CAVITATION IN PUMPS

When the liquid flows through a centrifugal or axial flow pump, the static pressure (suction pressure) at the eye of the impeller is reduced and the velocity increases. There is therefore a danger that cavitation bubbles may form at the inlet to the impeller.

- Local pitting of the impeller can result when the bubbles collapse on a metallic surface
- Noise is generated in the form of sharp cracking when cavitation takes place.

Cavitation will not occur if critical cavitation number is greater than cavitation available. Every pump has a critical cavitation number which can only be determined by testing to find the minimum value of NPSH before cavitation occurs.