12.3 Cavitation
Cavitation is a problem in certain devices where fluid interacts with a moving surface. It can occasionally
occur in sinusoidal pumps.
Where a surface moves through a fluid, low pressure areas are formed on the surface. The faster the
surface moves, the lower the pressure around it can become. If the static pressure of the liquid falls
below its vapour pressure, vapour bubbles form on the pressure side. These implode, causing very high,
short-term pressure peaks up to several thousand bar. These pressure peaks can cause material erosion
and are noisy.
To identify cavitation
If the pump is very noisy and vibrates vigorously, along with the pipe system attached to the pump,
cavitation is likely to be the cause.
To avoid or remove cavitation
Increasing the inlet pressure on the suction side, installing a larger diameter or shorter inlet pipe or
slowing the pump may solve the problem. Make sure that the pump is not starved of duty fluid at all
times.
l
To prevent cavitation, always ensure that NPSH
A
> NPSH
R
.
Cavitation can destroy the pump. The operator must ensure that the pump can
work free of cavitation.
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