Replacing more than 500 hangar heat detectors with 36 flame detectors
Field notesAviationCase study
An aviation maintenance hangar in Singapore relied on more than 500 heat detectors about 40 m above the floor. A 3D flame mapping study showed that 36 flame detectors, only six more than the hangar already had, could replace them at half the cost of a like-for-like replacement of the heat detectors.
The fire detection in an aviation maintenance hangar in Singapore included more than 500 point-type heat detectors, positioned approximately 40 m above the floor, alongside 30 flame detectors.
The heat detection had been designed to comply with legacy NFPA standards. The detectors had become obsolete and were costly to replace, and maintaining them in a busy hangar required access equipment and crews able to work at that height.
The cost was only part of the problem. At that height, rapid detection of a fire at the incipient stage, while it is still small, was improbable. The owner was paying to maintain a system whose ability to detect a fire in time was itself in doubt.
A change in the hangar standard
The team began from the engineering fundamentals: what the owner needed the detection to do, and what the governing standard now allowed. NFPA 409, the National Fire Protection Association standard for aircraft hangars, had been updated since the original system was designed. The updates opened the way to replace heat detection with IR3 flame detectors, which are designed to give early, reliable detection of hangar fires, including fires under the wings and overhead.
The two detector types work on different principles. A flame detector responds to radiation from a flame within its field of view, so it can register a fire as soon as the flame is in sight. A heat detector at about 40 m can only respond once hot gases from the fire have risen and accumulated at the ceiling around it, which in a space of that height takes time.
Because a flame detector’s coverage depends on what it can see, structures inside a hangar can block its view of part of the floor. The design question became how many detectors were needed, where they should go, and which way each should point, and how far the 30 flame detectors already in the hangar could form part of the answer.
Mapping coverage in three dimensions
Archer answered that question with 3D flame detection mapping. The hangar was modelled in three dimensions, including obstructions such as scaffolding and maintenance structures that sit between a detector and a possible fire. Coverage was then quantified across multiple planes and axes, which showed where each part of the floor was seen by more than one detector and where redundancy was missing.
The same model set the orientation of each detector along the x, y and z axes. Fixing each position and aiming angle in the model greatly simplified the installation. The final layout used 36 flame detectors, of which 30 were already installed, so six new detectors were added.
For engineersHow the mapping exercise was used
- Model. Build a 3D model of the hangar, including scaffolding and maintenance structures that can obstruct a detector’s view.
- Place. Position the flame detectors and set each one’s orientation along the x, y and z axes.
- Quantify. Measure coverage across multiple planes and axes to confirm redundant coverage across the facility.
- Demonstrate. Present the coverage results to the AHJ as evidence of technical reliability and compliance.
Traditional 2D mapping does not account for obstructions in the same way. The 3D analysis took in scaffolding and maintenance structures, so the coverage it reported reflected the hangar as it is used.
Approval and the operator interface
The mapping results formed the case put to the AHJ, the authority having jurisdiction that approves the fire protection design. Approval was secured by demonstrating the technical reliability of the layout and its compliance with the standard, with the owner involved throughout.
The mapping exercise justified eliminating the heat detector system and replacing it with fewer, strategically placed IR3 flame detectors.
Archer (S) Pte Ltd
One requirement came from the hangar operators. They preferred to keep their traditional push-button console as the operating interface. Archer kept it, and carried out custom electrical engineering to connect the console to the new detection system.
Results
- Detector count. More than 500 heat detectors removed; 36 flame detectors in the final design, six more than the 30 already installed.
- Cost. A 50% saving compared with a like-for-like replacement of the heat detectors, reducing the capital expenditure (CAPEX) required.
- Detection. Improved detection effectiveness and faster response, since flame detectors respond to radiation from the flame itself and do not wait for hot gases to reach a ceiling 40 m up.
- Maintenance. Lower maintenance complexity and cost, with no further need for specialised height-access maintenance crews.
With the AHJ’s approval, the hangar’s detection now rests on 36 flame detectors, six more than it already had, in place of more than 500 heat detectors at 40 m. The change cost half as much as a like-for-like replacement of the heat detectors and removed the height-access maintenance the heat detectors required.
