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Project
: FPSO Cidade De Paraty
Project Number
: HI.39490
SBM Purchase Order Number
: HI.39490
SBM P.O. Description
:
SBM Document Type
:
0043
#N/A
SBM Revision Number
: 0
Client Document Code
: Not Applicable
Client Document Type
: Not Applicable
Client Revision
: Not Applicable
(Other)
: Not Applicable
Vendor (Company) Name Vendor Document Handler E-Mail adress Vendor P.O. Reference Vendor Document Number Document Description Vendor Document Revision Total Pages Applicable Tag Number (s)
: Petrobras
: LER
SBM CDR Code + Sequence Number
Extra Notes :
Client
This document is part of VDB :
#N/A
: ABB AS OSLO : Arun.B.R. :
[email protected] : 01.39490.0043 : : HVAC SYSTEM FUNCTIONAL DESIGN DESCRIPTION : 0 : 28 :
HVAC System Functional Design Description Table of Contents Section
Description
Page
1.
General
2.
Fire and Gas Detection Philosophy
3.
HVAC Equipment
4.
Control of ACCU
5.
Temperature & Humidity Regulation
6.
Constant Volume Electric Reheater
7.
Pressure Regulation
8.
Compressor Capacity Regulation and Condensing System Protection
9.
System Start Up and Capacity Regulation
10.
Pump Down Operation
11.
Transformer Room Ventilation System
12.
F & G Dampers and Shut Off Dampers
13.
Unit Control Panel for HVAC System
14.
HVAC UCP Interface to F&G, PCS and ESD
15.
Alarm Management
16.
Password Protection
17.
Instruments
18.
ACMV System for Battery Room
ABBREVIATIONS AHU
Air Handling Unit
ACCU
Air Cooled Condensing Unit
UCP
Unit Control Panel
PLC
Programmable Logic Controller
HVAC
Heating, Ventilating and Air Conditioning
PCS
Process Control System
F&G
Fire & Gas
ESD
Emergency Shut Down
ESB
Emergency Stop Button
HMI
Human Machine Interface
ATM
Atmosphere
PDT
Pressure Differential Transmitter
PDS
Pressure Differential Switch
PDG
Pressure Differential Gauge
SAD
Supply Air Duct
RAD
Return Air Duct
EAD
Exhaust Air Duct
FAD
Fresh Air Duct
System Design Specification
HVAC System
1
1.0
General
The HVAC system is designed for two storey Local Equipment Room of FPSO CIDADE DE PARATY Project and that consists of the following compartments:LER Level - 1 1.
HVLV Switch Board Room,
2.
Transformer Room,
3.
Battery Room, and
4.
Air Lock – 1.
LER Level - 2 1.
Unit Control Room and
2.
Air Lock – 2.
The requirement of HVAC and pressurization level for compartments are as follows:-
Sr.No
Room Description
Air Conditioning
Mech. Ventilation
Pressurization
Level - 1 1
HVLV SB Room
Yes.
No.
+50 Pa @ ATM
2
Transformer Room
No.
Yes.
+25 Pa @ ATM
3
Battery Room
Yes.
Mech. Exhaust
+15 Pa @ ATM
4
Air Lock - 1
Yes.
No.
+25 Pa @ ATM
Level - 2 5
Unit Control Room
Yes.
No.
+50 Pa @ ATM
6
Air Lock - 2
Yes.
No.
+25 Pa @ ATM
Power Supply
:
440 V / 3 Ph / 60 Hz
Power Supply
:
220 V / 2 Ph / 60 Hz
Hazardous Area Classification
:
Class I Zone 2 Gas Group IIA T3 ( Outdoor )
:
Safe ( Non Hazardous ) Area ( Indoor )
:
Class I Zone 1 Gas Group IIC ( Battery Room )
Class 1, Zone 2, IIA, T3
The HVAC system for LER consists of two sub-systems:-
Reference shall be made to DEF49100 - FPSO HAZARDOUS AREA LAYOUT. The System – 1 is designed for cooling, dehumidifying, re-heating and pressurization requirement for HVLV switchboard room & Air Lock – 1 at LER level -1 and Unit Control Room & Air Lock – 2 at LER level -2. The mechanical ventilation system is designed to remove heat radiated from transformer room‟s equipments by means of ventilation and arranged slight positive pressure is maintained inside the system. The System – 2 is designed for cooling, dehumidifying and pressurization requirement for Battery room at LER level - 1. The mechanical exhaust air system is designed for Battery room to extract air from the compartment and there is no return air to the air conditioning equipments. System Design Specification
HVAC System
2
2.0
Fire and Gas Detection Philosophy
2.1
Fire and Gas Detection Philosophy ( System – 1 )
The gas detection instruments ( xxx-GD-001, xxx-GD-002 ) shall install inside the fresh air stream located at the LER level – 2. By gas detection at the intake of the LER HVAC system and depends on the level of gas detected, the vessel F&G system will gives the LER HVAC UCP ( xxx-UP-01 ) as follows:1.
Confirmed fire in HVLV Switchboard Room and vessel F&G system shall gives the shutdown signal to HVAC UCP - 01, then HVAC UCP will gives close signal to all dampers inside the system – 1 and the entire HVAC system – 1 will shutdown.
2.
Confirmed fire in Unit Control Room and vessel F&G system shall gives the shutdown signal to HVAC UCP - 01, then HVAC UCP will gives close signal to all dampers inside the system – 1 and the entire HVAC system – 1 will shutdown.
3.
Confirmed fire at False Floor ( fire detected under the module ) and vessel F&G system shall gives the shutdown signal to HVAC UCP - 01, then HVAC UCP will gives close signal to all dampers inside the system – 1 and the entire HVAC system – 1 will shutdown.
4.
Confirmed Gas Detected at Fresh Air inlet of the System -1 OR 2 and vessel F&G system shall gives the shutdown signal to HVAC UCP - 01, then HVAC UCP will gives close signal to all dampers inside the system – 1 and the entire HVAC system – 1 will shutdown.
5.
Confirmed fire in Transformer Room and vessel F&G system shall gives the Fire Detected inside the Transformer Room signal to HVAC UCP - 01, then HVAC UCP will gives close signal to all dampers inside the Transformer Room ventilation system and the mechanical ventilation system will shutdown.
2.2
Fire and Gas Detection Philosophy ( System – 2 )
The gas detection instruments ( xxx-GD-003, xxx-GD-004 ) shall install inlet of the Air Handling Unit - 2 located at the LER level – 2. By gas detection at the intake of the Battery Room ACMV system and depends on the level of gas detected, the vessel F&G system will gives the ACMV UCP ( xxx-UP-02 ) as follows:1.
Confirmed fire in Battery Room and vessel F&G system shall gives the shutdown signal to ACMV UCP - 02, then HVAC UCP will gives close signal to all dampers inside the system – 2 and the entire ACMV system – 2 will shutdown.
2.
Confirmed fire at False Floor ( fire detected under the module ) and vessel F&G system shall gives the shutdown signal to ACMV UCP - 02, then ACMV UCP will gives close signal to all dampers inside the system – 2and the entire ACMV system – 2 will shutdown.
3.
Confirmed Gas Detected at Fresh Air inlet of the System -1 OR 2 and vessel F&G system shall gives the shutdown signal to ACMV UCP - 02, then ACMV UCP will gives close signal to all dampers inside the system – 2 and the entire HVAC system – 2 will shutdown.
Pay attention on the length of the inlet duct between gas sensors and gas tight damper. 3.0
HVAC Equipment ( System – 1 )
The HVAC system - 1 is designed for continuous operation with two independent direct expansion (DX) type air conditioning systems ( 1 x 100% duty and 1 x 100% stand by unit ). Each unit has 100% capacity of cooling load, air flow and pressurization requirement for the system. The mechanical ventilation system for transformer room is designed with one set of mechanical supply air fan with one set of mechanical exhaust air fan. Exhaust air fan is sized to maintain slight positive pressure inside the compartment. All AHU & ACCU are fabricated with galvanized material painted suitable for marine and offshore application.
should be stainless steel System Design Specification
HVAC System
3
3.1
Air Handling Units
Ref. Document
:
Ducting & Instrument Diagram (D & ID), Air Flow Diagram
The air handling system is 2 x 100% and designed according to air capacity requirement for cooling and pressurization requirement of the building. Both units will install at LER level - 2. In normal operation, one unit
Rotate duty monthly.
will acts as duty and the other unit remains on stand-by.
The unit can be started and stopped independently. The AHU can be started even if the air cooled condensing system is not running. All AHU‟s supply air fans have stop, running and failure signal. Air Handling Unit is designed to be horizontal, continuous operating, draw through type complete with air mixing section, air filtration section, cooling section and blower section c/w motor and power transmission assembly. The AHU is designed to use both fresh air and re-circulating air. The AHU is direct expansion type of refrigerant R407 C and complete with supply air blower fan and cooling coil. The supply air outlet from blower fan is passed through the non return dampers and connect to the common plenum box with internal insulation to prevent condensation and noise level transmission. The unit has return air and fresh air connection and shut off damper is equipped at the common fresh air duct. The AHU has the following components for proper functioning of HVAC system. a. Shut off damper at fresh air intake, b. Non Return Damper at fresh air connection to AHU, c. Non Return Damper at AHU blower fan‟s inlet, d. Non return damper at blower fan‟s outlet, e. Pressure differential switches. The fresh air intake is fitted with bird screen, coalescing filters, gas detectors ( by other ) and is guided to the mixing section of the AHU. The fresh air duct is connected to mixing section of the AHU through an isolation shut off damper ( xx-SOD-001 ). In mixing section, the fresh air is mixed with return air from the LER level – 1 & level - 2. The mixed air entered the filtration section, it consists of HVAC air filter before it enters the direct expansion cooling coil. The by-passing of air to AHUs can be prevented by installation of non return dampers at each inlet and outlet of the AHU respectively. The non return dampers for duty AHU will be opened during operation and that for standby unit will be closed. The mixing air is conditioned (cooling and dehumidification process) while passing through the cooling coil. The duty centrifugal type blower fan conveyed conditioning air to the designated rooms/spaces via sheet metal duct work. The external supply air duct is fabricated with 3 mm thickness SS 316L material and complete with 50 mm thickness internal insulation and the internal one is fabricated with 1.2 mm thickness galvanized material complete with 25 mm thickness external insulation. The supply air duct is fitted with electric operated type fire & gas dampers if duct passing through class rated bulkhead and deck head, manual operated volume control dampers is fitted on each main duct and branch duct for proper balancing of the supply air to all serving rooms/spaces and supply air grilles. The return air duct is fitted with electric operated type fire & gas dampers if duct passing through class rated bulkhead and deck head, manual operated volume control dampers for proper balancing of the return air from all serving rooms/spaces, modulating damper ( xx-MD-101 & xx-MD-201 ) ( to regulate the return air flow rate to maintain required positive pressure inside the building ), humidity & temperature transmitter ( xx-MTT-101 & xx-MTT-201 ) ( to maintain constant return air temperature and displayed humidity level ) and return air grilles. The main supply air ducts and return air ducts to/from the AHU are routed outside of the building and guided to first floor and second floor of the LER building. System Design Specification
HVAC System
4
According to ABS "Facilities on offshore installations" must also be capable of being closed manually from both sides of the bulkhead or deck. All F&G and shut off dampers, remotely controlled with a fail safe actuator ( Fail Close ). When 24 VDC power is energized to the electric actuator and the damper will be in opened position. The electric actuator will close automatically if loss of power supply because of built-in spring return actuator ( fail safe actuator ). All F&G dampers are powered and controlled directly from the HVAC control panel ( xx-UP-01 ). The F&G system is responsible for safe operation of the HVAC system by giving separate shutdown signal mentioned above. The list of F&G damper & shut off dampers are as follows:-
Sr.No
Description
Tag No
Power & Control
Location ( Wall or Deck )
Roof ( Outside ) Shut Off Damper
1
xx-SOD-001
FAD – Roof ( Outside )
HVAC UCP-01
LER Level - 1 2
F&G Damper
xx-FD-001
SAD – Roof ( Outside ) ~ HVLV
HVAC UCP-01
3
F&G Damper
xx-FD-002
RAD – HVLV ~ Roof ( Outside )
HVAC UCP-01
4
F&G Damper
xx-FD-003
SAD – HVLV ~ Air Lock - 1
HVAC UCP-01
LER Level - 2 5
F&G Damper
xx-FD-004
SAD – Roof ( Outside ) ~ LER Level - 2
HVAC UCP-01
6
F&G Damper
xx-FD-005
RAD – LER Level – 2 ~ Roof ( Outside )
HVAC UCP-01
7
F&G Damper
xx-FD-006
SAD – UCR ~ Air Lock - 2
HVAC UCP-01
Transformer Room 8
F&G Damper
xx-FD-007
FAD – Outside ~ Transformer Room
HVAC UCP-01
9
F&G Damper
xx-FD-008
EAD – Transformer Room ~ Outside
HVAC UCP-01
The operator interface consists of a series of high visibility indicating lights, push buttons, selector function and touch screen panel located at the unit control panel. The PLC control system processes related input and outputs, control, protect and monitor the system with a number of programmable settings, e.g. temperature & humidity transmitters, pressure transmitters, modulating dampers, pressure switches, AHU start/ stop, control & monitoring of the air conditioning system.
The pressure differential switches c/w indicators are fitted across the filters to monitor the condition of filters.
Item
Tag No.
Location
Alarm Set Pt.
Alarm Message
Remark
1
xx-PDS-001
Fresh Air Filter
xxx Pa ( H )
Fresh Air Filter Dirty
2
xx-PDS-002
Main Air Filter
xxx Pa ( H )
Main Air Filter Dirty
AHU - A
3
xx-PDS-004
Main Air Filter
xxx Pa ( H )
Main Air Filter Dirty
AHU - B
System Design Specification
HVAC System
5
When the value reading from the respective pressure differential switch is higher than the alarm set point mentioned above and a general alarm will be generated at the UCP and PCS ( common fault alarm ). The UCP‟s HMI will indicate the respective filter‟s high differential pressure alarm message and the panel mounted Buzzer will generate an intermittent sound. The pressure differential switches are also fitted across the supply air blowers to monitor the proper functioning of blower to prevent loss of pressurization. .
Item
Tag No.
Location
Alarm Set Pt.
Alarm Message
1
xx-PDS-003
Blower Fan - A
xxx Pa ( Low )
Blower Fan A Fault
2
xx-PDS-005
Blower Fan - B
xxx Pa ( Low )
Blower Fan B Fault
Remark
When the value reading from the pressure differential switch is lower than the alarm set point mentioned above and a general alarm will be generated at the UCP and PCS ( common fault alarm ). The HMI will indicate the respective blower‟s low differential pressure alarm message and the panel mounted Buzzer will generate an intermittent sound (common alarm to PCS) and initiate automatic change over to standby system after a time delay of 60 seconds. If the HVAC system is operating in AUTO mode, either one of the Trip function ( HMI will specify which Trip function ) will Stop the duty system and change over to operate the Standby system as duty automatically. The electric motors inside the AHU is Ex‟e‟ protection and all electrical components and instruments equipped are suitable to operate in Hazardous Area Zone 2. 3.2
Air Cooled Condensing Units
Ref. Document
:
Piping & Instrument Diagram ( P & ID )
The air cooled condensing system is 2 x 100% independent refrigeration circuit and designed according to heat rejection requirement of system. Both units are installed at the open deck of LER level - 2. In normal operation, one unit acts as duty and the other unit remains on stand-by. The unit can not be started independently without running respective AHU in auto mode but it can be performed functional or rotation check on maintenance ( Test/Manual ) mode. The unit can be started only if the duty air handling unit is in running. The operator interface consists of a series of high visibility indicating lights, pushbuttons, selector functions and touch screen panel located at the unit control panel. The PLC control system processes related input and outputs, control, protect and monitor the system with a number of programmable settings, e.g. Temperature transmitters, Pressure Switches, etc,. The electric motors inside the ACCU is Ex‟e‟ protection and all electrical components and instruments equipped are suitable to operate in Hazardous Area Zone 2. The condensing unit equipment starter and overload protection are installed inside the HVAC unit control panel. Space heater power supply for motor of capacity 5.5 kW and above are fed from the same UCP. All ACCU fans, compressor motor have stop, running and failure signal. The ACCU is controlled by PLC based UCP and each system ( duty or standby ) consists of one set of open type reciprocating compressor direct coupling driven by electric motor, four sets of condenser fans c/w driving motors, one piece of refrigeration liquid line solenoid valve on each refrigeration circuit and others refrigeration system components, accessories and instruments. The ACCU work as a slave of the respective AHU. System Design Specification
HVAC System
6
4.0
Control of ACCU
The air cooled condensing unit compressor motor, condenser fan motor starter and overload protection are housed within the UCP. The UCP will be able to START or STOP the motor during maintenance mode for functional check or rotational check only. Power supply for motor‟s anti-condensation heaters are fed from the UCP. 4.1
ACCU START
The UCP will monitor the temperature and humidity reading from the moisture-temperature transmitters mounted inside the return air stream on each deck. Item
Instrument Tag No.
Location
Set Parameter
1
xx-MTT-101
RAD – First Floor
T = 24o C & RH = 50 %
2
xx-MTT-201
RAD – Second Floor
T = 24o C & RH = 50 %
Remark
These transmitters measure the temperature and humidity of the return air. When the return air temperature (average reading from the 2 transmitters) rises above 24o C ( adjustable ), the UCP will gives signal to start the duty ACCU while the duty AHU is in operation. The refrigeration compressor and condenser fan will operate simultaneously. The compressor operation is interlocked with condenser fans operation and it will not started without running all duty condensing fans. 4.2
System Safety Protection
During the duty ACCU is in operation, the UCP will continuously monitor the respective system low refrigerant pressure via low refrigerant pressure switch ( xx-PSL-001A or B ) mounted on the refrigeration suction line and high refrigerant pressure via high refrigerant pressure switch ( xx-PSH-001A or B ) mounted on the refrigeration discharge line. When the reading on the low refrigerant pressure switch fall below set point, the UCP will activate pump down function and stop the compressor. When the refrigerant pressure rises above set point, the compressor will be able to restart automatically. When the reading on the high refrigerant pressure switch goes above xx.x bar (g), the UCP will stop the compressor. When the refrigerant pressure drop below xx.x bar (g), the compressor will be able to restart but it required manual reset on PLC touch screen to eliminate high refrigerant pressure cut off alarm. The compressor can‟t be restarted within 5 mins (adjustable) with auto restart operation ( e.g compressor auto cutoff when temperature reach set parameter or pump down activated due to low refrigerant pressure reaches set point ). 4.3
Liquid Line Solenoid Valve Operating Sequence
The liquid line solenoid valve is installed on each refrigeration circuit and will be opened once received the START command from UCP and all the refrigeration system operating parameters are in normal condition. 4.4
Crankcase Heater Operating Sequence
Before first start up, the crankcase heater shall energize for 24 hours. When the duty compressor is running, the respective crankcase heater will be de-energized and the stand by compressor‟s heater shall be energized. 4.5
Condenser Fan Operating Sequence
All duty condenser fans are started simultaneously with respective compressor.
System Design Specification
HVAC System
7
4.6
Refrigeration Lube Oil Level
The UCP will monitor the refrigeration oil pressure in the system via oil differential pressure switch mounted on the system. The oil pressure should reach correct level within a few seconds after first start up the compressor. During the first start, the correct lube oil differential pressure is not reached in 15 ~ 20 seconds , stop compressor immediately and check oil system & accessories. During normal operation and when the compressor starts, refrigeration oil differential pressure shall reach to satisfactory level within 120 seconds. If the oil differential pressure fall below set point, the oil level switch will trip the compressor and show an alarm message at UCP ( common alarm to PCS ) and need to be reset manually from UCP. 4.7
List of Refrigeration System Safety Components
Sr.No
Description
1
High Refrigerant Pressure Switch ( System – A/B ) ( High )
2
Low Refrigerant Pressure Switch ( System – A/B ) ( Low )
3
Lube Oil Differential Pressure Switch ( Time Delay = 120 sec )
Tag No.
Set Pt.
Alarm (UCP)
Remark
xx-PSH-001 A/B
xx.x bar (g) ( High )
Refrigerant Pr. High ( System – A/B )
Manual Reset
xx-PSL-001 A/B
xx.x bar (g) ( Low )
N.A
Auto Reset
Lube Oil Pr. Low ( System – A/B )
Manual Reset
xx-ODPS-001 A/B
xx.x bar (g) ( Low )
When the value reading from the above instruments is higher / lower than the set point mentioned above, a general alarm will be generated. The UCP will indicate the respective alarm at the HMI and the panel mounted Buzzer will generate an intermittent sound. The common fault alarm is transmitted to the PCS. If the HVAC system is operating in AUTO mode, either one of the Trip function ( HMI will specify which Trip function ) will Stop the duty system and change over to operate the Stand-by system as duty automatically. 5.0
Temperature & Humidity Regulation
The duct mounted temperature and relative humidity transmitters ( xx-MTT-101 on LER 1st Floor, xx-MTT-201 on 2nd Floor ) are installed inside the return air stream of first floor and second floor ( HVLV Room and Unit Control Room). When the reading (average of the 2 readings) is higher than set point ( 24oC ) and the compressor will be in operation to bring down the temperature and humidity level inside the buildings. When the reading value reach set point ( 24oC ) or below, the refrigerant suction pressure will drop accordingly due to less cooling and dehumidification load. Based on the refrigeration suction pressure and control oil pressure, the compressor will be regulated in unload operation by factory assembled hydraulic capacity control unloader system to maintain humidity level inside the building. The compressor will load again if the cooling load demand increases. During fully unload condition and temperature reading falls below minimum set point ( 18oC ), the system will be pump down and compressor will be STOP in operation. The compressor will restart automatically when the sense temperature reaches above set point or the high temperature ( over 28oC ) alarm message will be displayed at UCP HMI and panel mounted Buzzer will generate an intermittent sound.
System Design Specification
HVAC System
8
6.0
Constant Volume Electric Re-Heater
The electric re-heater are installed inside the supply air stream of LER level – 1 & 2. The function of re-heater is programmed by UCP together with room temperature transmitter installed on each level. If temperature reading on the temperature transmitter falls below set point, it will send the signal to UCP. The UCP will send signal to activate the respective re-heater if all heater safety devices are normal. The heater will be de-activated if the respective temperature transmitter reading reaches set point. The power requirement of the heater is provided by xx-UP-01. The safety devices are housed in the heater casing for proper functioning and control requirement of heater. The power supply for heater capacity of 3 kW and above shall be 440V/3 Ph/60 Hz and that below shall be 220V/1 Ph/60 Hz. Heater Safety devices are as follows:Sr.No
Description
Tag No.
Set Pt.
Alarm (UCP)
Remark
1
Temperature Switch
N.A
87oC
N.A
Auto Reset
2
Temperature Switch
N.A
120oC
Heater Fault
Manual Reset
3
Air Flow Switch
N.A
25 Pa
Heater Fault
Heater will not work if no air flow.
4
Door Switch
N.A
N.A
Heater Fault
Heater will not work if door opened.
The list of heater and controlled temperature transmitter are as follows:Sr.No
Location
Heater Tag No.
TT Tag. No
Set Pt.
Remark
1
Level – 1, LER
xx-DH-001
xx-MTT-101
20oC
Heater activate if temp. < set pt.
2
Level – 2, LER
xx-DH-002
xx-MTT-201
20oC
Heater activate if temp. < set pt.
7.0
Pressure Regulation
7.1
Pressure Regulation ( HVLV Room )
The compartment is pressurized to 50 Pa( +/- : 10 / 15 Pa ). The supply and return air flow rate inside this compartment is balanced during testing and commissioning. The room differential pressure transmitter ( xx-PDT-101 ) is installed inside the HVLV room. During auto operation, this differential pressure transmitter monitors the room pressure. It also used as signal to modulating damper ( xx-MD-101 ) to regulate return air flow ( by opening or closing dampers ) and make sure the rooms are pressurized. When the value on the PDT is lower than minimum set point ( 35 Pa) after a time delay of 60 seconds ( adjustable ), a general alarm will be activated. The UCP HMI will show alarm message and Buzzer will generate an intermittent sound. The room low pressure differential alarm is transmitted to PCS. Supply air required to the air lock-1 is served by HVAC system and maintain +25 Pa above atmosphere by arranging no return air from the air lock. 7.2
Pressure Regulation ( Unit Control Room )
The compartment is pressurized to 50 Pa( +/- : 10 / 15 Pa ). The supply and return air flow rate inside this compartment is balanced during testing and commissioning. The room differential pressure transmitter ( xx-PDT-201 ) is installed inside the unit control room. During auto operation, this differential pressure transmitter monitors the room pressure. It also used as signal to modulating damper ( xx-MD-201 ) to regulate return air flow ( by opening or closing dampers ) and make sure the rooms are pressurized. When the value on System Design Specification
HVAC System
9
the PDT is lower than minimum set point ( 35 Pa) after a time delay of 60 seconds ( adjustable ), a general alarm will be activated. The UCP HMI will show alarm message and Buzzer will generate an intermittent sound. The room low pressure differential alarm is transmitted to PCS. Supply air required to the air lock-2 is served by HVAC system and maintain +25 Pa above atmosphere by arranging no return air from the air lock. 8.0
Compressor Capacity Regulation and Condensing System Protection :-
8.1
Capacity Control
The refrigeration compressor is fitted with hydraulic capacity control system it regulates according to changing load demands. 8.2
Condensing System Protection Devices a.
Compressor‟s Electric Motor Protection Devices,
b.
High Refrigerant Pressure Safety Device,
c.
Low Refrigerant Pressure Safety Device,
d.
Low Lube Oil Differential Pressure Safety Device,
e.
Crankcase Heater.
1.
Refrigeration Lube Oil Level,
2.
Setting and function of safety and protection devices,
3.
Setting of timing,
4.
Setting of refrigerant pressure safety devices,
8.3
Check before starting:-
The compressor lubrication should be checked immediately after starting. Maximum and recommended oil level during operation shall be within the sight glass range mounted of the compressor. Minimum oil level is monitored by an oil differential pressure switch. The time delay period for oil level switch is set to 120 seconds after start up the compressor. If there is not enough oil pressure and the refrigeration compressor must stop immediately. 8.4
Crankcase Heater
The crankcase heater must be energized during standstill. The crankcase heater in the compressor prevent high refrigerant dilution of the oil during standstill. It shall only be switched on if compressor is filled with oil. Note: If the oil pressure switch cuts-out during the starting stage or the oil level falls below recommended sight glass level, this indicates a severe lack of lubrication. It may happen due to small pressure difference. Check the oil return line before adding additional amount of lube oil or danger of liquid slugging. 9.0
Compressor Start Up and Capacity Regulation
The refrigeration compressor will start up if the following conditions are TRUE.
The duty AHU is in operation,
All system protection devices and operation parameters are normal,
No alarm active,
Respective Liquid line solenoid valve is opened.
The compressor operating sequence and capacity regulation is mainly controlled by System Design Specification
HVAC System
10
1.
Low Refrigerant Pressure,
2.
Average Return Air Temperature
Condition – 1 If Refrigerant Suction Pressure > / = 5 bar(g) AND Average Return Air Temperature > 24oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened Then
:
Refrigeration Compressor
:
START
The compressor will be in loading / unloading operation condition according to changing load demands. Condition – 2 If Refrigerant Suction Pressure > / = 2.5 bar(g) AND Average Return Air Temperature > 2 + 24oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened, Then
:
Refrigeration Compressor
:
Operate in Full Load Condition
Condition – 3 If Refrigerant Suction Pressure > / = 2.2 bar(g) OR Average Return Air Temperature > 1 + 24oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened, Then
:
Refrigeration Compressor
:
Operate in Unload condition
Condition – 4 If Refrigerant Suction Pressure < / = 1.4 bar(g) AND Average Return Air Temperature< / > / = 24oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened, Then
:
Refrigeration Compressor
:
Activate Pump Down & Stop the Compressor for 5 minutes
The cycle is repeated automatically. 10.0
Pump Down Operation
10.1
Pump Down Mode
The UCP can control the pump down sequence manually in the MAN mode. Operator has to access the maintenance control page in the HMI to control and start pump down operation. When pump down is activated, the liquid line solenoid valves will close, the compressor will keep running till the suction pressure reaches 1.4 bar(g) and the low pressure switch ( xx-PSL-001A or B ) will stop the compressor. 10.2
Pump Down System
Pump down system is required when danger of liquid migration exists for system where the compressor or parts of the suction line and suction accumulators can reach a lower temperature than the evaporator. The refrigerant suction pressure reaches 1.4 bar (g) ( the lowest temperature which shall occur ) and the system requires automatic pump down. During pump down, the compressor is controlled as a function of suction pressure. In case of a capacity demand during standstill, the liquid line solenoid valve ( liquid injection) to the corresponding duty evaporator is System Design Specification
HVAC System
11
opened first. The suction pressure increases up to a preset value, at which the compressor is switched on by means of suction pressure switch. When decreasing cooling load demand by reaching required temperature level, the solenoid valves closed and the evaporator is pump down to a preset pressure then the compressor will be switched off. 11.0
Transformer Room Ventilation System
The heat radiated from the equipments inside the transformer room is removed by mechanical ventilation system. The supply air fan capacity is estimated based on amount of heat radiated from the equipments and the average room temperature inside the compartment is maintained 8oC above average outside ambient air temperature. The exhaust air fan capacity is estimated based on amount of supply air to offset the air leakage through door cracks and any opening inside the compartment as well as to maintain slight positive pressure inside the transformer room. The transformer room ventilation system is powered and controlled by HVAC system – 1 unit control panel ( xx-UP-01 ). The F&G dampers ( xx-FD-007 & 008 ) are installed inside the supply and exhaust air stream. Temperature Regulation The temperature transmitter ( xx-TT-101 ) is installed inside the transformer room. When the reading on the temperature transmitter is higher than various set point and the ventilation fans will be in speed regulating operation according to requirement. If the temperature reaches ( 45oC ) and high temperature alarm message will be displayed at UCP HMI and panel mounted Buzzer will generate an intermittent sound. Pressure Regulation The compartment is maintained slight positive pressure relative to atmosphere and slight negative pressure than that of HVLV room. This room has a dedicated supply air fan ( xx-EMF-001 ), exhaust air fan ( xx-EMF-002 ) and it works as a slave of the supply air ventilation fan. The pressure differential switches ( xx-PDS-006 ) and ( xx-PDS-007 ) are installed across the supply air fan and exhaust air fan respectively. During auto mode, the fan operation is interlocked function with supply air duct and exhaust air duct fire dampers. When ventilation fan fail ( Pressure Differential Switch Reading < Set Pt.), the respective pressure switch will send the signal to UCP, generate an alarm after a delay of 90 seconds. The slight positive pressure in this room is achieved by balancing and manual adjustment of volumetric supply air flow rate and the exhaust air flow rate during commissioning. The supply air amount is designed to overcome leakage air to the external walls and doors. Conditions for the ventilation fan to start ( auto mode ) are , 1.
Fire & Gas Damper inside the ventilation air streams are opened,
2.
Safety Protection Devices for fans are healthy ( if not, HMI will display the alarm message and Buzzer will generate an intermittent sound).
12.0
Fire & Gas Dampers and Shut Off Damper
All fire & gas dampers and fresh air line shut off damper are electric type with 24 VDC electrical actuator operated and equipped with fail safe mechanism ( fail to close ). The power supply to the dampers shall be wired from HVAC UCP and send the all dampers close status to PCS via hard wired signal. The dampers are equipped with limit switches connected to UCP. The status for each damper can be read from System Design Specification
HVAC System
12
HVAC UCP. 13.0
Unit Control Panel for HVAC System ( xx-UP-01 )
The HVAC UCP ( xx-UP-01 ) is located in the HVLV Switchboard Room. This UCP acts as the main interface to the vessel‟s control and safety system. Indicator Lights on the front panels are as follows:
Normal Power Supply Incoming Light ( Red, Yellow, Blue ),
Normal Power Supply Available Light ( Red, Yellow, Blue ),
UPS #1 Incoming Light ( White ),
UPS #2 Incoming Light ( White ),
UPS Outgoing Light ( White ),
DC Power Outgoing Light ( White ),
Supply Air Fan(s) Status Indication Light ( Run, Stop, Trip ),
Condenser Fan(s) Status Indication Light ( Run, Stop, Trip ),
Compressor(s) Status Indication Light ( Run, Stop, Trip ),
Ventilation Fan(s) Status Indication Light ( Run, Stop, Trip ).
Other Features
HMI panel,
Voltmeter,
Ammeter,
Cabinet Ventilation Fan,
Cabinet Air Intake c/w Filter,
Auto / Manual Selector Switch,
Buzzer,
System Start Push Button,
System Stop Push Button,
Alarm Acknowledge Button,
Alarm Reset Button,
Lamp Test Button,
Earth Leakage Relay,
Under Voltage Relay,
Emergency Stop.
When the Feeder is turn on from the LV switchboard, the respective Feeder incoming light will also be turn ON to indicate the present of power supply. The power supply available light will be turn ON after the main isolator inside the UCP had been switch ON to indicate power available to the equipment‟s circuit breaker. The DC power outgoing light will be turn on accordingly. Document Reference
:
System Electrical Block Diagram, Electrical Single Line Diagram, System Control Diagram / Schematic
System Design Specification
HVAC System
13
When there is an Alarm in the HVAC system, the Buzzer on the front panel will be activated. PLC The UCP has a single PLC‟s Central Processing Unit ( CPU ) and communication units. The controller is a PLC based Allen Bradley‟s CompactLogix. The controller CPU together with the power supply and communication module will be housed in one chassis whilst the I/O cards modules and their corresponding modules will be housed in a separate chassis of its own. HMI The HMI ( Panel View Plus 1000 ) is fitted in UCP to indicate status of equipments and accessories ( run, stop and fault conditions ). The HMI is being used as an interface to the PLC for configuration settings. System Start / Stop The HVAC system shall be operated locally from the system START and STOP push buttons on the main UCP front panel. Emergency Stop push button is located on UCP front panel and it is hard wired in series with the field emergency stop push buttons located near the HVAC equipments. Emergency Stop contact is hard wired in series with system START command contact and will remain opened until being reset to its normal position manually. A Trip Alarm will be generated, the HMI will indicate the corresponding Emergency Stop Alarm message and Buzzer will generate an intermittent sound. Power Supply The HVAC UCP is fed from three independent power source.
Normal 440 V / 3 Ph / 60 Hz
( xx-xx-xx)
UPS #1 220 V / 2 Ph / 60 Hz
( xx-xx-xx)
UPS #2 220 V / 2 Ph / 60 Hz
( xx-xx-xx)
In the main UCP, the UPS # 1 & # 2 feeder will supply 220 VAC to the following :
PLC chassis,
DC power supply modules,
AC control,
3 pin switch socket outlet.
The two DC power supply units supply 24 VDC through Meanwell power supply module and Meanwell DC redundant module to power up :
The interposing relays,
PLC sub rack,
Transmitters,
Other components and accessories in the UCP
When there is a loss of one UPS feeder or a faulty DC power supply, the DC redundant module will still be able to maintain the 24 VDC supply as long as there is a UPS feeder to a healthy DC power
System Design Specification
HVAC System
14
supply. System Start Up Before start up the system, PLC will check on the pre-start conditions. If these conditions are fulfilled, the PLC control system will operate the HVAC system to start up as per requirement. In case of HVAC system shut down due to external factors ( i.e,. power failure, etc,. ), the HVAC system will automatically restart upon power resume. First Start / Restart Operation When power is energized to the UCP for the first time, the PLC will check on the Black Start Bit in the PLC Ladder Logic Software. If the Black Start Bit is turn ON, it means that the HVAC system was running before it was shut down due to external factors. Upon power resume, the HVAC system will automatically restart as per start up sequence without any operator. If the Black Start was OFF, it means that the HVAC was Stop by operator or tripped / shut down due to F&G system or internal causes and will start by either one of the following method: Pressing the System START push button at the UCP, Pre Start Condition Black Start / Manual Operation Before operating the HVAC system, the conditions that need to be checked manually during pre start conditions are : Isolator switch at the HVAC equipments, Emergency stop push button status, To energize refrigeration crankcase heater for minimum 24 hours. Normal Start / PLC Check Operation The PLC will check for the following pre start condition and give a permit to start indication on UCP HMI,
Isolator is to be switched on,
Fault should not be present to enable permit to start signal and it is checked by PLC code,
HVAC not running status is checked by “ Start HVAC”,
PCS and Emergency STOP signal shall not be present,
No active pressure alarm,
No trip alarm ( All trip functions reset ),
All the F & G dampers and shut off dampers are healthy according to zoning / grouping.
If the pre start conditions are fulfilled, the PLC control system will be standby to start up the HVAC and turn ON a permit to start bit in the PLC ladder logic software. This permit to start bit information will be copy to the memory map. This permit to start bit information will also be displayed at the HMI main menu. AUTO - MANUAL MODE On the main UCP HMI, the system operation mode can be selected to AUTO or MANUAL. In Auto mode, the system will be able to change over from duty to standby when conditions are met ( by time, by fault, by HMI or by PCS ). System Design Specification
HVAC System
15
The automatic changeover of system can only be performed in AUTO mode. Changeover will occur when any one of the event is activated :1.
Operator selects the standby HVAC equipment as the duty at the HMI,
2.
Duty HVAC equipment runtime – weekly timer expired,
3.
The duty AHU had a trip alarm
The alarm can be one of the following in AHU:a.
AHU fan feeder fault alarm,
b.
AHU duty blower fan low flow differential pressure alarm.
c.
The duty ACCU had trip alarm.
The alarm can be one of the following in ACCU:a.
High refrigerant pressure alarm,
b.
Fault in lubrication system,
c.
Compressor feeder fault alarm,
d.
Activate Emergency Stop push buttons to the duty unit.
In the HMI main menu, select the system setting soft button to go to the setting page. Within this system setting page operator has to perform the following:1.
Select the Duty HVAC system to run,
2.
Set the time period to perform a change over between the duty / standby HVAC units,
3.
Set the operator accessible parameter.
Start Up Sequence With the Permit to Start Bit ON, the HVAC can be started by either one of the following :1.
Press the system START push buttons on the front panel of the UCP,
In the event of receiving command from UPS & PCS at the same time, the following shall apply :Commend from UCP
Commend from PCS / F&G
Action of HVAC
System START push button
Shut Down Signal
Stop HVAC
System STOP push button
Shut Down Signal
Stop HVAC
Once the HVAC is started, the PLC ladder logic will 1.
Turn ON a HVAC running bit,
2.
Turn ON the Black Start Bit,
When the HVAC system running bit is ON, the duty AHU will start. After the duty AHU is running and confirmed healthy, the system will continue with the following:1.
The duty ACCU will start. The ACCU starting sequence will be depend on capacity control by bring in operation of one or more compressor. Each compressor is protected by the safety protection devices ( refrigerant low pressure, refrigerant high pressure and refrigeration oil safety system ),
2.
The ventilation fans will start.
3.
The ventilation fan is interlocked with respective F&G damper inside the air stream. Fan will not start
System Design Specification
HVAC System
16
when the F&G damper is closed and it will stop immediately if the fan is in running position. The below table shows interlock between fans and respective F&G dampers :Item
Tag No.
1
xx – FD – 007
Transformer Room Supply Air Fan
F&G damper at Supply Air Stream.
2
xx – FD - 008
Transformer Room Exhaust Air Fan
F&G damper at Exhaust Air Stream.
14.0
Fan Description
Inhibit Fan Run When damper Closed.
HVAC UCP Interface to F&G and PCS
Sr.No
From UCP
To PCS
1
HVAC Common Alarm Signal
N.O Volt Free Contact
2
HVAC Run Status Signal
N.O Volt Free Contact
3
HVAC Fault/Available Signal
N.O Volt Free Contact
4
Dampers Close Status Signal
N.O Volt Free Contact
5
Loss of Room Pressurization – Level - 1
N.O Volt Free Contact
6
Loss of Room Pressurization – Level - 2
N.O Volt Free Contact
7
Ventilation Fans Run Status Signal
N.O Volt Free Contact
Transformer Room Fans
8
Ventilation Fans Fault/Available Status Signal
N.O Volt Free Contact
Transformer Room Fans
9
Isolate Transformer Room
N.O Volt Free Contact
Confirmed Transformer Room‟s Fans Stopped and Dampers Closed.
From F&G
Remark
Confirmed All Dampers are Closed.
To UCP 1. Confirmed Fire in HVLV 2. Confirmed Fire in UCR
10
Shut Down Signal
24 VDC
3. Confirmed Fire in False Floor 4. Confirmed Gas Detected at HVAC Inlet
11
12
Shut Down Signal
24 VDC
From PCS
To UCP
1. Confirmed Fire in Transformer Room ( Isolate the Compartment )
Time Synchronization Signal
System Design Specification
HVAC System
17
15.0
Alarm Management :-
Alarm indication / message is displayed at the UCP‟s HMI and which serves as the operator interface. Alarm management is handled by the PLC and HMI mounted on the UCP. Buzzer is installed at the front door of the UCP. Warning and/or fault message will appears on the HMI in the event of a warning or shutdown to indicate the actual fault. Alarm at the UCP‟s HMI and common fault alarm to the PCS shall be implemented with time delay to prevent nuisance alarm due to specific fluctuations in measurement values. When warning alarm is activated, Buzzer will sound and fault message is prompted on the HMI. By pressing the Alarm Acknowledge Push Button, buzzer will go silent but the alarm message remain on the touch screen. Once the fault is rectified, press the RESET button mounted on the front panel of UCP to reset the HVAC system. All the alarms generated in the UCP are visible as common fault alarm on the PCS but RESET can be done only from UCP. Time Synchronization: PCS sends a time synchronization signal to UCP to synchronize the timing of the UCP with the PCS. 16.0
Password Protection :
Password protection is provided in the Log In / Log Out of the Touch Screen Panel View. This is to ensure that only authorized and trained personnel are allowed to enter the system control section for the operation of the HVAC system and changes of setting values. 17.0
Instruments:
When the instrument sensor is faulty, the analog input signal to the PLC will be out of the range which is between 4 ~ 20 mA. The PLC reads an open circuit sensor as 3.6 mA and the PLC logic will consider it as a sensor alarm and put the control to a safe state of operation. 18.0
ACMV System for Battery Room
ACMV Equipment ( System – 2 ) The ACMV system - 2 is designed for continuous operation with two independent direct expansion (DX) type air conditioning systems ( 1 x 100% duty and 1 x 100% stand by unit ). Each unit has 100% capacity of cooling load, air flow and pressurization requirement for the system. The mechanical ventilation system for battery room is designed with one set of mechanical exhaust air fan. Exhaust air fan is sized to maintain slight positive pressure inside the compartment. All AHU & ACCU are fabricated with galvanized material painted suitable for marine and offshore application.
should be stainless steel 18.1
Air Handling Units & Air Cooled Condensing Unit
Ref. Document
:
Ducting & Instrument Diagram (D & ID), Air Flow Diagram
The Air Handling Section and Air Cooled Condensing Section are mounted on the same skid. The ACMV system is 2 x 100% and designed according to air capacity requirement for cooling and pressurization requirement of the battery room. Both units will install at LER level - 2. In normal operation, one unit will acts as duty and the other unit remains on stand-by.
Rotate duty monthly.
The unit can be started and stopped independently. The AHU Blower can be started even if the air cooled condensing section is not running. All AHU‟s supply air fans have stop, running and failure signal. System Design Specification
HVAC System
18
Air Handling Unit is designed to be horizontal, continuous operating, draw through type complete with air intake section, air filtration section, cooling section and blower section c/w motor and power transmission assembly. The AHU is designed to use only 100% fresh air and no re-circulating air. The AHU is direct expansion type of refrigerant R407 C and complete with supply air blower fan and cooling coil. The supply air outlet from blower fan is passed through the non return dampers and connect to the common plenum box with internal insulation to prevent condensation and noise level transmission. The AHU has the following components for proper functioning of HVAC system. a. Non Return Damper at fresh air connection to AHU, b. Non Return Damper at AHU blower fan‟s inlet, c. Non return damper at blower fan‟s outlet, d. Pressure differential switches. The fresh air intake is fitted with bird screen, gas detectors ( by other ) and is guided to the intake section of the AHU. The fresh air entered the filtration section, it consists of HVAC air filter before it enters the direct expansion cooling coil. The by-passing of air to AHUs can be prevented by installation of non return dampers at each outlet of the AHU respectively. The non return dampers for duty AHU will be opened during operation and that for standby unit will be closed. The fresh air is conditioned (cooling and dehumidification process ) while passing through the cooling coil. The duty centrifugal type blower fan conveyed conditioning air to the battery room via sheet metal duct work. The external supply air duct is fabricated with 3 mm thickness SS 316L material and complete with 50 mm thickness internal insulation and the internal one is fabricated with 1.2 mm thickness galvanized material complete with 25 mm thickness external insulation. The supply air duct is fitted with electric operated type fire & gas dampers if duct passing through class rated bulkhead and deck head, manual operated volume control dampers is fitted on each main duct for proper balancing of the supply air to battery room and supply air grilles. The temperature transmitter ( xx-TT-102 ) is installed in the room to control room air temperature. All F&G and shut off dampers, remotely controlled with a fail safe actuator ( Fail Close ). When 24 VDC power is energized to the electric actuator and the damper will be in opened position. The electric actuator will close automatically if loss of power supply because of built-in spring return actuator ( fail safe actuator ). All F&G dampers are powered and controlled directly from the ACMV control panel ( xx-UP-02 ). The F&G system is responsible for safe operation of the ACMV system by giving separate shutdown signal mentioned above. The list of F&G dampers are as follows:Sr.No
Description
Tag No
Power & Control
Location ( Wall or Deck )
Battery Room 1
F&G Damper
xx-FD-009
SAD – Roof ( Outside ) ~ Battery Room
ACMV UCP-02
2
F&G Damper
xx-FD-010
EAD – Battery Room ~ Roof ( Outside )
ACMV UCP-02
The operator interface consists of a series of high visibility indicating lights, push buttons, selector function and Eliwell temperature controller located at the unit control panel. The control system processes related input and outputs, control, protect and monitor the system with a System Design Specification
HVAC System
19
number of settings, e.g. temperature sensor, pressure transmitters, pressure switches, AHU start/ stop, control & monitoring of the air conditioning system. The pressure differential switches c/w indicators are fitted across the filters to monitor the condition of filters.
Item
Tag No.
Location
Alarm Set Pt.
Alarm Message
Remark
1
xx-PDS-006
Main Air Filter
xxx Pa ( H )
Main Air Filter Dirty
AHU - A
2
xx-PDS-008
Main Air Filter
xxx Pa ( H )
Main Air Filter Dirty
AHU - B
When the value reading from the respective pressure differential switch is higher than the alarm set point mentioned above and a general alarm will be generated at the UCP and PCS ( common fault alarm ). The UCP mounted pilot light will indicate the respective filter‟s high differential pressure alarm message and the panel mounted Buzzer will generate an intermittent sound. The pressure differential switches are also fitted across the supply air blowers to monitor the proper functioning of blower to prevent loss of pressurization. .
Item
Tag No.
Location
Alarm Set Pt.
Alarm Message
1
xx-PDS-007
Blower Fan - A
xxx Pa ( Low )
Blower Fan A Fault
2
xx-PDS-009
Blower Fan - B
xxx Pa ( Low )
Blower Fan B Fault
Remark
When the value reading from the pressure differential switch is lower than the alarm set point mentioned above and a general alarm will be generated at the UCP and PCS ( common fault alarm ). The UCP mounted pilot light will indicate the respective blower‟s low differential pressure alarm message and the panel mounted Buzzer will generate an intermittent sound (common alarm to PCS) and initiate automatic change over to standby system after a time delay of 60 seconds. If the ACMV system is operating in AUTO mode, either one of the Trip function ( UCP will specify which Trip function ) will Stop the duty system and change over to operate the Standby system as duty automatically. The electric motors inside the AHU is Ex‟d‟ protection and all electrical components and instruments equipped are suitable to operate in Hazardous Area Zone 2. Air Cooled Condensing Section Ref. Document
:
Piping & Instrument Diagram ( P & ID )
The air cooled condensing system is 2 x 100% independent refrigeration circuit and designed according to heat rejection requirement of system. Both units are installed at the open deck of LER level - 2. In normal operation, one unit acts as duty and the other unit remains on stand-by. The unit can not be started independently without running respective AHU in auto mode but it can be performed functional or rotation check on maintenance ( Test/Manual ) mode. The unit can be started only if the duty air handling unit is in running. The operator interface consists of a series of high visibility indicating lights, pushbuttons, selector functions and Eliwell electronic temperature controller located at the unit control panel. The control system processes related input and outputs, control, protect and monitor the system with a number of settings, e.g. Temperature sensors, Pressure Switches, etc,.
System Design Specification
HVAC System
20
The electric motors inside the ACCU is Ex‟e‟ protection and all electrical components and instruments equipped are suitable to operate in Hazardous Area Zone 2. The condensing unit equipment starter and overload protection are installed inside the HVAC unit control panel. Space heater power supply for motor of capacity 5.5 kW and above are fed from the same UCP. All ACCU fans, compressor motor have stop, running and failure signal. The ACCU is controlled by hardwired based UCP and each system ( duty or standby ) consists of one set of open type reciprocating compressor direct coupling driven by electric motor, one set of condenser fan c/w driving motor, one piece of refrigeration liquid line solenoid valve on each refrigeration circuit and others refrigeration system components, accessories and instruments. The ACCU work as a slave of the respective AHU. Control of ACCU The air cooled condensing unit compressor motor, condenser fan motor starter and overload protection are housed within the UCP. The UCP will be able to START or STOP the motor during maintenance mode for functional check or rotational check only. Power supply for motor‟s anti-condensation heaters are fed from the UCP. 18.2
ACCU START
The controller will monitor the temperature reading from the temperature sensor mounted inside the battery room. Item
Instrument Tag No.
Location
Set Parameter
1
xx-TT-102
Battery Room
T = 25o C
Remark
The sensor measures the temperature of the room air. When the room air temperature rises above 25o C ( adjustable ), the UCP will gives signal to start the duty ACCU while the duty AHU is in operation. The refrigeration compressor and condenser fan will operate simultaneously. The compressor operation is interlocked with condenser fans operation and it will not started without running all duty condensing fans. 18.3
System Safety Protection
During the duty ACCU is in operation, the UCP will continuously monitor the respective system low refrigerant pressure via low refrigerant pressure switch ( xx-PSL-002A or B ) mounted on the refrigeration suction line and high refrigerant pressure via high refrigerant pressure switch ( xx-PSH-002A or B ) mounted on the refrigeration discharge line. When the reading on the low refrigerant pressure switch fall below set point, the UCP will activate pump down function and stop the compressor. When the refrigerant pressure rises above set point, the compressor will be able to restart automatically. When the reading on the high refrigerant pressure switch goes above xx.x bar (g), the UCP will stop the compressor. When the refrigerant pressure drop below xx.x bar (g), the compressor will be able to restart but it required manual reset on UCP - 02 to eliminate high refrigerant pressure cut off alarm. The compressor can‟t be restarted within 5 mins (adjustable) with auto restart operation ( e.g compressor auto cutoff when temperature reach set parameter or pump down activated due to low refrigerant pressure reaches set point ). 18.4
Liquid Line Solenoid Valve Operating Sequence
The liquid line solenoid valve is installed on each refrigeration circuit and will be opened once received the System Design Specification
HVAC System
21
START command from UCP and all the refrigeration system operating parameters are in normal condition. 18.5
Crankcase Heater Operating Sequence
Before first start up, the crankcase heater shall energize for 24 hours. When the duty compressor is running, the respective crankcase heater will be de-energized and the stand by compressor‟s heater shall be energized. 18.6
Condenser Fan Operating Sequence
All duty condenser fans are started simultaneously with respective compressor. 18.7
Refrigeration Lube Oil Level
The UCP will monitor the refrigeration oil pressure in the system via oil differential pressure switch mounted on the system. The oil pressure should reach correct level within a few seconds after first start up the compressor. During the first start, the correct lube oil differential pressure is not reached in 15 ~ 20 seconds , stop compressor immediately and check oil system & accessories. During normal operation and when the compressor starts, refrigeration oil differential pressure shall reach to satisfactory level within 120 seconds. If the oil differential pressure fall below set point, the oil level switch will trip the compressor and show an alarm message at UCP ( common alarm to PCS ) and need to be reset manually from UCP. 18.8
List of Refrigeration System Safety Components
Sr.No
Description
1
High Refrigerant Pressure Switch ( System – A/B ) ( High )
2
Low Refrigerant Pressure Switch ( System – A/B ) ( Low )
3
Lube Oil Differential Pressure Switch ( Time Delay = 120 sec )
Tag No.
Set Pt.
Alarm (UCP)
Remark
xx-PSH-002 A/B
xx.x bar (g) ( High )
Refrigerant Pr. High ( System – A/B )
Manual Reset
xx-PSL-002 A/B
xx.x bar (g) ( Low )
N.A
Auto Reset
Lube Oil Pr. Low ( System – A/B )
Manual Reset
xx-ODPS-002 A/B
xx.x bar (g) ( Low )
When the value reading from the above instruments is higher / lower than the set point mentioned above and a general alarm will be generated. The UCP will indicate the respective alarm with pilot light and the panel mounted Buzzer will generate an intermittent sound. The common fault alarm is transmitted to the PCS. If the ACMV system is operating in AUTO mode, either one of the Trip function ( UCP will specify which Trip function ) will Stop the duty system and change over to operate the Stand-by system as duty automatically. 18.9
Temperature Regulation
The room mounted temperature transmitters ( xx-TT-102 Battery Room, LER 1st Floor ) are installed inside the compartment. When the reading is higher than set point ( 25oC ) and the compressor will be in operation to bring down the temperature and humidity level inside the compartment. When the reading value reach set point ( 25oC ) or below, the refrigerant suction pressure will drop accordingly due to less cooling and dehumidification load. Based on the refrigeration suction pressure and control oil pressure, the compressor will
System Design Specification
HVAC System
22
be regulated in unload operation by factory assembled hydraulic capacity control unloader system. The compressor will load again if the cooling load demand increases. During fully unload condition and temperature reading falls below minimum set point ( 22oC ), the system will be pump down and compressor will be STOP in operation. The compressor will restart automatically when the sense temperature reaches above set point or the high temperature ( over 30oC ) alarm Buzzer at the UCP will generate an intermittent sound. 18.10
Pressure Regulation ( Battery Room )
The battery room is maintained at slight positive pressure relative to atmosphere and slight negative that of adjacent rooms. This room has 2 dedicated exhaust fans (2 x 100% duty) and each works as a slave of the duty supply air blower fan in auto mode. The slight positive pressure in this room is achieved by balancing and manual adjustment of volumetric supply air flow rate during testing & commissioning and by varying the exhaust air flow rate by changing the exhaust fan speed during operation. Room Pressure differential transmitter (xx-PDT-102) is installed inside the battery room. During auto mode, the fan operation is interlocked function with function of AHU supply air fan & exhaust air duct fire damper and it‟s operation is monitored by pressure differential switch ( xx-PDS-016/017 ) mounted downstream of the exhaust air duct. When AHU blower fan is in operation and exhaust fan fail ( Pressure Switch Reading < Set Pt.), the pressure differential switch will send the signal to UCP, generate alarm after a delay of 60 seconds and and initiate to start the standby fan. Conditions for the exhaust fan to start (auto mode) are , 1.
AHU is in operation,
2.
Fire & Gas Damper inside the exhaust air stream is opened,
3.
Safety Protection Devices for fans are healthy ( if not, UCP will display the alarm message and Buzzer will generate an intermittent sound).
18.11
Compressor Capacity Regulation and Condensing System Protection :-
18.11.1 Capacity Control The refrigeration compressor is fitted with hydraulic capacity control system it regulates according to changing load demands. 18.11.2 Condensing System Protection Devices a.
Compressor‟s Electric Motor Protection Devices,
b.
High Refrigerant Pressure Safety Device,
c.
Low Refrigerant Pressure Safety Device,
d.
Low Lube Oil Differential Pressure Safety Device,
e.
Crankcase Heater.
18.11.3 Check before starting:1.
Refrigeration Lube Oil Level,
2.
Setting and function of safety and protection devices,
3.
Setting of timing,
4.
Setting of refrigerant pressure safety devices,
The compressor lubrication should be checked immediately after starting. Maximum and recommended oil level during operation shall be within the sight glass range mounted of the compressor. Minimum oil level is monitored by an oil differential pressure switch. The time delay period for oil level switch is set to 120 seconds after start up the compressor. If there is not System Design Specification
HVAC System
23
enough oil pressure and the refrigeration compressor must stop immediately. 18.11.4 Crankcase Heater The crankcase heater must be energized during standstill. The crankcase heater in the compressor prevent high refrigerant dilution of the oil during standstill. It shall only be switched on if compressor is filled with oil. Note: If the oil pressure switch cuts-out during the starting stage or the oil level falls below recommended sight glass level, this indicates a severe lack of lubrication. It may happen due to small pressure difference. Check the oil return line before adding additional amount of lube oil or danger of liquid slugging. 18.12
Compressor Start Up and Capacity Regulation
The refrigeration compressor will start up if the following conditions are TRUE.
The duty AHU is in operation,
All system protection devices and operation parameters are normal,
No alarm active,
Respective Liquid line solenoid valve is opened.
The compressor operating sequence and capacity regulation is mainly controlled by 3.
Low Refrigerant Pressure,
4.
Room Air Temperature
Condition – 1 If Refrigerant Suction Pressure > / = 5 bar(g) AND Average Return Air Temperature > 25oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened Then
:
Refrigeration Compressor
:
START
The compressor will be in loading / unloading operation condition according to changing load demands. Condition – 2 If Refrigerant Suction Pressure > / = 2.5 bar(g) AND Average Return Air Temperature > 2 + 25oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened, Then
:
Refrigeration Compressor
:
Operate in Full Load Condition
Condition – 3 If Refrigerant Suction Pressure > / = 2.2 bar(g) OR Average Return Air Temperature > 1 + 25oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened, Then
:
Refrigeration Compressor
:
Operate in Unload condition
Condition – 4 If Refrigerant Suction Pressure < / = 1.4 bar(g) AND Average Return Air Temperature< / > / = 25oC ( adjustable Set Point ) AND Liquid Line Solenoid valve is Opened, Then
:
Refrigeration Compressor
:
Activate Pump Down & Stop the Compressor for 5 minutes
System Design Specification
HVAC System
24
According to ABS "Facilities on offshore installations" must also be capable of being closed manually from both sides of the bulkhead or deck. The cycle is repeated automatically.
18.13
Fire & Gas Dampers
All fire & gas dampers are electric type with 24 VDC electrical actuator operated and equipped with fail safe mechanism ( fail to close ). The power supply to the dampers shall be wired from HVAC UCP and send the all dampers close status to PCS via hard wired signal. The dampers are equipped with limit switches connected to UCP. The status for each damper can be seen from HVAC UCP. 18.14
Unit Control Panel for ACMV System ( xx-UP-02 )
The HVAC UCP ( xx-UP-02 ) is located in the HVLV Switchboard Room. This UCP acts as the main interface to the vessel‟s control and safety system. HVAC control panel shall be hard wiring type. Control panel enclosure shall be according to „Rittal‟ manufacturer standard. The control panel complete with electrical components and accessories shall be installed inside the HVLV room that classified as non hazardous safe area. Indication Light on the front panel are as follows:
Normal Power Supply Incoming Light ( Red, Yellow, Blue ),
Normal Power Supply Available Light ( Red, Yellow, Blue ),
UPS #1 Incoming Light ( White ),
UPS #2 Incoming Light ( White ),
UPS Outgoing Light ( White ),
DC Power Outgoing Light ( White ),
Supply Air Fan(s) Status Indication Light ( Run, Stop, Trip ),
Condenser Fan(s) Status Indication Light ( Run, Stop, Trip ),
Compressor(s) Status Indication Light ( Run, Stop, Trip ),
Ventilation Fan(s) Status Indication Light ( Run, Stop, Trip ).
Unit – 1, Loss of Air Flow Status Indication Light,
Unit – 2, Loss of Air Flow Status Indication Light,
Room Temperature High Status Indication Light,
F&G Damper Status ( Open/Close ) Indication Lights,
Loss of Room Pressurization Status Indication Light
Other Features
Voltmeter,
Ammeter,
Digital Displayed Electronic Temperature Controller,
Emergency Stop,
Buzzer,
Alarm Acknowledge Button,
Trip Reset Buttons,
System Design Specification
HVAC System
25
Duty and Standby Selector Switch,
When the feeder to the HVAC panel is turned on from the source, the respective feeder incoming light will also be turn on to indicate the present of power supply. The main MCCB inside the ACMV control panel is switch on and the power is available to the equipment‟s circuit breakers. When there is malfunction alarm in the HVAC system and the buzzer on the front panel will be activated. System Start / Stop The ACMV system shall be operated locally from the system START and STOP push buttons on the main UCP front panel. Emergency Stop push button is located on UCP front panel and it is hard wired in series with the field emergency stop push buttons located near the ACMV equipments. Emergency Stop contact is hard wired in series with system START command contact and will remain opened until being reset to its normal position manually. Power Supply The HVAC UCP is fed from three independent power source.
Normal 440 V / 3 Ph / 60 Hz
( xx-xx-xx)
UPS #1 220 V / 2 Ph / 60 Hz
( xx-xx-xx)
UPS #2 220 V / 2 Ph / 60 Hz
( xx-xx-xx)
18.15
Sr.No
ACMV UCP Interface to F&G and PCS
From UCP
To PCS
Remark
1
ACMV Common Alarm Signal
N.O Volt Free Contact
2
ACMV Run Status Signal
N.O Volt Free Contact
3
ACMV Fault/Available Signal
N.O Volt Free Contact
4
Dampers Close Status Signal
N.O Volt Free Contact
5
Loss of Room Pressurization
N.O Volt Free Contact
6
Ventilation Fans Run Status Signal
N.O Volt Free Contact
Battery Room Exhaust Air Fan
7
Ventilation Fans Fault Status Signal
N.O Volt Free Contact
Battery Room Exhaust Air Fan
8
From F&G
To UCP
Shut Down Signal
24 VDC
System Design Specification
HVAC System
Confirmed All Dampers are Closed.
1. Confirmed Fire in Battery Room 2. Confirmed Fire in False Floor
26
3. Confirmed Gas Detected at HVAC Inlet 18.16
Alarm Management
The ACMV control panel front mounted buzzer is activated when there is an alarm in the ACMV system and which serves as the operator interface. Alarm management is handled by ACMV control panel. Alarm from the pressure differential switches ( mounted across filters, blowers, room ) shall be implemented with time delay to prevent nuisance alarm due to specific fluctuations in measurement value. When warning alarm is activated, buzzer will sound and fault indication is prompted on the ACMV panel. By pressing the alarm acknowledged push button, buzzer will goes silent but fault indication is remained on. Once the fault is rectified, press the reset button on the front panel of ACMV control panel to reset the ACMV system. Differential pressure alarm generated due to high air pressure drop across the air filters and higher room temperature alarm shall be visible on the ACMV control panel as common fault. Loss of room pressure alarm, ACMV Unit A Fault alarm and ACMV Unit B Fault alarm generated in the ACMV control panel are visible as individual fault alarm in the PCS but reset can be done only from ACMV control panel.
18.17
Password Protection
Password protection can be done on the electronic temperature controller. This is to ensure that only authorized and trained personnel are allowed to enter the system control section for the operation of the ACMV system and changing of setting values.
18.18
Sensors
When the sensor is faulty, there is no input signal to the electronic temperature controller error massage will be displayed on the respective controller.
System Design Specification
HVAC System
27
