High-expansion foam fights hangar fires
In September 2008, the Tennessee Air National Guard (TANG) 164th Airlift Wing received one of the U.S. military's most advanced aircraft hangar fire suppression systems to date. The hangar fire protection project was led by architect-engineers Frankfurt Short Bruza (FSB), Oklahoma City; sprinkler design specialist Security Fire Protection (SFP), Memphis, Tenn.; and Tyco Fire Suppression & Building Products (FS&BP), Marinette, Wis. The group was able to move from FSB's prototype layout drawings to a fully tested, installed, and approved system under rigorous customer requirements.
These requirements included Engineering Technical Letter (ETL02-15) guidelines that encompassed every part of the fire suppression system, from getting water to the high-expansion foam generators, to generating the foam and getting it through the pipes to the aircraft. The system had to cover at least 90% of the floor with overlapping blankets within 1 min beneath the largest military aircrafts in the world.
SFP chose Tyco FS&BP's Ansul Jet-X high-expansion foam for the project. The system could service a 75,300-sq-ft maintenance hangar and a 67,700-sq-ft fuel cell/corrosion control hangar, which housed giant Lockheed C-5 Galaxy air transports . At 247 ft long and 222 ft from wingtip to wingtip, C-5s are some of the most difficult aircrafts to protect from fire.
Due to its low water requirements, minimal corrosive effects, and reduced environmental impact, high-expansion foam has become the preferred choice in fire suppression for civilian and military aircraft hangars. In addition, high-expansion foam systems are ideal for the large, open areas of an aircraft hangar. The highly mobile blanket of foam prevents the spread of fire by cooling surrounding surfaces and physically blocking the spread of flames.
To generate the foam in the quantities needed, a combination of Ansul Jet-X 15 and 20 high-expansion foam generators was the answer. Proven in such facilities as petroleum refineries and chemical manufacturing plants, these high-capacity generators can produce as much as 24,000 ft3/min of foam. Tyco FS&BP often assists its customers in obtaining the necessary data to prove the effectiveness of innovative but yet-untested solutions. In the case of SFP's prototype design, Tyco FS&BP located an empty warehouse of the same approximate dimensions of the TANG hangars to measure spread rates (time versus diameter of foam), foam patterns, optimum generator placement, and every other detail needed to establish design criteria.
SFP also had to ensure that water could flow through piping quickly enough to meet ETL requirements. In standard foam piping design, water reaches the generator through a series of right-angle pipes, always laid out from left to right. Instead, SFP chose a direct-route solution to shorten distances to the generators regardless of the angle, and shaved valuable seconds from delivery times to meet the 1 min delivery criteria. Other challenges that factored into the final design included the possibility of maintenance platforms obstructing foam discharge and sloping floors that could allow foam to drain away from its coverage area. These matters were overcome by carefully calculated sprinkler placement and foam volume.
Results of the final system design were confirmed by TANG and supported by an independent engineering firm, and upon successful acceptance testing, the C-5 hangar design was placed into operation in September 2008. The final production system met all requirements of the ETL and symbolized the perfect blend of product knowledge, a spirit of innovative problem solving, and the willingness to collaborate.
Information provided by Ansul .
At A Glance
The Tennessee Air National Guard 164th Airlift Wing needed a fire suppression system that could manage the wide, open spaces of aircraft hangars, and the presence of massive aircrafts. The Lockheed C-5 Galaxy aircraft holds enough aviation fuel to fill more than six railroad tank cars and is extremely difficult to protect from fire. The performance mandates for fire suppression set forth by the Engineering Technical Letter (ETL02-15) were a challenge for sprinkler design specialists Security Fire Protection.
With Ansul high-expansion foam from Tyco Fire Suppression & Building Products, the suppression system met the ETL requirements of:
Coverage of no less than 90% of the floor beneath the projected C-5 silhouette
Overlapping blankets of suppression agent
Finishing within 1 min of actuation.