Definition
A positive displacement pump traps a fixed volume of liquid within a chamber during each operating cycle (using gears, pistons, diaphragms, or similar mechanisms) and physically forces that trapped volume through the system, producing flow that stays largely constant regardless of system pressure, unlike a centrifugal pump's pressure-dependent output.
Key facts
- Traps and physically moves a fixed volume per cycle, distinct from a centrifugal pump's kinetic-energy-to-pressure conversion.
- Flow rate remains relatively constant regardless of system pressure, following the cycle rate rather than a pressure-dependent curve.
- Well suited to high-viscosity fluids, metering applications, or where precise, pressure-independent flow is required.
- Requires relief protection against excessive pressure buildup, since it will continue forcing fluid even against a blocked outlet.
How does Positive displacement pump work or appear?
A positive displacement pump works by trapping a fixed quantity of liquid within an enclosed space (between gear teeth, within a piston chamber, or under a moving diaphragm) and then mechanically forcing that trapped volume out through the discharge, repeating each cycle to produce a flow rate tied directly to the operating speed.
What should technicians inspect for Positive displacement pump?
A centrifugal pump's flow output varies with system back-pressure along a characteristic curve. A positive displacement pump instead delivers a nearly constant flow rate regardless of pressure, since it physically displaces a fixed volume each cycle: well suited to precise metering or high-viscosity fluids, but requiring pressure-relief protection since it will keep forcing fluid even against a blocked discharge.
FAQ
Frequently asked questions
What conveying principle does a positive displacement pump use?
It traps a fixed volume of liquid per cycle and physically forces it through the system, producing flow largely independent of system pressure: well suited to metering and high-viscosity applications.
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