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NPSH : Pump suction performance

NPSH - Net Positive Suction Head

Fluid is entering in centrifugal pump impeller eye.

Rotation of Impeller splits fluid to outer direction.

NPSH : Pump suction performance

This fluid spliting creates pressure drop (vacuum) and suck more liquid to pump.

This suction of fluid must have pressure above vapour pressure of liquid.

If suction pressure drops below pumping fluid suction pressure then fluid starts converting to vapour bubbles.

This is called Air aspiration Cavitation


Results of Cavitation

1. Erode impeller vanes and other internal parts
2. Noise and Vibration increasing
3. Seal leakages and bearing life reduction
4. Reduction in pump efficiency and head

Minimum pressure required above its vapour pressure pressure called NPSH.

Available suction pressure is called NPSHA ( Net Positive Suction Head Available)

Required minimum suction pressure is called NPSHR ( Net Positive Suction Head Required )

Below pressure than NPSHR creates cavitation.

NPSHR < NPSHA

Suction pressure available must higher than suction required.

Suction requirement is also increasing in square proportion with increasing in flow.

NPSHR ∝ RPM²

NPSHR never be Zero in VFD Pumps

Thanks for reading - Centrifugal pump NPSH Net Positive Suction Head
Naitik Patel
Industrial Guide

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