Metering pump assembly for liq. proportioning - has pump drive with pneumatic motor, whose supply is controlled in response to main liq. flow differential pressure drop

摘要

The metering pump is for the proportioning of liquids into a main stream flow. It has a drive, and in the main flow is incorporated a volumetric liquid counter. It is of particular application in explosive threatened environments. The pump drive comprises a compression air motor (5) and a control unit for the pressure air supply, responding to the dropping differential pressure at the counter (2) in the main stream flow. Pref. the control unit consists of an operating piston (18) and a valve (20) in the pressure air flow, controlled by the piston. Chambers (16) on either side of the valve controlling piston rod (19) may be coupled to the inlet or outlet side of the main flow at the liquid counter, the valve being of two-way type. The differential inlet and outlet pressure may be held almost at zero value. The coupling (4) between the counter and motor may be kept without force by pressure air supply control to the motor in response to dropping differential pressure at the counter.