Fire suppression foam is comprised of three parts: foam concentrate, water, and air. When mixed correctly, these parts form a homogeneous foam blanket that extinguishes flames by the combined mechanisms of cooling, separating the flame source from the product surface, suppressing vapors, and smothering. This makes foam suppression systems an effective option for protecting flammable and combustible liquids.
Firefighting foam is a foam used for fire suppression. Its role is to cool the fire and to coat the fuel, preventing its contact with oxygen, resulting in suppression of the combustion. Fire-fighting foam was invented by the Russian engineer and chemist Aleksandr Loran in 1902.[1]
The surfactants used must produce foam in concentration of less than 1%. Other components of fire-retardant foams are organicsolvents (e.g., trimethyl-trimethylene glycol and hexylene glycol), foam stabilizers (e.g., lauryl alcohol), and corrosion inhibitors.
Low-expansion foams have an expansion rate less than 20 times. Low-expansion foams such as AFFF are low-viscosity, mobile, and able to quickly cover large areas.
Medium-expansion foams have an expansion ratio of 20–100.
High-expansion foams have an expansion ratio over 200–1000. They are suitable for enclosed spaces such as hangars, where quick filling is needed.
Alcohol-resistant foams contain a polymer that forms a protective layer between the burning surface and the foam, preventing foam breakdown by alcohols in the burning fuel. Alcohol-resistant foams should be used in fighting fires of fuels containing oxygenates, e.g. MTBE, or fires of liquids based on or containing polar solvents.
Chemical Foam Fire Extinguishing System is considered obsolete and has generally been replaced by Air Foam Fire Extinguishing System. Being intended primarily for Flammable Liquids, Air Foam Fire Extinguishing System is installed at agencies, producers and storage site of explosives and combustibles. The system comprises Water Source, Fire Pump, Air Foam Concentrate, Proportioner, Foam Maker, Foam Discharge Outlet Control Panel, Pipe, Electric Wire, etc.
A variety of Foam Discharge Outlet is provided to meet any shape of Hazard, conditions of location, etc. The system is divided into the following types.
- Air Foam Chamber
- Air Foam Nozzle
- Air Foam Spray Head
- Subsurface Foam Injection
- Air Foam-Water Monitor Nozzle
- High Expansion Foam Generators
Air Foam Concentrate is made into a fixed ratio of Air Foam Solution by mixing with water flowing through Feed Pipe and is mechanically stirred by Foam Maker which sucks air and generates great deal of Air Foam to extinguish a fire involving flammable liquids with smothering and cooling effect.
Air Foam Concentrate makes fine foams with excellent stability and thermal resistance, and freely flows and develops on liquid surface such as petroleum to promptly extinguish a fire. It also sticks firm to a solid surface, level or vertical, to prevent the fire from spreading.
Of the Fixed Air Foam Fire Extinguishing System, Air Foam Chamber and Subsurface Foam Injection are intended mainly for extinguishing a fire set on Exterior Storage Tanks, and Air Foam Spray Head for Flammable Liquid Hazards.
Air Foam Nozzle is used as Supplemental Air Foam Hydrant for Exterior Storage Tanks or as Air Foam Hydrant for Flammable Liquid Hazard. Air Foam Monitor Nozzle is provided near the inlet port of Exterior Storage Tanks and particularly on a quay or a pier for extinguishing a fire set on oily outflow on the sea.