Offshore Platform Helideck Foam System: NFPA 418 and CAP 437

Helidecks are helicopter landing areas on offshore platforms. A Jet A fuel helicopter crash poses huge fire risk. NFPA 418 (Standard for Heliports) and CAP 437 (UK Civil Aviation) define Deck Integrated Firefighting System (DIFFS) and foam monitor rules. DIFFS became mandatory after the 2009 Cougar crash in Newfoundland.

DIFFS Deck Integrated Foam

• Design density: 5.5 L/min/m2 AFFF (pop-up nozzles)
• Deck area: 25 m D-value for S-92
• Nozzle: flush-mount recessed in deck
• Activation: full coverage in 15 sec
• Duration: 10 min (NFPA 418)

Fixed Foam Monitor

• Flow: 1,500-3,000 L/min per monitor
• Range: 50 m throw
• Number: 2-4 monitors along deck edge
• Remote control: joystick + auto sweep
• Fluorine-free foam (F3): 2026 transition per PFAS restrictions

CAP 437 vs ICAO

• CAP 437 (UK): strict - DIFFS mandatory
• ICAO Annex 14: minimum - monitors sufficient
• NFPA 418: US - monitor + deck hybrid
• API RP 14G: US offshore - references NFPA 418
• Class H1-H3: helicopter weight (5-13 t)

Firewater Ring Main

• Seawater: firewater pump (jockey + main + diesel backup)
• Ring main: platform perimeter, two-arm feed
• Dry riser: helideck + accommodation
• Velocity: monitor supply 2.5-5 m/s

Helideck Drainage

• Slope: 1-2 percent (fuel to edges)
• Perimeter drain: 300 mm diameter
• Fuel slop tank: collection tank - oil-water separator
• Fire pump room: 2-hour firewall
• Fresh water rinse: reduces salt corrosion after seawater

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