Metering liquid into water pipeline - over wide range of flow rates using flowmeter driven metering pump

摘要

In an apparatus for metering liquids into a water pipe having a flow meter driving a metering pump and a valve-controlled flow meter by-pass, a liquid storage vessel and a liquid feed pipe, (i) a further smaller flowmeter in series with the main flow meter is provided also driving the metering pump via a drive coupled via a free wheel device, (ii) the second flow meter lies in a by-pass to a valve in the water pipe, and (iii) the reduction ratio of the gears coupled to the smaller flowmeter corresponds to the volume ratio of the larger to the smaller flowmeter. Permits the metering of a liquid to water in proportionate amount on a wide range of flow rates (1:500) without incurring errors due to clearance losses in the flowmeter used to drive the metering pump.