Foam fire sprinklers
We design foam-water sprinkler systems for extinguishing flammable liquids and difficult to wet plastics. The water supply is similar to that of a water sprinkler system, but in addition there is a foaming device. The foaming agent can be added to the water in a set ratio from a tank with an internal bag or with volume pump. The method of admixture is determined by the stability of flow, volume of foam and whether periodic admixture tests are required. The foam is formed by spraying the foaming solution by the sprinkler or nozzle. The foams used are mostly the synthetic AFFF (aqueous film forming foam) type. The advantage of this foaming agent is that it forms a layer that spills over the surface of the burning liquid. If flammable liquids miscible with water, such as alcohol, are to be extinguished, AFFF-ARC foams are suggested.
Extinguishing flammable liquids
Foam sprinker systems are usually designed for flammable liquid storage. The properties of different flammable liquids vary greatly, some will ignite very easily while others may burn only barely. Compared to solids, flammable liquids have a higher rate of ignition and heat of combustion, foam sprinklers can also protect steel structures against the effects of fire.
Fire-fighting equipment shall be designed so that the extinguishing fluids drain in a predictable manner and do not cause unnecessary environmental damage.
Most flammable liquids are lighter than water. So the water used for extinguishing would sink below the burning liquid. However, the foam will form a layer on the surface and prevent air from entering.
Many flammable liquids have boiling points well above 100°C. For example, it is not advisable to extinguish burning oil with water. Water would warms up rapidly and turns into steam. And the steam spray the burning liquid into the space.
Adding wetting agent for extinguishing of plastics
When extinguishing some types of plastics, water runs down the surface without sticking to it. To reduce the surface tension of the water and thus improve wetting, AFFF foaming agent can be added to the water at 1% concentration. The extinguishing of plastics is then several times more effective.