Design and experimental characterization of a water-driven volumetric foam proportioning system for firefighting applications

In the firefighting field many fire protection systems, involve the mixing of extinguishing foam concentrate with water at prescribed mixing ratios in order to enhance the extinguishing performances of water alone. A wide variety of foam concentrates is available on the market and new formulations, such as fluorine-free foam concentrate (FFF), are being developed in response to environmental concerns. Some of these concentrates exhibit high, often non-Newtonian viscosity, which has forced manufacturers to adapt proportioning systems to a broad range of fluid properties. Since foam properties have a strong impact on proportioning performance, inappropriate mixing may lead to inaccurate ratios and degraded extinguishing capability. The present work aims to deepen the understanding and support the design of a foam-concentrate proportioning system for firefighting applications, capable of operating reliably across a wide range of foam-concentrate properties. The focus is placed on water-driven volumetric proportioning, a solution that offers robustness, independence from external power sources and predictable dosing behaviour.