Fire fighting foam is a collection of small, compact and stable bubbles that have a lower density than hydrocarbon compounds and therefore float on most hydrocarbons and non-polar solvents and while covering the surface of the burning liquid, they extinguish the fire. Foam bubbles in firefighting foams are composed of three substances: water, foam concentrate and air. When these three ingredients are mixed in the right proportion, they form a homogeneous coating of sticky and resistant bubbles.
Foam solution, which is also known as premixed solution, is a suitable combination of water and foam concentrate. A ratio of 3% means that 3 parts foam concentrate is added to 97 parts water to make 100 parts foam solution.
In extinguishing fires caused by the ignition of crude oil and its derivatives, fire extinguishing foams are one of the most effective and efficient fire extinguishing materials that help to manage and reduce the damages of some of the hardest possible fires, i.e. huge oil fires. Unfortunately, some fluorocarbon compounds (PFAS – Poly Fluoro Alkylated Substances) in firefighting foams, especially AFFF foams, have turned them into very dangerous chemicals for firefighters and pollute the environment, which makes the use of these materials It has been banned or restricted in many parts of the world, and the effort to replace such foams with environmentally friendly categories continues.
For many years, foam has been used as an effective material in extinguishing oil fires. Unlike other extinguishing agents (such as water, dry chemical powders, CO2, etc.), a stable aqueous foam can extinguish the fire caused by the ignition of hydrocarbon materials with the mechanism of cooling and isolating the source of the flame and finally “suffocating” the fire. If water is used as an extinguishing agent on the hydrocarbon, due to the weight of the water compared to the hydrocarbons, the water will sink to the bottom of the hydrocarbon and will have little effect on extinguishing or covering the vapor. If the temperature of the fuel reaches above 100 degrees Celsius and in this case water is used as an extinguishing agent, the water boils under the surface of the fuel and is thrown around (Boil Over phenomenon), which is actually the process of extinguishing the fuel. out of control and spreads the fire. For this reason, foam remains the primary fire extinguishing agent for all hazards arising from the ignition of hydrocarbons in which they are transported, processed, stored or used as an energy source.
What are the primary ingredients of firefighting foam?
In general, firefighting foams are produced from materials such as water, various solvents, chemical foaming compounds, pigments, etc. Some of these materials are mentioned below:
Diluents: The main ingredient in diluting foam is water.
Solvents: Different types of solvents are used in the production of fire fighting foams. The largest amount of solvents is usually used in the production of chemical foams, especially AFFF firefighting foam. In AFFF floors, a high percentage of glycol ether compounds are used, which are environmentally destructive solvents. This category of chemical solvents, apart from the toxic effects on the environment, is also harmful to the health of firefighters and should be Be careful not to touch the body.
Surface active substances: Surfactants or surface active substances are other chemical substances that are usually widely used in firefighting foams. These compounds are the basic ingredients and the main substance for creating bubbles in chemical foams, especially AFFF foam. AFFF firefighting foam usually contains a large amount of different categories of chemical surfactants.
Hydrolyzed proteins: Protein compounds are one of the most amazing ingredients used in firefighting foams. These compounds, which are produced from the hydrolysis of plant seeds or animal compounds, were used as the first natural foaming materials in firefighting foams. The hydrolysis of plant seeds and animal materials containing natural protein compounds creates a foaming substance with tiny bubbles and very resistant to heat, which practically plays the same role as the chemical surfactants in AFFF foams against fire. It is interesting to note that while natural protein materials are completely environmentally friendly and do not cause any toxicity or harm to firefighters, these materials have far better stability and resistance in fire performance. relative to Chemical surfactants in AFFF foams. Therefore, according to international standards, the minimum duration of resistance of AFFF foams to heat and fire return should be 10 minutes, while for FP and FFFP protein foams, this time is at least 15 minutes. Apart from the very good resistance of these materials to heat, the presence of high solids in protein foams (about 45%) compared to AFFF foams (about 5%) makes protein foams heavier, and as a result, the possibility of better throwing by foam monitors. It is for extinguishing tanks.
Firefighting foam is usually divided into two general categories:
Fire fighting floors are divided according to various factors. For example, factors such as chemical structure, manufacturing method, degree of expansion and concentration, fire class that can be extinguished, etc., all play a role in this division. However, for the sake of simplicity, firefighting foams are classified into two general categories: protein and chemical. It should be noted that nowadays, due to the discussions and destructive effects of chemical compounds in firefighting foams, especially “ether solvents and fluorocarbons”, the production of chemical foams, especially “AFF foam”
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