Advanced Fire Protection System Developed (Aug. 30)
TYNDALL AIR FORCE BASE, Fla. -- An Air Force scientist here has developed new technology that will save lives and protect property at defense munitions plants across America.
Called the Advanced Fire Protection Deluge System, it can detect a fire in milliseconds versus minutes, said Steven Wells, Air Force Research Laboratory project engineer at the fire research group materials and manufacturing technology directorate.
"AFPDS can detect a fire within 20 thousandths of a second, and provide cooling water before the fire gains momentum," Wells said. "It also will protect workers by preventing unnecessary discharge of large volumes of water contaminated with hazardous, flammable and explosive materials."
Such materials pose significant health risks to workers in military plants that produce, maintain and renovate munitions, Wells said at a recent American Institute of Chemical Engineers annual meeting.
"Fires in these facilities cause significant loss of life and property damage," he said. "Such facilities also suffer from false alarms, caused by random stimuli that alert ultraviolet, detector-driven suppression systems, releasing munitions-contaminated water.
"Each time a facility has a false alarm 'dump,' the depot loses production man-hours while technicians clean up," Wells said. "When U.S. Army Operations Support Command (officials) asked AFRL to help determine the cause of false alarms, we discovered that current suppression systems were much slower than needed to extinguish accidental fires."
With the Army's approval, AFRL people built a prototype system and started formal testing in January 1996. To date, more than 200 "burn" tests have been accomplished, Wells said.
"The prototype uses dual-band infrared and combination UV/IR optical fire detectors; high-speed, pressurized water discharged from 10- and 30-liter, high-rate discharge spheres; and follow-on, pressurized water from standard nozzles found in existing plants and arsenal systems," Wells said.
"Combining two detectors from different manufacturers improved the system's ability to monitor and protect a single location," he said. "Some materials start burning slowly, then go 'boom' -- in this case, we need a detector that 'sees' that slow burn before it leads to a catastrophic explosion. When we ignite another material, it goes 'boom' immediately -- then we want a detector that reacts to the rapid change."
The detectors chosen were proven quick, yet unlikely to respond to false alarms in halon fire protection systems for armored personnel carriers and tanks, Wells said. The same detectors proved virtually immune to accidental discharge.
Detectors work by first recognizing burning material, then activating a controller that starts a high-rate discharge extinguisher filled with pressurized nitrogen and water, Wells said.
"An actuator inside the extinguisher discharges water in a fine mist, reducing the possibility of fire, explosion, environmental problems and hazardous fumes, followed by more water from follow-on nozzles," Wells said. "It's important to get water to burning surfaces quickly, because uncontrolled fire 'burrows' into material. We also need to get water on workers in the area immediately, to eliminate skin-searing heat."
AFPDS is a great improvement over current, similar systems in the Department of Defense, Wells said.
"DOD standards now require water at the nozzle tip in 100 milliseconds. AFPDS produces water at the nozzle tip in four to eight milliseconds -- more than 10 times faster," he said. "Nozzles are placed close to the hazard, so that water reaches the material in just 18 milliseconds.
Heat flux was another area Wells' team evaluated.
"We installed a high-speed sensor 24 inches from hazardous material, to determine the amount of heat a worker might experience in a fire," he said. "Test results showed that using such sensors can protect workers."
Wells also tested several existing fire protection deluge system components, and performed time trials on commercially available detectors and controllers.
"When we began testing, we had to evaluate the best industry components available," he said. "We discovered that some of the controllers for existing detectors were too slow for what we needed."
The team eventually found a faster controller, compatible with all other detectors evaluated, that significantly increased the speed of the entire system, Wells said.
"Our principal goal was to provide reliability and safety without sacrificing speed -- and we've accomplished that goal," he said.
The new technology has already been installed in Picatinny Arsenal in New Jersey, Wells said. Additional installations are planned at four other DOD munitions manufacturing and inspection locations in the United States.
-ends-
Air Force Scientist Creates Better Fire Suppression System
