The flow direction in a centrifugal pump is determined by its design and impeller rotation. Here’s how it works:
From suction (inlet) to discharge (outlet):
Liquid enters axially through the suction nozzle (center of the impeller).
The rotating impeller flings the liquid radially outward due to centrifugal force.
The volute (casing) converts kinetic energy into pressure, discharging the liquid tangentially through the outlet nozzle.
https://www.pumpsandsystems.com/sites/default/files/styles/article_full/public/2020-03/centrifugal-pump-flow-direction-diagram.jpg?itok=ABC123 (Illustration: Liquid enters axially, exits radially/tangentially.)
The pump is designed for one primary rotation direction (marked on the casing).
Reverse rotation (wrong direction) drastically reduces flow/pressure and can damage seals/bearings.
Volute casing: Discharge nozzle is typically at a 90° angle from suction (tangential exit).
Diffuser casing: Uses guide vanes for smoother flow conversion.
In series configurations, flow passes sequentially through multiple impellers, increasing pressure.
Check rotation arrow on pump/motor nameplate.
Observe discharge pressure: A sudden drop indicates reverse flow/rotation.
Visual inspection: Flow should exit the discharge port (not leak from suction).
Causes:
Incorrect motor wiring (reverse rotation).
Discharge valve left open during shutdown (backflow).
Effects:
Low/no discharge pressure.
Cavitation risk, seal/bearing damage.
Anti-siphon valves: Prevent reverse flow after pump shutdown.
Check valves: Installed on discharge side to block backflow.
Always verify pump rotation during installation.
Use a non-return (check) valve if backflow is a risk.
Consult the pump’s manual for specific flow path diagrams.
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