AFFF

Low Expansion Foam

Expansion Ratio: Typically between 2:1 and 20:1. Characteristics: Produces a dense, heavy foam that is excellent at forming a seal on the surface of flammable liquids, providing a robust barrier against oxygen and suppressing vapor release.

Applications: Commonly used for spills and tank fires involving flammable liquids, as well as in municipal firefighting and industrial applications.

Medium Expansion Foam

Expansion Ratio: Generally falls between 20:1 and 200:1.

Characteristics: Offers a balance between covering large surface areas and maintaining a foam structure that can last long enough to effectively suppress fires and prevent reignition.

Applications: Suitable for use in fighting fires in warehouses, larger spills, and areas where the foam needs to be spread over a larger area but still provide substantial volume and cling to vertical surfaces.

High Expansion Foam

Expansion Ratio: Ranges from 200:1 to 1000:1, sometimes even higher.

Characteristics: Produces a very light, voluminous foam that can quickly fill large spaces and create a thick blanket that deprives the fire of oxygen.

Applications: Primarily used in situations where an enclosed space, such as an aircraft hangar, ship’s hold, or large storage facility, needs to be quickly filled with foam to suppress a fire. It is also useful in confined spaces where the foam needs to penetrate deeply into difficult-to-reach areas.

Relation and Usage

Target Fire Classes: All three types are effective against Class B fires, which involve flammable liquids such as oils, gasoline, and other hydrocarbons. They can also be adapted for use on Class A fires with suitable additives.

Functionality: The primary function remains the suppression of oxygen and cooling of the fire, but the method of delivery and the extent of coverage vary significantly.

Selection Criteria: The choice between low, medium, and high expansion foam depends on the specific fire scenario, including the type of fire, the area that needs coverage, and the required depth of the foam blanket.

In summary, the relationship among these foams is defined by their expansion ratios and the physical characteristics of the foam produced. This directly influences their suitability for different firefighting scenarios, with each type designed to maximize efficiency in specific environments or against certain types of fires.

Low expansion Aqueous Film Forming Foam (AFFF)

It is a type of firefighting foam specifically designed to extinguish flammable liquid fires, commonly known as Class B fires. This foam is widely used because of its effectiveness in rapidly suppressing fires by creating a barrier between the fuel and the air. Here are the key characteristics of low expansion AFFF foam:

1.?????? Expansion Ratio:

Low expansion foams typically have an expansion ratio of about 2:1 to 20:1. This means that the foam expands to 2 to 20 times its liquid volume after application. Low expansion AFFF foams are usually in the lower range of this scale, making them thicker and more viscous, which is ideal for covering large areas quickly.

2.?????? Aqueous Film Formation:

AFFF works by forming an aqueous film that rapidly spreads over the surface of a flammable liquid. This film separates the fuel from the oxygen, helping to halt the combustion process. The film is water-based, which also helps to cool the fuel and further prevents re-ignition.

3.?????? Water Content:

?The high water content in AFFF helps in cooling the fire and the heated surfaces surrounding the fire, which is crucial in preventing the fire from spreading and in extinguishing it completely.

4.?????? Fuel Resistance:

AFFF foams are resistant to breakdown when in contact with hydrocarbon fuels, which means they maintain their integrity and effectiveness even when directly applied to fuel surfaces.

5.?????? Application:

Low expansion AFFF is typically applied using various methods such as foam branches, monitors, foam sprinklers, and rapid intervention vehicles. It is suitable for various scenarios, including airport runways, oil refineries, and chemical plants.

6.?????? Knockdown Speed:

AFFF foams are known for their rapid fire knockdown capabilities. The foam quickly spreads and subdues the flames, which is critical in emergency response situations.

7.?????? Environmental Impact:

Traditional AFFF formulations contain fluorosurfactants, which can persist in the environment and have been linked to environmental and health concerns. As a result, there has been a push towards fluorine-free AFFF formulations that aim to reduce these impacts while maintaining firefighting effectiveness.

8.?????? Compatibility:

?AFFF can be used in conjunction with other firefighting agents like dry chemicals and can be applied with a variety of equipment, making it versatile for different firefighting needs.

9.?????? Storage and Handling:

AFFF concentrates are typically stored in sealed containers and require proper mixing with water at specified ratios before use. The storage conditions can affect the foam's effectiveness, so it must be stored according to the manufacturer's guidelines.

10.?? Re-ignition Prevention:

Once applied, the foam layer can help to prevent re-ignition by continuously cooling the fuel and isolating it from oxygen.

Understanding these characteristics helps in effectively using low expansion AFFF foam in scenarios that involve flammable liquids, ensuring rapid suppression of fires while minimizing potential environmental impact.