FPSO Hazard Issues 2012 VerA
Short Description
FPSO HAZARD...
Description
Fine Print
Educational/ Training Material Issued as a service to the industry for Free Distribution
Hazard & Identification
FPSO - Hazard Issues Based on industry practices • UKOOA FPSO Design Guidance Notes for UKCS Service • http://olf.no/en/FPSO-Experience-Transfer/FPSO-Lessons-overview/
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FPSO FPSO (Floating Production, Storage and Offloading) is an oil & gas plant built on a ship-like structure Process facilities or topsides on deck; Oil storage tanks in hull Built to 2 differing standards or philosophy - Process and Marine FPSOs stay in location for field life, 7-20 years. Process standards
based on repairs, inspections and maintenance carried out in situ Marine standards and codes assume periodic visits to port and occasional dry-docking with plenty of maintenance time in ports And the twins never meet!
Topsides at one level, built in modules around a central pipeway Half Deck to Full Deck Modules 800-2,500t; stick build 150t, 1990s;
Pallet build 500-800t, 2000s
FPSO’s Movements & Shipping Terms FPSO undergo axial, rotational & static motions affecting equipment & structural design. Turret mooring minimizes Surge, Sway and Yaw TLP mooring allows Surge and Sway Direction
Axial
Rotational
Static
X, Longitudinal
Surge
Roll (3-4°)
List (1°)
Y, Transverse
Sway
Pitch (2-3°)
Trim (1°)
Z, Vertical
Heave
Yaw Transient Rotational Motions Roll- Side to side rotation, about the fore-aft axis Pitch- Rotation about beam/ transverse axis, fore and aft ends rise & fall Yaw- Rotation about vertical axis, fore and aft ends to swing from side to side Stable Tilt Listing- Lasting, stable tilt, lean or heel, along longitudinal axis, due to flooding or improperly loaded or shifted cargo Trim- Ship's hull to waterline tilt
Heave
Transient Lateral Motions Surge: Fore and aft Sway: From side to side Heave: Up and down
Aft, Stern, Astern
y Swa Y
Yaw
Z
P or
t Si
Sta rb o ard Pitch
Bow, Fore
List
de
Roll Hog – Ballast; wave crest amidships X Su r ge
Trim
Sag – Full load; trough amidships
Motion Impact on humans FPSO is always in motion – in calmer or moderate or severe sea conditions. May induce sea sickness No acclimatization period on landing on FPSO and onshore after spell of duty Difficult to maintain balance while moving around. In moderate and severe weather, attention is more focused on self-protection and avoiding injury Sea sickness and motion impact may impair decision making Recommend: Human Response Analysis to ensure that risks arising out of motion sickness are clearly identified and the effects managed
Motion impact on Equipment Separation, Liquid levels, Weight & Center-of-gravity Vessels: Even after shut down, vessels, tanks and columns may contain liquid. Internals should withstand likely loads from sloshing liquid inventory Forces while transiting to site & after mooring at site Structural members suffer deflections, stresses and fatigue Hogging and sagging of deck plates during transit and at site Equipment support, tie-down and liquids impact acceleration loads
Equipment spec should identify site specific motions and accelerations Equipment should be sized to meet motion impact – high values for
non-operational and moderate values for operational cases Wind tunnel and model tank tests recommended to verify analytical modeling
Motion Impact-Liquid levels Separators & Columns Liquid remix, foam on motion. Use Inlet devices/perforated baffles Internals fail due to liquid acceleration load, sloshing, fatigue of internals. Provide good support Poor separation. Locate in center along ship length Sloshing uncovers liquid outlet, leads to gas blowby. Specify high LALL Uncovered vapor outlet leads to liquid carry-over. Use outlet devices
Storage Tanks: Sloshing leads to damaged coating and accelerated
corrosion of floor and wall plates Packed columns and stripper towers: Packing, trays and demisters may move. Potential loss or degradation in function. Design support rings, foundations and holding down bolting to suit Poor liquid distribution. Use high pressure drop distributor and high liquid circulation rate. Used packing instead of trays
GDU Reboiler: High pressure drop distributor for rich glycol; higher level
to submerge heating coils
Motion Impact-Liquid levels Level control & trip: Liquid levels may not be same at opposite ends of long vessels. Alarms and trips should consider this to avoid spurious action Floats affected by acceleration. Use DP switches Have time delay or averaging to smooth trip readings Provide additional nozzles on top with stilling wells
Line slope: Pitch and roll + list and trim affects free draining of liquids Drain system: Static slope due to FPSO trim affects gravity flow / self-draining. May lead to backflow and overflow Provide check valves in liquid outlets. Provide baffles in tank. Check seal loop levels
Flare header liquid hold-up may reduce blow down capacity and increase
back pressure on PSV/BDV/RV. Provide drip legs in flare header to remove collected liquid to eliminate liquid accumulation
Motion Impact-Liquid levels Rotating equipment, (centrifugal and reciprocating pumps and compressors along with their drivers, turbines, diesel engines and cranes) Lube oil, seal oil and hydraulic oil reservoirs should be able to handle
excessive sloshing of liquids, without damaging internal baffles or loss of pump suction Bedplates and holding down bolts should be designed accordingly
Compressor: Compressor KOD could get flooded momentarily, by liquid hold-up in
pipes that causes slugs and poor performance Liquid carried over to compressor:
cokes on blades. Results in unbalanced loads and shaft/ bearing failure Gas seal failures Cracked pistons due to liquid carry-over Repeated bundle change-outs
Install larger scrubbers than normal
FPSO Trim Impact Trim
Lube oil Tanks / Flare KOD/ Drain Vessel Pumps lose suction
Provide deeper tanks and baffles in tanks. Provide high LALL Pipe-work, especially larger size liquid lines at higher elevations above main deck - check forces
Deck Deflection Impact
Deck deflections affect Rotating equipment supports
Foundation
Hull Deck
Transverse Frame
Provide 3 point mounting with gimbals or soft support towards hog/ sag Provide inclinometers or accelerometers for equipment protection PAU (Pre-Assembled Units) structures & supports Excessive vibration of Recip compressors and pumps transfer noise to hull, flexing of compressor supports, excessive PAU stiffness Cracks in deck, pipework stresses due to moving independent of PAU Design for vessel movement, machinery vibration, vessel roll, wind and live liquid load and construction tolerances
Recip compressor vibration:
Elevated Deck
Piping supports
Topside Modules
Poor mounting, failure to fit bellows and flexi hoses may result in potential leaks and failures Vibration affects drive motors with isolating pads coming loose and damaging rotors. Noise is also a problem for personnel
Towers and columns: Consider higher over turning moments Flare Tower: Consider motion effects on structure Instrument and electrical control panels and cubicles: Adequately support to withstand motion forces and any associated vibrations
Layout Issues Hull might be to shipyard codes and topsides to IP/ Other codes. Main deck classification conflict. Use a single approach Generators close to LQ, exhaust and flare radiation Module overcrowded vis-à-vis others Poorly placed vents Access and escape routes restricted by cable and pipework Poor workshop and store locations
Cold venting of hydrocarbons Gas detectors are provided to trip process units. To avoid spurious
trips, route all vents up flare stack; on thrusters controlled FPSOs, downwind Size and locate vent lines to minimise risk of explosion or tripping gas detectors under all weather conditions
Safety Issues Topsides Safety There are 2 different school of thoughts: 1. “North sea”: UK/North sea/ Australia go by ‘goal-setting' regulations
- that all hazards are identified, risks evaluated, and measures taken to reduce risks to persons to as low as reasonably practicable (ALARP) 2. “Gulf of Mexico”: US and rest of the world go by risk-based as identified in API and other codes/ standards Compliance to codes is not enough to meet North sea regulations
Hull is generally to classification society requirements to maintain class in service for insurance and mortgage Lloyd's, ABS, DNV have their risk-based rules Full compliance with Classification Society Rules may not meet UK/
Northsea regulations
HVAC Issues HVAC design by shipyards is not adequate for a production facility
Usual to consider only LQ and machinery spaces Include other hull compartments or superstructures used for control panels, switchgear and storage. Include any enclosure in turret Provide smoke and gas detection; Prevent smoke ingress into accommodation and control areas Ventilation of Temporary Refuge and main control areas in emergencies and shutdown of non-essential users Provision of minimum life support in upset conditions Hazardous area classification. Dispersion of gas in areas where gas escapes may occur and use of supplementary mechanical devices Controls, control stations and control system configuration (avoiding undue complexity) Position of inlets and exhausts relative to hazardous areas (especially where LQ is downwind of production facilities). Pressurization of spaces and airlocks Fire protection and rating of dampers and ductwork. Testing of fire and gas and shutdown dampers Spare fans
Maintenance Issues Submersible pumps Debris in tanks, pipework and leaks in pipework
Hose care, when sliding in and out of the chute, Better procedures to handle messenger line reduces offloading issues
Provide sand and solids handling in separation system Water production increases sand load Clean up wells directly through test separator
Blanketing: Hydrocarbon to replace inert gas Eliminates venting or flaring Reduced use and maintenance of inert gas generator
Maintenance Issues Tanks: Internal cracks between tanks: stiffening and fatigue analysis
Ship standards for cargo and ballast pipework: Inadequate for FPSO’s: weld failures, leaks and corrosion. Reinforce
GRE pipes poor jointing Shipyards use butterfly valves in hull; limited life and damaged by marine growth. Use gate valves with provision to blank off externally for servicing
Sea water pumps: Deep in hull (forward or aft of main tanks). Cavitation when vessel is at
shallow draft or rough weather Difficult to access and maintain Inboard mounted caisson installed pumps. Reduces pipework, easy access, less cavitation and easy maintenance and marine growth removal
Maintenance Issues Sea chests: Ideal location for marine growth and difficult to clean Difficult to blank off sea chests when main seawater valve
leaks Fitting blanking plate: Time consuming and weather sensitive. Relying on a single blanking plate may be unacceptable. Review if sea chests, good in ships, are required in FPSO. Submersible pumps in a caisson are OK
Slops tank: Install one for high solids & drop out Route paint stripping or tank cleaning solids to this tank Provide jetting lines and solids/slurry handling pumps for
easy cleaning
Hull – Marine Issues Hull Capacity: Typical shuttle tankers are 900,000 bbls Match storage volumes to planned tankers to avoid waiting and a
second hook up. Extra waiting time is expensive
Power Generation: Diesels are reliable and flexible but not good for dual fuel; high
maintenance and noise LM 2500 engines are most successful in FPSOs Larger LM 6000, inappropriate for offshore use with variable loads (from thrusters) and demands of low NOx and dual fuel Best: Smaller gas turbine packages in combination with a large backup diesel generator Gas turbines provide ample waste heat for crude heating. Diesel for main power is OK only for smaller FPSO’s
Hull – Marine Issues Green water waves over bows:
Damage stairways, fire stations, LQ windows, cable trays & pipework
Shape: Sharp bow reduces mooring loads but less space for machinery, storage. Transition zone is prone to cracking Blunt bow increases spray and wave impact and mooring loads
Workshops: Should be accessible via forklift, same level and close to stores, with mechanical handling equipment, separate from accommodation (noise) and in a safe area for welding (forward) Good environment, access reduce repair costs, as crew gets confident to repair and service equipment on board
Tank entry for inspection and repair: Costly - time & resources. Tank washing, gas freeing, solids removal, tank and pipework isolation, and personnel access, repair and recoating methods Design crude and ballast tanks for maintenance
Hull – Marine Issues Cranes: Select cranes, forklifts, layout, storage and landing areas and protection, hydraulic manipulators, lifting beams and appliances in the hull Derate cranes. Hull moments: Allowances on crane hook load Op guidelines: Inefficient cranes, poor crane coverage and inadequate laydown areas, bumper bars and mechanical handling capabilities Solid boom are affected by wind; poor response due to their weight while offloading a supply vessel or working on equipment
Tank corrosion:
Coatings in tanks base minimise free water corrosion Cracks in coating allow SRB build up leading to pitting Difficult area to inspect and damage becomes extensive before detection Inspection programme - bottom coatings and wall thickness measurement High risk areas: slops tanks, areas under solids build up and where coatings may crack due to hull strains
Hull – Marine Issues Painting: Shipyards allot low priority and time Poor quality control of preparation and finishing. Painting in tropical
countries is poor due to humid conditions Topsides paint system failure - premature thickening of paint leads to remedial work
Inability to dry dock and limited LQ Initial painting should be to highest standard Painting is conducted late when the pressure for sail away is high Develop painting technology and methods compatible with project life
of 20- years in offshore
Develop methods to safely clean, prepare and paint hulls at splash zone while on location and in production
Hull – Marine Issues Moorings: Individual anchor winches allow winter installation and active
management of mooring system + movement of the chain wear point Permanently stopped design is simpler, reduced maintenance and lower capex. Wear could be a problem. Difficult to inspect top of chain and service the fairlead. Good experience may lead to increased use No problems with mooring lines and anchors
Helicopters: Forward accommodation and helideck: Not optimum for landing -
misaligned approach, no forward visual reference-point and increased vertical movement (cf. aft helidecks). Advantage: Clean air, no vessel-induced turbulence and no take off obstructions Provide reliable weather and heave monitoring equipment
Hull – Risers, Swivels, Drag Chains
Risers:
Swivels:
Good performance, no significant leaks; 2 failures and explosion in the oil filled 11KVpower transfer swivel, due to water entering insulation oil medium Long term wear and repair worries
Drag Chains:
Damage to outer sheath and seawater ingress reduce fatigue life Gas permeation leads to collapse; HP gas flow induces vibration or loosening of inner carcass Monitoring systems, ability to flush annulus and protect from damage
An alternative to swivel. Simpler. Hose and electric cable failure due to wear from bending, wear pads worn out, difficulty of access Drag chain limits free rotation requiring thrusters to be serviceable at all times High maintenance and operability problems indicate swivels a better option
Thrusters:
Failure in winter impact safety and production Most thrusters have to be withdrawn externally and ROV work is weather sensitive and high risk Thrusters should be designed for internal retrieval and service
Turret Issues Location: Vessel with turret at > 75% of hull length, weather-vanes free At 65%, thrusters are required to maintain/control heading Thrusters lock turret and reduce bearing / swivel wear. But introduce demand on thrusters, safety critical items and crew to mange turret repositioning Lower maintenance and crew demand with free turrets Safety of accommodation ensured by a firewall Free turret with swivel and thrusters for offloading only gives lowest Opex
Turret Design:
3 types of bearings Wheel and rail type - unsatisfactory - high point loading from wheels, excess construction tolerances, vessel deflection, poor rail heat treatment surface cracking and inadequate wheel lubrication Hydraulic turret bearings - pad wear, high starting friction, gripper failures, hydraulic imbalance and difficulty to access and repair components Heavy duty rails and multiple bogies with rubber pads spread the load Hydraulic pads for high mooring loads on a large turret, effective - no downtime but maintenance has been excessive
All components must be easily serviceable and replaceable.
Capex & Schedule Overruns Shipyards run to a tight schedule. Can not accept changes. Minimize changes to ship and topsides once hull is awarded Penalty: quality and opportunities to improve design at low cost Work with shipyard to maintain quality and assist to improve efficiency
Functional Specifications: Designer and shipyard - unable to interpret correctly. Too little
guidance. Select key equipment and spell clearly in specification
Inadequate documentation: Delayed documentation, missing data, paperless systems not running
even one year after start-up, missing as built drawing and loop diagrams, incompatible tags and poor links to maintenance databases. Specify documentation requirements at order placement and ensure before paying suppliers
Hazop/ Hazid Session
Add here project title
Presentations on Process Scheme …
Process Engineer Layout……………….. Piping Engineer Structures ……….. Structural Engineer Safety Alerts from similar facilities C:\Kumar\FPSO\FLNG Shell6.jpg
Hazop/ Hazid on Topsides only. Excludes: • Hull & Marine systems; Turret & Mooring; • Flowline & Risers, Umbilicals • Module fabrication, integration to hull, • Commissioning & Operation handover •Subsea systems, Mooring, CALM
Process Flow Scheme
Facility Layout
Exploded View of Decks
Key Project Information
Type of Facility
Type of Field Feed Products
Gas
Condensate Produced Water
: Onshore Offshore : LNG Oil & Gas Gas & Condensate : Refinery Petrochemical Chemical/ Fertilizer : Marginal Normal : Oil, Gas and Water : Gas compressed, dehydrated and exported via pipeline : Oil stabilized and exported via pipeline : Condensate injected into gas pipeline : Water deoiled and locally disposed : Daily Contractual Quantity (DCQ) XXX MMscfd : Max Daily Quantity (MDQ) YYY (DCQ + 10%) : Design ZZZ 125% MDQ : Normal / Maximum XX,000 / YY,000 BPD : Normal / Maximum/ Design XX,000 / YY,000 BPD
Key Project Information
Platform
Flare
Pressure Temperature
Location If Deep water, familiar with
: Wellhead Process Platform : No of Decks XX No of Piles YY Weight ZZ,000 t : Single lift Modular lift Float over : Bridge linked Wellhead LQ Flare Tripod : Helipad on LQ on another location : Unmanned Manned : Vertical on platform Cantilevered from platform : Separate bridge linked platform : Highest 165 barg lift gas; 75 barg export gas : Lowest (–) 40°C HP flare lateral; : Highest - 550°C GT exhaust : Shallow Water Deepwater
: Hydrate/ Wax Issues MEG/Methanol Injection : Line Flushing Wetwells Drywells If FPSO/ Semi-sub, familiar with or knows about : Impact of ship motion on topsides
Key Project Information
Hazardous & Corrosive Materials Lethal, Toxic Components : H2S 500 to 2,000 ppm Mercury Arsenic If H2S : Operator familiar. A few units in operation : Material Selection Personal H2S Monitor SCUBA : Familiar or knows pyrophoric issues If Hg or As : Removal Handling Al MOC Low accumulation points : Operator familiar Discharge to sea with produced water Corrosive : CO2 4 – 6% Acid cleaning - compressor piping : Wellfluids High Temp CO2 - H2O from regenerator Hypochlorite If CO2 : Operator familiar. A few units in operation Material Selection : Knows about wet CO2 issues Familiar or knows asphyxiation issues Potential incompatibilities : Solids Sand Drill mud Acid/alkali handling Wax Catalysts : Mercury Removal Dehydrator Mol Sieves None Dust Handling : None Firewater system uses : GRE pipes PE/ Cement lined pipes Alloy steel
Key Project Information
Owner-Operator
Key Issues
: First Installation Operates similar units : Sub-contract operation Operated by own crew : Isolation standards, including Double Block & Bleed : Sampling Draining Venting Philosophy : PSVs are spared not spared : Familiar with Rupture disks, if used : High Levels of H2S : First of a kind for client??
Safety Studies
Equipment and Building Location Study Smoke & Gas Ingress/ Toxic Gas Risk Analysis Fire & Explosion / Blast Risk Analysis EERA - Escape, Evacuation and Rescue Analysis ESSA - Emergency Systems Survivability Analysis Emergency Systems Reliability / Availability Analysis QRA - Quantitative Risk Assessment Studies EIA - Environmental Impact Assessment Studies Inherent Safety Analysis - Eliminate by process changes, minimize inventory Hazard Prevention - Overpressure protection, Area Classification, SIL Hazard Detection - Fire & Gas Detection, ESD stations Hazard Control - Isolation & Depressurization Hazard Mitigation - Active & Passive Fire Protection, Firewater/ Foam Systems Ship Collision Risk Analysis/ Dropped Object Risk Analysis AIV/ FIV Studies/ Noise Study/ Pipe Stress Study SIMOPS Study Human Factors Human Response Analysis Model Tank Testing Gas Turbine Exhaust Plume Dispersion Analysis
1) Feedback on FPSO issues http://olf.no/en/FPSO-Experience-Transfer/FPSO-Lessons-overview/ 2) “Ship-shaped offshore installations: design, building, and operation” Jeom Kee Paik, Anil Kumar Thayamballi
Your every action in a day, considering its impact on you, your family, your colleagues and friends, will make it a way of life!
THANK YOU - BE SAFE
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