This Cavitation effect on the pump can cause damage on the casing and impeller.
During Cavitation, a liquid/vapour mixture of varying density is produced.
This results in fluctuations in pressure (caused by the liquid column being drawn in), and causes fluctuations in the discharge pressure, pump power absorbed (shown on the ammeter), and hence pump revolutions.
Centrifugal Pumps - Cavitation
When the pressure falls below the vapour pressure of the liquid at a given temperature, boiling occurs and small bubbles of vapour are formed. These bubbles will grow in the low-pressure area and implode when they are transported to an area of pressure above vapour pressure. The term given to this local vaporisation of the fluid is Cavitation.
