Subsurface Foam Injection System
A subsurface injection of fluroprotein foam was demonstrated to municipal, industrial and government fire service personnel at the Fire School of the Baltimore City Fire Department last November 20.
The foam was pumped through hose to a pipe that went over the edge and down to the bottom of a 30-foot-diameter tank, 5 feet high, containing 20,000 gallons of Jet A fuel. It was explained by National Foam System, Inc., representatives, who conducted the experiment, that normally a product line or a foam line terminating at the tank is used.
A line proportioner and a high back pressure foam maker were used, and water was supplied by a Baltimore City Fire Department engine. The inlet pressure at the foam maker was 115 psi, and the foam application rate was 0.1 gpm per square foot.
The jet fuel was ignited with the use of gasoline, and the preburn time was approximately 1 minute. In 1 minute and 49 seconds after the subsurface foam injection started, the fire was extinguished. In about 4 minutes, a 4-inch foam blanket was built up. The wind velocity at the time was 25 mph, and the temperature was 42°F.
The manufacturer’s representatives declared that the subsurface application insures less chance of losing a foam system capability in the event of tank distortion. They also stated that there is an advantage gained through surface cooling of the flammable liquid as the movement of the injected foam rolls the cooler liquid at the bottom of the tank up to the surface. Other advantages cited were lower installation and piping costs and the ability to control tank fires some distance away.