The fire extinguishing principle and application scope of foam fire extinguishing agents

The fire-extinguishing mechanism of foam fire extinguishing agents mainly involves cooling and suffocation. That is, a continuous foam layer is formed on the surface of the burning material. The surface of the burning material is cooled by the foam itself and the mixed liquid it precipitates, and the covering effect of the foam layer isolates the burning material from oxygen to extinguish the fire.

Specifically as follows:

The foam covering layer formed by fire-extinguishing foam on the surface of the burning object can isolate the surface of the burning object from the air.

(2) The foam layer seals the surface of the burning material, which can block the thermal radiation of the flame to the burning material, prevent the evaporation or thermal decomposition and volatilization of the burning material, and make it difficult for flammable gases to enter the combustion zone.

(3) The liquid precipitated from the foam has a cooling effect on the surface.

(4) The water vapor produced by the heating and evaporation of foam has the effect of diluting the oxygen concentration in the combustion zone.

Application

Foam fire extinguishing agents are mainly suitable for fighting fires involving non-water-soluble flammable and combustible liquids and general solid substances (such as fires flowing from oil tanks into the fire dike or fires involving flammable liquids leaking from rotating machinery, etc.), as well as fires in confined Spaces like warehouses, aircraft hangars, basements, underground passages, mines, and ships. When there is a leakage in the storage tanks of cryogenic liquids such as liquefied natural gas, high-expansion foam can also be applied to prevent vapor evaporation and fire.

Due to its low specific gravity and good fluidity, under the action of the airflow that generates foam, it can be transported to a certain height or a relatively distant place through appropriate pipelines to extinguish fires.

When an oil tank catches fire, the upward air flow above the tank has a strong lift force, while the specific gravity of the foam is very small and cannot cover the oil surface. Therefore, high-expansion foam fire extinguishing agents cannot be used to put out oil tank fires. However, for fires involving a small amount of water-soluble flammable liquids stored indoors, total flooding can sometimes be used to extinguish them.

When using high-expansion foam to extinguish fires, it is important to ensure that the gas entering the high-expansion foam generator does not contain burned gas, smoke dust or acidic gas to avoid damaging the foam.

Protein foam fire extinguishing agent: It is mainly used to fight fires of general non-water-soluble flammable and combustible liquids, and can also be used to fight fires of general combustible solid substances. Due to its excellent thermal stability and covering performance, it is also widely used in fire extinguishing of oil storage tanks or spraying foam into unlit oil tanks to prevent the radiation heat from nearby burning oil tanks from igniting. When using protein foam to rescue crude oil and heavy oil storage tanks in case of fire, be cautious of possible oil foam boiling over or splashing.

Fluoroprotein foam fire extinguishing agent: Mainly used for fighting various non-water-soluble flammable and combustible liquid fires and some flammable solid fires. It is widely used for extinguishing fires in large storage tanks (submersible injection), bulk warehouses, conveying and transfer facilities, production and processing facilities, oil terminals and aircraft fires, etc.

Water-forming foam fire extinguishing agent: It is suitable for extinguishing hydrocarbon Class A and B fires, such as fires involving petroleum products, fuel oil, gasoline, flammable materials, etc., as well as for fighting large oil tank fires by 'submersible injection'. It is currently the most widely used foam fire extinguishing agent in domestic oil fields, oil depots, airports, underground garages, ships, docks and other places.

Alcohol-resistant foam fire extinguishing agent: Mainly used for fighting fires of general water-soluble flammable liquids such as ethanol, methanol, acetone and ethyl acetate, as well as fires of general solid substances. It is a kind of foam fire extinguishing agent that must be adopted by chemical units, coating units, pharmaceutical factories and units storing various dangerous chemicals.

High-expansion foam fire extinguishing agent: It features a high foaming ratio, strong sealing property, high fire extinguishing efficiency, and easy removal after fire suppression. In combination with high-expansion foam generation devices, total flooding and coverage methods can be adopted to extinguish Class A and Class B fires, effectively controlling the flowing fires of liquefied petroleum gas and liquefied natural gas, and having good permeability to Class A fires. High-expansion foam fire extinguishing agents can quickly fill large fire areas and are mainly used in solid material warehouses, flammable liquid warehouses, industrial plants (or workshops) with fire hazards, underground construction projects or underground tunnels.