Abstract
Positive displacement pumps operate on the principle of forcing a fixed volume of liquid from the inlet pressure zone into the discharge zone of the pump. The two basic types of positive displacement pumps are reciprocating and rotary. Whereas the total dynamic head developed by a centrifugal pump is determined uniquely by the speed at which the impeller rotates, a positive displacement pump ideally will produce whatever head is imposed on it by the restrictions to flow on the discharge side. Piston, plunger and diaphragm pumps are considered in detail as are the types of rotary pumps, viz. gear, screw, lobe, cam and vane. Applications of these pumps and suggestions for their appropriate selection are given. (P.J.B.)
