How Foam Extinguishes a Flammable Liquid Fire?
Fire burns because there are four elements present. These elements are heat, fuel, air (oxygen) and a chemical chain reaction. Under normal circumstances if any one of the elements is removed/interfered with, the fire is extinguished. Fire fighting foam does not interfere in the chemical reaction. Foam works in the following ways:
The foam blankets the fuel surface smothering the fire.
The foam blanket separates the flames/ignition source from the fuel surface.
The foam cools the fuel and any adjacent metal surfaces.
The foam blanket suppresses the release of flammable vapors that can mix with air.
Following is a list of mechanical foam concentrates that are the most common types:
Aqueous Film Forming Foam (AFFF)
Alcohol Resistant (AR-AFFF)
Synthetic – medium or high expansion types (detergent)
Class "A" Foam Concentrate
Wetting Agent
Fluoroprotein
Protein
Film Forming Fluoroprotein (FFFP)
AQUEOUS FILM FORMING FOAM CONCENTRATE (AFFF):
Available in either a 1%, 3% or 6% type concentrate. AFFF concentrate with a unique combination of hydrocarbon and fluorochemical surface active agents. It produces a vapour-sealing aqueous film that spreads rapidly over the fuel surface to provide rapid control and extinguishment.
■Film-forming for fast flame knock down and extinguishment.
■Burnback resistance and post-fire security.
■Foam blanket reseals when ruptured by personnel or equipment.
AFFF 1% should be used at 1% proportioned solution (1 part concentrate in 99 parts of water) in brackish, fresh or sea water. It may also be stored as a premix solution in fresh water.
AFFF 3% should be used at 3% proportioned solution (3 part concentrate in 97 parts of water) in brackish, fresh or sea water. It may also be stored as a premix solution in fresh water.
AFFF 6% should be used at 6% proportioned solution (6 part concentrate in 94 parts of water) in brackish, fresh or sea water. It may also be stored as a premix solution in fresh water.
FFFP-FILM FORMING FLUOROPROTEIN(FFFP):
Just like the FluoroProtein (FP) foam concentrates Film forming Fluoroprotein foams are based on advanced protein foam technology and are ideal for extinguishing and securing flammable hydrocarbon liquid fires. FFFP foams have the additional advantage that they can be used unaspirated due to their ability of film formation. The protein base provides a tough cohesive foam blanket with high resistance to heat that quickly smothers, cools, and seals the risk, and the film formation ability brings rapid knockdown.
Film forming Fluoroprotein foams are ideal to use in high risk situations where hydrocarbons (such as aviation kerosene, crude oil, gasoline, and diesel fuel) are stored, processed, or transported. They are used extensively on Rapid Intervention Vehicles at major international airports and military bases where fast extinguishment and postfire security with limited quantities of foam concentrate are essential.
■Film-forming for fast flame knock down and extinguishment.
■Stable and long-lasting foam blanket for excellent burnback resistance and post-fire security.
■Detergent-free for high resistance to fuel pick-up.
■Foam blanket re-seals when ruptured by personnel or equipment.
■Reduced stocks, low cost storage, long shelf-life, and low usage levels combine to provide maximum costeffectiveness.