The water motor driven proportioner can be applied to the low-expansion foam fire extinguishing system in petrochemical, wharf, hangar and other industries and fields. As the low-expansion foam system is usually a dry system (air control after the proportional mixing device), there is a process of system pressure establishment when starting, in which the system flow rate may exceed the release flow rate. At this time, the mechanical pump type proportional mixer will overspeed, so it is required that the mechanical pump type proportional mixer has a certain overflow capacity, and the overflow calculation of the system.

The F+W proportioner can run for more than 5 minutes at 15% overload flow rate to ensure that the ratio mixer cannot work due to starting overflow in the multiple foam system.