Around-the-pump foam proportioning systems mix foam compound to the whole amount of water. In doing so, drive water will be diverted from the pressure outlet back into the suction inlet. There is a Venturi set in the drive water line which creates suction for the foam compound. In this way, very high foam compound outputs can be generated - especially for turret operations.
In foam operation, the water pump is flooded with a water-foam compound mixture, i.e. water-foam compound mixture can be discharged from all outlets.
After operation the pump must be flushed and drained .
Due to the Venturi principle it is not possible to use the pump in hydrant mode and to produce foam at the same time, as in this mode no suction for foam compound can be generated.
These aroud-te-pump foam proportioning systems do not require their own foam compound pump, which is why there is no additional need for maintenance.