Introduction
A Fuel Gas Compressor (FGC) boosts low-pressure fuel gas to the stable pressure and quality required by prime movers (e.g., gas turbines, engines) or process users. The P&ID defines process flow, auxiliaries (lube oil, seal gas), anti-surge protection, safeguarding, and tie-ins to utilities and flare—crucial for design, operations, and maintenance.
1) Process Overview
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Fuel Gas Source → Suction Conditioning (filter/coalescer, KO drum) → Compressor (centrifugal or screw) → Aftercooler → Fuel Gas Receiver/Manifold → Users (Turbine/Heaters).
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Controls: suction pressure control, discharge pressure control, anti-surge recycle to suction, unit permissives/trips via PLC.
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Safety: PSVs to flare/vent, high-high temperature/pressure trips, fire & ESD tie-ins.
2) Major Equipment on the P&ID
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V-101 Suction KO/Separator with demister, level instrumentation, drain to closed drain.
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F-201 Fuel Gas Filter/Coalescer (duplex optional) with ΔP indicators.
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K-301 Fuel Gas Compressor (centrifugal or screw).
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E-401 Aftercooler (air or water cooled) + condensate pot & drain.
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V-501 Fuel Gas Receiver/Surge Drum (optional) for damping transients.
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Seal Gas Panel (for centrifugal, dry gas seals) or Distance Piece Vent (for screw/recip).
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LO-Skid: Lube oil reservoir, main/aux pumps, cooler, filters.
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Anti-Surge Recycle Line with control valve back to suction.
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Flare/Relief Header connections from PSVs, blowdown valves, and vent pots.
3) Key Piping & Valves
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Inlet Isolation: MOV-101 at battery limit; BDV-101 for depressurization to flare.
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Bypass/Start-Up: Manual bypass around filters; optional around compressor (for maintenance).
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Anti-Surge Loop: FCV-AS-301 from discharge to suction, sized for full recycle at surge conditions; NRV to prevent reverse flow.
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Discharge Isolation: MOV-301; PCV-302 to maintain header pressure or protect users.
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PSVs: On V-101, K-301 casings (if applicable), aftercooler outlet, V-501; relief to flare with tailpipes and thermal reliefs on blocked-in segments.
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Drains & Vents: Low-point drains to closed drain; high-point vents for commissioning.
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Sample Ports: Gas quality, dew point, and calorific value (if analyzer provided).
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Check Valves: At user manifold to avoid backflow.
4) Instruments & Typical Tags
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Pressure: PIT-101 (suction), PIT-301 (discharge), PDIT-201 (filter ΔP).
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Temperature: TIT-101 (suction), TIT-401 (aftercooler outlet), bearing metal temps (TIT-B1/B2).
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Flow: FIT-301 (through compressor), FIT-AS-301 (anti-surge loop).
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Level: LIT-101 on KO drum with LSH/LSL tied to trips/alarms.
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Vibration/Speed (centrifugal): VIB-K-301, SPT-301 (speed), combined into machine protection system (MPS).
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Controls:
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PIC-301: Discharge header pressure control (may trim anti-surge bias).
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SIC-301: Surge control using flow vs. head map (via ΔP across orifice or flowmeter and speed).
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LIC-101: KO drum level to drain valve LV-101.
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Analyzers (optional): Moisture analyzer (AIT-M), H2S/CO2 (if required), CV/BTU analyzer for turbine specs.
5) Control Philosophy (Simplified)
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Start-Up:
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Suction and discharge MOVs open on permissives;
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Recycle FCV-AS-301 opens (minimum flow);
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Lube oil system running & pressures OK;
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Seal gas pressure > process by set margin;
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Ramp to speed/flow while staying right of surge line.
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Normal Operation:
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Shutdown/Trip:
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On trip, FCV-AS-301 goes open (fail-open), suction/discharge isolate as logic dictates, BDV-301 opens to flare if ESD.
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Cool-down run if specified.
6) Typical Design/Operating Parameters (tune per project)
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Suction Pressure: 3–10 barg (fuel gas header).
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Discharge Pressure: 15–35 barg (as required by users).
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Gas Specs: Dew point below minimum metal temperature; particulates/oil mist within compressor limits.
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Temperatures: Suction 20–45 °C; discharge limited by compressor map/materials; aftercooler outlet ≤40 °C typical.
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Materials: Piping CS/SS; instrument tubing SS316; elastomers fuel-gas compatible.
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Area Classification: Class/Zone hazardous; use Ex-rated instruments, junction boxes, and motors.
7) Safety, Relief & ESD
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PSVs sized for fire case, thermal expansion, blocked-in scenarios; discharge to flare with appropriate backpressure checks.
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Blowdown: BDV-301 to flare for ESD; tie-in location shown on P&ID.
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Seal Gas: Maintain clean, dry seal gas > process pressure; include filter, regulator, flow indicator and differential alarm.
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Lube Oil: Dual filters with ΔP alarm; low LO pressure trip; high bearing temperature trip.
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Gas Detection: Fixed detectors near seals/vents; interlock to alarm/ESD as per HAZOP.
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Fire & Gas: ESD pushbuttons; fire detectors may drive unit trip and blowdown.
8) Utilities & Tie-Ins
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Instrument Air: for control valves (anti-surge CV, PCV, drain valves).
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Cooling Water or Air: for E-401 aftercooler & lube oil cooler.
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Power: MCC/UPS for PLC, MPS, auxiliaries.
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Closed/Open Drain, Flare Header, Nitrogen (purging/maintenance).
9) Cause & Effect (Excerpt)
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LSH-101 (KO Drum High-High) → Trip compressor; open BDV-301; alarm.
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PSH-301 (Discharge High-High) → Open FCV-AS-301; if persists, trip.
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Low LO Pressure → Immediate trip; permissive block for restart.
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High Vibration → Trip via MPS; open recycle; alarm.
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Gas Detected in Enclosure → Alarm; on Hi-Hi → trip and blowdown.
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ESD Pushbutton → Isolate, recycle open, BDV to flare, safe stop.
10) Deliverables & Download
Conclusion
This Fuel Gas Compressor P&ID template captures the essential process path, conditioning, anti-surge protection, and safety systems required to deliver clean, stable fuel gas to users. Customize setpoints, equipment selections, area classification, and materials to your project standards and HAZOP results.
Piping and Instrumentation Diagram (P&ID) of Fuel Gas Compressor
Introduction
A Fuel Gas Compressor (FGC) boosts low-pressure fuel gas to the stable pressure and quality required by prime movers (e.g., gas turbines, engines) or process users. The P&ID defines process flow, auxiliaries (lube oil, seal gas), anti-surge protection, safeguarding, and tie-ins to utilities and flare—crucial for design, operations, and maintenance.
1) Process Overview
Fuel Gas Source → Suction Conditioning (filter/coalescer, KO drum) → Compressor (centrifugal or screw) → Aftercooler → Fuel Gas Receiver/Manifold → Users (Turbine/Heaters).
Controls: suction pressure control, discharge pressure control, anti-surge recycle to suction, unit permissives/trips via PLC.
Safety: PSVs to flare/vent, high-high temperature/pressure trips, fire & ESD tie-ins.
2) Major Equipment on the P&ID
V-101 Suction KO/Separator with demister, level instrumentation, drain to closed drain.
F-201 Fuel Gas Filter/Coalescer (duplex optional) with ΔP indicators.
K-301 Fuel Gas Compressor (centrifugal or screw).
E-401 Aftercooler (air or water cooled) + condensate pot & drain.
V-501 Fuel Gas Receiver/Surge Drum (optional) for damping transients.
Seal Gas Panel (for centrifugal, dry gas seals) or Distance Piece Vent (for screw/recip).
LO-Skid: Lube oil reservoir, main/aux pumps, cooler, filters.
Anti-Surge Recycle Line with control valve back to suction.
Flare/Relief Header connections from PSVs, blowdown valves, and vent pots.
3) Key Piping & Valves
Inlet Isolation: MOV-101 at battery limit; BDV-101 for depressurization to flare.
Bypass/Start-Up: Manual bypass around filters; optional around compressor (for maintenance).
Anti-Surge Loop: FCV-AS-301 from discharge to suction, sized for full recycle at surge conditions; NRV to prevent reverse flow.
Discharge Isolation: MOV-301; PCV-302 to maintain header pressure or protect users.
PSVs: On V-101, K-301 casings (if applicable), aftercooler outlet, V-501; relief to flare with tailpipes and thermal reliefs on blocked-in segments.
Drains & Vents: Low-point drains to closed drain; high-point vents for commissioning.
Sample Ports: Gas quality, dew point, and calorific value (if analyzer provided).
Check Valves: At user manifold to avoid backflow.
4) Instruments & Typical Tags
Pressure: PIT-101 (suction), PIT-301 (discharge), PDIT-201 (filter ΔP).
Temperature: TIT-101 (suction), TIT-401 (aftercooler outlet), bearing metal temps (TIT-B1/B2).
Flow: FIT-301 (through compressor), FIT-AS-301 (anti-surge loop).
Level: LIT-101 on KO drum with LSH/LSL tied to trips/alarms.
Vibration/Speed (centrifugal): VIB-K-301, SPT-301 (speed), combined into machine protection system (MPS).
Controls:
PIC-301: Discharge header pressure control (may trim anti-surge bias).
SIC-301: Surge control using flow vs. head map (via ΔP across orifice or flowmeter and speed).
LIC-101: KO drum level to drain valve LV-101.
Analyzers (optional): Moisture analyzer (AIT-M), H2S/CO2 (if required), CV/BTU analyzer for turbine specs.
5) Control Philosophy (Simplified)
Start-Up:
Suction and discharge MOVs open on permissives;
Recycle FCV-AS-301 opens (minimum flow);
Lube oil system running & pressures OK;
Seal gas pressure > process by set margin;
Ramp to speed/flow while staying right of surge line.
Normal Operation:
PIC-301 holds discharge header setpoint.
Anti-Surge adjusts FCV-AS-301 to maintain surge margin using flow-head map; fast-acting with open-bias on trips.
Shutdown/Trip:
On trip, FCV-AS-301 goes open (fail-open), suction/discharge isolate as logic dictates, BDV-301 opens to flare if ESD.
Cool-down run if specified.
6) Typical Design/Operating Parameters (tune per project)
Suction Pressure: 3–10 barg (fuel gas header).
Discharge Pressure: 15–35 barg (as required by users).
Gas Specs: Dew point below minimum metal temperature; particulates/oil mist within compressor limits.
Temperatures: Suction 20–45 °C; discharge limited by compressor map/materials; aftercooler outlet ≤40 °C typical.
Materials: Piping CS/SS; instrument tubing SS316; elastomers fuel-gas compatible.
Area Classification: Class/Zone hazardous; use Ex-rated instruments, junction boxes, and motors.
7) Safety, Relief & ESD
PSVs sized for fire case, thermal expansion, blocked-in scenarios; discharge to flare with appropriate backpressure checks.
Blowdown: BDV-301 to flare for ESD; tie-in location shown on P&ID.
Seal Gas: Maintain clean, dry seal gas > process pressure; include filter, regulator, flow indicator and differential alarm.
Lube Oil: Dual filters with ΔP alarm; low LO pressure trip; high bearing temperature trip.
Gas Detection: Fixed detectors near seals/vents; interlock to alarm/ESD as per HAZOP.
Fire & Gas: ESD pushbuttons; fire detectors may drive unit trip and blowdown.
8) Utilities & Tie-Ins
Instrument Air: for control valves (anti-surge CV, PCV, drain valves).
Cooling Water or Air: for E-401 aftercooler & lube oil cooler.
Power: MCC/UPS for PLC, MPS, auxiliaries.
Closed/Open Drain, Flare Header, Nitrogen (purging/maintenance).
9) Cause & Effect (Excerpt)
LSH-101 (KO Drum High-High) → Trip compressor; open BDV-301; alarm.
PSH-301 (Discharge High-High) → Open FCV-AS-301; if persists, trip.
Low LO Pressure → Immediate trip; permissive block for restart.
High Vibration → Trip via MPS; open recycle; alarm.
Gas Detected in Enclosure → Alarm; on Hi-Hi → trip and blowdown.
ESD Pushbutton → Isolate, recycle open, BDV to flare, safe stop.
10) Deliverables & Download
P&ID Files: DWG (compressor train, auxiliaries, flare tie-ins).
Conclusion
This Fuel Gas Compressor P&ID template captures the essential process path, conditioning, anti-surge protection, and safety systems required to deliver clean, stable fuel gas to users. Customize setpoints, equipment selections, area classification, and materials to your project standards and HAZOP results.
draftsman