- Author
- Hill, S. A. | Scheffey, J. L. | Walker, F. | Williams, F. W.
- Title
- Tests of Alternative Fire Protection Methods for USAF Hangars.
- Coporate
- Hughes Associates, Inc., Baltimore, MD Air Force Civil Engineering Support Agency, Arlington, VA Naval Research Laboratory, Washington, DC
- Sponsor
- Air Force, Tyndall AFB, FL
- Report
- NRL/MR/6180-99-8337, February 8, 1999, 385 p.
- Keywords
- aircraft hangars | fire protection | aircraft fuels | fuel spills | aqueous films | aqueous foams | fire suppression | water | JP-8 jet fuel | fire growth | flame spread | sprinklers | sprinkler systems | spill fires
- Identifiers
- spill fires; air aspirated foam sprinkler system; Mobile Compressed Air Foam Fire Suppression System (MCAFFSS)
- Abstract
- The use of Aqueous Film Forming Foam (AFFF) in overhead suppression systems in aircraft hangars continues to create problems as a result of false discharges and environmental concerns. The U.S. Air Force (USAF) is conducting research and development to address these issues. As part of this R&D, two concepts were proposed: the use of water suppression systems to control JP-8 fires and limit fire growth to an acceptable level; and, the use of a Mobile Compressed Air Foam Fire Suppression System (MCAFFSS) to protect aircraft in a hangar. This report describes the results of test and evaluation of these two concepts. Fire tests were conducted in the large-scale fire test facility located at the Underwriters Laboratories complex in Northbrook, IL. The facility ceiling was set to a height of 15 m (48 ft.). A temporary concrete pad was constructed on which JP-8 fuel was spilled and ignited. The spill scenario involved 114 L (30 gal) of JP-8 fuel, which was ignited immediately after it was dumped. Without suppression systems, the fire grew at a constant rate and peaked at a maximum free-burn size of 37 m2 (400 ft2) 75 seconds after ignition. The total burn time was on the order of 2 minutes. Water suppression systems were tested to determine the impact on flame spread and fire growth. The suppression systems were designed to represent actual USAF hangar installations. The variables investigated included sprinkler application rate (6.9 and 10.2 Lpm/m2 (0.17 and 0.25 gpm/ft2)) and time of sprinkler water discharge. Deluge (open-head) sprinklers were activated immediately after ignition and 30 and 80 seconds after ignition, quick response closed-head sprinklers were also investigated. The results showed that the water sprinklers were not capable of preventing flame spread and fire growth on a JP-8 fuel spill. Fires typically grew to the full free-burn size 37 m2 (400 ft2) even with suppression systems activated. If JP-8 ignites, water suppression systems of the magnitude used in these tests cannot be relied upon to prevent continued fire growth. The fire will likely grow to the size of the spill. The MCAFFSS unit tested included a 454 L (120 gal) tank of premixed AFFF discharged through an oscillating monitor nozzle. Included was a combination UV/IR optical fire detector designed to sense a fuel fire when it is relatively small. The unit is intended to be located in a hangar to protect target hazard areas, e.g., areas in, around and under parked aircraft. The breadboard unit was tested using the same spill fire scenario as in the sprinkler tests. Variables evaluated included actuation time (with the unit set in the automatic and manual modes), effect of foam aspiration, effect of discharge methods ("targeting" a hazard compared to "pushing" foam along a hangar floor), and effect of obstructions (simulated aircraft frames and equipment). The breadboard MCAFFSS unit evaluated in these tests would not meet current military and national consensus standards as a one-to-one replacement for fixed hangar fire protection systems. Within the parameters tested, the MCAFFSS can detect and operate to control/extinguish JP-8 fuel spill fires. Obstructions which might be found in a hangar have an impact on performance. It was found that the current USAF fire protection design approach for floor nozzle orientation is the appropriate approach.