Understanding NEC Article 513: Aircraft Hangars
NEC Article 513 provides guidelines for the safe installation of electrical systems in aircraft hangars, where flammable liquids or vapors may pose a fire or explosion hazard. This article applies to facilities storing or servicing fueled aircraft but excludes areas exclusively for unfueled aircraft.
Scope of Article 513
Article 513 addresses:
- Hangars where aircraft with Class I (flammable) or Class II (combustible) liquids above their flash points are housed.
- Areas for aircraft maintenance, repairs, or alterations involving hazardous materials.
Excluded Areas:
- Locations used for aircraft that have never contained fuel.
- Areas storing aircraft with only Class II combustible liquids below their flash points.
Key Requirements for Aircraft Hangars
- Area Classification
- Below Floor Level: Pits or depressions are classified as Class I, Division 1 or Zone 1 up to floor level.
- Vicinity of Aircraft:
- Storage and Maintenance Hangars: Class I, Division 2 or Zone 2 within 5 feet of fuel tanks or engines, extending upward 5 feet above wings and engine surfaces.
- Painting Hangars: Class I, Division 1 or Zone 1 within 10 feet of aircraft surfaces, extending vertically 10 feet. Class I, Division 2 or Zone 2 applies from 10 to 30 feet.
- Ventilation and Separation
- Mechanically ventilated or suitably separated areas may be unclassified if ventilation provides at least four air changes per hour or uses positive air pressure.
- Wiring and Equipment
- Classified Locations: Wiring and equipment must meet requirements for Class I, Division 1 and 2, or Zone 1 and 2, as applicable.
- Fixed Wiring Above Classified Locations: Must be installed in metal raceways or use MI, TC, or MC cables.
- Portable Equipment: Devices like lighting and tools must be suitable for hazardous locations and use extra-hard usage cords with grounding.
- Special Equipment
- Battery Chargers: Must be located outside hazardous areas or in mechanically ventilated rooms.
- Mobile Servicing Equipment: Must be at least 18 inches above the floor in classified areas and display warnings to maintain a safe distance from engines and fuel tanks.
- Aircraft Energizers: Must ensure all electrical components are installed at least 18 inches above floor level.
- Grounding and Bonding
- All raceways, enclosures, and equipment must be grounded to prevent static discharge. Continuity must be maintained for portable luminaires and equipment.
Applications in Aircraft Hangars
- Storage Hangars: Generally classified as Class I, Division 2, or Zone 2.
- Maintenance Hangars: Classifications depend on the specific maintenance activity and aircraft type.
- Painting Hangars: Entire surfaces may be classified as hazardous due to spray application of flammable materials.
Conclusion
NEC Article 513 ensures electrical systems in aircraft hangars meet safety requirements to prevent ignition of flammable vapors. By addressing area classification, equipment design, ventilation, and grounding, this article provides comprehensive guidelines for fire and explosion risk mitigation.
