Upon completion of this lesson, you will be able to:
- Describe foam, composition & contents of foam.
- List the classification of foam.
- Describe the types of foam compounds.
- Describe the action of foam.
- Describe the foam equipment & their uses.
- Describe the foam application techniques.
- List of SOP’s for foam operation from fire vehicles (FRV & FTR).
In this post you will find the knowledge about Fire Fighting Foam and all Foam Making Equipment for a professional fire Rescuers. The chemical Action of AFFF (Aqueous Film Forming Foam), Foam Application, Techniques ,Equipment and Foam Classification. Best SOPs’ for Foam Operation on (FRV & ftr) Vehicle.
Foam is mostly used on class B fires. Foam consists of synthetic detergents, butoxyethanol, (ethyl alcohol) & water. According to NFPA the Foam proportion should be adequate to cover the burning place.
1.1 Foam composition & contents:
Before foam spray, its concentration is;
3% ==========>> Foam.
97% =========>> Water.
After foam has been discharged through FMBP (Foam Making Branch Pipe), its concentration becomes.
3% ==========>> Foam.
87% =========>> Water.
10% =========>> Air.
Classification of Foam:
Generally, foam is classified into 2 main classes irrelevant of the types of foam.
- Class A Foam.
- Class B Foam.
2.1.1 Class A Foam:
This type of foam is used to fight the fires involving ordinary combustibles. It is also effective on organic materials like hay & straw. The class “A” fire is also used to protect buildings in forest fires & brush fires where supply of water is limited.
2.1.2 Class B Foam:
This type of foam is used to fight class B fires. It is used in fires involving flammable and combustible liquids. There are various types of class “B” foam which can be used in case of class “B” fires.
Foam consists of & water.
2.2 Classification Expansion Ratio:
There are 4 types of foams:
On the basis of expansion:
- Normal expansion foam (5 to 15 times).
- Low expansion foam (20 times).
- Medium expansion foam (can expand up to 200 times).
- High expansion foam (can expand up to 1000 times).
3- Types of Foam compounds:
There are two types of foam compounds which are;
- Mechanical foam compound.
- Chemical foam compound.
3.1 Mechanical Foam Compound:
These foams are produced by air interruptions through mechanical means such as aspiration and air blowing. Mechanical foam compounds are further classified into 3 categories, i.e.
- Low expansion.
- Medium expansion.
- High expansion.
3.2 Chemical Foam Compound:
When two or more chemicals are added, foam is generated due to chemical reaction. The most common ingredients used for chemical foam are sodium bicarbonate and aluminum sulfate with added stabilizers. These types of compounds are used in portable fire extinguishers. Where sometimes, mechanical formation of foam is not possible.
3.3 Types (Concentrates of Foam):
There are following types of foams
- Protein foams
- Fluoro-protein foams.
- Synthetic foams.
- AFFF (Aqueous Film Forming Foam).
- Multipurpose AFFF.
- FFFP (Film Forming Fluoro Proteins).
- Alcohol resistance foam.
3.3.1 Protein Foam:
Protein foam is made from animal by-products, in 3% or 6% form available. Suitable for hydrocarbon fires.
3.3.2 Fluoro- protein Foam:
II contains added fluoro chemicals which increase its effectiveness
along with animal fails & by products It is used on low flash point fires.
3.3.3 Synthetic Foams:
Synthetic foam is based on foaming agents, their proteins and it includes AFFF medium & high expansion IS limited to ordinary spill fires.
AFFF (Aqueous Film Forming Foam):
These foam compounds consist of fluorocarbon surfactants, a foaming agent and a stabilizer. These compounds can be used with all types of water. This foam has quick knock down properties and is suitable for liquid hydrocarbon fires but the foam has a poor drainage rate. This type of mostly used by Rescue 1122 and all other departements for oil based fires.
Multipurpose AFFF (Aqueous Film Forming Foam):
These are synthetic foaming liquids designed for fire protection of water soluble solvents and water insoluble hydrocarbon liquids and can use all types of water. It foam cohesive polymeric layer on the liquid surface and thereby suppresses the vapors and extinguishes the fire.
Film Forming Fluoro Proteins (FFFP):
This is a combination of the AFFF and the fluoro protein foam and thereby provides a high level of knock down effect and post-fire security and burn back resistance. This foam is suitable for hydrocarbon liquid fuel fire including deep pool fires of low flash point fuels which have lengthy pre- burn time.
3.3.7 Alcohol resistance foam:
Alcohol resistance foam has properties similar to AFFF; however, it is formulated so that alcohols and other polar solvents will not dissolve the foam. Regular foams cannot be used on these alcohol fires.
4. Action of Foam:
Foam extinguishes the fire by the following methods;
- By excluding air (oxygen) from the fuel surface.
- By separating the flames from the fuel surface.
- By restricting the release of flammable vapors from the surface of the fuel.
- By forming a heat barrier to stop radiation feedback from flames to fuel surface and reduce the production of flammable vapors.
- By cooling the fuel surface. This process dilutes the oxygen around fire.
5. Foam Equipment:
Foam fire equipment is used to form proper foam layer & mixture of water and foam. This includes the following;
5.1 Foam proportioner / foam proportioning system: A foam proportioner is a device that mixes the foam concentrate in the proper percentage. There are two types of proportioners.
5.1.1 Foam Educator :
(Like foam generator) a foam educator uses a Ventury effect to draw foam content rate form a container or storage tank into a moving stream of water. It is used as pick up tube.
The Venturi effect means the reduction in fluid pressure that results when a fluid flows done a constricted section (or choke) of a pipe. The effect of Venturi is labeled after Giovanni Battista Venturi (1746–1822), an Italian physicist.
5.1.2 Foam injectors:
Add the foam concentrate to water system under pressure. This type of apparatus is normally installed or mounted on speed foam apparatus.
Foam Application Techniques:
Three foam application techniques are;
- Sweep method or roll on method.
- Bank shot method.
- Rain down method.
6.1 Sweep Method or Roll on Method:
This method should be used only on a pool of flammable product that is on open ground. The stream is moved back & forth in a slow, horizontal motion to gently push the foam forward until the
6.2 Bank shot Method:
Bank shot method is used at fires where the Fire Fighter can use an object to deflect the foam stream and let it flow down on the burning surface. This method to apply foam can be used on an open- top storage tank or rolled over transport vehicle.
6.3 Rain down Method:
This method consists of lofting the foam stream into the air above the fire and by letting it full down gently into the surface. The stream of foam should be broken to avoid breakup of the blanket & cover entire area.
SOPs’ for Foam Operation on (FRV & ftr)
- All necessary PPE (Personal Protective Equipment) including i.e. fire suit, safety gloves, safety shoes, safety helmet, shall be wear by the person/ crew member.
- Ensure vehicle is parked in safe area.
- Check the foam level in foam tank.
- Check the water level in water tank.
- 102-liter foam is required for 3300-liter water and 216-liter foam) is required for 7000 liters water if the foam and water proportion is kept 3% and 97% respectively.
- Check the availability of Foam Making Branch Pipe (FMBP),
- Ensure the by-pass valve is shut off. To avoid mixing of foam with water in water tank.
- Open the main valve of water tank.
- Start the pump at the normal pressure.
- Open at least one delivery outlet or monitor.
- Open the water to foam proportion valve (full).
- Set the percentage of foam by opening the foam proportion valve at required rate, (e.g.) 3% or more.
- After completion of foam operation the system must be “flushed”, i.e. pipe-lines, delivery hoses, all delivery outlet valves, monitor, hose real etc, opened and foam proportion %age valve shall be fully closed.
- Flushing process will continue until all pipe lines are cleaned of foam.
- After complete cleaning, all valves of water to foam valve shall be closed.
- While flushing, the water to foam proportion valve shall be opened.