Short Answer:
Yes, most centrifugal pumps require priming to remove air/gas from the suction line and impeller before startup. However, self-priming centrifugal pumps can evacuate air and create a vacuum to draw fluid without manual priming.
Centrifugal pumps work by accelerating liquid outward using an impeller. Air or gas is much less dense than liquid, so the pump cannot generate sufficient suction pressure if air is present.
Without priming:
The impeller spins but only moves air (cavitation risk).
No liquid flow occurs (dry running damages seals/bearings).
Pump overheats and loses efficiency.
Priming is needed if:
✔ The pump is above the liquid source (suction lift condition).
✔ The suction line has air pockets (e.g., after maintenance).
✔ The fluid has entrained gases (e.g., volatile liquids).
Exceptions (No Priming Needed):
Submerged pumps (e.g., in a well or tank).
Self-priming centrifugal pumps (designed to evacuate air).
Flooded suction (pump below liquid level, with a fully filled suction line).
Fill the Pump Casing & Suction Line
Pour liquid into the pump until it overflows (vent air via bleed valves).
Close vents and start the pump.
Use a Foot Valve & Priming Chamber
A foot valve (check valve) at the suction inlet prevents backflow.
A priming reservoir keeps the pump flooded.
Vacuum Priming (for large systems)
Use a vacuum pump to remove air from the suction line.
Contain a reservoir that traps liquid to recirculate and eject air.
Automatically re-prime if air enters the system.
⚠ Cavitation – Vapor bubbles form and implode, damaging the impeller.
⚠ Dry Running – No liquid cools seals/bearings, causing overheating.
⚠ Reduced Efficiency – Air pockets disrupt flow, lowering performance.
Install a self-priming centrifugal pump.
Use a flooded suction design (pump below liquid level).
Add an automatic priming system (e.g., ejector or vacuum pump).
Most standard centrifugal pumps require priming, but self-priming models or submerged pumps do not. Always ensure the pump and suction line are air-free before startup to prevent damage.
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