Water additive metering device - with flowmeter driving metering pump in by pass and control element actuated by flowmeter pressure drop

摘要

A device for the feed proportioning of liquid media into the water flowing in a water main uses a motorized flow-meter to drive a metering pump. The flowmeter is arranged in a bypass to the water main and its control element. The latter is opened and closed as a function of the pressure difference across the flowmeter by a double acting piston which actuates a spool valve for a spring-loaded single acting piston on the control element. The flow meter can thus be small enough to meter correct amounts of additives even at very small flow rates in the water main when large flow-meters do not register at all.