Mixer for fire extinguisher foam - feeds main supply line reference and foam agent pipe control signals to controller whose output actuates throttling damper

摘要

The control system for foam-producing installations maintains a constant ratio of foam producing agent admixture to water flow. The water is taken from source via suction pipe by pump fitted with bypass in which a Venturi element operates as a mixing unit in the direction of arrow. Water discharged by pump flows through the Venturi element and sucks foam-producing agent from the pipe via a non-return valve. The amount of foam agent added to the water flow is controlled by signals of the throughput measuring instrument in the foam agent line and by signals from a similar measuring instrument in the main foam mixture line. Both signals are fed into controller which emits a control signal to an actuator controlling the operating position of the throttling damper in the foam agent line.