Centrifugal pumps add velocity to a liquid and convert that velocity into pressure. Positive displacement pumps trap a defined volume and move it from inlet to outlet. That difference shapes how each design responds to viscosity, pressure and control.
Flow and pressure behaviour
A centrifugal pump’s flow changes with system resistance, speed and impeller diameter. A positive displacement pump delivers approximately fixed volume per cycle, so its flow is more directly related to speed. It can build dangerous pressure against a closed discharge and normally requires relief protection.
Liquid properties
Centrifugal pumps are widely used for clean, low-viscosity liquids at medium to high flows. Rotary positive displacement designs often retain efficiency with viscous liquids, while reciprocating types suit accurate dosing and high pressures. Abrasive solids, shear sensitivity and entrained gas require design-specific review in either family.
Making the choice
Compare efficiency across the real operating range, not only at one point. Include control valves or variable-speed drives, seal losses, pulsation, maintenance access and the consequences of dry running. The best choice is the pump whose operating envelope matches the whole process.
