Challenge
Brisbane Airport’s recently introduced an environmental protection policy whereby hangars will be approved only if their design prevents the release to the environment of any pollutants spilled inside the hanger. At a new 2500 square meter five start aviation hanger at Brisbane airport Delta Fire was contracted to install a firefighting system which needs to meet the new environment protection policy standards.
The Delta Fire installation needed to overcome the many shortcomings of both AFFF deluge systems and oscillating foam monitors. These include their lack of speed in extinguishing a typical hanger fire, the excessive amount of water used and unnecessary or excessive discharges of foam that have caused costly damage to aircraft and the unacceptable release of foam into the environment.
Solution
Delta Fire’s system facilitates ARFF and QFRS (Queensland Fire & Rescue) operations and complies with the Australian Building Code. It is a foam deluge system that is triggered by triple infrared flame detectors and uses a special high-expansion concentrate that is discharged via 36 high-level generators.
In addition to not requiring an electrical supply, the solution does not require external air for foam production – the system creates foam from smoke gases, smoke-contaminated air and hot air. This leads to a rapid decrease in temperature in the hanger as the hot aired is cooled in the generators, where it is aspirated and sprayed with water from the generator nozzles. Smoke emissions are reduced and fire ventilation is unnecessary.
The solution requires less than 1000 litres of concentrate to operate the system for 15 minutes, delivering about 2000 cubic metres a minute of the bio-degradable foam at an expansion ratio of between 650:1 and 700:1. Significantly, this is just one percent of the water that would be used by a comparable foam monitor installation. The system delivers a foam blanket across the hanger’s entire 50-metre by 50-metre floor area at the rate of 0.85 metres-a-minute or 0.3 metres deep in 21 seconds. A further 15-minute supply can be activated manually.
The flame detection system is configured to require two detectors to register the fire before the foam is discharged. However, discharge of the foam ceases as soon as fewer than two flame detectors no longer register the presence of a fire.
The hanger floor slopes towards a drain at the hanger door. Any liquids are collected in this drain and are contained in an underground tank beneath the fire pump house for licensed disposal off-site. This tank has a capacity to store approximately 61 cubic metres; more than sufficient to contain the 49 cubic metres of a 15-minute foam discharge and any other drained liquids. This compares with traditional hanger fire protection systems that would require tanks with capacities of between 300 cubic metres and 500 cubic metres.
Outcome
The system is believed to be the first of its kind in Australia, it complies with Brisbane Airport’s recently introduced environmental protection policy whereby hangars will be approved only if their design prevents the release to the environment of any pollutants spilled inside the hanger – including fuel spills, contaminated water and foam. A full-scale commissioning test was witnessed by both Brisbane Fire & Rescue and the Brisbane Airport’s ARFF (Airport Rescue & Fire Fighting) personnel.