DIAPHRAGM METERING PUMPS.

A diaphragm metering pump is a reciprocating power pump that displaces a predetermined volume of liquid in a specified period. This pump is a positive-displacement machine; it is also known as a controlled-volume, proportioning or chemical-injection pump. The pump is usually driven from an outside source, which may be at a constant or variable speed. The pump contains a flexible diaphragm, one side of which is in direct contact with the process liquid. One or more diaphragms may be used, which may be flat or shaped. The diaphragm can be driven hydraulically or mechanically. The pump also contains a mechanism for changing the effective displacement. Reagent-head assemblies, valves and stroke-adjustment mechanisms are major elements in a diaphragm metering pump. These give it the feature of zero leakage, flowrate insensitivity to pressure changes, high accuracy of flow adjustment, and capability of separating the pumping chamber from the rest of the pump. Design and operational details of the diaphragm metering pump are given, including pump specifications and control.