Structure and operation
A foam-based system consists of:
- pump station with a water tank;
- tank with foaming agent concentrate;
- proportioner;
- distributing pressure pipelines;
- substation with control-alarm valves;
- distributing pipelines;
- foam generators.
When the firefighting starts, the AFFF concentrate is mixed with water in the proportioner. This device is responsible for maintaining constant pressure of the foaming agent in the system. Then, the mixture flows through the distributing pipeline to a section where the fire has been detected. In foam generators, the foaming agent is mechanically aerated and is released onto the burning objects as foam.
The foam-based system can be designed and made to generate light, medium or heavy foam. Light foam totally fills large facilities, such as production or storage areas, in a very short time. Heavy foam, on the other hand, forms a film of the surface of the burning materials, cutting off the oxygen supply and reducing the temperature. Heavy foam is used mainly to extinguish burning liquids, such as gasoline or solvents.
In facilities with foam-based systems, the fire is detected by an external system. The fire alarm is sent immediately, and the foam system can be activated electronically, pneumatically, hydraulically or manually.
