Deluge System Design: Full Water Discharge for Hangars, Refineries, Transformers

A normal sprinkler system opens only the heads exposed to heat. A deluge system floods every sprinkler simultaneously on detection. Aircraft hangars, petrochemical units, high-voltage transformers — fires that grow in seconds call for deluge. This post covers architecture, valve control logic, and field applications.

How Deluge Works

In a deluge system, sprinklers are open (no thermal element). Pipes are normally empty. A separate detection system (rate-of-rise, UV/IR flame, linear heat cable) triggers the deluge valve, and water rushes to every sprinkler at once.

Where Used

• Aircraft hangar: Fuel leak + spark = massive fire in seconds (NFPA 409).
• Refinery / petrochemical: With NFPA 15 water spray and NFPA 30.
• High-voltage transformer: Equipment cooling + fire confinement.
• Flammable liquid tank perimeter: Prevents fire spread to neighbors.
• Conveyor belts: Coal and bulk-material lines.

Deluge Valve Types

• Diaphragm type: Most common. Detection holds clapper; loss opens it.
• Pneumatic release: Held by air pressure; loss opens.
• Hydraulic release: Water pressure; very high capacity.
• Electric release: Solenoid-controlled from FACP.

Detection

Deluge speed depends on detection. Three technologies:

1. Pneumatic rate-of-rise: Constant air pressure in small tubing; rapid temp rise drops it.
2. Electric thermal / UV / IR: Electronic detectors trigger solenoid via FACP.
3. Linear heat cable: Meter-by-meter detection along conveyors, tunnels.

Design Criteria

• Typical density 0.16-0.20 gpm/ft² (hangar); 0.30+ (petrochemical).
• All sprinklers simultaneous → very high pump flow (often 2000-5000 gpm).
• Water supply ≥ 60 min; 90-120 min for hangars.
• Cross-zoning: two zones required to open valve → fewer false discharges.

Foam Water Deluge (NFPA 16)

Pure water isn't enough for refinery and hangar hydrocarbon fires. NFPA 16 foam water deluge: AFFF or AR-AFFF at 3% or 6% proportion. Supplied via foam bladder tank or around-the-pump proportioner.

Common Mistakes

1. Single detection zone: False alarm = million-dollar water damage. Cross-zoning mandatory.
2. No air supervision: Pneumatic detection pressure drop should alarm.
3. Undersized pump: Not all sprinklers fed; only half active.
4. Deluge antifreeze: Trapped water in dry deluge freezes; heat trace or dry air needed.

Conclusion

Deluge is the big-hammer answer to fast-growing fires. Detection, valve, pump, and water supply must play the same orchestra. One weak link makes the whole system brittle. Common at Turkish refineries, hangars; done right it protects billion-dollar investments.

Deluge design in SprinkCalc

Deluge valve selection, all-sprinkler concurrent flow calc, pump sizing.

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