Various types of foam proportioners for precisely proportioning foam concentrate in the water-stream of an extinguishing system can be used. The choice of proportioner depends on a number of factors: the type of extinguishing system, the required capacity, and the available energy, space (inside/outside/size) and pressure.
The ‘around-the-pump’ proportioner is a foam concentrate proportioning unit designed for connec- tion in a by-pass between the pressure and suction side of the fire water pump. This system diverts a small part of the feed water flow through the APP, with a negligible effect on the fire water line pressure. The proportioner inducts a rich solution which becomes the required proportion in the main stream. Commonly used in marine applications, ‘around-the-pump’ inductors are also used on specialised foam trucks or fixed systems where a dedicated water pump is available.
