Cogeneration/trigeneration plants run natural-gas turbines (GE Frame 5, Siemens SGT, Solar Taurus). On 50-100 MW class units lube oil, fuel gas and high temperatures drive fire risk. NFPA 37 (Stationary Combustion Engines and Gas Turbines) defines enclosure ventilation, CO2 protection and gas-detection rules.
Enclosure Ventilation
- Normal: 30-50 ACH for cooling
- Maximum: >55 C internal - increase fan
- Emergency: close dampers before CO2
- Purge: 30 ACH mandatory after CO2
CO2 Total Flooding
- Concentration: 50 percent (gas turbine)
- Hold time: 20 min
- Discharge: 1 min (surface fire)
- Reserve: 100 percent reserve bank (NFPA 37 option)
- Alarm: 20 sec pre-discharge warning
Lube Oil System
- Tank: 1,500-3,000 L, bearing cooling
- Pump: AC + DC emergency pump
- Level alarm: low-level shutdown
- Fire detection: linear heat (Listec), IR3 flame detector
- Water spray: lube oil tank and cooler (NFPA 15 alt)
Natural Gas Regulator
- Pressure reduction: 70 bar -> 30 bar -> 5 bar (turbine inlet)
- ESDV: dual Emergency Shut-Down Valves
- Gas detector: 20 percent LEL alarm, 40 percent ESD
- PSV: over-pressure vent to safe location
- Filter separator: removes liquid/solid particulates
Detection and Interlock
- UV/IR3 flame: detects within 3 sec
- Vibration: bearing/compressor fault
- Exhaust temp: >650 C alarm
- Hot gas path inspection: every 8,000 hours
- Trip logic: CO2 activation -> turbine shutdown
Gas turbine with MEP Calc
MEP Calc sizes gas turbine enclosure ventilation, CO2 total flooding and gas regulator per NFPA 37.
Download MEP Calc on the App Store
Sources & Further Reading
NFPA 37, NFPA 12, NFPA 54 Fuel Gas Code, ASME B31.3, API RP 556. NFPA 37 Combustion Engines standard.