PositiveDisplacementVerfahren

Positive displacement pumps are a class of pumps that move fluid by trapping a fixed volume and delivering that exact amount with each pumping cycle. The flow rate is primarily determined by the pump speed and the displacement per cycle, making these pumps well suited for precise dosing and high-pressure delivery. Unlike dynamic pumps, their discharge pressure can vary with system resistance, but the pumped volume per cycle remains essentially constant.

The main types are reciprocating pumps and rotary pumps. Reciprocating pumps use a piston, plunger, or diaphragm to trap and push fluid through one or more valves, delivering highly controllable volumes. Rotary pumps include gear, lobed, vane, crescent, and screw designs, in which rotating elements trap and move fluid between suction and discharge ports. Materials and sealing technologies are chosen to suit the pumped fluid, with common wetted parts made of steel, ductile iron, or polymers.

Key characteristics include the ability to handle highly viscous or entrained-fluid mixtures, good suction performance, and the potential for steady, high-pressure output at low to moderate speeds. However, flow can be pulsatile in many designs, and wear of seals and valves requires regular maintenance. Efficiency depends on design, clearances, and fluid properties, and some configurations tolerate cavitation poorly at high speeds.

Common applications span chemical processing, oil and gas, hydraulic systems, and precise dosing in pharmaceuticals and food and beverage industries. See also centrifugal pumps, metering pumps, and diaphragm pumps for related technologies.