Yes, screw pumps are positive displacement (PD) pumps.
Positive displacement pumps move fluid by trapping a fixed volume and forcing it through the pump. Screw pumps operate exactly this way:
Trapping Mechanism – The rotating screws create sealed cavities between the screw threads and pump casing.
Fixed Displacement per Rotation – Each turn of the screw moves a set volume of fluid from suction to discharge.
Flow Independent of Pressure – Unlike centrifugal pumps, flow rate remains nearly constant even as pressure changes (though slip can occur at very high pressures).
| Feature | Screw Pump (PD) | Centrifugal Pump (Non-PD) |
|---|---|---|
| Flow Type | Smooth, continuous | Pulsation-free but pressure-dependent |
| Viscosity Handling | Excellent for thick fluids (oil, sludge) | Loses efficiency with high viscosity |
| Pressure Sensitivity | Flow remains steady under pressure changes | Flow drops sharply as pressure rises |
| Self-Priming | Yes (good for suction lift) | No (requires priming) |
✔ Handles high-viscosity fluids (e.g., asphalt, syrup).
✔ No internal valves (unlike reciprocating PD pumps).
✔ Low shear (gentle on sensitive fluids like food or polymers).
✔ Multiphase capability (can pump liquids with gases or solids).
Gear Pumps: Screw pumps offer smoother flow and handle abrasives better.
Piston Pumps: Screw pumps have no valves and require less maintenance.
Progressive Cavity Pumps: Twin/triple-screw pumps handle higher pressures.
Would you like details on a specific screw pump application (e.g., oil, food, wastewater)?
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