Expertise

Foam action

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Action de la mousse BIOEX

Combustion is a chemical reaction in which a  combustible substance or fuel is oxidised by an oxidiser in the presence of an energy source.

Combustible :

  • Class A (wood, cardboard, paper, textile…),
  • Class B (petrol, oil, white-spirit…),
  • Class C (gases such as propane, butane, acetylene, hydrogen, methane…),
  • Class D (finely divided metals such as powdered aluminium, steel wool, magnesium…).

Oxidising agent: Oxygen from the air, chlorine, oxygenated water, nitric acid, chlorates, perchlorates...

Energy : Mechanical from friction, electric (lightning or static electricity), chemical, biochemical, solar...

Schémas triangle du feu EN

A fire is the result of the interaction of these three elements (the triangle of fire). The removal of one of them extinguishes the fire.

 

Fire-fighting foam acts in two phases:

  • Insulation: it prevents the action of the air and the evaporation of the combustible, thus removing the oxidising agent
  • Cooling: the water in the bubbles decants and evaporates, thus removing or reducing the energy that combustion requires

Foam action

Low, Medium and High Expansion

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Bas moyen et Haut foisonnement Mousse BIOEX

Expansion is the ratio between the Foam Volume obtained and the Volume of Foaming Solution used to produce it.

For example: 100 litres of water + foam concentrate pre-mix give 1000 litres of foam. Expansion is therefore 1000/100 = 10.

The more air is introduced the higher the expansion. There are 3 types of expansion depending on the equipment used:

  1. Low expansion – usually used on widespread hydrocarbon fires (storage tanks, holding tanks). Its higher density allows the use of long range jets using hoses or monitors. Low Expansion foam is little sensitive to atmospheric conditions, wind or rain: it is stable and provides a strong cover. Its high water content guarantees significant additional cooling.
  2. Medium Expansion – used for smaller surfaces (solvent storage, cellars) as a rule in closed or partially closed areas of which the walls limit the spread. Medium Expansion foam can be sprayed up to about ten metres. Its low density makes it sensitive to wind and bad weather.
  3. High Expansion – preferably used on dry product fires or on premises on which there are mixed risks (stores, warehouses). As the range is almost nil, the spreading orifice must be brought to the immediate area of the fire.

Expansion closely depends on the type of foam concentrate and the type of hose used. Thus, protein foam concentrates are usually suitable for Low and Medium expansion. Synthetic foam concentrates are suitable for Low, Medium and High Expansion.

Expansion

 

Direct and indirect applications of an AFFF or AR foam concentrate on class B fires

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Applications directes ou indirectes de la mousse

Extinguishing a fire requires a suitable foam concentrate, and a controlled application.

There are 2 application modes, recognised by the European (EN1568) and international (ISO7203) standards.

 

 

 

Direct application

Lapplication directe

This is the direct spraying of the foam into the heart of the liquid. 
The fire fighting teams use a hose or a monitor in the "solid jet" position. This makes it possible for them to fight the origin of the fire from a distance and thus be less exposed to intense heat.
Static installations are concerned in the case of long distance static monitors, or classic headed sprinklers. The jet of spray strikes the liquid directly.
This type of spray can only be applied to class B fires of the hydrocarbon type (water-immsicible liquids), using AFFF foam concentrates (Aqueous Film Forming Foam).

 

Application directe

Application directe 2

 

 

 

 

 

 

 

 

 

 

Indirect application

Application indirecte-Schéma1

It is imperative for all polar solvent liquid fires (miscible with water).
The foam is sprayed onto a vertical surface and then runs onto the burning liquid to spread evenly on its surface without contaminating it. The foaming agent therefore strikes a surface before coming into contact with the polar product. This is the case for most fire brigade interventions and for mobile resource operating tactics.

The sprayed foam can also be applied directly onto the liquid but using Medium or High expansion. This is the case for almost all static installations (crown with ME foam box on a holding tank, HE flooding, foam head sprinkler...).
This process is mandatory so that the foam is not directly absorbed by the polar solvent. 
This method of application also allows to extinguish hydrocarbon type fires (water-immiscible liquid). 

 Application indirecte

 Application indirecte 2Application indirecte 1

 

 

 

 

 

 

 

 

There are thus 2 actions have the same extinguishing effectiveness: 

  •  Chemical action with direct application

Action chimique en application directe AFFF ENG

 

The foam generated by an AFFF foam concentrate has the property of quickly draining thus allowing the quick formation of a thin fluorine compound film at the surface of the hydrocarbon.

This heat resistant film creates a barrier that prevents the hydrocarbon vapours from igniting. 

 

 

 

 

 

 

  •  Mechanical action with indirect application 

Action mécanique en application indirect AR ENG

 

Through the accumulation of foam, a mattress forms to isolate the burning liquid.

This heat resistant thickness of foam creates a barrier that prevents the solvent vapours from igniting.

 

 

 

 

 

 

 Triangle du feu barrée EN

 

In all cases the foam concentrate makes it possible to break "the fire triangle" by isolating from the air and a cooling action of the fire's environment.

ECOPOL for example, the 1st fluorine free foam concentrate in the world, is AR and therefore perfectly effective on all class B fires. 

 

 

 

Foam action

Foam action

Combustion is a chemical reaction in which a  combustible substance or fuel is oxidised by an oxidiser in the presence of an energy source. Combustible : Class A (wood, cardboard, paper, te...

Find out more

Low, Medium and High Expansion

Low, Medium and High Expansion

Expansion is the ratio between the Foam Volume obtained and the Volume of Foaming Solution used to produce it. For example: 100 litres of water + foam concentrate pre-mix give 1000 litres of foam. ...

Find out more

Direct and indirect applications of an AFFF or AR foam concentrate on class B fires

Direct and indirect applications of an AFFF or  AR foam concentrate on class B fires

Extinguishing a fire requires a suitable foam concentrate, and a controlled application. There are 2 application modes, recognised by the European (EN1568) and international (IS...

Find out more