Fire Engineering - Chapter 06. Type of Foam


TYPE OF FOAM CONCENTRATION:-

Sr. No
Type of FOAM

1
PF
PROTEIN FOAM
2
FFFP
FILM FORMING FLUORO - PROTEIN FOAM
3
AFFF
AQUEOUS FILM FORMING FOAM
4
SF
SYNTHETIC FOAM

FOAM EXPANSION RATE:-
Volume of finished foam divided by the volume of foam solution used to create the finished foam; i.e., a ratio of 5 to 1 would mean that one gallon of foam solution after aeration would fill an empty 5-gallon container with the expanded foam mass.

i)            Low Expansion Foam:- Foam aerated to an expansion ratio of between 2 to 1 and 20 to 1.

ii)           Medium Expansion Foam:- Expansion ratio between 20 to 1 and 200 to 1.

iii)         High Expansion Foam:- Expansion ratio above 200 to 1.

FOAM PROPORTIONING RATE:-

(Correct amount of foam concentrate to be mixed with water)
The amount is normally shown on the pail or drum of concentrate. The container will normally display a figure or combination of figures. Normal figures shown are 1%, 2%, 3% or 6% or a combination of 1% and 3%, 3% and 3%, or 3% and 6%. If the container of foam concentrate has 3% shown, it means that for every 100 gallons of foam solution required, 3 gallons of the foam concentrate must be used in the solution with the balance being 97 gallons of water.
If 6% were displayed, this would mean that 6 gallons of the foam concentrate would be required to be mixed with 94 gallons of water to form the 100 gallons of foam solution. From the above, it becomes obvious that a 3% foam concentrate is twice as concentrated as a 6% foam concentrate. On the same size and type of flammable liquid fire, half as much 3% foam concentrate would be required than if the 6% foam concentrates had been used.




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:
  1. The foam blankets the fuel surface smothering the fire.
  2. The foam blanket separates the flames/ignition source from the fuel surface.
  3. The foam cools the fuel and any adjacent metal surfaces.
  4. The foam blanket suppresses the release of flammable vapors that can mix with air.














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