary spaces cannot take place without having first evacuated the secondary spaces, or ensuring that they will be both evacuated simultaneously.
The operating procedure is as follows: (All valves are assumed SHUT) (See Illustration 4.2.4c). •
•
Isolate any pressure gauge, transducer or instrument which should be damaged by the vacuum and install temporary manometers to allow pressures in the insulation spaces to be monitored. On each tank, open the valve 542, 532, 522, 512 connecting the pressurisation header with the dewatering columns of the secondary insulation spaces.
•
In the compressor room, open the valve 569 and the valves 571, 572 to the suction of the vacuum pumps.
•
Prepare the vacuum pumps for use.
•
Start both vacuum pumps.
•
Monitor the secondary insulation spaces pressure; when it has been reduced to 200mbar abs in all the spaces, stop the pumps.
•
Close the valves 542, 532, 522, 512 on trunk deck.
•
Then, on each tank, open valves 541, 531, 521, 511 connected the pressurisation header with the aft transverse of the primary insulation spaces.
•
Open valve 568, the vacuum pumps suction from the primary pressurisation header.
•
Start both vacuum pumps.
•
Monitor the primary insulation spaces pressure; when it has been reduced to 200mbar abs in all the spaces, stop the pumps.
•
Close the valves 541, 531, 521, 511 on trunk deck.
•
Close the valves 568, 569 and the valves 571, 572 at the pumps’ suction.
LNG LERICI General notes on the vacuum pumps Ensure cooling water is available and on. Ensure lub oil tank is full and power supply to the pumps is available. Ensure that bulkhead seal system is full. Ensure that pump is free to rotate Ensure that lub oil is feeding Close pump drains. Adjust cooling water flow to obtain 30/40° at cooling water outlet from vacuum pipes. After shut down clean suction filter. •
Total volume of the primary and secondary space is about 5700m3.
• Stop the vacuum pumps. During the evacuation of the insulation spaces the tightness of the primary and secondary insulation spaces relief valves has to be confirmed and if suspected of leaking, blanked until operation completed. Blanks must be clearly marked and notices posted.
Two electrically driven vacuum pumps, cooled by sea water, are installed in the cargo compressor room. They draw from the pressurisation headers and discharge to the vent riser No. 3. Issue: 1
4.2 Initial Insulation Space Inerting - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.4d Filling From Liquid Nitrogen (Second Step)
No 1 Cofferdam
No 2 Cofferdam
Insulation Spaces Exhaust Control 552 554 557
540 550
551
560 556
553 555
512
511 No 3 Cofferdam 501
522
No 4 Cofferdam 521
To No 1 Tank Secondary Space 532 No 5 Cofferdam
1 k n Ta
531 Primary Space 542 480
541
CLO36FO
To No 2 Tank Secondary Space
Supply from Nitrogen Storage Tank
Secondary Space
nk a T
To No 3 Tank Secondary Space
2
Vacuum Pump (Inboard) 456
Vacuum Pump (Outboard) FCV 568 TCV 573 To No 4 Tank Secondary Space
CLO43FO
k4 n Ta
Issue: 1
Main Vaporiser
k3 n Ta
502
Key Liquid Nitrogen Shore Supply
Nitrogen Supply To Secondary Insulation Spaces Nitrogen Supply To Primary Insulation Spaces Liquid Nitrogen
4.2.4d Filling from Liquid Nitrogen (Second Step)
Cargo Systems and Operating Manual Second Step: Initial Filling From Liquid Nitrogen (see figure 4.2.4d) After evacuation, the next step consists in filling the insulation spaces with nitrogen. The cycle is repeated until the oxygen content in the spaces is less than 3%. The nitrogen is supplied from shore as liquid nitrogen. It is vapourised in the main vaporiser, then feeds the insulation spaces. The operating procedure is as follows: • Install the spool piece CL.036FO and open the valve 480 to supply liquid nitrogen to the vaporiser.
•
When the pressure in the insulation spaces is 950mbar a, stop the liquid nitrogen supply to the vaporiser. Close manifold valves 502 or 501. All valves at the inlet and outlet of the vaporiser will be kept open until warming up of the lines.
•
Close 573, and set the opening of the control valves 540, 560 at 4mbar.
Three cycles are usually necessary. Operating Procedure for the Completion of the Nitrogen Filling •
The final filling of the insulation spaces, between about -50mbar and the atmospheric pressure + 2mbar is carried out at reduced flow rate from the on board nitrogen production plant.
Prepare the main vaporiser for use and set the temperature control of the delivery gas at 20°C.
•
The same operating procedure as for the normal service is used (see figure 4.3.5a).
•
Open control valves 456 at vaporiser inlet.
•
•
Install the spool piece CL.043FO and open the valves 573, 568 to supply nitrogen to the pressurisation headers.
After the final filling, check the oxygen content in all the spaces. If it is higher than 3%, repeat inerting operation.There is also the possibility to check the o2 content at the vacuum pump discharge.
•
Open the isolation valves 551, 552, 556, 557 for the insulation exhaust control system.
•
Crack open the primary space supply valves 541, 531, 521, 511 on each tank.
•
When shore is ready, open the manifold valve 502 or 501.
•
Gaseous nitrogen is produced by the vaporiser in manual mode until the conditions are stabilised, then the vaporiser is put in automatic mode.
•
Adjust the opening of the primary space supply valves for balancing the pressure rise in all the spaces. During filling, always maintain the pressure in the primary space 100mbar above the secondary space.
•
When the pressure in the primary spaces reaches 300mbar a (100mbar above the pressure in the secondary spaces), crack open the secondary space supply valves 542, 532, 522, 512 on each tank. Then, adjust the opening of these valves for balancing the pressure rise in all the spaces.
•
Adjust the set point of the exhaust valve 540 to create a leak in order to balance the vaporiser production with a 300mbar per hour pressure rise in the insulation spaces.
•
Ensure that the pressure intake from which the vaporiser might be tripped on high pressure, is in service on the primary header.
•
Issue: 1
LNG LERICI
! CAUTION Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
4.2 Initial Insulation Space Inerting -Page 2
Cargo Systems and Operating Manual
LNG LERICI
No 1 Cofferdam Insulation Spaces Exhaust Control
Illustration 4.2.5a Insulation Space Inerting During Normal Service No 2 Cofferdam
554 540 557
550 560
552
556 512
511
No 3 Cofferdam
522
No 4 Cofferdam 521
To No 1 Tank Secondary Space
k1 n a
532
T
No 5 Cofferdam 531 Primary Space 542 To No 2 Tank Secondary Space
541 Supply from Nitrogen Storage Tank
Vacuum Pump (Inboard)
563
562
566
564
k2
n Ta
To No 3 Tank Secondary Space 561
Secondary Space
510 Insulation Spaces 520 Distribution 530 Control
567
Vacuum Pump (Outboard)
k an
3
T To No 4 Tank Secondary Space
Key Nitrogen Supply To Secondary Insulation Spaces
4 nk a T
Issue: 1
Nitrogen Supply To Primary Insulation Spaces
4.2.5a Insulation Space Inerting During Normal Service
Cargo Systems and Operating Manual Insulation Space Inerting During Normal Service The primary and secondary insulation spaces are filled with dry nitrogen gas which is automatically maintained by alternate relief and make up as the atmospheric pressure or the temperature rises and falls, under a pressure of between 2 and 6mbar above atmospheric.
In the event of cargo gas leakage into insulation spaces, this can be swept with a continuous feed of nitrogen by opening the exhaust from the space, allowing a controlled purge. Close monitoring of the gas analyser on this space will be necessary during purging.
The nitrogen provides a dry and inert medium for the following purposes: • To prevent formation of a flammable mixture in the event of an LNG leak.
In cases where other consumers reduce the availability of nitrogen for the insulation spaces, the pressure may temporarily fall below the atmospheric pressure.
•
To permit easy detection of an LNG leak through a barrier.
• To prevent corrosion. Nitrogen, produced by generators and stored in pressurised buffer tank, is supplied to the pressurisation headers through make-up regulating valves located on the compressor room. From the headers, branches are led to the primary and secondary insulation spaces of each tank. Excess nitrogen from the insulation spaces is vented to the mast No. 1 through regulating relief valves. Both primary and secondary insulation spaces of each tank are provided with a pair of pressure relief valves which open at a pressure, sensed in each space, of 10mbar above atmospheric. A manual by pass with a cut out valve and a ball valve is provided from the primary space to the pressure relief valves mast for local venting and sweeping of a space if required. 3
The two high capacity units (57.5m /h each), will operate in parallel when high nitrogen demand is detected and will start automatically, i.e. during initial cooling down. When loading only one unit will need to be run - the other unit being kept on standby. (see section 2.10). The operating procedure for the normal inerting is as follows: (see figure 4.2.5a) • Adjust the set point of the nitrogen supply regulating valve 520 to the secondary header at 2mbar and regulating valve 510 to the primary header at 4mbar •
At the forward part of the trunk deck, ensure that the valves 552, 554, 556, 557 are open.
•
Adjust the set point of the nitrogen exhaust regulating valve 540 (primary) at 6mbar and regulating valve 560 (secondary) at 4 mbar.
There is a standby exhaust regulating valve 550, which can be connected to either the primary or secondary system in the event of failure of one of the master regulating valves. The nitrogen supply to the insulation spaces has a standby regulating valve 530, which can be connected to either the primary or secondary system in the event of failure of one of the master regulating valves. Issue: 1
This condition is NOT CRITICAL insofar as the differential pressure (Ps - Pp) between the secondary spaces pressure (Ps) and the primary space pressure (Pp) does not exceed 30mbar: (Ps - Pp) < 30mbar
! WARNING When the depression in the primary insulation spaces relative to the secondary insulation spaces reaches 30mbar, the two insulation spaces shall be immediately inter-connected - which will involve a manual operation. When put in communication and therefore subjected to the same nitrogen pressure, the primary and secondary insulation spaces can withstand a large depressurisation without any damage. It should be noted that, even with the tanks fully loaded, a pressure lower than atmospheric pressure in the primary insulation spaces is not harmful to the primary membrane. In this respect, it should be recalled that this membrane is subjected to a -800mbar gauge vacuum pressure - both during global testing at the construction stage and also for the insulation spaces cycles purging. In Service Tests Classification society regulations require that the barriers of a membrane tank should be capable of being checked periodically for their effectiveness. The following covers the practice, recommendations and the precautions which should be taken during the inservice periodical examination of the primary and secondary membranes.
! CAUTION Measurement devises which may otherwise be damaged should be isolated prior to the commencement of the test. The barrier spaces must at all times be protected against over pressure, which might otherwise result in membrane failure.
LNG LERICI Method For Checking The Effectiveness Of The Barriers 1 Primary Membrane Since each primary insulated space is provided with a permanently installed gas detection system capable of measuring gas concentration at intervals not exceeding thirty minutes, any gas concentration in excess with regard to the steady rates would be the indication of primary membrane damage. It results that each primary membrane is in terms of tightness, continuously monitored and a special test would not be required to check its effectiveness. However that maybe, each primary membrane can be tested according to the method described below for the secondary membrane. 2 Secondary Membrane In order to check its effectiveness, the secondary (or primary) membrane is submitted to a global tightness test, which is the reiteration of the equivalent test carried out during the cargo containment building. Procedure 2.1 Reduce the insulated space pressure at the back of the membrane to be tested to 200mbar a. 2.2 After a stabilising period of about 8 hours, record by means of an accurate measuring device, the vacuum decay over the next 24 hour period. 2.3 From the results obtained, the selection of the 10 hours continuous period during which the temperature variations of the compartments surrounding the tested membrane are minimum. 2.4 The allowable limit for vacuum decay of the space is given by the equation: ∆P≤ ≤ 0.8 e where e = the thickness in meters of the insulated space at the back of the membrane. In Service Global Tightness Test The global test is carried out either during a maintenance period, or when the cargo tanks have been warmed up and gas freed. To overcome any doubtful results arising from possible leaks through equipment connected with the insulated spaces ie valves, pressure relief valves, electric cable glands etc, their effectiveness must be carefully checked, and eventually replaced with blank joints, insofar as the spaces remain protected against any over pressure. Test Of Secondary Membrane 3.1 The pressure of the secondary space is reduced to 200mbar a, while the primary space is maintained at a slight vacuum (i.e. -100mbar) Under these conditions, the secondary membrane is
submitted by one side to the atmospheric pressure existing inside the primary space, by the other to the reduced pressure existing inside the secondary space. 3.2 The vacuum decay is carried out on this space only by the method described in 2.2/2.4. In spite of the precautions taken for providing against leaks of the equipment, it is important to check whether ∆Ps) the vacuum decay of the secondary barrier space (∆ corresponds with a pressure reduction of the primary ∆Pp). If this is not the case there may be an space (∆ external leak which must be located and rectified before another test is conducted. ∆Ps) it is necessary to take ∆Pp) and (∆ When comparing (∆ into account the primary and secondary space volumes as shown in the equation below: ∆Pp = ∆Ps es ep where (es) and (ep) represents the thickness of the secondary and primary spaces. Primary Membrane Test Procedure 4.1 The pressure of the primary and secondary barrier spaces is reduced to 200mbar a simultaneously, in communication, in order to prevent the potential collapse of the secondary barrier due to a higher pressure than that of the primary space. 4.2 The primary and secondary spaces are isolated and the vacuum decay procedure is followed on the primary space only. Method as described in 2.2/2.4. Under these conditions, the primary membrane is submitted by one side to the atmospheric pressure existing inside the tank, and by the other to the reduced pressure existing inside the primary space. Since both faces of the secondary membrane are in an equal pressure system, no flow can be generated through any eventual leak of this membrane. Therefore the measured vacuum decay is the correct figure of the tightness of only the primary membrane.
! CAUTION Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes. 4.2 Insulation Space Inerting - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.6a Loaded Voyage With Normal Boil-Off Gas Burning
491
Vapour Dome Liquid Dome
492
Vent Gas Heater
Vapour Dome Liquid Dome
2 1 493
k an
1
T
2 1 Vapour Dome Liquid Dome 404
k2 n a
494
T
Jettison
2 1
Vapour Dome Liquid Dome
Dual Purpose Heaters
453
460 TCV
454 450
TCV FCV
2
451
FCV
To Insulation Spaces
k an
452
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
FCV
ME001VR
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
411
To Engine Room
FCV
LNG Vapour
Demister
Inert Gas from Engine Room
421 HD Compressor No. 2 (Outboard)
n Ta
k4
431 FCV
Anti-Surge Control
LD Compressor No. 1 (Inboard)
Main Vaporiser
441 FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.2.6a Loaded Voyage With Normal Boil-Off Gas Burning
Cargo Systems and Operating Manual 4.2.6 Loaded Voyage with Normal Boil-Off Gas Burning Introduction During a sea passage when the cargo tanks contain LNG the boil-off from the tanks is burned in the ship’s boilers. The operation is started on deck and controlled by the ship’s engineers in the Engine Control Room. If for any reason the boil-off cannot be used for gas burning, or if the volume is too great for the boilers to handle, any excess vapour is heated and vented to atmosphere (Section 2.2.3) via main mast riser. Operation The cargo tank boil-off gas enters the vapour header via the cargo tank gas domes. It is then directed to one of the LD compressor which pump the gas to the boil-off gas heater. The heated gas is delivered to the boilers at a maximum temperature of +25°C via control valve ME001VR. The compressor/s speed and inlet guide vane position is governed by cargo tanks pressure. The system is designed to burn all boil-off gas normally produced by a full cargo and to maintain the cargo tank pressure (i.e. temperatures) at a predetermined level. If the propulsion plant steam consumption is not sufficient to burn the required amount of boil off, the tank pressure will increase and eventually the steam dump will open dumping steam directly to the main condenser. The main dump is designed to dump sufficient steam to allow the boiler to use all the boil off produced even when the ship is stopped. The flow of gas through the LD compressors is controlled by adjusting the compressors speed and inlet guide vane position. This is directed by the boiler combustion control when gas burning is initiated. The normal boil off in the boiler combustion control have to be selected as well as the maximum and minimum allowed tank pressures and the tank pressure at which the main dump operates. For normal operation the normal boil off valve is selected at 60% (boil-off provides 60% of the fuel required to produce 90% of the boiler full steam capacity) and the minimum and maximum tank pressures are selected at 1050 and 1090mbar a.
If the normal boil off valve has been correctly adjusted, the tank pressures will remain within the selected values. Should the selected normal boil off value be too large, the tank pressure will slowly be reduced until it reaches the minimum value selected. If the tank pressure value reduces to below the minimum value selected, the normal boil off value will be reduced until the tank pressure has increased again above the selected value. If the selected normal boil off value is too small, the tank pressure will slowly increase until it reaches the maximum value selected. If the tank pressure value increases above the maximum selected value, the normal boil off value will be increased until the tank pressure reduces again below the selected value.
2 3
The steam dump is designed to open when the normal boil off valve is 5% above the original selected value and when the tank pressure has reached the preselected dump operating pressure. With the present setting, an increase of 5% of the normal boil off corresponds approximately to an increase of tank pressure by 40mbar above the maximum tank pressure selected. The cargo and gas burning piping system is arranged so that excess boil-off can be vented should there be any inadvertent stopping of gas burning in the ship’s boilers. The automatic control valve 487 at the main mast riser is set at 1150mbar absolute to vent the excess vapour to atmosphere. If the gas header pressure falls to less than 40mbar above the primary insulation spaces pressure an alarm will sound. In the event of automatic or manual shut down of the gas burning system (or if the tank pressure falls to 10mbar above the insulation spaces pressure), valve ME001VR will close and the gas burning supply line to the engine room will be purged with nitrogen via valve XH5321G.
Open 487 forward mast isolating valve on gas burning header. Tank gas domes
Should the system shut down for any reason valve ME001VR will close automatically. 10 Stop the compressor.
Open and lock in position valve 491 (Tank No. 1) Open and lock in position valve 492 (Tank No. 2)
When stopping gas burning for any reason
Open and lock in position valve 493 (Tank No. 3)
11 Stop LD compressor/s
Open and lock in position valve 494 (Tank No. 4)
Close valve ME001VR gas supply to engine room
The valves should already be locked in the open position.
Adjust set point of vent mast control PIC 487 to 1100mbar a.
4
Open valve 404 and 421 vapour supply to compressors and gas heaters.
5
Boil-off gas heater
If the tank pressure continues to increase because the steam consumption is not sufficient to burn all the required boil off, the steam dump will open.
Operating Procedures (See Illustration 4.2.6a) It is assumed that all valves are closed prior to use: 1 Prepare LD compressors YA5122 A or B, the boil-off heaters and the engine room gas burning plant for use.
Issue: 1
LNG LERICI
Open 451 and 453 heater inlet and outlet Open glycoled water supply to heater In Cargo Control Room 6
Forward mast Position mast selector to gas burning header Adjust set point PIC 487 to 1150mbar a.
7
Gas compressors Adjust normal boil off valve (IGV) to 60% for loaded condition, tank pressures minimum and maximum at 1060mbar a and 1090mbar a and steam dump opening pressure at 1130mbar a.
When the Engine Room is ready to start gas burning, ensure that there is sufficient nitrogen to purge the lines to the boiler i.e. >5.0 bar in storage tank. 8
Ensure that the gas outlet temperature of the heater is approximately 25°C Open valve ME001VR Start LD compressor/s
This operation will then be controlled and monitored from the Engine Control room. Note: If the volume of boil-off exceeds demand in the boilers the steam dump should be put into operation.
4.2 Loaded Voyage with Normal Boil-Off Gas Burning - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.6b Loaded Voyage With Forced Boil-Off Gas Burning
114 491 118
115 191
116
110
Vapour Dome Liquid Dome
124
492
125 192
126
Vent Gas Heater
128
170 120
Vapour Dome Liquid Dome
2 1 134 493 138
135
k an
193 136
T
2 1
130
190
1
Vapour Dome Liquid Dome
404
180
k2 n a
494 144
Jettison
T
145 194
146
148
2
041
1
Vapour Dome Liquid Dome
Dual Purpose Heaters
453
460 TCV
454 TCV FCV
To Insulation Spaces
2
451
FCV
k an
452
T
HD Compressor No. 1 (Inboard)
1
455 FCV
ME001VR
Forcing Vaporiser
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
TCV
To Engine Room
LNG
Demister
Inert Gas from Engine Room
421 480
HD Compressor No. 2 (Outboard)
n Ta
k4 LD Compressor No. 1 (Inboard)
LNG Vapour
Main Vaporiser
441 FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.2.6b Loaded Voyage With Forced Boil-Off Gas Burning
Cargo Systems and Operating Manual Loaded Voyage with Forced Boil-Off Gas Burning Introduction Consideration must be given to economics of gas versus fuel oil burning before undertaking forced boil off. If during a loaded passage, additional fuel gas from the cargo tanks is required to be burned in the ship’s boilers, it can be made available by forced vaporisation using the equipment on board. The above operation, called Forced Boil-Off will be used to complement gas burning up to 100% of the boilers fuel requirement. Operation The normal gas burning arrangement is maintained and the forcing vaporiser is brought into operation. A single stripping / spray pump is used to pump LNG to the forcing vaporiser. The excess flow from the pump is returned to the tank through the spray ring control valves (144, 134, 124, 114). The following tank valves are adjusted to maintain a suitable pressure at the vaporiser.
LNG LERICI
The boiler combustion control has to be switched to Forced Boil-Off (FBO) mode.
8
Run up forcing vaporiser (See 2.6.3).
9
Set boiler combustion control on FBO mode.
The amount of forced boil-off to be produced is controlled by the throttling of the FCV to the forcing vaporiser operated by the Boiler Combustion control.
10 Start second LD compressor depending on gas demand.
When changing over to 100% gas burning, the fuel oil (FO) flow through the FO rails is adjusted to minimum. The FO supply to the burners will then be cut out and the FO system put on recirculation. The FO combustion control loops are maintained energised to enable relighting of FO burners in an emergency.
11 Set control of liquid supply to vaporiser and LD compressors control to auto mode.
In the event of automatic or manual shut down of the gas burning system (or if the tank pressure falls to 5mbar above the insulation spaces pressure), valve ME001VR will close and the gas burning supply line to the engine room will be purged with nitrogen via valve XH5321G. FO booster devices are incorporated in the control loop to allow a quick change-over should the gas burning be tripped. Operating Procedures (See Illustration 4.2.6b) For illustration purposes No. 3 tank stripping/spray pump and return operation is shown.
Tank No. 1: 191 Tank No. 2: 192
The cargo piping system is arranged for normal gas burning during loaded voyage as detailed in 4.2.6a.
Tank No. 3: 193 Tank No. 4: 194 Note: In normal operation the controlled return is directed back to the same tank where the liquid is being drawn from.
It is assumed, that all valves are closed prior to use. 1
Prepare the forcing vaporiser for use.
2
Open the stripping/spray isolating valve on the tank/s to be used. Tank No. 1: 114, 115, 116, 118
After vaporisation the LNG vapour produced passes through a demister where the possibility of liquid LNG carry-over is eliminated. The vapour then combines with the natural boil-off gas from the vapour header before being drawn into the suction of the LD compressors.
Tank No. 2: 124, 125, 126, 128 Tank No. 3: 134, 135, 136, 138 Tank No. 4: 144, 145, 146, 148 If cargo tanks No. 1 or No. 2 is used, open stripping/ spray header isolating valve 170. If tank No. 4 is used open stripping/spray header isolating valve 180.
One or two LD compressors are used depending on the amount of fuel gas required by the boilers. The flow of gas through the compressors is controlled via the boiler combustion control unit by adjusting the opening of the guide vanes.
Issue: 1
3
Open valve 190 stripping/spray header supply to the forcing vaporiser.
4
Open stripping pump discharge valve, 110, 120, 130, 140. Start stripping/spray pump and adjust return flow to tank through spray control valves 191, 192, 193, 194.
4.2 Loaded Voyage with Forced Boil-Off Gas Burning - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.7a(i) Discharging With Gas Return From Shore 003
001 491 053
051
401 012 007
173
005
057
011
055
Vapour Dome
175 Liquid Dome
492
Vent Gas Heater
022 021
170
403
Vapour Dome Liquid Dome
2
160
1
137 134 493 138
k an
032 031
T
2 190
1
1
130 Vapour Dome Liquid Dome
180
090
k2 n a
494
T
052
Jettison 054
002
042
004
2
041
402 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1
056 058 006 008
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
Degassing Line Into Main Cargo Pump Cable Penetration
LNG Vapour
HD Compressor No. 2 (Outboard)
n Ta
Key
LNG
Demister
Inert Gas from Engine Room
3
k4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.2.7a(i) Discharging With Gas Return From Shore
Cargo Systems and Operating Manual 4.2.7 Discharging with Gas Return from Shore Introduction During a normal discharge only the main cargo pumps will be used and a quantity of cargo will be retained on board for cold maintenance of the cargo tanks. The quantity to be retained is according to voyage duration of ballast passage.
During the discharge period, the ship is kept on an even keel. If it is required to empty a cargo tank, the ship is trimmed according to terminal maximum draught by the stern to assist in stripping of the tank.
During cargo discharge, LNG vapour is supplied from shore to maintain pressure in the cargo tanks. Operation The main cargo pumps discharge LNG to the main liquid header and then to shore via the midship liquid cross-over manifold connections. After an initial rise in pressure, the pressure in the tanks decreases and it becomes necessary to supply LNG vapour from shore via the manifold and cross-over to the vapour header into the cargo tank gas domes in order to maintain a pressure of 1090mbar a. Should the vapour return supply from shore be insufficient to maintain tank pressures, other means of supplying vapour to the tanks either by using the tank sprayers or the main vaporiser have to be used. See ‘Discharging without Gas Return from Shore Section 4.4.1a for more information.
Preliminary preparation: 1 Checks to be made prior to starting cargo operations Test remote operation of all tank discharge valves and manifold ESD valves.
Each tank is normally discharged to the following levels:-
Test remote operation of ballast valves.
Tank No. 1 0.47m (216m3),
Test operation of Emergency Shut Down Systems (ESDS).
Tank No. 2 0.30m (242m3), If the ship has to warm-up tanks for technical reasons the stripping/spray pumps will be used to discharge the remaining cargo on completion of bulk discharge with the main cargo pumps.
LNG LERICI
2
Tank No. 3 0.30m (242m3),
This is the required capacity to maintain normal boil off of the tanks in a cooled condition on the ships normal trade route. If the length of the ballast voyage is extended, then required capacity would be altered accordingly in order to maintain the normal boil off for tank cooling and boiler consumption.
Safety precautions:
Prepare fire fighting equipment, water hoses and protective clothing for use. 3
Prepare vent gas heater for use (See 2.5.1).
4
Cargo tanks level alarms
12 Liquid connections
13 Test Emergency Shut Down System (ESDS) from shore and from ship as required. Re-open liquid and vapour ESD valves. When it is agreed with shore that cool-down may commence: 14 To cool down the cargo and discharge lines proceed as follows (assuming using stripping/spray pump No. 3 and centre manifold lines). 14.1
Switch on high level alarms. 5
If the vessel is to warm-up one or more tanks for technical reasons, the ship shall be trimmed according to terminal maximum draught. The cargo remaining in the tanks to be warmed up will be discharged to shore or to other tanks using the stripping/spray pumps on completion of bulk discharge.
14.2
Tank vapour domes - confirm that: Open and lock in position valve 491
(Tank No. 1)
Open and lock in position valve 492
(Tank No. 2)
Open and lock in position valve 493
(Tank No. 3)
Open and lock in position valve 494
(Tank No. 4)
These valves must be locked open at all times when the ship has cargo on board, unless a tank is isolated and vented for any reasons.
Stripping pump is run together with the remaining main pump until the main pump stops on low discharge pressure cut-out. 6 On completion of discharge, the loading arms and pipelines are purged and drained to No. 4 cargo tank and the arms are then gas freed and disconnected.
Open manifold ESD valve 401.
Open manifold ESD valves 003, 005, 001, 007.
Ensure sprays for hull water curtain at midships are in operation.
Tank No. 4 0.30m (200m3).
If shore agree: 11 Vapour manifold
7
Vapour cross-over Open valve 403 Cargo pumps
14.3 14.4
Open discharge valve 130 from No. 3 stripping/ spray pump to 20%. Open the following valves 160, 173, 053, 175, 055, 134, 137, 138. Crack open 190 and 090. Start stripping/spray pump When hard-arms and shore side lines have cooled down to -100 °C, open valves 190 and 090 fully and valves 010 and 040 to 20%. This will now cool down the ships liquid line.
The cooling down is complete when the manifold and ships liquid line is approximately -130°C. 14.5 Stop the stripping/spray pump. 14.6
Shut valves 090, 130 173, 175. When spray line has warmed up, close valves 190, 160, 134, 137, 138.
Check that power supply to cargo pumps.. The boil-off gas heater should be prepared and lined up for use in order to avoid venting cold LNG vapour through the main mast riser. Ballasting is undertaken concurrently with discharging. The ballasting operation is programmed to keep the vessel within the required limit of draught, trim, hull stress and stability following indications obtained from the loading calculator.
Due to the manifold configuration it is necessary to purge the cargo lines using nitrogen at a pressure of at least 3.0 bar; this being done several times to ensure successful draining at the manifold connections. The vapour arm remains connected until just before sailing if a delay is expected. Operating Procedures (See Illustration 4.2.7a(i)) It is assumed that all valves are closed prior to start.
8
Check connections of liquid and vapour arms Check communications with shore.
On completion of cool down and when shore is ready for discharge, proceed as follows as shown on the following page.
Check ship/shore link. When shore is ready to purge manifold connections with nitrogen: 9 Liquid manifold connections (assuming port-side discharge with 2 liquid hard-arms) Purge connections then close valves.
10 Vapour manifold connection Purge connection then close valve.
Issue: 1
4.2 Discharging with Gas Return from Shore - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.7a(ii) Stripping Cargo Tanks With Gas Return From Shore 161 003 163
491 053
401 164 005
165 166 055
167
110
Vapour Dome Liquid Dome
492
Vent Gas Heater
170
403
120
Vapour Dome Liquid Dome
2
160
1
493
T
2
k an
1
1
130 Vapour Dome Liquid Dome 180
k an
494 144
Jettison
052 147
054
2
T
148
2 140
1
Vapour Dome Liquid Dome
Dual Purpose Heaters
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
T
Degassing Line Into Main Cargo Pump Cable Penetration
LNG Vapour
HD Compressor No. 2 (Outboard)
k an
Key
LNG
Demister
Inert Gas from Engine Room
3
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.2.7a(ii) Stripping Cargo Tanks With Gas Return From Shore
Cargo Systems and Operating Manual 15 Open No. 3 tank main cargo pump discharge valve 031 or 032 to 20%. Inform the Engine Control Room that a main cargo pump is about to be started. Start pump.
Stop main cargo pumps in each tank at approximately 0.47m in tank No.1 and 0.3m in tanks No. 2,3 and 4. Throttle in main cargo pump discharge valve to 40% before stopping the pump. If 2 main cargo pumps are in use in a tank, when the level reaches 0.65m, throttle in the discharge valve on one pump to 40% and stop that pump. This is in order to reduce turbulence around the pump suction.
16 Check lines for leakage. Open discharge valve fully on the running pump. 17 When shore is ready to receive further cargo, proceed as for 15 and 16.
On completion of final tank and after all cargo pumps have been stopped: 26 Drain liquid line 27 Stop gas return from shore.
The preferred sequence in chronological order of cargo pump starting, to obtain a stable discharge operation is as follows: Tank No. 3, Tank No. 2, Tank No. 4, Tank No. 1, 18 Monitor tanks pressure. 19 Request vapour return from shore and continue to monitor pressure to confirm that it stabilises. 20 As the discharge pressure and flow rate increase, continue to monitor the pipework and hard arms for leakage. 21 Adjust pump discharge valves to obtain optimum performance as indicated by current, discharge pressure and pump graph. 22 It is important to maintain the tanks at a pressure of at least 1090mbar a in order to avoid cavitation and to have good suction at the pumps. If the tanks pressure falls to 1040mbar a request shore to increase gas return. If shore can no longer supply gas return, the main vaporiser will have to be started up to restore the tanks pressure. 23 Start ballasting operations Keep draught, trim and hull stresses within permissible limits by controlling the various ballast tank levels.
If stripping of tanks ashore is required: (See Illustration 4.2.7a(ii))
LNG LERICI Purging and draining of loading arms. Purging is carried out one line at a time. When shore terminal is ready to inject nitrogen and the pressure at the manifold is 2.5 bar, open manifold bypass valves 164, 166. 32 Close bypass valve when pressure on manifold drops to 0 bar. Repeat operation a further twice. On the last operation shut bypass valve at approximately 1 bar in order to eliminate the risk of liquid back flow from ship’s liquid line. Open the test drain valve on the loading arm to ensure that there is no liquid present. When the required amount of methane (usually less than 1%) is showing at the drain valve, close the shore terminal ESDS valves.
28 At manifold crossover Open valves 164, 166 etc. Close valves 053, 055 etc. 29 Stripping/spray header Open 180, 170 and check that 003 and 005 are still open Open 160 stripping/spray header to liquid manifold cross-over 30 At required tanks Open stripping/spray discharge valves from individual tanks to give the required performance, 110, 120, 130, 140. Start stripping/spray pump. On completion: 31 Stop final pump
33 When purging is completed proceed with the disconnection of the liquid arms. 34 Complete ballasting operations for final measurement and for sailing condition. Shortly before departure: 35 Vapour line connection Purge the vapour line with nitrogen from the shore terminal at a pressure of 2 bar. Close valve 401 and 403. Confirm that the gas content is less than 1% by volume at drain valve 489. After confirming that gas content is less than 1% volume: 36 Disconnect the vapour arm. 37 Prepare cargo system for gas burning at sea.
Close valves 164, 166. Open valves 144, 147, 148 to drain down the header line to tank No. 4. When completed: Leave open valves 144, 147, 148, 160, 170, 180, in order to warm up line. When the line has warmed up close these valves.
Refer to trim and stability data provided. 24 Continue to monitor tanks pressure and cargo pumps current and discharge pressures. 25 Throttle each pump discharge valve as required to prevent tripping on low current as level in each tank drops.
Issue: 1
4.2 Discharging with Gas Return from Shore - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.2.8a Ballast Voyage With Normal Boil-Off Gas Burning
491
Vapour Dome Liquid Dome
492
Vent Gas Heater
Vapour Dome Liquid Dome
2 1 493
1 k n
Ta
2 1 Vapour Dome Liquid Dome 404
k an
494
2
T
Jettison
2 1
Vapour Dome Liquid Dome
Dual Purpose Heaters
453
460 TCV
454 450
TCV FCV
To Insulation Spaces
2
451
FCV
k an
452
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
ME001VR
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
411
To Engine Room
LNG Vapour
Demister
Inert Gas from Engine Room
421 HD Compressor No. 2 (Outboard)
k4
n Ta
LD Compressor No. 1 (Inboard)
431 FCV
Main Vaporiser
441 FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.2.8a Ballast Voyage With Normal Boil-Off Gas Burning
Cargo Systems and Operating Manual 4.2.8 Ballast Voyage A characteristic of the cargo tanks of the Gas Transport membrane type is that as long as some quantity of LNG remains at the bottom of the tanks, the temperature at the top will remain below -50°C. However, if the ballast voyage is too long, the lighter fractions of the liquid will evaporate. Eventually most of the methane disappears and the liquid remaining in the tanks at the end of the voyage is almost all LPG with a high temperature and a very high specific gravity which precludes pumping. Due to the properties of the materials and to the design of the membrane cargo containment, cooling down prior to loading is, theoretically, not required for the tanks. However, to reduce the vapour generation and to prevent any thermal shock on the heavy structures, eg the pump tower, loading takes place when the tanks are in a “cold state”.
Cold Maintenance During Ballast Voyage Different methods are used to maintain the cargo tanks cold during ballast voyages. 1 For short voyages a sufficient amount of LNG is retained in each tank at the end of discharge. The level must never be above 10% of the length of the tank and the quantities can be calculated by considering a boil-off of approximately 0.18% per day and the need to arrive at the loading port with a minimum layer of 10cm of liquid spread over the whole surface of the tank bottom (with the ship even keel). These actual quantities will have to be confirmed after a few voyages. With this method of cold maintenance, the tank bottom temperature should be below -150°C and the top below -50°C which allows loading without further cooling down. 2
During longer ballast voyages, the lighter parts of the liquid layer remaining in the tank, will evaporate, thus making the liquid almost LPG and at temperatures of higher than –100°C. The upper parts of the tanks will reach almost positive temperatures and under these conditions it will be necessary to cool down the tanks before loading.
Three methods of cooling down are possible, and the one selected will depend on the operating conditions of the ship.
Issue: 1
2.1 Cool down the tanks with LNG supplied from shore 2.2 Cool down the tanks just before arrival at the loading terminal. At the previous cargo discharge, a LNG heel is retained in one of the tanks, provided that the heel does not exceed 10% of the tank length. On top of the quantity to be sprayed, the amount of the LNG heel to be retained will be calculated by assuming a boil off equivalent of 50% of the boil off under laden conditions.
LNG LERICI After refit the first ballast voyage will have to be made using fuel oil only. Due to the different calorific values of fuel oil and gas, engine power will require controlling to prevent overloading the boilers.
2.3 Maintain the cargo tanks at cold during the ballast voyage by periodically spraying the LNG so that the average temperature inside the tanks does not exceed -120°C/-130°C. As before, a LNG heel is kept in one of the tanks, provided that the level does not exceed 10% of the tank length. On top of the quantity to be sprayed, the amount of the LNG heel to be retained will be calculated by assuming a boil off equivalent of 50% of the boil off under laden conditions. Cooling down is carried out by spraying LNG inside the tanks for whichever method is used. Each tank is provided with two spray rings, one capable of a large flow rate (equivalent to 55m3/h for all the tanks) and another of small flow rate (equivalent to 35m3/h for all the tanks). Note: It is obvious that this system will generate more boil-off than the first proposed system. The quantity of LNG to be retained on board will have to be calculated with enough margin to avoid the situation at mid-voyage where the residual is too heavy for the pump to operate. Conservation of bunkers is important, consequently the co-operation of all members of the management team is essential to ensure as much boil-off gas as possible is used to supply boiler fuel demand, thus keeping fuel oil consumption to a minimum. The LD. gas compressor is used for gas burning on the ballast voyage in the same way as on loaded, with control of compressor from vapour header pressures. (see section 4.2.8a gas burning operation) If a long delay at the loading port is experienced, the remaining heel will slowly boil off and the gas available for burning will reduce, care must be taken to stop gas burning as the tank system pressures continue to drop as the temperature rises. The degree of natural warm-up will depend on the time factor, voyage and weather conditions.
4.2 Ballast Voyage - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.1a Drying Cargo Tanks 482 481
487 492
491
010 483
Vapour Dome
Liquid Dome
485
Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
1 k n
Ta
2 030
063
1 Vapour Dome
Liquid Dome 090 494
k an
480
405
2
T
Jettison CL045FO
2 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1 453
460
454 450
470
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
Degassing Line Into Main Cargo Pump Cable Penetration
Wet Air
HD Compressor No. 2 (Outboard)
k4
n Ta
Key
Dry Air
Demister
Dry Air From Engine Room
3
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.1a Drying Cargo Tanks
Cargo Systems and Operating Manual 4.3 Out of Service Operations 4.3.1 Drying and Inerting Tanks During a dry docking or inspection, cargo tanks which have been opened and contain wet air must be dried to avoid primarily the formation of ice when they are cooled down and secondly the formation of corrosive agents if the humidity combines with the sulphur and nitrogen oxides which might be contained in excess in the inert gas. The tanks are inerted in order to prevent the possibility of any flammable air/LNG mixture. Normal humid air is displaced by dry air. Dry air is displaced by inert gas produced from the dry air/inert gas plant. The inert gas is primarily nitrogen and carbon dioxide, containing less than 1% oxygen with a dew point of -45°C or below. ! WARNING Inert gas from this generator and pure nitrogen will not sustain life. Great care must be exercised to ensure the safety of all personnel involved with any operation using inert gas of any description to avoid asphyxiation due to oxygen depletion. Dry air and inert gas are introduced at the bottom of the tanks through the filling piping. The air is displaced from the top of each tank through the dome and the vapour header, and is discharged from the vent mast No. 2.
•
Open the valves 460 and 063 to supply dry air to the LNG header.
•
Open tank filling valves 040, 030, 020, 010.
•
Open tank vapour valves 494, 493, 492, 491.
•
Open 481, 482, 483, 485 to vent through the mast No. 2. Eventually, tank pressure is controlled via the regulating valve 487. In this case, close 482.
•
Start the dry air production. When dew point is -45°C, open the valve XH/5321G upstream the two non return valves on the dry air/inert gas discharge line.
•
Monitor the dew point of each tank by taking a sample at the vapour domes. When the dew point is -40 °C or less, close the filling and vapour valves of the tank.
•
Wet air which may be contained in the discharge lines from the cargo pumps, float level piping and any associated pipe work in the cargo compressor room must be purged with dry air.
•
When all the tanks are dried, stop the plant. Close the supply valve 063 to the LNG header and close valve 481 to the venting system at the mast riser No. 2.
LNG LERICI
Note: It is necessary to lower the tanks dew point by dry air to at least -25°C, before feeding tanks with inert gas in order to avoid formation of corrosive agents.
The operation, carried out at shore or at sea, and will take approximately 40 hours to reduce the oxygen content to less than 2% and the final dew point to -40°C. During the time that the inert gas plant is in operation for drying and inerting the tanks, the inert gas is also used to dry (below -40°C ) and to inert all other LNG and vapour pipework. Before introduction of LNG or vapour, pipework not purged with inert gas must be purged with nitrogen. Operating Procedure for Drying Tanks (see figure 4.3.1a) Dry air, with a dew point of -45 °C, is produced by the dry air/inert gas plant at a 6500 m3/h about flow rate. • Prepare the dry air/inert gas plant for use in the dry air mode. •
Install the spool piece CL.045FO to connect the outlet of the heaters with the LNG header.
•
Ensure that the valves 450, 453, 454, 470, 405, 090 are shut.
Issue: 1
4.3 Out of Service Operations - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.1b Inerting Tanks Prior To Gas Filling
481
487 492
491
Vapour Dome
010 483
Liquid Dome
485
Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
k an
T
2 030
063
1
1 Vapour Dome
Liquid Dome 090 494
k2
n Ta
480
405
Jettison CL045FO
2 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1 453
460
454 450
470
k3
To Insulation Spaces
2
n Ta
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
Inert Gas
HD Compressor No. 2 (Outboard)
k an
T
Degassing Line Into Main Cargo Pump Cable Penetration Dry Air
Demister
Inert Gas from Engine Room
Key
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.1b Inerting Tanks Prior to Gas Filling
Cargo Systems and Operating Manual
LNG LERICI
Operating Procedure for Inerting Tanks (see figure 4.3.1b) Inert gas, with an oxygen content less than 1% and a dew point of -45 °C, is produced by the dry air/inert gas plant with a flow rate of 6500m3/h. • Emergency pump wells have to be inerted with nitrogen before inerting the cargo tanks. •
Prepare the dry air/inert gas plant for use in the inert gas mode.
•
Install the spool piece CL.045FO, to connect the outlet of the heaters with the LNG header.
•
Ensure that the valves 450, 453, 454, 470, 405 and 090 are shut.
•
Open the valves 460 and 063 to supply inert gas to the LNG header.
•
Open tank filling valves 040, 030, 020, 010.
•
Open tank vapour valves 494, 493, 492, 491.
•
Open 481, 482, 485 to vent through the mast No. 2. Eventually, tank pressure is controlled via the blow off valve (on/off) 487. In this case, close 482, open 483.
•
Start the inert gas production. When oxygen content is less than 1% and dew point is -45 °C, open the valve XH/5321G upstream of the two non return valves on the dry air/inert gas discharge line.
•
By sampling at the vapour dome, check the atmosphere of each tank by means of the portable oxygen analyser. O2 content is to be less than 2% and the dew point less than -40 °C.
•
During tank inerting, purge for about 5 minutes the air contained in the lines and equipment by using valves and purge sample points.
•
When the inerting of the tanks, lines and equipment is completed, set the regulating valve 487 to 1060mbar a in order to pressurise all the tanks to this pressure.
•
When the operation is completed, stop the supply of inert gas and close the valves XH/5321G and 063 and remove the spool piece CL.045FO.
Issue: 1
4.3 Out of Service Operations - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.1c Drying And Inerting Cargo Tanks Using Nitrogen From Shore 113
482 481
487 492
491
Vapour Dome
010 483
Liquid Dome
485
Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
k an
T
2 030
063
1
1 Vapour Dome
Liquid Dome
494
k2
n Ta
480
405
Jettison
2 502 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1 453
460
454 470
k3
To Insulation Spaces
2
n Ta
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room FCV
Demister
Inert Gas from Engine Room
456
Key Degassing Line Into Main Cargo Pump Cable Penetration Liquid Nitrogen
TCV
Gaseous Nitrogen
HD Compressor No. 2 (Outboard)
Wet Air
k an
T
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.1c Drying And Inerting Cargo Tanks Using Nitrogen From Shore
Cargo Systems and Operating Manual
LNG LERICI
Note: Until the ship is ready to load LNG, the tanks may be maintained under inert gas as long as necessary. If required, pressurise the tanks 20mbar above atmospheric pressure and, to reduce leakage, isolate all the valves at the forward venting system. Drying and Inerting Tanks with Nitrogen (see figure 4.3.1c) Drying and inerting of the cargo tanks can be carried out in one operation by using nitrogen instead of dry air and inert gas. Considering the large quantity of nitrogen required for this operation (about 160m3), liquid nitrogen is supplied from shore; it is then vapourised in the main vaporiser (see 2.6.2) and supplied to the tanks according to the same procedure as described above for dry air and inert gas. Note: Keep tanks in an inert gas condition as short as possible, due to the possibility of corrosion being formed.
Issue: 1
4.3 Out of Service Operations - Page 3
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.2a Displacing Inert Gas (Gassing Up) With LNG Vapour
491
062 CL/042F0
487
492
Vapour Dome
010 483
Liquid Dome
485
Vent Gas Heater
403
Vapour Dome
020 Liquid Dome
2
160
1
493
k an
T
2 190
030
063
1
1 Vapour Dome
Liquid Dome 404
180 494
090
k an
152
405
2
T
Jettison 154
002 004
2 156 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
402
1 453
460
406
158
006 008
454 470
To Insulation Spaces
2
k an
410
HD Compressor No. 1 (Inboard)
T
420
1 Forcing Vaporiser
FCV
To Engine Room
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
440 FCV FCV
Demister
Inert Gas from Engine Room
456
LNG
TCV
LNG Vapour
HD Compressor No. 2 (Outboard)
LNG Vapour and Inert Gas Mixture
k4
n Ta
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.2a Displacing Inert Gas (Gassing Up) With LNG Vapour
Cargo Systems and Operating Manual 4.3.2 Displacing Inert Gas with LNG Vapour As the first step in preparing to receive cargo after the tanks and piping have been dried and inerted, the inert gas in the tanks is displaced with LNG vapour at a temperature of about +20°C. The inert gas must be removed before the tanks are cooled down to avoid the formation of solidified CO2. The LNG vapour is lighter than the inert gas and is introduced at the top of the tank through the vapour piping. The mixture of inert gas and LNG vapour is discharged from the bottom of the tank through the normal filling piping into the LNG deck header. The discharged mixture is normally vented to atmosphere until the methane content reaches 5%; then, it is discharged to shore via the HD compressors. Depending on the port authorities, the discharge mixture may be returned to shore during the entire operation. The displacing operation is continued on each tank until the discharge from the bottom of the tank indicates a methane content of 90% and a CO2 concentration of less than 1% (or less if required by the terminal). The inert gas in the piping used for cooling down is displaced with dry nitrogen to avoid the possibility of blocking the sprayers with solidified CO2. Other piping may remain filled with inert gas. The LNG vapour is produced by the main vaporiser from LNG received from the shore terminal. The operation will take approximately 20 hours.
•
Prepare the main vaporiser for use.
•
Prepare both HD compressors for use.
Operating Procedure (see figure 4.3.2a) The operating procedure is as follows: • At the vaporiser, set the outlet temperature of the vapour at +20°C and pressure control valve at the LNG inlet at 60mbar above atmospheric pressure. •
At the venting mast No. 2, open 062, 483, 485. set the pressure control valve 487 at 150mbar above atmospheric pressure.
•
Open 160 connecting the stripping/spray header with the manifolds.
•
Close 180, 170 to limit the section of the header used for the supply of the main vaporiser.
•
Open 190 to supply LNG to the vaporiser.
•
Open 470, 405 to supply LNG vapour in the vapour header.
•
Open vapour valves 494, 493, 492, 491 on each tank.
•
Open filling valves 040, 030, 020, 010 on each tank.
•
Open 152 to supply LNG from the manifold.
•
Ensure that water curtain under the manifolds is in operation.
•
When shore is ready to supply LNG, open ESDS valve 002.
•
Monitor the exhaust gas at the sample intake of each filling line and at the mast No. 2. When the methane content is 5% (or less according to the port authorities requirements), prepare to discharge gas to the terminal.
Preparation •
Check that the nitrogen pressurisation system for the insulation spaces is in fully automatic operation.
•
Check that the gas detection system is in normal operation.
•
Set the compressor control to maintain a tank pressure of 60mbar above atmospheric pressure.
•
Install the following spool pieces:
•
Open the inlet and outlet valves of the HD compressors 420, 440 or 410, 430.
•
Open the valves 063 compressor suction from the LNG header and 406 compressor discharge to the vapour manifold.
•
Open 402 (or 401) the vapour manifold valve.
•
Start one or both HD compressors as necessary.
•
After the vapour return to shore with the compressors has been stabilised, reset the regulating valve 487 to 100mbar above atmospheric pressure to avoid venting except for safety.
•
• CL.045FO compressor suction from the LNG header. • CL.036FO LNG supply to main vaporiser from the stripping/spray header. • CL.043FO outlet of the vaporiser to the vapour header. • CL.042FO LNG header to venting system at mast No. 2. Fit the special conical strainer in the crossover connection through which LNG will be supplied.
Issue: 1
LNG LERICI •
Monitor the exhaust gas at the sample intake of each filling line. When the methane content is 90% or higher and the C02 content 1% or less, throttle the filling valves until they are only just cracked open.
•
Request the terminal to stop the LNG supply.
•
Stop both compressors.
•
Close valve 152 at the liquid manifold.
•
Do not shut down the main vaporiser until it has been warmed up.
4.3 Out of Service Operations - Page 4
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.3a(i) Tank Cool Down With Return Through LNG Header
114 118
115 191
116
481 487 124
010 483
Vapour Dome
Liquid Dome
484
485 486
125 192
126
Vent Gas Heater
128
170
Vapour Dome
020 Liquid Dome
2
160
1
134
1 k n
138
135 193
Ta
136
2 030
063
1 Vapour Dome
Liquid Dome 180
k an
152 144
Jettison
T
145 194
2
146
154
148
002 004
2 156 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
402
1 406
158
006 008
To Insulation Spaces
2
k an
410
HD Compressor No. 1 (Inboard)
420
1 430 FCV
To Engine Room
Forcing Vaporiser
T
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
440 FCV
LNG
Demister
Inert Gas from Engine Room
LNG Vapour
HD Compressor No. 2 (Outboard)
k4
n Ta
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.3a(i) Tank Cool Down With Return Through LNG Header
Cargo Systems and Operating Manual 4.3.3 Tank Cool Down Introduction Arriving at the loading terminal to load the first cargo after refit or when repairs requiring the vessel to be gas free the cargo tanks will be inert and at ambient temperature. After the cargo system has been purge-dried and gassed up, the headers and tanks must be cooled down before loading can commence. The cool-down operation follows immediately after the completion of gassing up, using LNG supplied from the terminal. The rate of cool-down is limited for the following reasons: a) To avoid excessive pump tower stress. b) Vapour generation must remain within the capabilities of the HD compressors to maintain the cargo tanks at a pressure of 70mbar (about 1085mbar absolute ). c) To remain within the capacity of the nitrogen system to maintain the interbarrier and insulation spaces at the required pressures.
Cool-down of the cargo tanks is considered complete when the top and bottom temperature sensors in each tank indicate temperatures of -130°C or lower. When these temperatures have been reached, and the Foxboro CTS registers the presence of liquid, bulk loading can begin. Vapour generated during the cool-down of the tanks is returned to the terminal via the HD compressors and the vapour manifold as in the normal manner for loading. During cool-down, nitrogen flow to the primary and secondary spaces will significantly increase. It is essential that the rate of cool-down is controlled so that it remains within the limits of the nitrogen system to maintain the primary and secondary space pressures at 4.0mbar and 3.0mbar respectively.
Issue: 1
•
• Use the spool piece CL.045FO (already in use for the gassing up), open the valve 063 from the LNG header and close 404 from the vapour header. • Open the inlet and outlet valves of the compressors 410, 420, 430, 440. • Open the valve 406 compressor discharge to the vapour manifold. • Open the filling valve 040, 030, 020, 010 on each tank. All the tanks are kept connected to the vapour header.
•
At the venting mast No. 2, open 481, 483, 484, 486.
•
Set the pressure control valve 487 at 100 mbar to avoid venting, except for safety.
Once cool-down is completed and the build up to bulk loading has commenced, the tank membrane will be at or near to liquid cargo temperature, it will take some hours to establish fully cooled down temperature gradients through the insulation. Consequently boil-off from the cargo will be higher than normal. Monitor the tank pressure and temperature cool down rate, Adjust the opening of the control valves 191, 192, 193, 194 to obtain an average temperature fall of 20/25oC per hour during the first 5 hours. There after 10/15oC per hour Preparation for Tank Cool-down •
Place in service the heating system for the cofferdams.
•
Close the valve 403 connection between the vapour header and the crossover.
•
Prepare the records for the tank, secondary barrier and hull temperatures.
•
•
Check that the nitrogen pressurisation system for the insulation spaces is in automatic operation and lined up to supply the additional nitrogen necessary to compensate for the contraction from cooling of the tanks. Prior to the cooling down, the nitrogen pressure inside the primary insulation spaces will be raised to 6mbar. Pressurise the buffer tank at maximum pressure.
Monitor the tank pressure and temperature cool down rate, Adjust the opening of the control valves 191, 192, 193, 194 to obtain an average temperature fall of 20/25oC per hour during the first 5 hours. There after 10/15oC per hour
Unlike rigid cargo tank designs, vertical thermal gradients in the tank walls are not a significant limitation on the rate of cool-down. LNG is supplied from the terminal to the cool-down bobbin piece and from there direct to the spray header which is open to the cargo tanks. Once the cargo tank cool-down is nearing completion the liquid manifold cross-overs, liquid header and loading lines are cooled down.
LNG LERICI
•
Check that the gas detection system is in normal operation.
•
Fit the special conical strainer in the crossover connection through which LNG will be supplied.
•
Prepare all the nitrogen generators for use.
•
Prepare both HD compressors for use.
•
Prepare the vent steam heater YA/5142 for use.
Operating Procedure - Gas Return Through LNG Header (See figure 4.3.3a(i) As reported by several ship operators, it seems accepted that the vapour return through the LNG header instead of the vapour header, makes the cool-down operation more efficient and prevents liquid droplets in the vapour stream. As far as the pressurisation of the insulation spaces and the LNG spraying lines to the tanks are concerned, the operating procedure of 6.5.2 is applicable. The only alternative concerns the return of the vapour to shore via the LNG header and the HD compressor(s). The lines are arranged as follows: • Suction of the HD compressor(s) from the LNG header:
Note: This is the preferred operational procedure which will normally take approximately 10/12 hours.
! CAUTION Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
4.3 Out of Service Operations - Page 7
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.3a(ii) Tank Cool Down With Return Through Vapour Header 117 114
481
491 118
115 191
116
Vapour Dome
487 124
492 127
125 192
126
483
Liquid Dome
484
486 Vent Gas Heater
128
170
Vapour Dome Liquid Dome
2
160
1
137 134 493 138
135 193
Ta
136
2
1 k n
1 Vapour Dome Liquid Dome 180 152
494 144
Jettison
147
145 194
146
154
148
nk Ta
2
002 004
2 156
Liquid Dome
402
1
Vapour Dome Dual Purpose Heaters
406
158
006 008
To Insulation Spaces
2
k an
410
HD Compressor No. 1 (Inboard)
420
1 430 FCV
To Engine Room
Forcing Vaporiser
T
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
440 FCV
LNG
Demister
Inert Gas from Engine Room HD Compressor No. 2 (Outboard)
n Ta
LNG Vapour FCV
k4 LD Compressor No. 1 (Inboard)
Main Vaporiser
FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.3.3a(ii) Tank Cool Down With Return Though Vapour Header
Cargo Systems and Operating Manual Operating Procedure - Gas Return Through Vapour Header (see figure 4.3.3a(ii)) •
Arrange nitrogen piping to preferentially feed the primary insulation spaces. Open the additional supply valves 561, 564.
•
Adjust set point of the nitrogen supply regulating valves 530, 510 at 6mbar and 520 at 3mbar.
•
Adjust set point of the nitrogen regulating relief valves 540 at 8mbar and 560 at 5mbar.
•
Open the valve 160 connecting the stripping/spray header with the manifolds.
•
Open the valves 180, 170 on the stripping/spray header.
•
Open 152 to supply LNG from the liquid manifold.
•
At each vapour dome Open the spray valves 144, 145, 146, 148; 134, 135, 136, 138; 124, 125, 126, 128; 114, 115, 116, 118, open the control valves 194, 193, 192, 191 to supply LNG to the spray rings.
•
Open vapour valves 494, 493, 492, 491 on each tank.
•
At the venting mast No. 2, open 481, 483, 484, 486. set the pressure control valve 487 at 100mbar above atmospheric pressure to avoid venting, except for safety.
•
Open the inlet and outlet valves of the compressors 410, 420, 430, 440.
•
Open the valves 404 compressor suction from the vapour header and 406 compressor discharge to the vapour manifold.
•
Open 402 (or 401) the vapour manifold valve.
•
When shore is ready to supply LNG, open ESDS valve 002.
•
After cooling down of the lines, request the shore to supply a pressure of 4 to 5 bars at the ship’s rail.
•
Monitor the tanks pressure and the temperature cooling down rate.
•
Adjust the opening of the control valves 194, 193, 192, 191 to obtain an average temperature fall of 20/25°C per hour during the four to five first hours and then 10/15°C per hour.
•
Start one compressor (or both as necessary) in order to maintain the tank pressure at about 30mbar above atmospheric.
•
Adjust the opening of the control valves supplying LNG to the spray rings in order to an even cool-down for all the tanks. If necessary open the by pass valves 147, 137, 127, 117.
Issue: 1
•
Check the nitrogen pressure inside the insulation spaces. If it has a tendency to fall, reduce the cooling down rate.
•
In case where other consumers reduce the availability of nitrogen for the insulated spaces, the pressure may temporarily fall below the atmospheric pressure. This condition is not critical insofar as the differential (Ps Pp) between the secondary space pressure (Ps) and the primary space pressure (Pp) does not exceed 30 mbars. (Ps - Pp < 30 mbars)
•
When the average of the temperatures shown by the sensors installed on the pump towers is -130°C, request the terminal to stop LNG supply and close the valve 152. The other valves will remain open until the lines warm-up.
•
Stop the compressor(s) if the loading does not take place after cooling down.
LNG LERICI
Note: This operating procedure is very time consuming and is not the preferred method. The operation preferred is gas return through LNG header.
! CAUTION Changes in temperature or barometric pressure can produce differentials far in excess of 30mbar in the insulation spaces which are shut in. With the cargo system out of service and during inerting, always maintain the primary insulation space pressure at or below tank pressure and always maintain the secondary insulation space pressure at or below the primary insulation space pressure. Severe damage to the membranes will result if the differentials exceed 30mbar. In case of emergency, put in communication the primary and secondary membranes.
4.3 Out of Service Operations - Page 8
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.4a Tank Warm Up 482 481
487 492
491
Vapour Dome
010 483
Liquid Dome
484
485 486 Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
k an
T
2 030
063
1
1 Vapour Dome
Liquid Dome 404
nk Ta
494
Jettison CL045FO
2
2 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1 453 TCV
454 TCV FCV
2
451
FCV
To Insulation Spaces
k an
410 452
HD Compressor No. 1 (Inboard)
420
1 430 FCV
To Engine Room
Forcing Vaporiser
T
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
440 FCV
LNG Vapour
Demister
Inert Gas from Engine Room
Warm LNG Vapour
HD Compressor No. 2 (Outboard)
n Ta
k4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.4a Tank Warm Up
Cargo Systems and Operating Manual 4.3.4 Tank Warm Up Tank warm up is part of the gas freeing operations carried out prior to a dry docking or when preparing tanks for inspection purposes.
Preparation •
The tanks are warmed up by recirculating heated LNG vapour. The vapour is recirculated with the two HD compressors and heated with the cargo heaters to 80°C. In a first step, hot vapour is introduced through the filling lines to the bottom of the tanks to facilitate the evaporation of any liquid remaining in the tanks. In a second step when the temperatures have a tendency to stabilise, hot vapour is introduced through the vapour piping at the top of the tanks. Excess vapour generated during the warm up operation is vented to atmosphere when at sea, or returned to shore if in port. (The instructions which follow apply to the normal situation, venting to atmosphere at sea). The warm up operation continues until the temperature at the coldest point of the secondary barrier of each tank reaches 5°C. The warm up operation requires a time dependent on both the amount and the composition of liquid remaining in the tanks, and the temperature of the tanks and insulation spaces. Generally, it requires about 30 hours.
•
•
Open the heater inlet and outlet valves 451, 452, 453, 454.
•
Open the vapour valves 494, 493, 492, 491 on each tank.
•
Open the filling valves 040, 030, 020, 010 on each tank.
Strip all possible LNG from all tanks as follows: • When discharging the final cargo, remove the maximum LNG with the stripping pumps. • If discharge of LNG to shore is not possible, vaporise it in the main vaporiser and vent the vapour to the atmosphere through the mast No. 2. • If venting to the atmosphere is not permitted, the vapour must be burned in the boilers. • For maximum stripping, the ship should have zero list and should be trimmed down at least 0.8m by the stern. • Run the stripping pumps until suction is lost. • Switch cargo/stripping pumps power lock ‘on’. Remove the emergency pump that may have been placed in a cargo tank.
Rolling and pitching of the vessel will assist evaporation. Temperature sensors at the aft end of the tank give a good indication of the progress of warm-up. Slight listing of the vessel will assist in correcting uneven warm-up in any one tank. Gas burning should continue as long as possible, normally until all the liquid has evaporated, venting ceased and tank pressures start to fall.
Initially, the tank temperatures will rise slowly as evaporation of the LNG proceeds, accompanied by high vapour generation and venting. A venting rate of approximately 8000 m3/h at 60°C can be expected. On completion of evaporation, tank temperatures will rise rapidly and the rate on venting will fall to between 1000 and 2000 m3/h at steadily increasing temperatures. Temperatures within the tank and insulation are indicated in the cargo control room
Operating Procedure (see figure 4.3.4a) During the tank warm up, gas burning may be used by directing some vapour from the heater outlet, to the boilers and by controlling manually this operation. • Install the spool piece CL.015FO and open the valve 063 to discharge heated vapour to the LNG header. •
Prepare the gas heaters YA/5141 A and B for use.
•
Prepare the glycoled water heaters
Rolling and pitching of the vessel will assist evaporation. Temperature sensors at the aft end of the tank give a good indication of the progress of warm-up. Slight listing of the vessel will assist in correcting uneven warm-up in any one tank.
•
Adjust temperature set point at 80°C.
•
Prepare both HD compressors YAI5121 A and B for use.
•
At vent mast No. 2, open the valves 481, 483, 484, 486.
Gas burning should continue as long as possible, normally until all the liquid has evaporated, venting ceased and tank pressures start to fall.
•
Adjust the set point of 487 at 190 mbars.g.
•
Prepare the vent heater YA/5142 for use.
•
Open the valve 404, the suction of the compressors from the vapour header.
•
Open the compressor inlet and outlet valves 410, 430, 420, 440.
Issue: 1
LNG LERICI
•
Start both HD compressors manually and gradually increase flow by the inlet guide vane position.
•
Monitor the tank pressure and adjust the compressor flow for maintaining the tank pressure to about 1180 mbars a.
•
•
•
•
Check that the pressure in the insulation spaces which have a tendency to increase remains inside the preset limits. Monitor the temperatures in each tank and adjust the opening of the filling valve to make uniform the temperature progression in all the tanks. After twenty/twenty-four hours, the temperature progression slows down. Eventually, the procedure of the second method described below, may be more efficient. At the end of the operation, when the coldest temperature of the secondary barrier is at least +5°C, or before switching to the second step, stop and shut down gas burning system if used. Stop both HD compressors, shut the filling valves on all tanks and restore the normal venting from the vapour header.
Operating Procedure 2nd Method Considering the waste of time for changing the position of heavy spool pieces, which must be put back in their original position for the next operation (gas freeing), the ship operators are not in favour of the above procedure and it may be regarded as optional.
At vent mast No. 2, install the spool piece CL 042FO and open the valves 062, 483, 484, 486. Adjust the set point of 487 at 190mbar g. Prepare the vent heater YA/5142 for use. Install the spool piece CL 045FO and open the valve 063, the suction of the compressors from the LNG header. Open the compressor inlet and outlet valves 440, 410, 420, 430. Open the heater inlet and outlet valves 454, 453, 451, 452. Open the vapour valves 491, 492, 493, 494 on each tank. Open the filling valves 010, 020, 030, 040 on each tank. Start both HD compressors manually and gradually increase flow by the inlet guide vane position. Monitor the tank pressure and adjust the compressor flow for maintaining the tank pressure at about 190mbar g above atmospheric pressure. Ensure that the pressure in the insulation spaces, which have a tendency to increase, remain inside the preset limits. Monitor the temperatures in each tank and adjust the opening of the vapour valve to make uniform the temperature progression in all the tanks. At the end of the operation, when the coldest temperature of the secondary barrier is at least +5°C, stop and shut down the gas burning system if used, stop both HD compressors and shut the filling valves on all the tanks and restore the normal venting from the vapour header.
During tank warm up, gas burning may be used by directing some vapour from the heater outlet to the boilers, and by manually controlling this operation. Open the valve 405 to discharge heated vapour to the vapour header. Prepare the gas heaters YA/5141 A and B for use. Adjust the temperature set point to 80°C. Prepare both HD compressors YA/5121 A and B for use.
4.3 Out of Service Operations - Page 9
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.4b One Tank Warm Up
491
Vapour Dome
010 487
483
492
Liquid Dome
484
485 486 Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
k an
T
2 030
063
1
1 Vapour Dome
Liquid Dome 404
k2
n Ta
494
Jettison
2 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1
400
406
453 TCV
454 TCV FCV
To Insulation Spaces
2
k3
451
FCV
n Ta
452
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
FCV
To Engine Room
FCV
Degassing Line Into Main Cargo Pump Cable Penetration LNG Vapour
Demister
Inert Gas from Engine Room
Key
Warm LNG Vapour
HD Compressor No. 2 (Outboard)
FCV
k an
T
4 LD Compressor No. 1 (Inboard)
Main Vaporiser
FCV LD Compressor No. 2 (Outboard)
Issue: 1
4.3.4b One Tank Warm up
Cargo Systems and Operating Manual
LNG LERICI
4.3.4b One Tank Warm Up When it is required that a single cargo tank be warmed up for maintenance procedures to be carried out, the operational procedures are as follows. Gas burning will be maintained as long as possible before the tank warm up procedure is commenced. It is assumed that the tank to be warmed up has been stripped are cargo as far as practical. Operating Procedure (see illustration 4.3.4b) Install spool piece CL 045FO •
Open bypass cross connecting valves 400 and 406. This enables the HD and LD compressors to be bypassed.
•
Open valve 062, 483 and 485 at No.2 vent mast riser. Adjust the set point of valve 487 at 150mbar g
•
Open liquid filling valve to tank 040
•
Bring into line one of the duel purpose heaters. Open 451,453.
•
Control the vapour outlet temperature to 80 °C
Follow the procedure described in 4.3.6 Tank Warm, for temperature rise control rates.
Issue: 1
4.3 Out of Service Operations - Page 10
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.5a Gas Freeing
481
487 492
491
010 483
Vapour Dome
Liquid Dome
485
Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
Ta
2 030
063
1 k n
1 Vapour Dome
Liquid Dome
nk Ta
494
Jettison CL045FO
2
2 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1 460
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
XH5321G
Degassing Line Into Main Cargo Pump Cable Penetration
Inert Gas
HD Compressor No. 2 (Outboard)
n Ta
Key
LNG Vapour
Demister
Inert Gas from Engine Room
3
k4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.5a Gas Freeing
Cargo Systems and Operating Manual 4.3.5 Gas Freeing After the tanks have been warmed up, the LNG vapour is displaced with inert gas. Inert gas from the inert gas plant is introduced at the bottom of the tanks through the LNG filling piping. Gas from the tanks is vented from the top of the tank through the vapour header to the vent mast No. 2, or to shore if in port. (The instructions which follow apply to the normal situation, venting to the atmosphere at sea). Inerting is necessary to prevent the possibility of having an air/LNG vapour mixture in the flammable range. The operation is continued until the hydrocarbon content is reduced to less than 2.5% (50% of the LEL). The operation requires about 20 hours. In addition to the cargo tanks, all pipe work and fittings must be gas freed. This is best done with inert gas or nitrogen, while the plant is in operation for gas freeing the tanks . The operating procedure is as follows: (see figure 4.3.5a) • Prepare the inert gas plant for use in the inert gas mode. •
Open the vapour valves 494, 493, 492, 491 on each tank.
•
At vent mast No. 2, open the valves 481, 483, 485 and Adjust the set point of 487 at 20 mbars.g.
•
Install the spool piece CL.045FO and open the valves 460, 063 for the supply of inert gas to the LNG header.
•
Open the filling valves 040, 030, 020, 010 on each tank.
•
Start the inert gas generator and run it until the oxygen content and dew point are acceptable.
•
On the dry air/inert gas discharge line, open the isolating valve XH/5321G located before the two non return valves. Change the spectacle blank over into the open position, which is located after the non return valves on A deck forward of the accommodation block port side.
•
Monitor tank pressures and adjust the opening of the fill valves to maintain an uniform pressure in all the tanks. Ensure that the tank pressures are always higher than the insulation space pressures by at least 10 mbars, but that the tank pressures do not exceed 180 mbars above atmospheric pressure. In any case, during gas freeing the pressure in the tanks must be kept low, to maximise the piston effect.
Issue: 1
•
Approximately once an hour, take samples of the discharge from the vapour dome at the top of each tank and test for hydrocarbon content. Also verify that the oxygen content of the inert gas remains below 1%, by testing at a purge valve at the filling line of one of the tanks being inerted.
•
Purge for 5 minutes all the unused sections of pipelines, machines, equipment and instrumentation lines.
•
When the hydrocarbon content sampled from a tank outlet falls below 2.5%, isolate and shut in the tank. On completion of tank and pipeline inerting, stop the inert gas supply and shut down the inert gas plant. Reset the valve system for aerating.
•
If the tanks remain inerted without aerating, shut the valve 481, raise the pressure to 100 mbars gauge, then shut in the tanks.
LNG LERICI
! WARNING If any piping or components are to be opened, the inert gas or nitrogen must first be flushed out with dry air. Take precautions to avoid concentrations of inert gas or nitrogen in confined spaces which could be hazardous to personnel.
4.3 Out of Service Operations - Page 10
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.3.6a Aerating
491
062 CL042F0
487
492
010
Vapour Dome
Liquid Dome
483 485
Vent Gas Heater
020
Vapour Dome
Liquid Dome
2 1 493
1 k n
Ta
2 030
1 Vapour Dome
Liquid Dome
494
nk Ta
405
Jettison
2
2 040
Vapour Dome
Liquid Dome
Dual Purpose Heaters
1 460
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
XH5321G
Dry Air
Demister
Dry Air from Engine Room
Inert Gas
HD Compressor No. 2 (Outboard)
n Ta
k4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.3.6a Aerating
Cargo Systems and Operating Manual mixture inert gas / dry air from the LNG header.
4.3.6 Aerating Introduction Prior to entry into the cargo tanks the inert gas must be replaced with air. With the Inert Gas and Dry-Air System (see 2.6) in Dry-Air production mode, the cargo tanks are purged with dry air until a reading of 20% oxygen by volume is reached. Operation The Inert Gas and Dry-Air System produces dry air with a dew point of -55°C to -65°C.
•
At the vent mast No. 2, open the valves 062; 483, 485. Adjust the set point of 487 at 20 mbars above atmospheric pressure.
•
Open the filling valves 040, 030, 020, 010 on each tank.
•
Open the vapour valves 494, 493, 492, 491 on each tank.
•
On the dry air/inert gas discharge line, open the isolating valve XH/5321G located before the two non return valves. Change the spectacle blank over into the open position, which is located after the non return valves on A deck forward of the accommodation block port side.
•
Start the dry air generator.
•
Open the valves 460, 405 to supply dry air to the vapour header.
•
Observe the tank pressures and insulation space pressures, to ensure that the tank pressures are higher than the space pressures by 10mbar.g at all times.
•
Approximately once an hour, take samples from the filling pipe test connections to test the discharge from the bottom of the tanks for oxygen content.
•
When the oxygen content reaches 20%, isolate and shut in the tank.
•
When all the tanks are completed and all piping has been aired out, raise the pressure to 100mbar g in each tank and shut the filling and vapour valves on each tank. Restore the tank pressure controls and valves to vent from the vapour header.
•
During the time that dry air from the inert gas plant is supplied to the tanks, use the dry air to flush out inert gas from vaporisers, compressors, gas heaters, crossover’s, pump risers and emergency pump wells. Piping containing significant amounts of inert gas should be flushed out. Smaller piping may be left filled with inert gas or nitrogen.
The dry air enters the cargo tanks via the vapour header, to the individual vapour domes. The inert gas/dry-air mixture is exhausted from the bottom of the tanks to the atmosphere at No. 2 mast riser via the tank loading pipes, the liquid header, and removable bend CL/042FO. During aerating the pressure in the tanks must be kept low to maximise a piston effect. The operation is complete when all the tanks have a 20% oxygen value and a methane content of less than 0.2% by volume (or whatever is required by the relevant authorities) and a dew point below -40°C. Before entry test for traces of noxious gases (carbon dioxide less than 0.5% by volume, and carbon monoxide less than 50ppm) which may have been constituents of the inert gas. In addition take appropriate precautions as given in the Tanker Safety Guide and other relevant publications. The pressure in the tanks is adjusted to 1020 mbars a. Aeration carried out at sea as a continuation of gas freeing will take approximately 20 hours
! WARNING Take precautions to avoid concentrations of inert gas or nitrogen in confined spaces which could be hazardous to personnel. Before entering any such areas, test for sufficient oxygen > 20% and for traces of noxious gases: CO2 < 0.5% and CO < 50 ppm. The operating procedure is as follows: (see figure 4.3.6a) • Prepare the inert gas plant for use in the dry air mode.
•
LNG LERICI
! CAUTION During the time a tank is opened for inspection, dry air will be permanently blown through the filling line to prevent the entry of humidity from the ambient air.
Install the spool piece CL.042FO for venting the
Issue: 1
4.3 Out of Service Operations - Page 11
Cargo Systems and Operating Manual 4.4
Emergency Operations and Procedures
Fire in Cargo Area and Use of Dry Powder Operate ESDS to stop cargo operations. Sound ships fire alarm. Start water spray pumps.
d) Attack fire with a maximum of application of dry powder. Do not agitate the surface of any pool of LNG. e) Remain on guard against possible re-ignition. The exact procedure will depend upon the nature of the incident.
Stop vent fans and secure crew quarters zone. If vessel is in port the fire fighting gear (pressurised fire main) will already be arranged on deck. Fire parties should be dressed in fire suits with B.A. Using a fine water spray curtain, ensure that the source of fuel (gas/liquid) to the fire is isolated. Dry powder either through hand held hoses or fixed monitors is the most effective fire fighting medium. Firefighting Procedures Although the flash point of LNG is -175°C, the rapid vapourisation of any exposed LNG prevents any ignition of the liquid itself and an LNG fire is thus a cold vapour fire. Ignition of a flammable mixture of natural gas vapour requires a spark of similar ignition energy as would ignite other hydrocarbon vapours. The auto-ignition temperature of methane in air (595°C) is higher than other hydrocarbons. Electrostatic ignition on LNG is not a hazard during normal operations. This is because the permanent, positive pressure in LNG tanks maintained by gas boil-off prevents air entering these spaces to form flammable mixtures in tanks or lines. Burning of LNG vapours produces a similar flame size and heat radiation to other hydrocarbon fires, but little smoke is produced. From a firefighting viewpoint LNG/cold vapour fires have the characteristics of both liquid and gaseous hydrocarbon fires. The procedure for fighting these fires is: a) Isolate the source of leak, stop loading/discharging, shut all manifold valves. b) Sound the alarm. c) Provide protection for adjacent equipment and for firefighters.
Issue: 1
Firefighting The following firefighting media can be used Water Water should not be used to extinguish LNG fires. A water spray or fog should be used to protect personnel and to cool areas adjacent to the fire. Care is necessary to avoid water running off any adjacent structure and aggravating burning LNG, or splashing into spill trays which may contain LNG, thus causing them to overflow onto unprotected steelwork. Foam Foam adequately applied to a depth of between 1 and 2m, will largely suppress the radiation from the flame to the liquid below, thereby reducing the vaporisation rate and rate of burning. The difficulty arises in trying to contain the foam mat covering, due to the lack of structures acting as containment areas and the effects of wind dispersing the foam. High expansion foam has been used successfully on LNG pool fires. If a stable foam is used, it has been found that if is freezes at the interface, the rate of vaporisation is reduced. If, on the other hand, the foam breaks down into the liquid beneath, the vaporisation rate may increase. In general, unless the foam can be contained, foam fixed installations are not fitted to LNG ships for liquified gas firefighting. Smothering Systems CO2 and nitrogen smothering systems are only effective when injected into enclosed spaces, or spaces that can be isolated by the closing of doors, flaps and hatch covers. The process by which these gases fight fires, is by displacing oxygen to a level which will not support combustion. It is therefore not considered practical for fighting fires on the open cargo deck.
LNG LERICI Dry Chemical Powder The extinguishing power of dry chemical powder depends on the chemical reaction of the small particles when exposed to flame. They are flame inhibiting agents and have been widely proved in LNG fire tests.
Rollover •
The rollover phenomenon is characterised by a sudden rapid generation of vapour. This problem arises because LNG is a multi-component mixture whose boiling point increases as its density increases. It mainly occurs in the land storage tanks when an heavier, warmer liquid is added to the bottom of a tank containing a lighter liquid. The energy transmitted into the tanks contents though the walls is partially used to vapourise the lighter layer and to warm-up the heavier layer. When its density approaches that of the lighter layer, it suddenly rises and, without the confining effect of the colder layer, rapid boiling and mixing occur. If exhaust devices and vents have insufficient capacity to handle the vapour so generated, tank failure may result.
•
Rollover is not expected to occur on ship since the motions in open sea serve to mix the cargo.
Various types of powder are marketed, potassium based powders are more effective than sodium based or multipurpose powders, but not all are foam compatible. All powders are liable to compact when subject to humid conditions or vibration, so filling and maintenance instructions should be carefully observed. The maximum possible rate of application of dry powder is desirable. As many high velocity jets as possible should be brought to bear at once, preferably in a down wind direction. Jets should be aimed with the objective of reducing boil-off rate by sweeping over whole fire area and on no account must the surface of LNG pool be agitated. Possible re-ignition must be guarded against. Fire in the Cargo Compressor Motor Room The cargo compressor and motor rooms are protected by a fixed CO2 smothering system consisting of 18 cylinders, each with a capacity of 60 litres. They are arranged in 2 banks that are housed in the CO2 bottle store, which is located aft of the motor room. The compressor room requires all 18 of the CO2 cylinders, while the motor room requires 9 of the 18 CO2 cylinders. Injection of CO2 is carried out from designated compressor and motor room control box stations, located in the CO2 bottles store. Operating instructions are contained inside the control box stations. Opening the control box station door trips the ventilation fans. Ventilation of Hazardous Spaces No tank, cofferdam or other enclosed space may be entered until it has been thoroughly ventilated. The atmosphere must be tested for hydrocarbons and oxygen and a safe entry certificate issued by a responsible officer. The compressor house and motor room fans must be running at all times. Ballast tanks and cofferdams must be ventilated and atmospheres tested, and safe entry permits issued by responsible officer prior to entry. Safety trolley to be standing by point of entry. Personnel entering must be kitted out with cap lamp and battery, cyalume light stick, VHF transceiver and personal oxygen analyser.
4.4 Emergency Operations and Procedures - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.4.1a Cargo Discharging Without Gas Return From Shore 003
001 491 053
051 012
007
005
057
011
055
Vapour Dome Liquid Dome
492
Vent Gas Heater
022 021
Vapour Dome Liquid Dome
2 1 493
k an
032 031
1
T
2 1 Vapour Dome Liquid Dome 090
nk Ta
CC/036FO 494
405
Jettison
2
042
2
041
1
Vapour Dome Liquid Dome
Dual Purpose Heaters
470
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1
455 FCV
Forcing Vaporiser
3
Key Degassing Line Into Main Cargo Pump Cable Penetration
TCV
To Engine Room
FCV
Demister
Inert Gas from Engine Room
456
LNG
TCV
LNG Vapour
HD Compressor No. 2 (Outboard)
k an
T
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.4.1a Cargo Discharging Without Gas Return From Shore
Cargo Systems and Operating Manual
LNG LERICI
4.4.1 Cargo Discharging without Gas Return from Shore Introduction If the shore is unable to supply LNG Vapour to maintain tank’s pressure, the spray system and, if necessary, the Main Vaporiser is used to generate vapour in order to maintain the required pressure. The discharging is in all other aspects the same as when being supplied with gas return from shore. Operation Discharging is carried out in exactly the same manner as line cool-down and detailed in Section 4.2.3 except that the manifold vapour connection is not used. The main Vaporiser is set to maintain the tank’s pressure at 1100mbar a. and it will operate during the entire discharge period.
•
If the LNG header pressure should be lost, in an emergency or other special situations, supply LNG through the stripping/spray header from one of the stripping pumps.
•
If the vaporiser is to be used as the normal supply for vapour while discharging cargo, the LNG is taken from the LNG header, with an alternative supply available from the stripping/spray header in an emergency.
•
Prepare main vaporiser for use.
•
Open main vaporiser outlet valve 470 and valve to vapour header 405.
•
Open valve 090 to supply LNG from the LNG header or 190 to supply LNG from the stripping/spray header
•
Open LNG inlet valve to the vaporiser 456 and position bend CL/036FO.
•
Start up manually the vaporiser. When the vaporiser has stabilised transfer control to the Cargo Control Room.
•
During cargo discharge, monitor tanks pressure.
•
When cargo discharge is completed, stop the main vaporiser by closing the valve 470 or 405, leave other valves open until the warming up of the lines is complete.
Issue: 1
4.4 Emergency Operations and Procedures - Page 2
Cargo Systems and Operating Manual
LNG LERICI
! WARNING Before commencement of operation, lower tank pressure to just above atmosphere. 1
2
3
4
5
6
7
8
Nitrogen gas pressure displaces LNG from column
Inert column with nitrogen gas After inerting, stop nitrogen gas, then bleed off nitrogen gas pressure in column
Remove blind flange Install column flange gasket Prepare to install the pump using lifting cable
Lower pump Lift pump and head plate Lifting assembly in 'closed' position
Install head plate with lifting assy in 'closed' position Install electrical assembly and support bracket Install deck power cable assembly Start cool down for pump by suspending above suction valve
Pressurise with nitrogen gas to open suction valve with lifting assembly in 'closed' position After opening maintain nitrogen gas pressure in column
Lower pump completely by adjusting lifting assembly to 'open' position Cool down pump Bleed off pressure in column to slowly introduce LNG into the column
Operate Pump
Cable Guide Support Plate Assy
Lifting Assembly Head Plate
LNG Discharge Pipe Nitrogen Gas Blind Flange
Column Flange Gasket
Nitrogen Gas
Lifting Cable Deck Power Cable Nitrogen Gas
Nitrogen Gas
Nitrogen Gas
Nitrogen Gas
Nitrogen Gas
Tank Top
Lifting Cable Auxiliary Cargo Pump
In-Tank Power Cable
Tank LNG Liquid Level
Cable Guide
In-Tank Power Cable Support Block and Spreader Bar Assembly
Column
N2 Gas
N Gas 2
Suction Valve
Illustration 4.4.3a Emergency Cargo Pump Fitting Sequence
Issue: 1
4.4.3a Emergency Cargo Pump Fitting Sequence
Cargo Systems and Operating Manual 4.4.3 Use of Emergency Cargo Pump The emergency cargo pump is used in the event that both main cargo pumps have failed in a cargo tank. The pump is suppled with a set of lifting pipes, three phase cargo power cables, cable terminal box, mounting plate and spring loaded roller guides. The cables are attached to the lifting pipe at regular intervals of 457mm. The roller guides are set out at intervals of 2438mm apart.
Install the power cables on the pump. Ensure power cables are carefully laid down on deck and suitably protected to avoid any damage. The power cable ends are marked “A”, “B” and “C” and should coincide with the same markings on the pump to ensure correct phase rotation. Lower the pump in the column. Attach the head plate and lift pump and head plate with lifting assembly in the closed position. -
The pump is suspended over the column into which it is being lowered by a portable set of sheer legs. Also fitted to the column is a nitrogen purge point and an outlet purge point on the cable outlet bend. The pump discharges into the column and out onto the liquid line via a discharge connection and valve at the top of the column. Installation in the Tank (See Illustration 4.4.3a) When all equipment, pump, cables, electrical connection box and accessories are in position near the tank in which the pump is to be installed, prepare the sheer leg to lift the pump and start the pump installation. -
The cargo tank will inevitably contain LNG, therefore the column into which the emergency pump is being lowered will require the liquid to be evacuated. This is achieved by injecting nitrogen into the column. In the case of a full cargo tank, a pressure of between 2 and 3bar is required. The nitrogen forces the liquid out through the foot valve located at the bottom of the column. On completion of the expulsion of the liquid, a check must be made at the purge cock to ensure complete inerting has taken place. The tank pressure must be reduced to just above atmospheric, before removing the column top blank flange. Install a new column flange gasket, then begin to install the pump using the lifting gear.
! CAUTION When working near the open pump column all tools and equipment used have to be attached to avoid anything falling in the column. All personal items have to be removed from pockets and column opening should be temporarily covered at all time whilst blind flange is removed.
Issue: 1
LNG LERICI Check operation very carefully to ensure that there is no leakage at top of column or discharge piping. Fire hoses must be under pressure and ready in the vicinity before starting. Adjust opening of the discharge valve to have required discharge flow and pressure within the pump capacity. If the first start is not successful refer to Section 4 for the allowable number of starts.
When the pump is lowered into position above the suction valve, install head plate with lifting assembly in closed position, being very careful with the gasket. Install electrical assembly and support brackets. Install deck power cable assembly making sure that “A”, “B” and “C” markings are matched at all connecting points.
Pump Cool-down and Operation Start cool-down for pump. Pump should be left suspended in the empty column for 10 to 12 hours for a correct cooldown. After 10 to 12 hours introduce nitrogen pressure in the column to open suction valve with lifting assembly in the closed position. Decrease the nitrogen pressure slowly to let the liquid rise in the column at a speed of approximately 75 to 125 mm / minute until it covers the pump completely. (Approximately 2 meters). When the liquid level is above the pump, maintain the nitrogen gas pressure and lower the pump completely by adjusting the lifting assembly to the open position. Stop the nitrogen supply when the liquid is at the same level in tank and column and bleed the nitrogen from the top of the column. The pump will have to stay for one hour immersed in the liquid before being started. Before starting the pump, the discharge valve has to be opened to ensure that there is no pressure built up at the top of the column when starting the pump. If necessary excess pressure can be bled off via the purge cock. When ready to start the pump, open the discharge valve 20 per cent and start the pump normally.
4.4 Emergency Operations and Procedures - Page 3
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.4.5a Jettisoning Of Cargo
Vapour Dome Liquid Dome
Vent Gas Heater
021
Vapour Dome Liquid Dome
2 1
k an
1
T
2 1 Vapour Dome Liquid Dome
k2
000
n Ta
061
Jettison
2 1
Vapour Dome Liquid Dome
Dual Purpose Heaters
k an
To Insulation Spaces
2
T
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
Key Degassing Line Into Main Cargo Pump Cable Penetration LNG
Demister
Inert Gas from Engine Room
3
HD Compressor No. 2 (Outboard)
k4
n Ta
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.4.5a Jettisoning Of Cargo
Cargo Systems and Operating Manual 4.4.4 In Service Repairs to Tanks It maybe necessary for in-tank repairs to be carried out with the vessel in service in which one tank can be warmed up, inerted, aerated, entered and work undertaken on tank internals i.e. change cargo pump investigate and cure problems with tank gauging system etc. It is not envisaged that tank barrier repairs will be carried out with one tank only warmed up.
The discharge rate must be limited to the capacity of one cargo pump only and, if necessary, reduce to allow acceptable dispersal within the limits of the prevailing weather conditions. It is preferable for the vessel to be moving slowly away from the vapour cloud as jettisoning takes place. Jettisoning
The warm-up, inert, aerating can be carried out with the remaining cold tanks providing gas for gas burning. Aeration should be continued throughout the repair period, to prevent ingress of humid air to the cargo tank. Tank venting will be via its own riser, inerting time can be reduced by floating the tank relief valves.
Under extreme circumstances it may be necessary, as a last resort, to consider jettisoning of cargo to the sea. Dispersion models based on extensive experimental data exist to predict the downwind concentrations for defined weather conditions, wind velocity and surface roughness. These allow prediction of downwind flammable hazard zones arising from spills of refrigerated LNG and LPG.
4.4.5 Jettisoning of Cargo
! WARNING The jettisoning of cargo is an emergency operation. It should only be carried out to avoid serious damage to the cargo tank and/or inner hull steel structure. A membrane or insulation failure in one or more cargo tanks may necessitate the jettisoning of cargo from that particular cargo tank to the sea. This is carried out using a single main cargo pump, discharging LNG through a portable nozzle fitted at ships stern via spool piece. As jettisoning of LNG will create hazardous conditions: a) All the circumstances of the failure must be carefully evaluated before the decision to jettison cargo is taken. b) All relevant fire fighting equipment must be manned, in a state of readiness and maintained so during the entire operation. c) All accommodation and other openings and all vent fans must be secured. d) The NO SMOKING rule must be rigidly enforced. Weather conditions, and the heading of the vessel relative to the wind, must be considered so that the jettisoned liquid and resultant vapour cloud will be carried away from the vessel. In addition, if possible, avoid blanketing the vapour with exhaust gases from the funnel.
Issue: 1
Wind tunnel tests have been undertaken on the release of liquefied gases from a small sea-going tanker so as to provide recommendations for the safe venting of gas and jettisoning of liquid. This section considers the characteristics of some of the principle cargoes and factors additional to the characteristics of the cargo itself including:
LNG LERICI slumping upwind and extending downwind from the source, growing in height and gradually becoming diluted by mixture with air. The distance at which the average concentration has been diluted to the Lower Flammable Limit or toxic limit, i.e. the hazard distance, will depend not only on the quantity and rate of spill but also on the flammability/toxic limits of the cargo itself, wind speed and atmospheric stability, with distances tending to be greatest in a stable atmosphere and low wind speeds of 5-6 knots. Information indicating the maximum downwind hazard distances for the jettisoning of LNG and LPG onto the sea is available. The Incident Controller and concerned Authority may decide to seek guidance specific to the site conditions. The ambient humidity will also be a major factor on the visible limits of the plume, since cooling of the entrained air to below its dewpoint will result in a white visible cloud. For humidities in the range ot 60-90%, propane plumes cease to be visible at dispersion distances well short of the LFL (2%) but beyond the UFL (10%). LNG plumes, however, remain visible beyond the LFL point (5%) for all humidities greater than about 50%.
The Effect of the Ship’s Hull Unhindered dispersion models which can reliably predict the vapour dispersion characteristics of unhindered land and sea cargo spills are not appropriate when the spill occurs in the direct vicinity of an obstacle of comparable size with the dimensions of the vapour source. This is normally the case during jettisoning where the turbulence of the wind field generated by the ship’s hull in the prevailing wind direction can significantly modify not only the distribution of the vapour concentrations in the immediate vicinity of the ship itself but also the extent of the downwind hazard zone. Eddy currents on the down wind (lee) side of the ship can drag vapour concentrations onto the deck and also back onto the sea surface adjacent to the ship’s side from a liquid pool adjacent to the ship. Under some conditions the concentrations can exceed the LFL (or toxic limit). The turbulence generated by the ship’s hull can considerably reduce the downwind distance to LFL (or toxic limit) for midships jettisoning with a cross wind.
While little direct experimental dispersion data is available for the sea spills of ammonia. it may be expected that, for similar spill conditions, the behaviour of an ammonia plume will be broadly similar to LNG/LPG spill plumes with the exception that:
The Windspeed and Direction Relative to the Ship and the Position of Discharge from the Ship
Full scale tests at sea with an astern cargo jettison connection have demonstrated that LNG cargo discharge rates up to 1,200 m3/hr from the stern are practicable with the ship steaming ahead or stationary under the following conditions:
All spills of liquefied gases initially generate a cold dense heavier-than-air vapour cloud and show the same general trends in downwind dispersion.
• Due to the toxic limit of about 500 ppm (0.05%) considerably greater dispersion distances may be required • A release of liquefied ammonia under pressure may behave as a heavier-than-air gas until completely dispersed • The higher LFL concentration (15%) should ensure that for normal atmospheric humidities, the flammable zone will be generally well within the visible cloud. • Due to the considerable heat of reaction of ammonia/water mixtures and the low relative density of ammonia vapour, there will be a more rapid upward dispersion of the ammonia plume above a spill of liquid ammonia into the water.
Such liquefied gases will include not only all refrigerated cargoes including LNG, LPG and ammonia but also all pressurised cargoes that become auto-refrigerated on release to the atmosphere. These vapour clouds will form a low spreading plume on the sea surface, initially
Ecological considerations may make it very undesirable to jettison a substantial quantity of liquid ammonia into shallow seas. In these circumstances, slow atmospheric dispersion may be preferable so as to minimise local concentrations in the sea.
• The effect of the ship’s hull • The wind speed and direction relative to the ship • The position of discharge from the ship i.e. bow, stern or midships • Use of cargo hose or fixed discharge nozzle and degree of vaporisation The salient features relating to jettisoning derived from these tests are summarised below. In addition, from the present limited knowledge of the vaporisation and dispersion characteristics of other liquefied gas cargoes e.g. ammonia, an attempt is made to indicate the likely differences in their jettison behaviour relative to LNG/LPG. Cargo Characteristics Relevant to Jettisoning
Experimental data on jettisoning has been derived from both full-scale tests and model simulation in a wind tunnel
• The ship can manoeuvre to maintain the wind direction ideally between 300 and 600 off the bow to ensure that eddy effects do not drag flammable vapour concentrations back onto the ship. • The relative wind speed is not less than 5 knots. • The nozzle exit velocity is 40-50 m/s. Under these conditions it was found that: •
A large proportion of the LNG vaporised before reaching the sea and liquid pools on the sea surface were limited to small isolated patches that presented no risk to the ship’s hull.
4.4 Emergency Operations and Procedures - Page4
Cargo Systems and Operating Manual • At an average wind speed of 5 knots, the flammable region of the vapour cloud produced extended no further than 700 m downwind although the visible cloud extended appreciably further due to the condensation of atmospheric moisture. Higher wind speeds would have reduced this distance even further. Despite the low wind speed, the vapour cloud dispersed without trace within 20 minutes of stopping the discharge. The results of wind tunnel model simulation tests of LNG jettisoning from a 75,000 m3 carrier are available. These illustrate the limiting safe heading of the ship relative to the wind direction for jettisoning either from the bow or from the midships manifold for discharge rates of about 2,000 m3/hr and wind speeds in the range of 20-40 knots. Eddy currents caused by the hull structure can drag flammable vapour concentrations back onto the deck for all wind directions beyond about 150 either side of the longitudinal centre line of the ship. Vertical elevation of the nozzle to 450 can reduce these concentrations for wind directions across the ship in the direction of the LNG jet by projecting the liquid above and beyond these eddy currents. Bow (and to a similar extent, stern) discharge is possible for virtually all relative wind directions except within 300 of the direction of the nozzle discharge. In these cases the nozzle elevation has little effect. Wind tunnel tests simulating the jettisoning of pressurised propane amidships at a rate of 80m3/hr from a small sea-going tanker have also confirmed that the relative wind direction should be near to 00 or 1800 and that hazardous gas concentrations can occur at deck level at other wind directions. Hose or Nozzle Discharge and Degree of Vaporisation These references have confirmed that the use of a fixed nozzle so as to achieve a liquid velocity of 40-50 m/s is to be preferred over the use of a simple pipe extension or flexible hose led down to the water line, which result in gas concentrations close to the hull. Use of a correctly sized nozzle to achieve the recommended liquid velocity, or sonic two-phase flow for pressurised liquefied gas, results in gas cloud formation separated from the ship’s side. All Iiquefied gases should always be jettisoned clear of the steel huII structure to prevent risk of brittle fracture. Experiments have shown that water spray jets can entrain large quantities of the air or vapour surrounding the liquid
Issue: 1
jet (around 6,000 m3 air/vapour per m3 of water). Under jettisoning conditions, the cargo jet may be expected to entrain similar large quantities of atmospheric air and moisture. Thus, in addition to any two-phase flow at the jet outlet due to flashing of the cargo, sensible and latent heat exchange will occur between the cargo and the entrained air/moisture. This will result in further cargo vaporisation along the trajectory prior to striking the sea surface. This phenomena has been noted in the full-scale LNG jettison tests. Refrigerated ammonia, although similar in pressure and temperature to propane, will generally show less vaporisation due to its appreciably greater latent heat. Although the vaporisation of the jet trajectory does not affect the total amount of vapour generated for a given cargo and discharge rate, it does cause more vapour to be generated at or near deck level and consequently increase the probability of hazardous vapour concentrations under unfavourable wind conditions. Ammonia is readily absorbed in water and there may be occasions when it is thought preferable to discharge liquid ammonia through a hose down to the water surface with the ship going astern to ensure that the ammonia liquor does not enter the ship’s cooling water systems. Smallscale experiments indicate that up to 60% of the ammonia may go into solution in the sea water and therefore substantially reduce the dispersion distance for the toxic hazard. It is important that water is not drawn up through the hose and back into the cargo tank. The powerful absorption of ammonia into water can result in vacuum damage to the tank. Ecological considerations may suggest that atmospheric dispersion is preferable as described earlier.
LNG LERICI There is also a possibility of spillage of liquid nitrogen if it is loaded to the main vaporiser for inerting the cargo tanks with nitrogen, during insulation space first inerting. i)
The Midships Manifold Any spillage occurring at the manifold will fall onto the manifold spillways which direct the spillage overboard. The ships hull in the vicinity of the manifolds is protected by a water spray curtain supplied by the deck fire main; this curtain should be in use at all times during cargo handling operations. The manifold area on each side is also protected by spray nozzles which can be supplied by the deck spray system in the event of major spillage. The ship/shore emergency manifold valve shut down system (ESDS) is intended to reduce any such spillage to a minimum.
ii) Cargo Piping Joints and Valves The possibility of leakage due to piping joints has been reduced to a minimum by the use of extensive welding as opposed to flanging. Regular maintenance of valve glands will reduce the possibility of leakage from valves. Leakage from these sources will normally be of a minor nature, but each valve is also protected with a spray nozzle supplied by the deck spray system.
Manifold Hull water spray curtain to be in operation;
3
Fire fighting equipment to be laid out ready for use;
4
Constant patrol of cargo area to be maintained;
! WARNING
5
Protective clothing and tools to be available at hand;
Too rapid a flow of LNG will result in R.P.T when liquid hits the sea water.
6
Deck spray pump system ready for use.
Introduction Cargo spillage should not occur under normal circumstances but may occur due to failure of valves or pipelines by inherent or external means. Spillages are normally of a minor nature when they first occur and vigilance is required during cargo operations so that any faults may be quickly identified and dealt with to prevent the situation escalating. The potential sources of spillage are from: i) The midships manifold; ii
Cargo piping joints and valves.
START
deck water spray system.
SHUT
ship and shore manifold valves.
SOUND
the general alarm.
SHUT
all accommodation doors and STOP all ventilation fans. all smoking and the use of naked lights.
STOP USE
all necessary fire fighting equipment, breathing apparatus and protective clothing.
USE
hand spray to disperse liquid overboard and to warm the deck and if necessary to deflect the gas cloud. After a major spillage all affected areas should be thoroughly inspected for any signs of cold shock fractures.
Dealing with Spillages During any cargo handling operations the following precautions should be observed : 1 Deck fire main to be pressurised; 2
4.4.6 Cargo Spillage on Deck and Piping Leakage
Major Spillage A major spillage will normally necessitate the use of the water spray system backed up by portable fire hose water sprays. The spray system not only protects the deck area and deck housings from brittle facture but also helps dispense and evaporate the LNG and acts as a fire curtain to protect the accommodation. In the event of a major spillage the following action is to be taken : STOP cargo operations.
Minor Spillage Minor spillages will normally be due to leakage from flanges or glands and can be dealt with by a fire hose water spray whilst the leak is being stopped by tightening down and/or the use of wet rags. If such a leakage cannot be stopped and it requires attention, cargo operations should be suspended whilst the fault is being rectified. Protective clothing and, if necessary, breathing apparatus should always be used when dealing with ANY form of cargo leakage. A second person should stand-by in order to alert the Cargo Control Room if the leakage develops into one of a major nature.
4.4 Emergency Operations and Procedures - Page 5
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.4.7a Overfilling Of Cargo Tanks
491 401
Vapour Dome Liquid Dome
492
Vent Gas Heater
021
403
Vapour Dome Liquid Dome
2 1 493
k an
T
2 030
1
1 Vapour Dome
Liquid Dome
k2 n a
494
T
Jettison
2 1
Vapour Dome Liquid Dome
Dual Purpose Heaters
k an
To Insulation Spaces
2 1
Forcing Vaporiser
To Engine Room
Degassing Line Into Main Cargo Pump Cable Penetration LNG
Demister
LNG Vapour
HD Compressor No. 2 (Outboard)
n Ta
Key
T
HD Compressor No. 1 (Inboard)
Inert Gas from Engine Room
3
k4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.4.7a Overfilling Of Cargo Tanks
Cargo Systems and Operating Manual
LNG LERICI
4.4.7 Overfilling of Cargo Tanks In the unlikely event of a cargo tank being overfilled, the high level trips will shut tank filling valves and initiate an ESDS situation and stopping cargo loading. Gas burning and compressors must be shut down. There will possibly be LNG in the vapour header, this will require draining into a slack tank. Vapour pressure will rise rapidly. Use of a main cargo pump will enable the cargo to be transferred from the overfull tank into slack tanks, Request shore to take vapour as soon as possible. Recovery from Off Limit Level Shutdown •
Shut the fill valves on any tanks which are near the full level.
•
Turn the control of any valves affected by the shutdown to shut.
•
Request the terminal to restore the vapour shore return system. Then, proceed as follows:
•
•
• Block the tank very high level alarm. • Reset the shut down. • Reopen the vapour crossover manifold valve. • Verify pressure at the crossover. Transfer LNG from the overfilled tank into another cargo tank, to restore the tank level to normal: • Open the fill valve of the tank to which the transfer will be made. • Start one cargo pump in the overfilled tank. • Transfer LNG until the tank level reaches normal. As soon as the shutdown condition is corrected, restore the very high level blocking switch to normal and resume the loading conditions.
Issue: 1
4.4 Emergency Operations and Procedures - Page 6
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.4.8a Secondary Barrier Space De-Watering
Nitrogen Supply Column to Secondary Barrier
Secondary Insulation Space
Air Driven Water Pump
Issue: 1
4.4.8a Secondary Barrier Space De-Watering
Cargo Systems and Operating Manual 4.4.8 Structural Failure of Inner Hull Introduction (See Illustration 4.4.8a) Ballast water leakage from the ballast tanks to the insolation spaces may occur due to fracture of the inner hull plating. If the leakage remains undetected and accumulates in these spaces: a) Ice formation could cause deformation and possible rupture of the insulation with subsequent cold spot occurring due to cold convection paths being opened through the insulation. b) Destruction of the insulation due to sloshing of the water.
! CAUTION It is important to note that the design pressure limitations is 0.3 meters water head. To reduce the risk of damage from these causes, a system of leakage detection and removal has been installed in the vessel for secondary insulation spaces. Leak Detection and Removal Each secondary insulation space is fitted with water detectors which initiate alarms in the CCR identifying the affected space. A group cargo alarm is also initiated in the wheelhouse via the IMS, to indicate that water has been detected in a secondary insulation space, which may mean an inner hull failure.
! CAUTION
LNG LERICI
Operating Procedure If the moisture detector alarm is initiated or if there is any other reason to suspect ballast leakage into a secondary insulation space, the following action should be taken IMMEDIATELY : 1
If ballast is being carried adjacent to the suspect leak, pump out immediately, having due regard to stress and stability.
2
Close the nitrogen supply as appropriate to isolate the affected space.
3
Start pump and run continuously if necessary.
On completion of leakage removal. 4 Inspect inner hull thoroughly in way of the affected tank to establish the cause of failure and repair the fracture. Even after discharging the bulk of the water, appreciable moisture will remain in the insulation and over the bottom area of the tank. In order to assist drying out of the insulation. 5 Open nitrogen supply to the affected secondary space. Increase flow rate of secondary space nitrogen until the dew point measure at the exhaust is back to -40°C or below.
! CAUTION No cargo should be carried in the affected cargo tank until satisfactory repairs have been carried out and until the moisture content in the secondary space has been reduced to an acceptable level.
It is essential that the correct functioning of the alarms of these detectors is checked frequently and that any alarm condition is investigated immediately. For water leakage removal, a permanently installed air driven pump is located in a well at the foot of the secondary barrier space nitrogen filling column. The pump is permanently connected to an air supply and water discharge hose. Should a water indication alarm be activated in a space, the air supply should be opened on that pump and the water discharged overboard.
Issue: 1
4.4 Emergency Operations and Procedures - Page 7
Cargo Systems and Operating Manual 4.4.9 Ship Shore Operations in Event of Fire or Emergency Introduction In order to minimise the possibility of an emergency situation occurring, it is essential for close liaison between ship and shore during cargo operations and during the entire stay alongside a terminal.
affected area should be covered with sterile dressing. Otherwise, the treatment should be as for hot burns. Safety training, such as ‘Gas Carrier Safety Courses’ should have been attended by all personnel involved with the cargo operations handling LNG.
Detailed plans and procedures to be followed for both normal conditions and abnormal/emergency conditions have been established and are given in the Cargo Handling Regulations of the LNG terminals which are carried on board.
Protective clothing, boiler suit, helmet, gloves, goggles and safety shoes are to be used at all times when working with LNG systems. Under special conditions low temperature protection suites should be available. LNG will dilute oxygen in an atmosphere and precautions must be taken against oxygen deficiency in any space where methane can build up. SCBA must be available.
These manuals detail the procedures to be followed by both ship and shore for all normal cargo operations together with the procedures to be followed for all foreseeable emergencies which may occur.
LNG cold burns should be treated in the same way as hot burns, with immersion in tepid water or wrap in a blanket to restore circulation to the burnt area, then covered with a sterile dressing, blisters must not be opened.
4.4.10 Personnel Contact with LNG In contact with LNG or vapour, the main risks for the personnel are: asphyxia, low temperature and flammability.
Oxygen from a resuscitator should be used in the case of respiratory failure.
In casualties involving asphyxia: • Remove from exposure. •
Apply Artificial Respiration if required.
•
Apply external Cardiac massage.
•
Loosen clothing.
•
Give oxygen if laboured breathing.
•
Give non alcoholic drinks if desired.
•
Keep as rest.
•
Unless symptoms are minor, seek medical advice.
Cold liquefied gas spilled onto the skin removes sensible heat on contact and latent heat on evaporation. These effects can cause extensive burns to exposed skin. In case of cold burns, the affected part should be warmed with the hand or woollen material in the first instance. If the finger or hand has been burned, the casualty should hold his hand under his armpit. The affected part should then be placed in warm water at about 42°C. If this is not practicable, then the casualty should be wrapped in blankets and the circulation should be allowed to re-establish itself naturally. If possible, the casualty should be encouraged to exercise the affected part while it is being warmed. Blisters should never be cut or opened, nor clothing removed if it is adhering firmly. The entire
Issue: 1
4.4.11 Fire Control Procedure for Main Vent Mast (Nitrogen Injection) Vent Risers Under certain circumstances, excess boil-off gas must be vented to atmosphere via the cargo tank vent risers. Apart from the purging operations before and after docking or repair, venting will be via the vent riser No. 2, i.e. well away from machinery and accommodation spaces. Under normal venting circumstances, however, LNG vapour diffuses rapidly and due to its low density, flammable concentrations will not occur below the level on the vent outlet. Should the vapour be ignited at the vent outlet by lightning or atmospheric discharge, each riser is provided with a snuffing valve and nitrogen injection points at the bottom to extinguish the fire. Vent mast riser No. 2 is fitted with a nitrogen smothering injection system which can be operated remotely from the wheel house and cargo control room. Vent mast risers No. 1 and 3 are fitted with nitrogen smothering, but the injection has to be operated locally at the individual mast riser. The most important action is to remove the source of fire by operating the snuffer valves. Then the fire fighting medium. The fire will re-ignite if the steelwork of the riser is hot enough after the nitrogen is shut off.
LNG LERICI 4.4.12 Cargo Piping Valve Freeze-up Procedure This will result from allowing moist air into the cargo system and not replacing it with dry air. The humidity in the air will condense and form moisture, which with the introduction of LNG will freeze, causing pipeline blockage and cargo valve seizure. Methanol cannot be used as a de-icer on LNG as it has a freezing point of -97°C. 4.4.13 Cargo and Ballast Valve Failure Procedure The cargo and ballast system valves are hydraulically operated. Failure of the hydraulic supply system will result in these valves becoming inoperable remotely. Each valve is fitted with a remote distribution block furnished with in/out pipes from the remote control station. Shut off valve emergency operating connections are of the push on instantaneous type. An emergency hand pump with hoses can be connected and the valve operated using the hand pump. In the event of a deck valve failure, the hydraulic actuator will be connected up to the emergency hand pump and the valve operated. Failure of ballast tank actuators will mean personnel entry into the cofferdam and duct keel.
A sudden rise in the percentage of methane vapour in one primary insulation space Some porosity in the primary barrier weld will allow the presence of methane vapour in the primary insulation space. The amount of this vapour should be kept to a minimum by the nitrogen purging. If a fracture occurs in the primary barrier below the level of the liquid in the tank, the vapour concentration will increase slowly and steadily. If the fracture is above the liquid level, the concentration will exhibit a fluctuating increase. The vapour concentration in each primary insulation space is recorded daily, to detect any small and steady change. An increase in pressure in one primary insulation A fracture above the liquid level in a cargo tank will allow a direct flow of vapour into the primary insulation space. This flow will vary according to the pressure in the tank. A fracture below the liquid level in a cargo tank, resulting in a small amount of liquid vapourising as it passes through the fracture, will cause a small increase in pressure. (Any small quantity of liquid which enters the primary space, then vapourises, will have the same effect). This increase is dependant upon the height of liquid above the fracture and the pressure in the tank. As the pressure relief system is common to all the primary insulation spaces, any increases in pressure caused by vapour leakage will be difficult to determine.
4.4.14 Primary Membrane Failure Introduction All test carried out on the primary membrane have shown that a fatigue fracture in the membrane will not extend. Fatigue fractures in the primary membrane are generally small and will pass either vapour only, or a sufficiently small amount of liquid which will vapourise as it passes through the fracture. It is possible, however, that a larger failure of the membrane could occur, allowing liquid to pass through and eventually gather at the bottom of the inter barrier space. Leakage Detection Vapour Leakage A small leakage of vapour through the membrane may not be readily obvious, however, indications are likely to be:
Temperature variation No temperature change will be obvious, unless the fracture is in the immediate vicinity of the sensors below the cargo tank. Leakage of methane vapour into the primary insulation space presents no immediate danger to the tank or vessel. As much information as possible concerning the fracture and leak should be obtained and recorded. Determine whether the leak is increasing as follows: 1 After the leak is detected (and without changing the flow of nitrogen to the primary insulation space), record the gas concentration and primary space temperatures every hour for eight hours. 2
Then, if necessary, adjust the flow of nitrogen to maintain the gas concentration below 30% LEL and record the gas concentration and primary insulation space temperatures every four hours.
3
In conjunction with the above, record all pressure changes occurring in the cargo tank and primary insulation space.
4.4 Emergency Operations and Procedures - Page 8
Cargo Systems and Operating Manual
LNG LERICI Flexible Hose Drain Valve
Illustration 4.4.15a Barrier Punch
Nitrogen Connection
Nitrogen Bottle Reducing Valve
SITUATION NORMAL
BARRIER PUNCH SYSTEM IN OPERATION
Stripping Pump Cable Conduit Bellows Nitrogen Piping
Perforations Expansion Tube
Diaphragm
Bellows Support Arm Base of Cargo Tank Trellis Structure Support for Equipment on Trellis Structure LNG Liquid Tank Bottom/ Primary Barrier Primary Insulation Space Secondary Insulation Space
Duct Keel
Issue: 1
4.4.15a Barrier Punch
Cargo Systems and Operating Manual Liquid Leakage A major failure in the primary membrane, allowing liquid into the primary insulation space, will be indicated as follows: 1 A rapid increase in the methane content of the affected space. 2
A rise in pressure in the primary insulation space nitrogen header, accompanied by continuous increased venting to atmosphere.
3
Low temperatures alarms at all temperature sensors in the insulation below the damaged cargo tank.
4
A general lowering of inner hull steel temperatures.
The operation procedure for using the punching device is as follows: (see figure 4.4.15) • The use of the punching device depends on the following indications of liquid in the primary space:
Although this will be limited to a few degrees only and may take some hours to establish, it should, nevertheless, be noticeable and an added confirmation of major membrane failure. There should be no immediate danger to the tank or vessel as the secondary barrier is of identical construction to the primary barrier. • If a major failure is indicated by the above symptoms, carry out the following to avoid contamination of the intact primary insulation spaces:
•
4.4.15 Punching Device A punch diaphragm, fitted below the pump tower in each cargo tank, permits the punching of an opening in the primary membrane. This operation will be necessary in the event that damage to the membrane has permitted LNG to accumulate as a liquid in the primary insulation space. If the cargo tanks were pumped out with a head of liquid remaining the the primary space, severe damage to the membrane would result. For this reason, it is necessary to intentionally puncture the primary membrane when the damaged tank is pumped out, and to pump the tank slowly enough to enable the level of the liquid imprisoned in the insulation space to fall at the same rate as the tank, without over pressurising the membrane. The device punches a 50mm opening at the bottom of the tank. Liquid from the side walls will drain out through the opening. Liquid in the bottom portion of the insulation space must be removed by evaporation during warmup. Use of the punching device is an extreme measure. It floods the insulation space with LNG, and requires that the tank be gas freed and entered in order to replace the punched diaphragm. Issue: 1
•
•
• If liquid is indicated by all the temperature sensors up to the level of the sensor 5 A/B, the membrane should be punched at the start of the pumping operation. • If liquid is indicated by all the temperature sensors in the bottom and by either the sensor 9 A/B or 8 A/B or 7 A/B or 6 A/B, the membrane should be punched when the LNG level in the tank is 4 meters above the level of either the sensor 9 A/B or 8 A/B or 7 A/B or 6 A/B. • If liquid is indicated by all the temperature sensors in the bottom and not by the sensor 6 A/B, the membrane should be punched when the LNG level in the tank is at the level of the sensor 6 A/B. • If liquid is indicated only by some of the temperature sensors in the bottom, it is evidence that a head of liquid is not present in the side walls, and the membrane needs not be punched. After punching, use only one pump at a reduced pumping rate, corresponding to a liquid level fall of 0.4 m/h. The punching device is operated as follows: (see figure 4.4.15a) • Connect the portable nitrogen flask with the attached pressure reducer to the punch connection at the liquid dome of the damaged tank; • Close the equalising valves between the punch piping and the well of the back up level. • Open the valves at the hose connection and on the nitrogen flask, and apply full pressure from the reducing valve (12 bars) • After about one minute close the valves, disconnect the nitrogen flask, and reopen the equalising valves to the well of the back up level. After the tank has been gas freed and repaired, the punching diaphragm will be replaced by welding in a new one. After re installation of the punch device, purge all lines with nitrogen at a low pressure (150mbar) to avoid actuation of the system.
LNG LERICI Note: If a primary membrane has been punched or damaged to such an extent that the primary insulation space is in free communication with the tank, it is not possible to pull a vacuum on the space without pulling a vacuum on the tank. At 10mbar below atmospheric pressure, the tank safety valves will open and admit air to the tank. • With damage of this type, the cargo tank should be gas freed and inerted, but not filled with air until the insulation space is gas freed. • The insulation space should be gas freed by sweeping with nitrogen from the pressurisation system, or by combination of the two. • The vacuum pumps may be used in this situation to assist the sweeping with nitrogen or inert gas, to reduce the pressure created in the insulation space by evaporation of the imprisoned LNG or to maintain the space pressure lower than the tank pressure when the tank is opened. Primary Barrier Temporary Protection During Tanks Maintenance The primary consideration during cargo tank entry and maintenance is to protect the primary barrier from mechanical damage. Therefore the floor of the tank must be lined with plywood over the whole area where damage may occur from personnel entering the tank, equipment and tools etc. lighting should be hung from the cargo pump/pipe tower. The pressure in the tank will be at atmospheric so that the primary insulation space should be maintained at a few mbars below this to ensure that the primary barrier is held tight against the insulation boxes at all times.
! CAUTION Ensure that the differential pressure between the 2 insulation spaces remains between 0 and -30 mbar. Severe damage will occur to membranes if differentials exceed 30mbar.
Before cooling down of the tank, open the equalising valves to the well of the back up level. These valves should remain blocked open at all times when the tank is in service to avoid the inadvertent actuation of the punching device.
4.4 Emergency Operations and Procedures - Page 9
Cargo Systems and Operating Manual
LNG LERICI
Illustration 4.4.16a Loaded Voyage Without Gas Burning
481
491
Vapour Dome
487
483
Liquid Dome
484
492 486
Vent Gas Heater
Vapour Dome Liquid Dome
2 1 493
k an
1
T
2 1 Vapour Dome Liquid Dome
k an
494
2
T
Jettison
2 1
Vapour Dome Liquid Dome
Dual Purpose Heaters
k3
To Insulation Spaces
2
n Ta
HD Compressor No. 1 (Inboard)
1 Forcing Vaporiser
To Engine Room
LNG Vapour
HD Compressor No. 2 (Outboard)
k an
T
Degassing Line Into Main Cargo Pump Cable Penetration LNG Vapour Warm
Demister
Inert Gas from Engine Room
Key
4
Main Vaporiser
LD Compressor No. 1 (Inboard) LD Compressor No. 2 (Outboard)
Issue: 1
4.4.16a Loaded Voyage Without Gas Burning
Cargo Systems and Operating Manual 4.4.16 Loaded Voyage without Gas Burning It is possible for short periods to supply boilers on free flow with all compressors isolated. Open 400 and 406, this bypasses the compressors and supplies gas at header pressure direct to C.R. This system can only be used for short periods due to rise in pressure/ temperature of the cargo. It prevents total change over to fuel oil burning.
3
LNG LERICI
Set control valve 487 to 1200mbar a.
When clear of port limits 4
Start up the boil-off heater (Refer to Section 2.9).
5
Adjust set point of PIC to 1150mbar abs.
When arriving at port limits In the event that free flow is not an option, the following procedure is to be followed, venting via forward mast riser No. 2 and heater.
6
Adjust set point of PIC to 1200mbar abs.
7
Prepare cargo systems for discharge (Section 4.2.4).
Introduction If, for any reason, the gas burning plant cannot be used during sea passage, the boil-off will have to be heated and vented to atmosphere via vent mast riser No. 2. This course of action should only be taken as a last resort, since this will be a costly exercise which would also contribute to global warming due to the destruction of the ozone layer by methane. Operation The cargo tank boil-off gas enters the vapour header via the cargo tank gas domes. It is then heated in the boil-off heater, before being fed to the mast riser. This is to increase gas speed and then to permit the gas to escape quickly from the ships deck. Venting to atmosphere will not normally take place until the vessel is clear of port limits. Many port authorities forbid the discharge of gas to atmosphere. As far as is possible it is preferable to burn the boil-off in the boiler and use the steam dump system, rather than to vent gas to atmosphere. Operating Procedures (See Illustration 4.4.16a) It is assumed that all valves are closed prior to use: 1 Tank gas domes Open and lock in position valve 491 (Tank No. 1) Open and lock in position valve 492 (Tank No. 2) Open and lock in position valve 493 (Tank No. 3) Open and lock in position valve 494 (Tank No. 4) The valves should already be locked in the open position. 2
Open valve 481, 483, 484 and 486 at the vent mast heater.
Issue: 1
4.4 Emergency Operations and Procedures - Page 10
Part 5 Safety Systems
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.1.1a Deck Water Spray System
From Engine Room
Sea Chest
Accomidation Spray Manifold
IR001VF IR005VF
IR004VF
Cargo Manifolds Platform
IR006VF Emergency Cargo Jettison Area
From Pumps XA/405A/B
IR014VF
IR 009VD
Life Boat Freefall Spray
Gas Liquid Sprinkler Dome Dome Main Drain
IR015VF
Spinkler Main Drain
IR018VF IR019VD Gas Dome
Liquid Dome
Liquid Dome
Gas Dome
Liquid Dome
Gas Dome
IR 016VF
Compressor House
Cargo Manifolds Platform
IR007VF
Sea Chest
Issue: 1
5.1.1a Deck Water Spray System
Cargo Systems and Operating Manual PART 5: SAFETY SYSTEMS 5.1 Deck Salt Water Systems 5.1.1 Spray System The accommodation block front, compressor house, cargo tank domes, and manifold areas are protected by water spray from the effects of fire, gas leakage, or liquid spill. There is a 800m3/h spray pump (XA/491), mounted on the bottom platform in the engine room, delivering to 4 spray rails across the accommodation block front, compressor house sides and deck domes/manifolds. The nozzle arrangement is as shown below: For plain vertical surfaces, nozzles are set 800mm apart and at 45° to the vertical. Headers are 250mm from bulkheads and nozzles are flat cone design. 250mm 45 0
800mm
Nozzle types:- 1, 2, 4
AAW 3194 Each 194 ltr/min.
3
AAW 2780 Each 78 ltr/min.
5
AAW 3310 Each 250 ltr/min.
7
GAW 2246 Each 21.5 ltr/min.
6
GAW 2246 Each 17.3 ltr/min.
Pressure at Nozzles
LNG LERICI
1, 2, 3, 4
3 bar
5
2 bar
6
1.5 bar
7
2.3 bar
The spray pump has control stop/start locally in the engine room and from push buttons on the main deck close to the accommodation exits. There is a drain connection provided at main deck level and one at the forward end of the main.
Flat surfaces are protected by full cone nozzles. These are: 4 pump towers (liquid domes) 4 gas vent domes Jettison valve area Lifeboat boarding area 2 manifold spill trays Nozzle numbers and capacity i)
4 x pump towers - 4 x 4 nozzles at 46.56m3/h
ii) 4 x gas domes - 4 x 4 nozzles at 46.56m3/h iii) 2 x manifolds - 2 x 16 nozzles at 149.76m3/h iv) Jettison valve area - 1 x 1 nozzle at 11.64m3/h v) Lifeboat boarding area - 1 x 1 nozzle at 15.00m3/h vi) Accommodation front - 123 nozzles at 136.53m3/h vii) Compressor house walls - 67 nozzles at 88.44m3/h
Issue: 1
5.1 Deck Salt Water Systems - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.1.2a Deck Fire Main System Cofferdam Bilge Eductor
Emergency Cargo and Machinery Cooling Water Supply
AI/052VF AI/054VF
AI/014VF
AI/025VF
Spill Tray Filling Line
AI/058VF AI/056VF
To Fire Main Drain
AI/019VF AI/059VF
Hawespipe Cleaning
AI/053VF AI/023VF
Fire Main Drain
XA/405B To Cofferdam Eductor
AI/022VD XA/405A
AI/015VF To Cofferdam Eductor
To Cofferdam Eductor
Hawespipe Cleaning
To Cofferdam Eductor
Spill Tray Filling Line
Bosun Store From Emergency Fire Pump
Issue: 1
5.1.2a Deck Fire Main System
Cargo Systems and Operating Manual 5.1.2 Firemain System The firemain system is supplied from the engine room, by two, two speed centrifugal pumps XA/405 A and B 160m3/h at 2.3 bars or 90m3/h at 12.8bar.
Pressure reducing valve 200-15bar Pressurisation valve for container Safety valve set at 12bar Pressure reducer 15 to 10bar
The emergency fire pump YA/480 is mounted forward in the emergency fire pump room.
Tank depressurisation valve Lever safety valve set at 16bar
Isolating valves mounted on the cargo deck, allow isolation of the forward or poop decks. 3 further isolating valves are situated at regular intervals along up the deck, to allow any part of the system to be supplied from either end of the ship.
0 - 25bar pressure gauge
LNG LERICI 5.1.6 CO2 Protection in Cargo and Motor Compressor Rooms The compressor room and motor room are protected by a self contained CO2 system housed in its own CO2 room on the starboard aft corner of the motor room. The system consists of 2 packs of 60 Ltr cylinders. Pack 1 of 14 cylinders. Pack 2 of 4 cylinders. The system is so arranged that all 18 cylinders are available for discharge to the compressor room and 9 to the motor room.
2 distribution valves Pneumatic control powder on/off valves
The volume of the spaces protected are: Compressor room 870m3 and motor room 401m3
The cofferdam eductors are driven from this system, as is the manifold water curtain for ship side wetting during loading and discharge.
Pneumatic control station contains 1 x 4 ltr 200bar pilot nitrogen cylinder, for opening of associated distribution valve.
There are 12 fire hydrants situated along the cargo deck, each with its fire hose mounted adjacent. The firemain also supplies anchor washing water.
Each of these 1550kg units supply 2 x 10kg/s monitors mounted forward and aft above each manifold. Each monitor has a 10m throw. The 1550kg units also supply 8 hose stations. Each hose has a 3.5kg/s nozzle and is 30 metres long.
The emergency fire pump can be started locally, from the bridge or the fire station. Under normal operating conditions the firemain will be under pressure during port time, supplying the manifold sprays and with hoses run out as a fire precaution. 5.1.3 Air locks The motor room is fitted with a double door air lock, to ensure that any hydrocarbon vapour which may be present on deck cannot enter the room. The doors are fitted with micro switches connected to an alarm which will sound if both doors are open together. The motor room and air lock are maintained above atmospheric pressure by a supply fan. The motor room is vented by a natural exhaust trunk. 5.1.4 Dry Powder System The system is supplied by Silvani Antimcendi S.P.A and consists of: (A) 2 x 1550kg units mounted forward of the accommodation block on ‘A’ deck. (B) a 1000kg unit mounted in the cross alleyway between the accommodation and engine casing.
The manifold monitors have a control station port and starboard outboard and aft on No. 3 cargo tank liquid dome. Each dry powder hose unit has a remotely operated powder valve. (B) 1000kg unit mounted in the X-alleyway between accommodation and engine casing. This unit supplies a 10kg/s monitor with a 10 metre throw mounted above the poop deck and positioned to protect the jettison line and nozzle.
5 x 50 ltr at 200 bar nitrogen cylinders to expel the powder.
Each release control station has a 4ltr nitrogen cylinder which releases into the actuator pipework for the cylinders selected. Both protected spaces are fitted with a pre-release alarm siren, to warn personnel of impending CO2 release.
The action of opening the pneumatic control station operates the pre-release alarm, the main discharge is delayed by a mechanical device, actuated by hand for up to 30 seconds before release.
A portable hose unit is mounted on the poop deck with 20 metre hose and 3.5 kg/s nozzle.
The ball valve to the required space is also operated remotely and CO2 flooding takes place through nozzles mounted below the deckheads in both or either space.
The pneumatic actuator for this unit is mounted aft end, port side of ‘A’ deck. All equipment is similar to the 1550kg units except that there are only 4 x nitrogen cylinders.
The system is fitted with a pre-alarm test connection and a flushing connection to be used to flush out any remaining CO2 after a release.
5.1.5 Ship Side Water Curtain Spray This system is used when loading and discharging and is fitted to both manifolds to protect the deck, deck edge, shearstrake and vertical ship’s side from the effects of cold embrittlement in the event on liquid leakage at the manifold. The nozzles are spaced 600mm apart and at 500mm from the vertical shipside inboard.
Each unit consists of:A powder container holding 1550kg ‘winnex’ powder.
Each space has a pneumatic control station which can be operated manually locally or electrically via an intrinsically safe circuit and barriers from the fire station on the upper deck.
The water for these sprays is taken from the firemain/ wash down system pipeline. There are 30 GAW2761 nozzles at each manifold delivering 136.8m3/h. at 3 bar.
In the case of inadvertent release, the system is fitted with a relief valve which discharges to atmosphere. 5.1.7 Vent Mast Extinguishing No. 2 vent mast riser is fitted with a fixed nitrogen smothering system. Activation is carried out from the main console in the wheel house, or from the main console in the cargo control room. The gas heater regulating valve and snuffer valves in the vent mast are shut, before injection of nitrogen takes place.
Pneumatic/manual actuator 5pc Issue: 1
5.1 Deck Salt Water Systems - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.2.1a Emergency Shutdown System
EMERGENCY SHUT DOWN SYSTEM MANUAL RELEASE - Cargo control room. - Wheel House. - Manifolds - port and starboard sides - Compressor room - Fore main deck - After deck - port and starboard sides
FUSIBLE PLUGS - Each tank gas dome (4 units) - Each tank liquid dome (4 units) - Port and starboard manifold platforms (3 units). Cargo compressor room (2 units).
HEADERS PRESSURE
SHORE LINKS FROM SHORE
TO SHORE
(on each tank) Pvh : vapour header pressure Pph : primary space header pressure Patm : atmospheric pressure Pvh = Pph
Pvh < Patm + 3mbar
OR
OR
TANKS LEVEL
TANKS PRESSURE
Ptk : tank pressure Pps : primary space pressure Ptk < Pps + 5mbar
OR
(2 independent sensors per tank) VERY HIGH LEVEL 99%
HIGH LEVEL 98.5% OVERRIDING AT SEA
Ptk = Pps
AND
OR
STOP MAIN CARGO PUMPS AND EMERGENCY PUMP STOP STRIPPING PUMPS STOP HIGH DUTY COMPRESSORS CLOSING MANIFOLD VALVES
STOP LOW DUTY COMPRESSORS
CLOSING MANIFOLD VALVES
CLOSING OF FILLING VALVE ONLY ON TANK IN ALARM CONDITION
Issue: 1
5.2.1a Emergency Shutdown System
Cargo Systems and Operating Manual 5.2
Emergency Shutdown System
5.2.1 ESD System In the event of fire or other emergency condition, the entire cargo system, gas compressors and gas isolating valve to the engine room may be shut down by a single control. Shut down of the cargo system is actuated either manually or automatically by fire or certain off limit conditions.
LNG LERICI
! CAUTION - Before using the blocking switch, determine exactly what has caused the shutdown. - Before using the blocking switch, turn the controls for all crossover valves to the shut position. - Use the blocking switch when absolutely necessary to recover from an emergency condition. - When the emergency condition is corrected, immediately restore the shutdown system to normal.
Description (see illustration 5.2.1a) •
•
•
•
The manual emergency controls are located as follows: • Cargo control room. • Cargo console on bridge. • Each tank liquid dome (4 units). • Port and starboard manifold platforms (2 units). Automatic shutdown for fire is controlled by eight fuse plugs located as follows: • Each tank liquid dome (4 units). • Port and starboard manifold platforms (2 units). • Cargo compressor room (2 units). In port, an electrical link will inform the shore of any ship’s ESDS actuation and will stop the loading or discharge pumps, and close the shore liquid valves. Automatic shutdown occurs when any of the following conditions occurs: • Vapour header pressure falls to within 3mbar of atmospheric pressure. • Vapour header pressure falls to primary insulation space header pressure. • Each tank pressure falls to within 5mbar of the primary insulation space pressure. • Each tank pressure falls to the primary insulation space pressure. • Very high liquid level (99%) in any tank. • Automatic shutdown for fire. • Shutdown signal from the terminal.
Issue: 1
5.2 Emergency Shutdown System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.3.1a Gas Detection Systems
Gas Analyser Indication Panel (Bridge)
Gas Detection in Nitrogen
Analyser Cabinet (CCR)
N AI
AI
2
AI Analyser Purging
AT
AT 0-5%
D C B A
AT 0-100%
0-60%
Engine Room
Tank 3
Tank 4
Tank 2
MDXi No.1 CHANNELS
Tank 1
Tank 2
Tank 3
Manual Stop Valve (Outside CCR)
Tank 4
Tank 4
Tank 3
Tank 2
Tank 1
Analyser Exhaust
DESIGNATION
00
COMPRESSOR ROOM
01
ELECTRIC MOTOR ROOM
02
ELECTRIC MOTOR ROOM AIRLOCK
03
TOWER PUMP COFFERDAM NO.1
04
TOWER PUMP COFFERDAM NO.2
05
TOWER PUMP COFFERDAM NO.3
06
TOWER PUMP COFFERDAM NO.4
07
GLYCOLE WATER AIR VENT
08
EMERGENCY FIRE PUMP ROOM
09
CARGO CONTROL ROOM
10
TOP OF ENGINE ROOM (ABOVE BOILER NO. 1)
11
TOP OF ENGINE ROOM (ABOVE BOILER NO. 2)
12
ENGINE ROOM FAN AIR INTAKE (AFT PORT)
13
ENGINE ROOM FAN AIR INTAKE (AFT STB.)
14
ENGINE ROOM FAN AIR INTAKE (FORE STB.)
15
AIR CONDITIONING STATION AIR INTAKE
16
GLYCOLED WATER EXPANSION TANK NO. 1
17
GLYCOLED WATER EXPANSION TANK NO. 2
18
STEAM CONDENSATE OBSERVATION TANK W.D.
19
STEAM CONDENSATE OBSERVATION TANK E.R.
20
MANIFOLD CRANE AIRLOCK
Tank 1
MDXi No.2 AL 1
AL 2 FAULT
AL 1
CHANNELS
DESIGNATION
00
VENTED DUCTS SURROUNDING THE GAS PIPE TO THE BOILERS (OUTLET)
01
ENGINE ROOM FAN AIR INTAKE (FORE PORT)
PRIMARY INSULATION SPACE INFRARED ANALYSER NO. 1 AND NO. 3
ALARM 1
ALARM 2
AL 2
FAULT
PRIMARY INSULATION SPACE INFRARED ANALYSER NO. 2 AND NO. 3
ALARM 1
ALARM 2
TANK NO. 1 TANK NO. 2 TANK NO. 3 TANK NO. 4
FIRST PROGRAMMER COMBUREX IR
SECOND PROGRAMMER COMBUREX IR
FAULT
Cargo Tank
Secondary Barrier Safety Valve Piping
Issue: 1
RESET BUZZER
LAMP TEST
Primary Barrier Safety Valve Piping
5.3.1a Gas Detection Systems
Cargo Systems and Operating Manual 5.3
-
1 Infrared analyser system in Primary Insulation Space,
-
1 Infrared analyser system in Secondary Insulation Space,
-
Catalytic combustion type detectors for gas detection in air for various spaces,
-
Catalytic combustion type detectors for continuous measurement in boiler exhaust gas main,
-
Catalytic combustion type detector for steam condensate,
-
Control panel to be located in the CCR,
-
Repeater panels,
-
Portable detectors & calibration equipment.
5.3.1 Infrared Gas Analyser System This gas detection equipment consists of A Cabinet Housing 4 Independent Gas Detection Systems Based on 2 Different Principles of Detection
Systems Based on the Principle of Infrared Absorption for the Detection of Insulation Spaces -
An independent system consisting of an IR Comburex programmer and an IREX infrared detector (scale 05% CH4 by volume) for detecting the primary insulation spaces in the 4 tanks. This system has an associated sampling system driven by two pumps PA1 and PA2 and a gas circuit. Each sampling line includes a BP 143 flame arrestor for the analysis channels and a BP 101 sampling nozzle for the “pure air” channel.
-
This system has an associated sampling system driven by two pumps PA3 and PA4 and a gas circuit.
Gas Detection System
The System is supplied by ‘ICARE’ France Societe Nouvelle and consists of - 1 Infrared analyser system switchable from primary to secondary insulation spaces,
An independent system consisting of an IR Comburex programmer and an IREX infrared detector (scale 040% CH4 by volume) for detecting the secondary insulation spaces in the 4 tanks.
Issue: 1
LNG LERICI
Each sampling line includes a BP 143 flame arrestor for the analysis channels and a BP 101 sampling nozzle for the “pure air” channel. -
An IREX detector (scale 0-100% CH4 by volume), common to the two IR Comburex programmers and switchable to one of the insulation spaces by a key switch, located on the cabinets front panel and marked “IREX 100% Vol. CH4”.
Press the “ ” key: - message “CALL CHAN. Val. or ” Press the “VALID” key: - message Channel: X? or Val.” Press one of the number keys, e.g. “1”: - message “Call channel 1” or press “VALID”: message “Call P A “ Repeat this procedure for each channel called up.
Operation of MDXi Units The operations of these units is detailed in the MDXi technical manual. Operation of the Cabinets Alarm Buzzer A “synthesis” function groups together the alarms and faults of the systems described in § A and B above, and rings a buzzer and also illuminates a specific LED for each unit. Isolating Valves Panel
Operation of their Comburex and IREX Systems Each of the 2 IR Comburex programmers can thus display and manage the gas concentration output by the two IREX systems. The IREX analyser that has been validated is identified on the IR Comburex programmer LCD by a symbol at the right of the LCD as follows: - A1 indicates that the non-redundant IREX system is selected (IREX scale 0-5% by volume for the primary insulation space programmer and IREX scale 0-40% by volume for the secondary insulation space programmer).
For details of the operation of these units, refer to their respective technical manuals (IR Comburex and IREX). Operation of the Printer The 40-column printer in this cabinet prints out the concentrations in the primary insulation space when the IREX 0-100% volume scale is switched in. 5.3.2 Catalytic Gas Analyser Systems Based on the Principle of Catalytic combustion -
-
A2 indicates that the redundant IREX system is selected (IREX scale 0-100% by volume for one of the programmers). The symbols A1 and A2 are also used to distinguish each analyser when the user menu parameters (Alarm 1 & 2 thresholds, value of standard gas, etc.) are programmed and the alarm messages or faults are displayed. To standardise the operation of the two programmers, the two push buttons on each IR Comburex have been eliminated and the functions they performed (i.e. stop horn and select channel) have therefore been reorganised as follows: - The “stop horn” function for the two units is performed by the cabinet front panel push button marked “RESET BUZZER”. -
The “select channel” function is available on the menu and can be accessed via the keyboard of each programmer by following the procedure below:
Press the “FUNCT” key: - message “ACCESS CODE Val. or
”
An independent system consisting of an MDXi unit and two SX202 explosimeter detectors for detection of the ventilated ducts surrounding the gas pipe to the boilers. These detectors incorporate hardware for case assembling and are designated DTX 279 An independent system consisting of a MDXi unit and nineteen (19) SXY202 and SX202.H detectors for environment detection in various room and at specific spots.
These 19 detectors will be located as follows: *
12 SX202 environment detectors in various rooms designated DTX 285
*
4 SX202 detectors with hardware for flange assembling (AS 233 flange) for detection on the pipe casings.
*
3 SX202.H detectors fitted with a tracer ribbon, plus their accessories and mounting hardware, and classified as EEx d. These detectors are installed on the 2 glicolate water expansion tanks and on the steam condensate observation tank.
A panel groups together the valves isolating each sampling line of the two insulation spaces Connecting the Portable Detectors on the Lines Sampling the Insulation Spaces Three-way valves are used to connect the portable detectors on each sampling line. It should be noted that, when one of these valves is switched for connecting a portable detector, the sampling flow to the cabinet is cut off. A flow fault will possibly be triggered if the channel in question is scanned at the same time by the cabinet. These valves are designed for padlocking in the normal position, i.e. sampling to the cabinet. Repeater Panel Three alarm/fault repeater panels providing audible and visual warnings are located in: - the engine room, - the wheel house, - the ECR. The audible warning is generated by a buzzer which, after the occurrence of an event, must mandatorily be acknowledged locally, even if the alarm or fault has been acknowledged on the unit (cabinet).
5.3 Gas Detection System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
5.3.3 Hand Held Gas Analyser (O2, CO2, CO, Dew point, CH4) Portable Detectors The ICARE portable detectors can analyse the following gases: - Methane in air or in nitrogen, scale 0-100% LEL, i.e. 0-5% CH4 by volume. This portable unit operates with dual dilution. It is equipped with a small flowmeter chassis for checking and adjusting the analysis sampling flows and the dilution flow from the air cylinder. The injected airflow must be adjusted using the flowmeter cock to be the same as the analysis flow. It is mandatory for these two flows to be equal (ball at the same height). -
Oxygen, scale 0-25% O2 by volume.
-
Carbon Monoxide, scale 0-1000 ppm CO.
-
Carbon Dioxide, scale 0-20% CO2 by volume.
The operation of these units is detailed in the ICARE technical manual.
Issue: 1
5.3 Gas Detection System - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.4.1a De-Watering Pump Arrangement
Nitrogen Supply Column to Secondary Barrier
Secondary Insulation Space
Air Driven Water Pump
Issue: 1
5.4.1a De-Watering Pump Arrangement
Cargo Systems and Operating Manual 5.4
Inner Hull Failure
5.4.1 Leakage Detection Water Leakage to Secondary Insulation Space In the event of a crack in one of the boundary bulkheads between the cargo tanks and the ballast tanks, the secondary insulation space may be flooded with sea water. Corrective action must be taken immediately on the sounding of a water detection alarm, to stop the leakage and to remove water from the insulation space. A water leak is very serious, and prevents further operation until the leak is repaired. The damage to the membrane and to the secondary insulation will be much less if the corrective action described below is taken very quickly. If the water level rises higher than 0.3m in the insulation space, the pressure increases higher than the design pressure limitation and can permanently damage the secondary membrane. For these reasons, it is most important that the water detection system be kept permanently in operation and in good conditions. As soon as an alarm is sounded, the operation procedure is as follows: (see figure 5.4.1a) • As corrective action, immediately empty all of the ballast tanks having a common boundary with the affected secondary space. adjust the level in the other tanks as necessary to maintain acceptable hull stress loadings. do not exceed the hull stress limits for shear or bending moment at the loadmaster. •
Isolate the leaking secondary space from the pressurisation system by closing the valve AW/901, 915, 927 or 932VX.
•
Connect up hoses for water discharge and for compressed air supply and exhaust to the couplings fitted on the cover of the well, then start the pump. The dewatering pump is permanently installed in a sump, at the lower part of a well.
•
Run the pump continuously if necessary until all traces of water are removed.
•
Inspect carefully the inner hull surrounding the affected tank to establish the cause of failure and repair the fracture.
•
To dry the moisture remained in the secondary space after pumping out the sea water, proceed with evacuation and nitrogen refilling cycles until the moisture content is at an acceptable level.
•
After any period of use, the dewatering pump should be lifted out of the well, disassembled, cleaned and re-lubricated to maintain it in a condition ready for immediate use.
Issue: 1
LNG LERICI
! WARNING Depending on the water level in the sump or due to priming problems with the pump, it may happen that no water be discharged when the pump is running. Before concluding that, in spite of the water detector alarms, no water leakage exists, a sounding through the well, by means of a water reagent, will be carried out. Corrective actions will be taken accordingly. Water leakage from the secondary insulation space drains into a well built into the double bottom of the adjacent cofferdam. A gas tight well built through the cofferdam contains the air driven pump and moisture detectors. The moisture detectors sounding and alarm in the CCR. Every loaded voyage the water detectors must be tested and proved to operate.
! WARNING It is important to note that the design pressure limitation is 0.3 metres water head.
! WARNING It is essential that the correct functioning of the alarms of the water detectors are checked frequently and that any alarm condition is investigated immediately.
! CAUTION No cargo should be carried in the the affected cargo tank until satisfactory repairs have been carried out and until the moisture content in the secondary space has been reduced to an acceptable level.
! WARNING Always be aware that a crack in the inner hull will allow nitrogen into the ballast tank. All entry must be accompanied by recognised entry procedures.
5.4 Inner Hull Failure - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.5.1a Fire Detection System K/IJ3 Wheelhouse Main Alarm and Control Panel
K/IJ3A K/IJ4
Forward Rooms Paint Store
I.S. cable way (Automation pipe cable way)
0301
K/IJ4A K/IJ4C Gastight push button
IJ/002QI
2
K/IJ4B
Entrance
1
IS alarm push button
IJ/001QI 0301
Smoke detector gastight
0305
0304
Bosun Store
Cargo Machinery Rooms
Smoke detector with short circuit protection
0306
0307
0308
0309
Barrier for IS circuit 2 circuits Electric Motor Room
1
0303
Hydraulic Station
Smoke detector IS type optical addressable
2
0302
Compressor House
Barrier for IS circuit 1 circuit
0404
0405 Emergency Fire Pump Motor Room 0311
0401
0402
0403
0407
0406 0313
Issue: 1
0310
0312
Bowthruster Room
5.5.1a Fire Detection System
Cargo Systems and Operating Manual 5.5
Fire Detection System
5.5.1 Fire Detection System The vessel is fitted with a full cover fire detection system divided into 5 loops as follows. Accommodation zone Loop 00 Bridge deck A, B, C, D Decks Upper deck Accommodation stairways Engine room Loop 01 E.R. main floor 1st, 2nd, 3rd flat Engine casing Aft zone rooms Loop 02 Steering gear room Aft stores (upper deck) Fwd zone rooms Loop 03 Bow thruster room Emergency fire motor p/p room Various fwd rooms Cargo machinery rooms Loop 04 Electric motor room Compressor room The system is controlled from the master control unit on the bridge. Power for this unit is supplied from 220V emergency switch board or 18 hour battery unit via a rectifier There is an all fire spaces mimic alarm panel mounted on the bridge port side and a cargo fire space, compressor and motor room mimic alarm panel in the cargo control room. The engine room space mimic alarm panel is mounted in the engine control room. A cumulative alarm repeater panel type is mounted in the fire station located on upper deck. System Tests A weekly function test must be carried out, to test the control unit with a number of smoke detector heads tested in rotation with proprietary smoke test kit. The operation should be entered into the bridge log.
LNG LERICI
Cargo Rooms Loop 004 The supply/return cables to this loop are blue, and circuits intrinsically save and supplied via zener barriers The motor room loop consists of:1 x 1.5 Alarm push button 2 x 1.5 Smoke detectors (optical addressable intrinsically safe type)
Illustration 5.5.1b Fire Sensor Control Panel
13 9
12
The entrance to forward spaces 1 x gas tight alarm push button 1 x smoke detector (optical addressable gas tight type)
Bow thruster room 1 x smoke detector (optical addressable gas tight type) 1 x smoke detector (optical addressable gas tight type) with short circuit protection unit mounted on detector socket Emergency fire pump room 1 x smoke detector (optical addressable gas tight type) 1 x smoke detector (optical addressable gas tight type) with short circuit protection unit mounted on detector socket.
2
3
16 11 15
"A" DECK
17
"C" DECK
"D" DECK
22
ELECTRIC MOTOR 23 ROOM
ENTRANCE COMPRESSOR ROOM
21
18
BRIDGE DECK PAINT STORE 28
20 D.A.
RUBBISH STORE
"B" DECK
19
AFT STORE
4
7
10
14
24
29 26
BOSUN STORE
HYDRAULIC CENTER 27
25
UPPER DECK EM. FIRE MOTOR PUMP ROOM 30
Hydraulic station 2 x smoke detectors (optical addressable type gas tight) Bosun store 1 x gas tight alarm push button 3 x smoke detector (optical addressable gas tight type)
5
1
The compressor room loop consists of:1 x 1.5 Alarm push button 3 x 1.5 Smoke detectors (optical addressable intrinsically safe type) The Fwd room loop- 03 is supplied via a zener barrier type IJ/001Q1 and consists of the following Paint store 1 x smoke detector (optical addressable intrinsically safe type)
6
8
38
34
MAIN SWITCH BOARD ROOM 41
40
37
31
BOW THRUSTER ROOM
E.C.R. 35
33
32
STEERING GEAR ROOM
39
36 E.R. CASING
2nd E.R. FLAT 3rd E.R. FLAT 42
LAMP TEST
46 48
47
45
49
TURBO/GEN. ZONE 50
ACKN. 44
43 PURIFIERS ROOM
In addition, power to the unit should be switched off to prove the back up battery system.
Issue: 1
E.R. MAIN FLOOR
1st E.R. FLAT
5.5 Fire Detection System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.6.1a Gas Dangerous Zones
Issue: 1
5.6.1a Gas Dangerous Zones
Cargo Systems and Operating Manual 5.6
LNG LERICI
Gas Dangerous Spaces and Zones
(See Fig 5.6.1a) Under the IMO Code for the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk: Gas-dangerous spaces or zones, are zones on the open deck within 3.0 metres of any cargo tank outlet, gas or vapour outlet, cargo pipe flange, cargo valve, and entrances and ventilation openings to the cargo compressor house. The entire cargo piping system and cargo tanks are also considered gas-dangerous. The port trunkway is also considered a gas-dangerous zone. In addition to the above zones, the Code defines other gas-dangerous spaces. The area around the air-swept trunking, in which the gas fuel line to the engine room is situated, is not considered a gas-dangerous zone under the above Code. All electrical equipment used in these zones, whether a fixed installation or portable, is certified ‘safe type equipment’. This includes intrinsically safe electrical equipment, flame-proof type equipment and pressurised enclosure type equipment. Exceptions to this requirement apply when the zones have been certified gas free, e.g. during refit.
Issue: 1
5.6 Gas Dangerous Spaces and Zones - Page 1
Cargo Systems and Operating Manual
LNG LERICI Illustration 5.7.1a Glycol Heating System
To Icare Gas Detector
GLYCOL RESERVE TANK
LA
Glycol Pump
L Trip
GLYCOL EXPANSION TANK LS
GLYCOL EXPANSION TANK LS
LA
Glycol Pump
L
WATER / GLYCOL STORAGE TANK
Trip
Steam Low Flow
To Gas Detector Unit
High Flow Stand-by Main Supply YA/5500A Main Supply Stand-by Main Return Condensate
90°C H TA
Main Return
100°C HH TI
TA
TIC
VDU
KBD
TI HC TI
PI
TT
TS
TT
TI
YA/5141A
451
Steam Low Flow
High Flow
453
YA/5500B
Condensate 90°C H TA
100°C HH TI
TA
TIC
VDU
YA/5141B
KBD
452
TI HC TI
PI
TT
TS
YA/5501A
454 TT
TI
GAS SEPARATOR
Key LNG Vapour
YA/5501B
Electric Motors Room
Cargo Compressor Room
Glycol Heating to Boil-off Heaters Glycol Heating to Cofferdams and Liquid Domes Steam Heating
YA/5501C
Condensate BULKHEAD
Control Air
Issue: 1
5.7.1a Glycol Heating System
Cargo Systems and Operating Manual 5.7
Glycol Heating System
5.7.1 Description (see illustration 5.7.1a) The glycol heating system is located in the cargo motor room and is comprised of two distinct heating circuits. One circuit is used for maintaining the temperature inside the cofferdam spaces and the casing around the cargo pump tower penetration, while the second circuit is used for heating LNG vapour in the dual purpose vapour heaters YA/5141A/B. The separation must be maintained due to the potential risk of a tube failure on the dual purpose heaters and possible leakage of LNG vapour into the system. It is possible, when warming up the cargo tanks, to utilise the cofferdam glycol circulating pump after first changing over the isolating spectacle blanks. For this reason there is an Icare Gas Detection monitoring system connected on the glycol outlet side from both the dual purpose heaters and on both system expansion tanks.
LNG LERICI
It is possible, if required, to operate the cofferdam circulating pump on the dual purpose LNG heater system. This is achieved by changing over a series of spectacle blanks and then running the three pumps and steam heaters YA/5500A/B in parallel. This operation might only be considered necessary when warming up the cargo tanks prior to refit due to the high demand on the system.
The system is comprised of:Three glycol circulating pumps, YA/5501 A, B and C, each rated at 40m3/h Two 800kW steam heaters, YA/5500A/B, each with high and low steam demand regulating valves. An expansion tank of capacity 0.8m3, on both the cofferdam and dual purpose heating circuits, each with gas detection sample lines. A 4m3 glycol storage tank. A 3m3 glycol / water storage tank. 5.7.2 Glycol Heating for LNG Dual Purpose Heaters Glycol is circulated via pump YA/5501C, through the steam heat exchanger YA/5500A, which raises the temperature of the glycol to 80°C. It is then flows into the dual purpose LNG vapour heaters YA/5141A/B located in the cargo compressor room. The glycol will raise the LNG vapour temperature to a range between 0 and 50°C, depending upon the temperature control setting. Pump YA/5501B is maintained in a stand-by mode to ensure continued circulation of the dual purpose heaters in the event of failure of the main circulating pump. The spectacle blanks and isolating valves are maintained open onto this system, while the isolating valves and spectacle blanks onto the cofferdam system remain closed If it is required that pump YA/5501B takes over the duties of the cofferdam circulating system, the isolating valves and spectacle blanks onto the dual purpose heating system must first be closed and isolated.
Issue: 1
5.7 Glycol Heating System - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.7.2a Cofferdam Heating System
Liquid Dome No. 3
Liquid Dome No. 4
Liquid Dome No. 2
Liquid Dome No. 1
Key FL005VR
FL005VR
FL005VR
FL005VR
Stand-by Glycol Water Main Glycol Water
FL005VR
FL006VR
FL006VR
FL006VR
FL006VR
NO 5 COFFERDAM
Issue: 1
FL005VR
NO 4 COFFERDAM
FL005VR
FL006VR
FL006VR
FL005VR
FL006VR
FL006VR
NO 3 COFFERDAM
FL006VR
FL006VR
NO 2 COFFERDAM
NO 1 COFFERDAM
5.7.2a Cofferdam Heating System
Cargo Systems and Operating Manual
LNG LERICI
Cofferdam Heating System The purpose of this system is to ensure that the cofferdam and casing around the cargo pump tower penetration are kept at all times at 5°C, when the cargo tanks are in a cold condition. Each cofferdam is heated by two independent systems, one is in service, while the other is on stand-by. The maximum heating condition is determined by the following extreme operating conditions:External air temperature :- -18°C Sea water temperature:- 0°C The requirements for the individual cofferdams are as follows:No 1 Cofferdam 44kW with a heating coil length of 382m No 2, 3 and 4 Cofferdams each require 53kW, each having a coil length of 462m No 5 Cofferdam 10kW with a heating coil length of 90m. The cargo pump tower penetrations ie liquid domes, each require 3kW under the same extreme operating conditions, with a coil length of 26m. Pump YA/5501A and glycol heater YA/5500B are assigned to heating the cofferdam system. It is normally isolated from the dual purpose LNG glycol heating system by spectacle blanks and valves, but in the event of a breakdown of pump YA/5501A, pump YA/5501B can be used as a stand-by, having first changed over the isolating valves and blanks. Any failure of the cofferdam heating system with cargo on board must be treated as serious and repairs must be effected immediately. In the case of suspected leaks, regular soundings of the cofferdams will indicate into which space glycol water is leaking. Each cofferdam is fitted with two temperature sensors which will also give an early indication of a heating tube failure.
In the event of pump YA/5501A being required for duty on cargo tank warming up with its subsequent connection with the dual purpose LNG vapour heaters, a gas sample line is led off from the glycol expansion tank due to the possible risk of LNG vapour entering the system.
Issue: 1
5.7 Glycol Heating System - Page 2
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.8.1a Nitrogen Sweeping With Gas Concentration Below Alarm Point No 1 Cofferdam Insulation Spaces Exhaust Control No 2 Cofferdam
540 513
550 560
AW/943VD
512
514 511
No 3 Cofferdam 523
524 522 AW/931VD No 4 Cofferdam
533
521
534 AW/926VD
k an
532
1
T
No 5 Cofferdam 543
531 Primary Space 544 AW/918VD
542 574
541
Secondary Space
nk Ta
Supply from Nitrogen Storage Tank 561
562
563
Vacuum Pump (Inboard)
2
510 Insulation Spaces 520 Distribution 530 Control 575 567
Vacuum Pump (Outboard)
k3
Main Vaporiser
Key Nitrogen To Primary Insulation Spaces
566
k4 n Ta
Issue: 1
n Ta
Nitrogen/Methane Mixture From Sweeping Action
5.8.1a Nitrogen Sweeping With Gas Concentration Below Alarm Point
Cargo Systems and Operating Manual 5.8
LNG LERICI
Insulation and Barrier Systems
5.8.1 Leakage Detection LNG Vapour Leakage to the Primary Insulation Space If the gas detection system indicates an excessive concentration of LNG vapour in one or more primary insulation spaces and if the temperature sensors installed on the bottom of the secondary membrane do not indicate a drop in temperatures, the leakage is a vapour leakage. The following steps are taken, as soon as possible, to: • reduce the excessive concentration of LNG vapour and, •
prevent the spread of LNG vapour to other spaces.
Gas Concentration Below the Alarm Point (see figure 5.8.1a) A level of gas concentration of 15% in volume or slightly more, is controlled by increasing the normal flow of nitrogen to produce a sweeping action through the insulation space. The sweeping is made by opening the small bypass valve between the primary space connection and the vent mast of the tank. • Open the isolating valve AW/918, 926, 931 or 943VD on the bypass of the tank affected. •
Open valve 544, 534, 524 or 514 on the tank affected.
•
Sweep in this manner by venting through the bypass valve for a number of hours. Then, return all valves to their normal positions, and shut the valves on the bypass used for sweeping.
•
Observe the level of gas concentration in the insulation space after the valves are repositioned for normal operation, and repeat the sweeping procedure, if necessary. If the gas concentration requires, the sweeping operation is maintained and the ball valve adjusted to reduce the gas concentration below of the alarm point.
Gas Concentration Above the Alarm Point If the primary space is contaminated with a concentration of gas which cannot be controlled by sweeping through with the small manual bypass valve, then the large bore bypass valves 543, 533, 523, or 513 must be used. This will place a high demand on the nitrogen production system.
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5.8 Insulation and Barrier Systems - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.8.2a Evacuation Of Damaged Insulation Spaces No 1 Cofferdam Insulation Spaces Exhaust Control No 2 Cofferdam 540 513
550 560
AW/943VD
512 514
511 No 3 Cofferdam 523
524 522 AW/931VD No 4 Cofferdam
533
521
From No 1 Tank Secondary Space
534 AW/926VD 532 No 5 Cofferdam 543
k1 n Ta
531 Primary Space 544
542
AW/918VD
From No 2 Tank Secondary Space
541 Supply from Nitrogen Storage Tank
From No 3 Tank Secondary Space
Secondary Space
nk Ta
2
Vacuum Pump (Inboard) 572 AW/827VX AW/826VX
571 Vacuum Pump (Outboard) 568 569
Main Vaporiser
3 Key Nitrogen From Secondary Insulation Spaces
From No 4 Tank Secondary Space
k4 n Ta
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T
k an
Nitrogen From Damaged Primary Insulation Spaces
5.8.2a Evacuation Of Damaged Insulation Spaces
Cargo Systems and Operating Manual 5.8.2 Damage to Primary Insulation Space -Gas in Interbarrier Space When a membrane leak is stopped or the tank itself has been gas freed, it is necessary to gas free the insulation space affected. The gas freeing is carried out in an identical manner to the initial inerting described in 4.3.2, by evacuating and refilling with nitrogen. Care must be exercised with the vapour evacuated from the insulation space to avoid forming a combustible mixture with air. The evacuation procedure may have to be repeated two or more times to reduce the gas concentration to an acceptable level (0.2%). The operating procedure is as follows: (see figure 5.8.2a) • If the insulation spaces of the non affected tanks are under their normal operating conditions, increase their pressure up to 8mbar g. •
Isolate the primary and secondary insulation spaces of the non affected tanks from the primary and secondary pressurisation headers by closing the valves 541, 531, 928 or 511 and 542, 532, 522 or 512.
•
Connect the insulation spaces of the affected tank with the pressurisation headers by opening the corresponding valves.
•
Evacuate both the primary and secondary spaces of the affected tank as described in 4.3.1. It is assumed that the membrane damage, if large, is temporarily made tight.
•
Refill with nitrogen, either produced from the ship’s generators or supplied from shore, both spaces as described in 4.3.2.
•
If the hydrocarbon content is not reduced sufficiently, repeat the cycle; of evacuation and nitrogen filling.
•
The hydrocarbon content of the primary space is checked after each nitrogen sweep. It is measured with a portable gas detector, or with the inboard gas detection equipment or from samples taken at the sample connections provided on deck and analysed with shore equipment.
•
During the gas freeing of a contaminated insulation space, and particularly when welding work for membrane repairs are necessary, the following points must to be carefully met: • Once the insulation space is gas freed and before any hot work, the gas mixture flowing through the leak is checked by means of a portable gas detector. When three samples, carried out every 15
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•
•
minutes, show an hydrocarbon content of less than 0.2%, cutting and welding can proceed. The nitrogen in the insulation spaces must be replaced by air if large areas of membrane are to be worked upon. The hydrocarbon content of the barrier spaces must be checked daily, with the vacuum pump discharge analysed. As the safety depends on the analysis of the gaseous mixture contained in the insulation space, it is essential that the portable gas detectors to be selected according to the nature of the mixture and the accuracy required for the final hydrocarbon content. • For measuring the residual content of hydrocarbon in air, a gas detector with a range 0-100% of the lower flammability limit (LFL), or preferably with a range 0-10% LFL, is acceptable. • Due to the low residual hydrocarbon content, the gas analyser should be one which is normally used to measure non combustible mixtures. • If the above portable detector is not accurate enough to measure low hydrocarbon contents, a sample is taken from the vicinity of the leak and analysed with the ship’s gas detection equipment previously re-calibrated.
5.8.3 Damage to Primary Insulation Space Emergency Discharge of LNG In the event of an accidental break in the primary membrane of a tank, the primary insulation space will be filled with LNG in a time proportional to the size of the break. A break in the membrane will be signalled by: • the gas detection alarm, not immediately after the break, but few minutes later when the insulation space is sampled by the gas detection system; • a drop in temperatures of the secondary barrier; • a rise in pressure in the tank and in the primary insulation space with the possibility of lifting the insulation space safety valves.
LNG LERICI Segregating and Venting the Damaged Primary Insulation Space •
The damaged primary insulation space is isolated from the others and vented to atmosphere via valves 543, 533, 523 or 513.
•
Shut the gas detection sampling valve at the damaged space.
•
Check the pressure in the damaged space and adjust the bypass valve to reduce the pressure below safety valves lifting point, 10mbar g.
•
Check the heating in both cofferdams aft and forward the tank.
•
At the first opportunity, the damaged tank should be emptied and gas freed and the primary space gas freed. • If the tank is to remain out of service for one or more voyages before repairs, the tank should be filled with inert gas and shut in at a slight overpressure (about 100mbar g). • Depending on the size of the break in the membrane, the primary insulation space (after gas freeing) may either be left in communication with the tank and isolated from the other spaces, or be connected with the pressurisation system as for normal service.
In this event, it is necessary to immediately segregate the damaged insulation space from the others and to vent it to atmosphere. Leakage of LNG into the primary insulation space also lowers the temperature of the hull surrounding the tank, and requires additional heating in the cofferdams.
5.8 Insulation and Barrier Systems - Page 2
Cargo Systems and Operating Manual
LNG LERICI Flexible Hose
Illustration 5.8.4 Primary Insulation Space Drainage - Barrier Punch Systems
Drain Valve Nitrogen Connection
Nitrogen Bottle Reducing Valve
SITUATION NORMAL
BARRIER PUNCH SYSTEM IN OPERATION
Stripping Pump Cable Conduit Bellows Nitrogen Piping
Perforations Expansion Tube
Diaphragm
Bellows Support Arm Base of Cargo Tank Trellis Structure Support for Equipment on Trellis Structure LNG Liquid Tank Bottom/ Primary Barrier Primary Insulation Space Secondary Insulation Space
Duct Keel
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5.8.4 Primary Insulation Space Drainage - Barrier Punch System
Cargo Systems and Operating Manual 5.8.4 Primary Insulation Space Drainage - Barrier Punch Systems Punching Device for the Membrane A punch diaphragm, fitted below the pump tower in each cargo tank, permits the punching of an opening in the primary membrane. This operation will be necessary in the event that damage to the membrane has permitted LNG to accumulate as a liquid in the primary insulation space. If the cargo tanks were pumped out with a head of liquid remaining in the primary space, severe damage to the membrane would result. For this reason, it is necessary to intentionally puncture the primary membrane when the damaged tank is pumped out, and to pump the tank slowly enough to enable the level of the liquid imprisoned in the insulation space to fall at the same rate as the tank without overpressurising the membrane.
•
After punching, use only one pump at a reduced pumping rate corresponding to a liquid level fall of 0.4m/h.
•
The punching device is operated as follows: (see figure 5.8.4)
•
The device punches a 50mm dia opening at the bottom of the tank. Liquid from the side walls will drain out through the opening. Liquid in the bottom portion of the insulation space must be removed by evaporation during warmup. Use of the punching device is an extreme measure. It floods the insulation space with LNG, and requires that the tank be gas freed and entered in order to replace the punched diaphragm. The operation procedure for using the punching device is as follows: (see figure 5.8.4) • The USE of the punching device depends on the following indications of liquid in the primary space. • If liquid is indicated by all the temperature sensors up to the level of the sensor 5 A/B, the membrane should be punched at the start of the pumping operation. • If liquid is indicated by all the temperature sensors in the bottom and by either the sensor 9 A/B or 8 A/B or 7 A/B or 6 A/B, the membrane should be punched when the LNG level in the tank is 4 metres above the level of either the sensor 9 A/B or 8 A/B or 7 A/B or 6 A/B. • If liquid is indicated by all the temperature sensors in the bottom and not by the sensor 6 A/B, the membrane should be punched when the LNG level in the tank is at the level of the sensor 6 A/B. • If liquid is indicated only by some of the temperature sensors in the bottom, it is evidence that a head of liquid is not present in the side walls, and the membrane need not be punched.
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•
LNG LERICI
• Connect the portable nitrogen flask with the attached pressure reducer to the punch connection at the liquid dome of the damaged tank; • Close the equalising valves between the punch piping and the well of the emergency level. • Open the valves at the hose connection and on the nitrogen flask, and apply full pressure from the reducing valve (12 bars). • After about one minute close the valves, disconnect the nitrogen flask, and reopen the equalising valves to the well of the emergency level. After the tank has been gas freed and repaired, the punching diaphragm will be replaced by welding a new one. After re installation of the punch device, PURGE all lines and the internal bellow with nitrogen at low pressure (150mbar) to avoid actuation of the system. Before cooling down of the tank, open the equalising valves to the well of the emergency level. These valves should remain blocked open at all times when the tank is in service to avoid the inadvertent actuation of the punching device.
Notes: - If a primary membrane has been punched or damaged to such an extent that the primary insulation space is in free communication with the tank, it is not possible to pull a vacuum on the space without pulling a vacuum on the tank. At 10mbar below atmospheric pressure, the tank safety valves will open and admit air to the tank. - With damage of this type, the cargo tank should be gas freed and inerted, but not filled with air until the insulation space is gas freed. - The insulation space should be gas freed by sweeping the inert gas from the tank through the damaged barrier, or by sweeping with nitrogen from the pressurisation system, or by combination of the two. - The vacuum pumps may be used in this situation to assist the sweeping with nitrogen or inert gas, to reduce the pressure created in the insulation space by evaporation of the imprisoned LNG or to maintain the space pressure lower than the tank pressure when the tank is opened.
5.8 Insulation and Barrier Systems - Page 3
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.9.1a Ventilating the Ballast Tanks
Removable Watertight Manhole Cover
(View Outboard)
Removable Watertight Manhole Cover
Removable Watertight Manhole Cover
Removable Watertight Manhole Cover
FWD
From Cofferdam / Duct Keel Supply Fan
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5.9.1a Ventilating the Ballast Tanks
Cargo Systems and Operating Manual 5.9
LNG LERICI
Ventilation of Ballast and Trunk Void
5.9.1 Ventilating a Double Hull Ballast Tank Ventilation of ballast tanks is necessary to ensure that the atmosphere inside the tank is safe before entry can take place. The oxygen content in the tank may be low, for example, due to the effects of corrosion. The SNAM regulations for tank entry must be complied with. A permit to work must be completed prior to entry and adhered to. The double hull ballast tanks can be ventilated via the duct keel and cofferdam forced ventilation system. The ballast tank to be inspected must first be deballasted via the main and stripping line. Warning notices must then be posted in the CCR and ECR that the ballast pumps are isolated and should not be started. Once empty, there are two man hole covers on deck that are removed (two per tank), warning notices and guard rails are arranged around the openings. Entry can now take place, tank entry procedures being followed for this action. In the duct keel there are two man hole covers for each double hull ballast tank, one in a forward and one in an aft position. Removal of these covers will now allow the forced ventilation for the duct keel and cofferdam to flow through the ballast tank and ventilate (see illustration 5.9.1a ). See Section 6 Inner Hull Inspection Routes.
! WARNING The spaces to be inspected must be thoroughly ventilated before entry as there is the possibility of very low oxygen content due to corrosion of the steelwork.
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5.9 Ventilation of Ballast and Trunk Void - Page 1
Cargo Systems and Operating Manual
LNG LERICI
Illustration 5.9.2a Ventilating the Trunk Void Spaces
Removable Watertight Manhole Cover FWD
Cofferdam / Duct Keel Supply Fan (On No. 1 and No. 5 Cofferdams)
Flexible Hose Connection
Above Tank Void Space
Flexible Hose Connection
Duct Keel
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5.9.2a Ventilating the Trunk Void Spaces
Cargo Systems and Operating Manual
LNG LERICI
5.9.2 Ventilating the Trunk Deck Void Space The trunk deck void spaces have five man hole covers per tank, two on the port side slope forward and aft, two on the starboard side slope forward and aft and one on the top area of the cargo tank. The cofferdam space has a man hole cover, one port and one starboard. Removal of two man hole covers on the trunk deck void and one man hole cover on the cofferdam, will allow a flexible hose with the correct size flanges to be connected between the two tanks. The forced ventilation system for the duct keel and cofferdam is now led into the trunk deck void so ventilating the space. Tank entry regulations must be followed before entry. (see illustration 5.9.2a ) See Section 6 Inner Hull Inspection 5.9.3 IMO Code for Existing Ships Carrying Liquefied Gases in Bulk Ships complying with the IMO code are, after an initial structural survey, issued with a Certificate of Fitness. Periodical structural surveys of renewal of the certificate are held at intervals not exceeding 5 years and intermediate surveys of safety equipment, pumping and piping systems at intervals not exceeding 30 months. A Certificate of Fitness may be extended for a period of grace of up to one month from the expiry date. The Code requires that ships be equipped with five firemen’s outfits and three sets of safety equipment for personnel protection, each having an approved SCBA. The safety equipment sets as supplied to LNG ships should be similar to the firemen’s outfits except that in place of the fire resistant suit, suitable clothing is provided to protect personnel from LNG when worn with either SCBA or a protective face mask, it should be either a solvent proof material or PVC and consist of trousers capable of being worn over sea-boots and a jacket complete with hood. Additionally the axe is excluded from the safety equipment set. Where possible the respective sets of equipment should be stowed in pairs and clearly identified as either a fireman’s outfit or safety equipment. All compressed air equipment should be inspected monthly, and should be inspected and tested by an expert: at least once a year. Inspections should be recorded in the Record of Safety Appliances and Inventory of Equipment.
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5.9 Ventilation of Ballast and Trunk Void - Page 2
Part 6 Inner Hull
Cargo Systems and Operating Manual PART 6: INNER HULL 6.1 Introduction General An Inner Hull Inspection (also known as a cold spot/paint coating inspection) is an integral part of vessel maintenance procedure. It takes place during the loaded voyage and essentially serves two purposes : 1 Indication of possible breakdown of the cargo tanks insulation; 2
Detection of damage to structural coatings.
A breakdown of the cargo tank insulation membranes may allow LNG ( -160°C ) to enter the insulation spaces. This will effectively reduce structural steel temperatures and, if severe and prolonged, will be recognisable through the formation of frost (cold spots) on the internal structures of the ballast tanks, void spaces, or the cofferdams. (Continued contact with such low temperatures could cause fracturing of the structural steel, leading to possible ingress of water from ballast tanks, subsequent extensive damage, and expensive repair costs). Whilst checking for possible breakdown of the cargo tanks insulation the condition of internal structural paint coatings may also be monitored. Early detection of damage, together with prompt repair, will prevent further deterioration and subsequent corrosion development. Hence, each ballast tank, void space, and cofferdam inspection comprises all structural surfaces adjacent to the cargo tank plus all remaining surfaces. The inspections of the Fore and Aft Peaks are purely for Paint Coating inspection. If the damaged area is accessible, it may be possible to carry out minor repairs during the inspection, otherwise identified damage should be recorded and reported for further attention. Every ballast tank is inspected every xxxx? months. Each void space and cofferdam, compartments are inspected every xxxx? months. On departure from the loading port it is necessary to delay inspection for approximately xxxx? hours. This allows ample time for cargo tank insulation temperatures to stabilise and for any faults to become apparent. The inspection is a rigorous and time consuming procedure. It is therefore important that inspection personnel are physically fit and maintain concentration throughout to ensure a thorough examination is accomplished.
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Contents This part of the manual contains pages of illustrations in a double sided format, each page showing a perspective illustration of the tank in question. Each illustration provides information to enable routine inspections of the wing and double bottom ballast tanks (port and stbd), the fore and aft peaks, the above tank void spaces, and the cofferdams. The pages are laminated, allowing Snam personnel to use them as a photocopy master document or to carry an individual page into the relevant ballast tank, void space, or cofferdam without worry of damage, and to allow any problem areas identified to be marked on the illustration with a coloured pen or chinagraph pencil. Each illustration shows the inspection route to be followed, the individual compartment labelling, and the point of access. This ensures that : 1
Every compartment within the relevant ballast tank, void space, and cofferdam is entered;
2
Location of personnel in an emergency situation is without unnecessary delay.
Inspection
! CAUTION When undertaking any ballast tank, void space, or cofferdam inspection the relevant sections of the ICS Tanker Safety Guide (Liquefied Gas) and SMS procedures should be consulted and the recommendations adhered to. The Chief Officer is personally responsible for inner hull inspections. The inspection team should consist of at least two men who will carry out the inspection and a third man, positioned just inside the ballast tank, void space, or cofferdam being inspected, who will be in constant communication with the inspection team via portable VHF equipment. A further two men are to be in position near the ballast tank, void space, or cofferdam entrance with breathing apparatus, resuscitation equipment and, to monitor progress of the inspection team, a copy of the relevant page from this section.
LNG LERICI carried as the areas being inspected may have a low oxygen content in parts, even after ventilation. On sighting a cold spot it is important to: 1 Ascertain the centre of the cold spot. Use a portable thermistor type temperature meter to periodically record the temperature distribution in and around the cold spot - this will assist in discovering the location and extent of the fault in the cargo tank insulation;
! WARNING Before entry to any ballast tank, void space, or cofferdam personnel carrying out an inspection should ensure that : - the ballast tank, void space, or cofferdam has been opened up in good time and remains open; - a valid permit to work has been issued by the appropriate authority; - all personnel concerned are informed that the inspection is taking place.
2
Observe any change in recorded temperatures. If the situation deteriorates be prepared to take contingency measures. The entry precautions listed below must be observed. Entry Precautions Apart from oxygen deficiency, which can be expected in ballast tanks, void spaces, or cofferdams which have been closed for some time, there is a danger of natural gas or nitrogen leakage from an insulation space. Natural gas is non-toxic but can suffocate rather than poison. Any leakage of natural gas or nitrogen into an enclosed ballast tank, void space, or cofferdam will tend to lower the oxygen content by displacing air. Furthermore, natural gas is odourless and therefore gives no warning of its presence by smell. It is also lighter than air at ambient temperatures and so will tend to concentrate in the underdeck stiffening structures. It is important that testing of these areas is carried out to ensure ventilation has effectively dispersed any gas.
! WARNING To avoid danger of oxygen starvation it is necessary before entering any enclosed ballast tank, void space, or cofferdam to : - Ventilate thoroughly; - Test the oxygen content with the portable oxygen analyser; - Confirm absence of all hydrocarbon vapours with an explosimeter. It should be remembered that explosimeter readings are unreliable where the oxygen content is low; - Position the safety equipment at or near the point of entry of personnel. The safety equipment should be checked weekly.
Access The entry point to the wing and double bottom ballast tanks (port and stbd) is through watertight hatches from the main deck, or through the manhole access points in the duct keel. The entry point to the above tank void spaces is from either the port or stbd passageways or through watertight hatches on the trunk deck. The entry to the cofferdam spaces separating the cargo tank, is via the individual watertight hatches located on the starboard side of the main deck. To access the WB Deep Tank enter the focsle space, descend through two compartments and use one of two watertight manholes. Compartment Numbering Every internal compartment within a ballast tank, void space, or cofferdam has a unique matrix type alphanumeric label : 1
Ballast tanks make use of frame numbers (preceded by Fr) cross referenced with a level number or athwartship identifier, eg P and S
2
Void spaces also use frame numbers (preceded by Fr) but cross referenced with an individual compartment identification A
3
Cofferdams’ internal compartments have an individual number cross referenced with the particular cofferdam number and a level letter.
Protective clothing must be worn and all equipment carried must be thoroughly checked before proceeding with the inspection. Personal oxygen analysers must be
6.1 Introduction
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1a No. 1 Cofferdam Perspective View No. 1 Cofferdam Perspective View Watertight Manhole
FWD
C6
C5
C4 STARBOARD
C3
C2
C1 PORT F9
A5 A4 A3 Key A2
Inspection Route
Frame 246 A1 Frame 243
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6.1a No. 1 Cofferdam Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1b Tank No. 1Perspective Port Ballast Tank Perspective View o. 1 Port Ballast View
Watertight Manhole Upper Deck
(View Outboard)
Watertight Manhole
Wing Tank P17
P16
Turn of Bilge P15
Double Bottom P14
Frame 246 Fr 243 Fr 239 P13 Fr 235 Fr 231
Key
Fr 227 Inspection Route
Fr 223
P12 Fr 219 P11
Fr 215 P10
FWD
Fr 211 Frame 207
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6.1b No. 1 Port Ballast Tank Perspective View
Cargo Systems and Operating Manual
LNG LERICI
No. 1 Starboard Ballast Tank Perspective View Illustration 6.1c No. 1 Starboard Ballast Tank Perspective View
Watertight Manhole Upper Deck
(View Outboard)
Watertight Manhole
Wing Tank S17
S16
Turn of Bilge S15
Double Bottom S14
Frame 246 Fr 243 Fr 239 S13
Fr 235 Fr 231
Key Fr 227 Fr 223
S12
Inspection Route
Fr 219 FWD
S11
Fr 215 Fr 211
S10
Frame 207
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6.1c No. 1 Starboard Ballast Tank Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1d No. 1 Above Tank Void Space Perspective View
Position of Vapour Dome Access Hatch to Cofferdam No. 1
PORT
Frame 246
A2 A3 A1
Fr 243 A4 Fr 239
Position of Liquid Dome A5
Fr 235 A6
Fr 231 A7
FWD
Fr 227 Fr 223 A8
Fr 219
STARBOARD
Key
Fr 215 Inspection Route
A9 Fr 211 Frame 207
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6.1d No. 1 Above Tank Void Space Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1e No. 2 Cofferdam Perspective View No. 2 Cofferdam Perspective View Watertight Manhole
C6 FWD C5
STARBOARD C4
C3
C2
C1
B9 PORT
B8 B7
B6
B5
Key
B4 Inspection Route B3
Frame 62 Frame 59
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B1
B2
6.1e No. 2 Cofferdam Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 2 Port Ballast Tank Perspective View No. 26.1f PortNo. Ballast Tank Perspective View
Upper Deck
Watertight Manhole
(View Outboard)
Watertight Manhole
Wing Tank
P17 Turn of Bilge
P16 Double Bottom
P15
P14
Frame 207 Fr 204 Fr 200 Fr 196 Fr 192 Fr 188
P13
Fr 184 Key
Fr 180 Fr 176
FWD
Inspection Route
Fr 172
P12 Fr 168 P11 Fr 164 P10
Fr 160 Frame 156
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6.1f No. 2 Port Ballast Tank Perspective View
Cargo Systems and Operating Manual No. 26.1g Starboard Ballast Tank Perspective View Illustration No. 2 Starboard Ballast Tank Perspective View
LNG LERICI
Upper Deck
Watertight Manhole
(View Outboard)
Watertight Manhole
Wing Tank
S17 Turn of Bilge
S16 Double Bottom
S15
S14
Frame 207 Fr 204 Fr 200 Fr 196 Fr 192 Fr 188
S13
Fr 184 FWD
Key
Fr 180 Fr 176
Inspection Route Fr 172
S12 Fr 168 S11 Fr 164 Fr 160
S10
Frame 156
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6.1g No. 2 Starboard Ballast Tank Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1h No. 2 Above Tank Void Space Perspective View No. 2 Above Tank Void Space Perspective View
Position of Vapour Dome
Access Hatch to Cofferdam No. 2
PORT
Frame 207 A2
Fr 204 A3 Fr 200
A1 A4 Position of Liquid Dome
Fr 196 A5
Fr 192 Fr 188 A6 Fr 184 A7 Fr 180 Fr 176 FWD
Fr 172
A8
STARBOARD Fr 168 Fr 164
A9
Key Inspection Route
Fr 160 Frame 156
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6.1h No. 2 Above Tank Void Space Perspective View
Cargo Systems and Operating Manual
LNG LERICI
IllustrationNo. 6.1i No. 3 Cofferdam Perspective 3 Cofferdam Perspective View View Watertight Manhole
C6 FWD C5
STARBOARD C4
C3
C2
C1
D9 PORT
D8 D7
D6
D5
Key
D4 Inspection Route D3
Frame 156 Frame 153
Issue: 1
D1
D2
6.1i No. 3 Cofferdam Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1j No. 3 Port Ballast Tank Perspective View No. 2 Port Ballast Tank Perspective View
Upper Deck
Watertight Manhole
(View Outboard)
Watertight Manhole
Wing Tank
P17 Turn of Bilge
P16 Double Bottom
P15
P14
Frame 207 Fr 204 Fr 200 Fr 196 Fr 192 Fr 188
P13
Fr 184 Key
Fr 180 Fr 176
FWD
Inspection Route
Fr 172
P12 Fr 168 P11 Fr 164 P10
Fr 160 Frame 156
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6.1j No. 3 Port Ballast Tank Perspective View
Cargo Systems and Operating Manual Illustration 6.1k No. 3 Starboard Ballast Tank Perspective View No. 3 Starboard Ballast Tank Perspective View
LNG LERICI
Upper Deck
Watertight Manhole
(View Outboard)
Watertight Manhole
Wing Tank
S17 Turn of Bilge
S16 Double Bottom
S15
S14
Frame 156 Fr 153 Fr 149 Fr 145 Fr 141 Fr 137
S13
Fr 133 FWD
Key
Fr 129 Fr 125
Inspection Route Fr 121
S12 Fr 117 S11 Fr 113 Fr 109
S10
Frame 105
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6.1k No. 3 Starboard Ballast Tank Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1l Tank No. 3Void Above TankPerspective Void SpaceView Perspective View No. 3 Above Space
Position of Vapour Dome
Access Hatch to Cofferdam No. 3
PORT
Frame156 A2
Fr 153 A3 Fr 149
A1 A4 Position of Liquid Dome
Fr 145 A5
Fr 141 Fr 137 A6 Fr 133 A7
Fr 129 Fr 125 FWD
Fr 121
A8
STARBOARD Fr 117 Fr 113
A9
Key Inspection Route
Fr 109 Frame 105
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6.1l No. 3 Above Tank Void Space Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1m No. 4 Cofferdam Perspective View No. 4 Cofferdam Perspective View Watertight Manhole
C6 FWD C5
STARBOARD C4
C3
C2
C1
E9 PORT
E8 E7
E6
E5
Key
E4 Inspection Route E3
Frame 105 Frame 102
Issue: 1
E1
E2
6.1m No. 4 Cofferdam Perspective View
Cargo Systems and Operating Manual
LNG LERICI
4 Port Tank Perspective View View IllustrationNo. 6.1n No. 4Ballast Port Ballast Tank Perspective Upper Deck
Watertight Manhole
(View Outboard)
Watertight Manhole Wing Tank
P17 Turn of Bilge P16
Double Bottom P15
P14 Frame105 Fr 102 Fr 98 Fr 94 Fr 90
P13 Fr 86
Key
Fr 82 Fr 78 P12
FWD
Inspection Route
Fr 74 Fr 70
P11 Fr 66 P10
Fr 62 Frame 59
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6.1n No. 4 Port Ballast Tank Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1o No. Ballast 4 Starboard TankView Perspective View No. 4 Starboard Tank Ballast Perspective Upper Deck
Watertight Manhole
(View Outboard)
Watertight Manhole Wing Tank
S17 Turn of Bilge S16
Double Bottom S15
S14 Frame 105 Fr 102 Fr 98 Fr 94 Fr 90
S13 Fr 86
FWD
Key
Fr 82 Fr 78
Inspection Route S12
Fr 74 Fr 70
S11 Fr 66 Fr 62
S10
Frame 59
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6.1o No. 4 Starboard Ballast Tank Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1p No. 4 Above Tank Void Space Perspective View No. 4 Above Tank Void Space Perspective View
Position of Vapour Dome Access Hatch to Cofferdam No. 4
PORT
A2 A1
A3
Frame 105 Fr 102
Position of A4 Liquid Dome Fr 98 A5
Access Hatch to Cofferdam No. 5
Fr 94 Fr 90
A6 Fr 86 A7 Fr 82 Fr 78 A8
FWD
Fr 74 STARBOARD
Key
Fr 70 Fr 66
A9
Inspection Route
Fr 62 Frame 59
Issue: 1
6.1p No. 4 Above Tank Void Space Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Illustration No. 6.1q5No. 5 Cofferdam Perspective Cofferdam Perspective View View Watertight Manhole
C6 FWD C5
STARBOARD C4
C3
C2
C1
F9 PORT
F8 F7
F6
F5
Key
F4 Inspection Route F3
Frame 62 Frame 59
Issue: 1
F1
F2
6.1q No. 5 Cofferdam Perspective View
Cargo Systems and Operating Manual
LNG LERICI
Fore Peak Ballast Tank (Port Side Perspective View) Illustration 6.1r Fore Peak Ballast Tank (Port Side Perspective View)
Enterance to Bow Thrust Room
Chain Locker
Fr 281 Fr 278 Fr 274 Fr 270 Fr 266 Fr 262 Frame 258
Issue: 1
6.1r Fore Peak Ballast Tank (Port Side Perspective View)
Cargo Systems and Operating Manual
LNG LERICI
Illustration 6.1s Fore Peak Ballast Tank (Starboard Side Perspective View) Fore Peak Ballast Tank (Starboard Side Perspective View)
Chain Locker
Fr 281 Fr 278 Fr 274 Fr 270 Fr 266 Fr 262 Frame 258
Issue: 1
6.1s Fore Peak Ballast Tank (Starboard Side Perspective View)
Part 7 Stress and Damage Stability
Cargo Systems and Operating Manual
LNG LERICI
PART 7 : STRESS AND DAMAGE STABILITY 7.1 Introduction
Type- The type of voyage, e.g. cargo or ballast can be selected from predefined list by clicking on the type required.
Deadweight- This calculates the deadweight from displacement and lightship displacement.
Aft draught- This is a computed value of the aft draught, corrected to take into account the actual position of the draught sensor.
Procedures The Stability Information supplied on board is comprehensive and requires careful study to appreciate the amount of information available.
Loading Port- The pre-entered loading ports can be selected in a similar way
Calc Trim- This is computed as the difference between forward and aft draught. This is shown as negative if the ship is trimmed by the stern.
Sea Water Density- This is pre-defined as 1.025t/m3
Displacement- This gives the total of all loaded weights including cargo, ballast and other tanks, plus deadweight. If this value exceeds the permitted maximum for full load draught, a warning message will be shown, displacement not allowed. In this case the operator must cancel the warning by clicking on OK to continue to enter loading conditions.
Date- The date of the operation can be automatically set by computer time or input manually.
EG, KG, YG- These give the co-ordinates in metres of the ship’s centre of gravity.
Note- Up to 80 characters can be entered for a user note. When the data is entered, either the OK or Cancel button can be selected to close the form or return to main menu.
Angle of heel- This gives the value of the heel angle in degrees.
Volumes 1 and 2 cover Damage Stability. 26 cases of damage are studied in various conditions of loading. Two volumes cover bending moments and shear forces at various load conditions. One volume covers stability and draft for set loading conditions. One volume covers the instructions for the Master. One complete set must be retained in an approved place and be stamped for approval by the Classification Society. These must be produced upon renewal of Statutory Certification.
! WARNING There is a limit on partially filled cargo tanks, between 10% of the tank length and 80% of the tank height. 7.1.1 Loading Stability Computer The Loading Stability Computer is an R.I.N.A. approved PC running Windows 3.1 environment. The Loading Stability software is produced by CETENA and is provided with compartment volumes, ship characteristics, Bonjean curves and hydrostatics. This data allows the program to calculate any loading condition for an intact condition or a damaged stability condition. Operation-Main Menu In common with other Windows applications the program opens to a main menu. The tool bar, immediately below the ship name, allows pop-up menus and sub-menus to be selected. These are as follows: Loading Condition New this allows the data for a new loading condition to be entered and ports, terminals, loading condition name, voyage number, type etc can be entered or selected. These are Loading Condition Name-This describes the loading condition to be entered Voyage Number- This parameter gives the voyage identification code in numerics or alphanumeric.
Issue: 1
Unloading Terminal- Again these can be selected from the pre-defined list.
Open- This enables a previously stored loading condition to be opened and all the pre-defined conditions are listed by name. The required file can be selected by pointing and clicking on the required name. When the loading condition has been set-up, data may be input using the added loads function. This shows a screen form which allow cargo tanks and all other tanks contents to be entered. For each tank either the sounding or ullage should be entered and the specific gravity selected from the list of fluids. The volume filling percentage and weight will therefore be calculated. Data entry is by selection of the field to enter the data by clicking a cell. When the data has been entered and confirmed by pressing the enter key or by selecting another cell, the data is automatically performed. Options- When each value is entered normally the entire stability calculation is performed and results shown in the lower part of the screen. Manual, automatic and periodic recalculation can be selected from the options functions, and the timing of periodic recalculations can be selected through this function. To complete the definition of the loading condition, it is also possible to introduce additional masses via the added loads which allow a weight to be added at a longitudinal centre of gravity, vertical centre of gravity and transverse centre of gravity, or by frame number. This is useful if the vessel is carrying heavy equipment, e.g ship to ship transfer equipment. In the matrix of results, the loading condition is summarised on screen. Cargo- This gives the cargo value for all four tanks in tonnes and metre cubed. Ballast; this gives the total value of ballast in tonnes and cubic metres.
Max SF percent- This gives the maximum value of sheer in percentage in either harbour or navigation mode and its position forward of the aft perpendicular. Max BM percent- This gives the maximum value of bending moment in percentage in harbour or navigation mode and its position forward of the aft perpendicular. INSTANT rate- This value is automatically entered if the computer is in on-line mode and is not given if any of the load gauges are out of order. This calculates the rate of ship loading from the difference in measured tank level after a given interval. AVG rate- This value gives the average rate of the loading and unloading operation calculated by considering the difference between the cargo in m3 when the on-line key is pressed and the cargo measured last time of acquisition. This value is only available when computer is in on-line mode. Residual- This shows the remaining time required to complete loading or unloading operations, assuming that the current rate value is constant. In order to calculate the residual time, the value of total final cargo in cubic metres is required and is only available if the computer is in online mode.
GM Solid- This is the computed value of the transverse metacentric height above the centre of gravity corrected for free surface effect. The central part of the screen shows the calculation results while keys are provided to switch to different result pages or graphical presentations. Bending Moment Sheer Force- These provide a table of bending moment and sheer force from frames 15 to 258, showing the actual moment and actual sheer for allowable at sea (navigation) and allowable at port (harbour) conditions. Bending moment is shown in tonne metres (TM) and %, and sheer force is shown in tonnes and percent. The maximum sheer force, bending moment and frames are shown at the bottom of the screen. GZ Levers- The KN value and GZ levers in metres against heel angle in degrees from 0-75 degrees are shown for each condition. Trim & Stability- A table of trim giving displacements to draughts and LCG, and stability giving KG, KMT, GM solid and GM fluid, plus correction for free surface effect is shown by this key. In each case graphs sowing the values of bending moment and sheer force and shown together with a GZ stability diagram when these are selected. Printing- This allows printing of the data used for calculations and results obtained. Damaged stability; the precalculated ship damaged conditions are shown from cases 1-26 which show combinations of flooded compartments. These may be selected and the hull and flooded compartments are shown graphically on the screen. Keys 1-26 allow the flooded compartments to be chosen and the key label in red indicates the condition chosen. A window showing the precalculated results can be obtained by pressing the key labelled HIDE DATA.
Fore draught- This is the computed value of forward draught corrected to take into account the actual position of the draught sensor. LBP/2 draught- This is a computed value of midships draught.
Introduction 7.1 - Page 1
Cargo Systems and Operating Manual
LNG LERICI
7.2 Cases Twenty six cases have been studied in the Damage Stability volumes for various states of loading. The Cargo Systems and Operating Manual give pictorial representations of information that can be readily obtained from these volumes. For reference the first page displays the location of assumed damaged compartments. Following on from these pages are various damage conditions when the vessel is FULLY LOADED (Condition No. 4). Note that GZ curves have been drawn to display clearly the righting lever about an assumed centre of gravity for various angles of heel.
Issue: 1
Damage No Heel 1 GZ 2 GZ 3 GZ 4 GZ 5 GZ 6 GZ 7 GZ 8 GZ 9 GZ 10 GZ 11 GZ 12 GZ 13 GZ 14 GZ 15 GZ 16 GZ 17 GZ 18 GZ 19 GZ 20 GZ 21 GZ 22 GZ 23 GZ 24 GZ 25 GZ 26 GZ
0 0 -0.219 -0.602 -0.841 -0.79 -0.792 -0.559 -0.561 -0.251 -0.268 -0.007 -0.001 -0.001 -0.001 -0.206 -0.001 -0.642 -0.001 -0.86 -0.001 -0.802 -0.008 -0.414 -0.001 -0.002 0
2
GZ - CURVES FOR FOLLOWING ANGLE OF HEEL 4 6 9 12 0.077 0.149 0.232 0.365 0.508 -0.15 -0.086 -0.011 0.107 0.232 -0.549 -0.496 -0.436 -0.34 -0.236 -0.794 -0.746 -0.693 -0.606 -0.51 -0.741 -0.69 -0.634 -0.543 -0.444 -0.743 -0.692 -0.636 -0.545 -0.446 -0.506 -0.455 -0.396 -0.297 -0.188 -0.508 -0 457 -0.397 -0.299 -0 19 -0.208 -0.166 -0.111 -0.019 0.087 -0.225 -0.186 -0.135 -0.049 0.049 0.045 0.092 0.149 0.244 0.347 0.063 0.123 0.192 0.306 0.432 0.063 0.123 0.192 0.306 0.432 0.064 0.124 0.194 0.308 0.43 -0.135 -0.068 0.008 0.132 0.264 0.062 0.121 0.189 0.3 0.418 -0.574 -0.51 -0.436 -0.315 -0.184 0.076 0.148 0.23 0.361 0.501 -0.785 -0.714 -0.632 -0.497 -0.35 0.075 0.147 0.229 0.36 0.5 -0.727 -0.655 -0.571 0.435 -0.286 0.086 0.159 0.243 0.376 0.519 -0.357 -0.305 -0.239 -0.126 0.001 0.054 0.105 0.168 0.272 0.388 0.058 0.115 0.183 0.294 0.417 0.056 0.105 0.167 0.27 0.384
15 0.665 0.368 -0.123 -0.406 -0.335 -0.337 -0.066 -0.068 0.208 0.163 0.466 0.575 0.575 0.567 0.409 0.551 -0.04 0.654 -0.186 0.654 -0.12 0.677 0.141 0.52 0.556 0.515
20
25 0.963 0.627 0.097 -0.19 -0.112 -0.114 0.179 0.177 0.447 0.394 0.71 0.859 0.859 0.828 0.684 0.803 0.239 0.945 0.131 0.946 0.203 0.978 0.418 0.784 0.831 0.777
1.31 0.932 0.371 0.088 0.176 0.175 0.49 0.488 0.747 0.691 1.022 1.203 1.203 1.144 1.01 1.099 0 57 1.273 0.511 1.279 0.592 1.329 0 75 1.113 1.167 1.104
30 1.682 1.286 0.683 0.419 0.515 0.513 0.855 0.854 1.091 1.033 1.358 1.58 1.58 1.519 1.374 1.433 0.951 1.605 0.945 1.618 1.023 1.717 1 108 1.494 1.558 1.483
36 2.064 1.679 1.052 0.813 0.92 0.919 1.27 1.27 1.433 1.365 1.668 1.985 1.986 1.941 1.767 1.791 1.369 1.925 1.416 1.953 1.481 2.138 1.496 1.859 1.932 1.848
43 2.193 1.781 1.183 0.999 1.106 1.107 1.427 1.426 1.579 1.516 1.785 2.113 2.113 2.067 1.894 1.94 1.568 2.053 1.642 2.079 1.696 2.259 1.696 1.97 2.044 1.956
50 1.964 1.634 1.099 0 968 1.063 1.064 1.336 1.335 1.492 1.44 1.674 1.906 1.906 1.927 1.732 1.85 1.512 1.956 1.615 1.973 1.651 2.1 1.656 1.817 1.887 1.799
Cases 7.2 - Page 1
Cargo Systems and Operating Manual
LNG LERICI
7.2.1 Damaged compartments numbers 41 and 214. This is damage to the forecastle space and forward dry space. Expected heel to port Freeboard to deck opening immersion No. 13 &14 Angle of heel to immersion of opening No. 10 Permisable minimum GM Excess GM Trim
0° 7.99m 33.5° 0m 2.606m -1.54m
214 10 13/14 7.99m
Draught Aft 10.19m
Draught Fwd 8.65m
41
0°
10 13
214 14 Midships Draught 9.42m
10
2.2 2.0 1.8 1.6 1.4 GZ (Metres) 1.2 1.0 0.8 Angle of Loll 0°
0.6
Location of Damage
0.4 0.2
LNG Cargo
0 0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 2
Cargo Systems and Operating Manual
LNG LERICI
7.2.2 Damaged compartments 41, 214, 213, 49, 34, 400 and 500. This is extensive assumed damage to the forecastle space, Boatswain’s store, forward paint store and pump space, 1 port ballast tank and 1 centre cargo tank. Secondary flooding occurs in the duct keel and cofferdam spaces. 400
Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
6.3° 6.83m 35.6° 0.261m 2.345m 0.28m
214
10
213 6.83m
Draught Aft 9.95m
Draught Fwd 10.23m
41
6.3°
49 10
34 Midships Draught 10.09m
213
214
10
1.8 1.6 1.4 1.2
500
1.0
GZ (Metres) 0.8 0.6 Angle of Loll to Port
0.4 0.2
Location of Damage
0 0.2
Compartments Connected to Damage Zone
0.4
LNG Cargo
0.6 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 3
Cargo Systems and Operating Manual
LNG LERICI
7.2.3 Damaged compartments 34, 35, 49, 51, 401 and 500. 401
This is extensive damage to 1 port and 2 port ballast tanks and 1 and 2 centre cargo tanks. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
17.9° 3.65m 33.6° 1.240m 1.366m -0.43m
10 3.65m
Draught Fwd 9.19m
Draught Aft 9.61m
17.9°
51
49
35
34
10
Midships Draught 9.40m
10
1.6 1.4 1.2 1.0
500
0.8
GZ (Metres) 0.6 0.4 Angle of Loll to Port
0.2 0
Location of Damage
0.2 0.4
Compartments Connected to Damage Zone
0.6
LNG Cargo
0.8 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 4
Cargo Systems and Operating Manual
LNG LERICI
7.2.4 Damaged compartments 35, 36, 51, 53, 402, 500. This is extensive damage to 2 port and 3 port ballast tanks and 2 and 3 centre cargo tanks. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
23.5° 2.18m 32.3° 1.768m 0.838m -0.29m
402
10 2.18m
Draught Fwd 8.87m
Draught Aft 9.17m
23.5°
53
51
36
35
10
Midships Draught 9.02m
10
1.4 1.2 1.0 0.8
500
0.6 GZ (Metres) 0.4 Angle of Loll to Port
0.2 0 0.2 0.4
Location of Damage
0.6
Compartments Connected to Damage Zone
0.8
LNG Cargo
1.0 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 5
Cargo Systems and Operating Manual
LNG LERICI
7.2.5 Damaged compartments 36, 37, 53, 55, 403, 500. 403
This is extensive damage to 3 port and 4 port ballast tanks and 3 and 4 centre cargo tanks. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
22.1° 2.45m 31.5° 1.847m 0.759m -0.49m
10 2.45m
Draught Aft 9.41m
Draught Fwd 8.93m
22.1°
55
53
37
36
10
Midships Draught 9.17m
10
1.6 1.4 1.2 1.0
500
0.8 GZ (Metres) 0.6 0.4 Angle of Loll to Port
0.2 0
Location of Damage
0.2 0.4
Compartments Connected to Damage Zone
0.6
LNG Cargo
0.8 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 6
Cargo Systems and Operating Manual
LNG LERICI
7.2.6 Damaged compartments 36, 37, 54, 56, 403 and 500. 403
This is extensive damage to 3 starboard and 4 starboard ballast tanks and 3 and 4 centre cargo tanks. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to starboard Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
-22.1° 2.44m 31.5° 1.853m 0.753m -0.49m
10 2.44m
Draught Aft 9.41m
Draught Fwd 8.93m
-22.1°
10
37
Midships Draught 9.17m
36
10
56
54
1.6 1.4 1.2
500
1.0 0.8 GZ (Metres) 0.6 0.4 Angle of Loll to Starboard
0.2 0 0.2
Location of Damage
0.4
Compartments Connected to Damage Zone
0.6
LNG Cargo
0.8 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 7
Cargo Systems and Operating Manual
LNG LERICI
7.2.7 Damaged compartments 37, 55, 201, 404 and 500. This is extensive damage to 4 port ballast tank, port bunker tank and 4 centre cargo tank. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
16.5° 3.29m 28.4° 1.062m 1.544m -1.54m
404
10 3.29m
Draught Aft 10.50m
Draught Fwd 8.96m
16.5°
201
55
10
37
Midships Draught 9.73m
10
1.6 1.4 1.2 1.0
500
0.8
GZ (Metres) 0.6 0.4 0.2
Angle of Loll
0
Location of Damage
0.2 0.4
Compartments Connected to Damage Zone
0.6
LNG Cargo
0.8 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 8
Cargo Systems and Operating Manual
LNG LERICI
7.2.8 Damaged compartments 37, 56, 202, 404 and 500. This is extensive damage to 4 starboard ballast tank, starboard bunker tank and 4 centre cargo tank. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to starboard Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
-16.5° 3.28m 28.4° 1.066m 1.540m -1.54m
404
10 3.28m
Draught Aft 10.50m
Draught Fwd 8.96m
-16.5°
10
37
Midships Draught 9.73m
10
202
56
1.6 1.4 1.2 1.0
500
0.8
GZ (Metres) 0.6 0.4 Angle of Loll to Starboard
0.2 0
Location of Damage
0.2 0.4
Compartments Connected to Damage Zone
0.6
LNG Cargo
0.8 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 9
Cargo Systems and Operating Manual
LNG LERICI
7.2.9 Damaged compartments 200, 201 and 207. This is extensive damage to the port bunker tank and machinery spaces with secondary flooding to the machinery store starboard aft. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
9.6° 2.26m 17.7° 1.518m 1.088m -7.06m
10
200 Draught Fwd 6.88m
2.26m
Draught Aft 13.94m
9.6°
201 10
200 207
Midships Draught 10.41m
10
1.8 1.6 1.4 1.2 1.0 GZ (Metres) 0.8 0.6 Angle of Loll to Port
0.4 0.2
Location of Damage
0 0.2
Compartments Connected to Damage Zone
0.4
LNG Cargo
0.6 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 10
Cargo Systems and Operating Manual
LNG LERICI
7.2.10 Damaged compartments 200, 202 and 207. This is extensive damage to the starboard bunker tank and machinery spaces with secondary flooding to the machinery store starboard aft. Expected heel to starboard Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
-10.6° 1.82m 16.9° 1.766m 0.840m -7.34m
10
200 1.82m
Draught Aft 14.08m
Draught Fwd 6.74m
-10.6°
10
200 Midships Draught 10.41m
207
10
202
1.8 1.6 1.4 1.2 1.0 GZ (Metres) 0.8 0.6 Angle of Loll to Starboard
0.4 0.2
Location of Damage
0 0.2
Compartments Connected to Damage Zone
0.4
LNG Cargo
0.6 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 11
Cargo Systems and Operating Manual
LNG LERICI
7.2.11 Damaged compartments 200, 208 and 1. This is extensive damage to the machinery spaces on the port side, the CO2 room and refrigeration spaces with secondary flooding to the machinery store starboard. Expected heel to port Freeboard to deck opening immersion No.9 Angle of heel to immersion of opening No.9 Permisable minimum GM Excess GM Trim
0.3° 8.74m 27.9° 0.140m 2.466m -9.43m
9
200
8.74m
Draught Aft 15.51m
Draught Fwd 6.08m
1
0.3°
9
200 208 Midships Draught 10.79m
9
2.0 1.8 1.6 1.4 1.2 GZ (Metres) 1.0 0.8 0.6
Angle of Loll to Port
0.4
Location of Damage
0.2 0
Compartments Connected to Damage Zone
0.2
LNG Cargo
0.4 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 12
Cargo Systems and Operating Manual
LNG LERICI
7.2.12 Damaged compartments 206 and 1. This is damage on the port quarter to the CO2 room, refrigeration spaces and aft peak ballast tank. Expected heel to port Freeboard to deck opening immersion No.14 Angle of heel to immersion of opening No.9 Permisable minimum GM Excess GM Trim
0° 7.53m 37.5° 0.000m 2.606m -2.24m
9
206 Draught Aft 10.70m
Draught Fwd 8.46m
1
0°
9
206
14 Midships Draught 9.58m
9
2.2 2.0 1.8 1.6 1.4 GZ (Metres) 1.2 1.0 0.8
Angle of Loll
0.6
Location of Damage
0.4 0.2
LNG Cargo
0 0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 13
Cargo Systems and Operating Manual
LNG LERICI
7.2.13 Damaged compartments 208 and 1. This is damage aft to the machinery store, refrigeration spaces and aft peak. Expected heel to port Freeboard to deck opening immersion No.15 Angle of heel to immersion of opening No.9 Permisable minimum GM Excess GM Trim
0° 2.83m 37.5° 0.000m 2.606m -2.24m
9
208 15 Draught Aft 10.70m
2.83m
Draught Fwd 8.46m
1
0°
9
208 Midships Draught 9.58m
15 9
2.2 2.0 1.8 1.6 1.4 GZ (Metres) 1.2 1.0 0.8 Angle of Loll 0° 0.6
Location of Damage
0.4 0.2
LNG Cargo
0 0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 14
Cargo Systems and Operating Manual
LNG LERICI
7.2.14 Damaged compartments 41, 215, 49, 50 and 500. This is underwater damage to the forecastle space, forward dry space and 1 port and starboard ballast tanks. Secondary flooding occurs in the duct keel and cofferdam spaces. Expected heel to port Freeboard to deck opening immersion No.13,14 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 8.26m 35.1° 0.000m 2.606m 1.34m
10
13/14 8.26m
Draught Fwd 11.12m
Draught Aft 9.78m
41
0°
49 10 13
14 Midships Draught 10.45m
10
50
2.2 2.0 1.8 1.6
215
1.4 GZ (Metres) 1.2 1.0 0.8 Angle of Loll 0° 0.6 0.4
Location of Damage
0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 15
Cargo Systems and Operating Manual
LNG LERICI
7.2.15 Damaged compartments 41, 215 and 49. This is underwater damage to the forecastle space, forward dry space and 1 port ballast tank. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
5.8° 7.15m 35.6° 0.088m 2.518m -0.34m
10 7.15m
Draught Fwd 9.45m
Draught Aft 9.79m
41
5.8°
49 10
Midships Draught 9.62m
10
2.0 1.8 1.6
215
1.4 1.2 GZ (Metres) 1.0 0.8 0.6
Angle of Loll to Port
Location of Damage
0.2 0
LNG Cargo
0.2 0.4 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 16
Cargo Systems and Operating Manual
LNG LERICI
7.2.16 Damaged compartments 49, 50, 51, 52 and 500. This is underwater damage to 1 port and 1 starboard ballast tanks, 2 port and 2 starboard ballast tanks and the duct keel. Expected heel to port Freeboard to deck opening immersion No.13,14 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 8.33m 35.1° 0.000m 2.606m 3.17m
10
13/14 8.33m
Draught Aft 9.62m
Draught Fwd 12.78m
0°
10 13
14 Midships Draught 11.20m
10
2.2 2.0 1.8 1.6
51
49
52
50
500
1.4 GZ (Metres) 1.2 1.0 0.8
Angle of Loll 0°
0.6
Location of Damage
0.4 0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 17
Cargo Systems and Operating Manual
LNG LERICI
7.2.17 Damaged compartments 49 and 51. This is underwater damage to 1 port and 2 port ballast tanks. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
15.8° 4.74m 35.8° 0.704m 1.902m 1.04m
10 4.74m
Draught Aft 9.16m
Draught Fwd 10.20m
15.8°
10
Midships Draught 9.68m
10
1.6 1.4
51
1.2
49
1.0 0.8 GZ (Metres) 0.6 0.4 Angle of Loll to Port
0.2 0
Location of Damage
0.2 0.4
LNG Cargo
0.6 0.8 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 18
Cargo Systems and Operating Manual
LNG LERICI
7.2.18 Damaged compartments 51, 52, 53, 54 and 500. This is underwater damage to 2 and 3 ballast tanks and the duct keel. Expected heel to port Freeboard to deck opening immersion No.13,14 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 7.28m 30.1° 0.000m 2.606m 1.21m
10
13/14 7.28m
Draught Aft 10.77m
Draught Fwd 11.97m
10 13
14 Midships Draught 11.37m
10
2.2 2.0
53
1.8 1.6
500
1.4
GZ (Metres) 1.2
54
1.0
52
0.8 Angle of Loll 0° 0.6
Location of Damage
0.4 0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 19
Cargo Systems and Operating Manual
LNG LERICI
7.2.19 Damaged compartments 51 and 53. This is underwater damage to 2 and 3 port ballast tanks. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
18.1° 3.53m 32.1° 0.717m 1.889m -0.06.m
10 3.53m
Draught Fwd 9.61m
Draught Aft 9.67m
18.1°
10
Midships Draught 9.64m 10
1.8 1.6 1.4 1.2
53
51
1.0 0.8 0.6 GZ (Metres) 0.4 Angle of Loll to Port
0.2 0 0.2
Location of Damage
0.4
LNG Cargo
0.6 0.8 1.0 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 20
Cargo Systems and Operating Manual
LNG LERICI
7.2.20 Damaged compartments 53, 54, 55, 56 and 500. This is underwater damage to 3 and 4 ballast tanks and the duct keel. Expected heel to port Freeboard to deck opening immersion No.13,14 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 6.16m 25.6° 0.000m 2.606m -1.73m
10 Draught Aft 12.03m
13/14 6.16m
Draught Fwd 10.30m
0°
10 13
14 Midships Draught 11.17m
10
2.2 2.0
55
1.8 1.6
53 500
1.4 GZ (Metres) 1.2
56
1.0
54
0.8 Angle of Loll 0°
0.6
Location of Damage
0.4 0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 21
Cargo Systems and Operating Manual
LNG LERICI
7.2.21 Damaged compartments 53 and 55. This is underwater damage to 3 and 4 port ballast tanks. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
17° 3.15m 28.9° 0.687m 1.919m -1.74m
10 Draught Fwd 8.74m
3.15m
Draught Aft 10.48m
17°
10
Midships Draught 9.61m 10
1.8 1.6 1.4 1.2
55
1.0
53
0.8 0.6 GZ (Metres) 0.4 Angle of Loll to Port
0.2 0 0.2 0.4
Location of Damage
0.6
LNG Cargo
0.8 1.0 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 22
Cargo Systems and Operating Manual
LNG LERICI
7.2.22 Damaged compartments 55, 56, 12 and 500. This is extensive underwater damage to 4 port and starboard ballast tanks, the duct keel and extending through to the engine room double bottom tank (void space). Secondary flooding occurs in the engine room. Expected heel to port Freeboard to deck opening immersion No.13,14 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 6.64m 27.5° 0.564m 2.042m -2.10m
10
13/14 Draught Fwd 9.47m
6.64m
Draught Aft 11.57m
0°
10 13
14 Midships Draught 10.52m
10
2.4 2.2
55
2.0 1.8
500
1.6 GZ (Metres) 1.4
56
1.2 Angle of Loll 0°
1.0 0.8 0.6
Location of Damage
0.4
Compartments Connected to Damage Zone
0.2
LNG Cargo
0 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 23
Cargo Systems and Operating Manual
LNG LERICI
7.2.23 Damaged compartments 200, 16, 207 and 55. This is extensive underwater damage to 4 port ballast tank and the engine room double bottom tank. Secondary flooding occurs in the engine room and machinery store. Expected heel to port Freeboard to deck opening immersion No.10 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
12° 1.3m 16.8° 1.793m 0.813m -7.32m
10 1.3m
Draught Aft 13.93m
200
Draught Fwd 6.61m
12°
10
Midships Draught 10.27m
10
1.8 1.6
55
1.4 1.2 GZ (Metres)
203
1.0 0.8 0.6
Angle of Loll to Port
0.4 0.2
Location of Damage
0 0.2
Compartments Connected to Damage Zone
0.4
LNG Cargo
0.6 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 24
Cargo Systems and Operating Manual
LNG LERICI
7.2.24 Damaged compartments 200, 204 and 207. This is extensive underwater damage to the engine room double bottoms with secondary flooding to the engine room and machinery store. Expected heel to port Freeboard to deck opening immersion No.11 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 4.86m 19.9° 2.286m 2.042m -6.20m
11 Draught Aft 13.46m
4.86m
Draught Fwd 7.26m
200
0°
10 11
Midships Draught 10.36m
11 10
2.2 2.0 1.8
204
1.6 1.4 GZ (Metres) 1.2 1.0 0.8 Angle of Loll 0°
0.6
Location of Damage
0.4 0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 25
Cargo Systems and Operating Manual
LNG LERICI
7.2.25 Damaged compartments 200, 203 and 207. This is extensive underwater damage in the engine room towards the aft end. secondary flooding occurs in the engine room and machinery store. Expected heel to port Freeboard to deck opening immersion No.11 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0.1° 4.75m 20.3° 0.159m 2.447m -6.35m
11 Draught Aft 13.57m
4.75m
Draught Fwd 7.21m
200
0.1°
10 11
Midships Draught 10.39m
11 10
2.2 2.0 1.8
204
1.6
203
1.4 GZ (Metres) 1.2 1.0 0.8 Angle of Loll to Port
0.6 0.4
Location of Damage
0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 26
Cargo Systems and Operating Manual
LNG LERICI
7.2.26 Damaged compartments 200, 207, 9 and 5. This is extensive underwater damage near the propeller in the engine room. Secondary flooding occurs in the engine room and machinery store. Expected heel to port Freeboard to deck opening immersion No.11 Angle of heel to immersion of opening No.10 Permisable minimum GM Excess GM Trim
0° 4.93m 20.1° 1.100m 1.506m -6.11m
11 Draught Aft 13.40m
4.93m
Draught Fwd 7.28m
200
0°
10 11
Midships Draught 10.34m
11 10
2.2 2.0 1.8 1.6 1.4 GZ (Metres) 1.2 1.0 0.8 Angle of Loll 0°
0.6 0.4
Location of Damage
0.2
Compartments Connected to Damage Zone
0
LNG Cargo
0.2 0
4
8
12
16 20 24 28 32 36 40 44 Heal (Degrees)
48 52
GZ Curve
Issue: 1
Cases 7.2 - Page 27
