Not surprisingly, the further development of foam compounds also affects the proportioning technology. In addition to the trend to use ever more highly concentrated foam compounds and thus to reduce the proportioning ratio, fluorine-free foam compounds pose new challenges for proportioning technology due to their generally higher viscosity.
Impacts on the proportioning technology
In premixing systems, water (so-called motive water) is used to generate a vacuum in the admixing unit through which foam concentrate is fed to the extinguishing water on the suction side. The accuracy of the systems is heavily influenced by the viscosity of the foam compound. In the worst case, the foam compound cannot be added at all.
In pressure proportioning systems, a separate foam pump is used to suck the foam compound out of the canister or the foam tank installed in the vehicle. The pressure is increased so that the foam compound can be added to the extinguishing water at the discharge outlet. These systems are also influenced by the viscosity, as the maximum amount of foam compound is no longer reached or, depending on the system, the accuracy of the proportioning also decreases.