What is cavitation in my pressure washer?
Monday, 4 November 2019 | Ben Marriott
In 1754 Swiss mathematician Leonhard Euler postulated that cavitation was a physical phenomenon which occurs when the oxygen suspended in a liquid implodes, in our application this can be felt as vibration in the machines hoses and lance.
Rapid changes in areas of low pressure (suction hose) cause the formation of small vapour filled cavities when subjected to high pressure these bubbles collapse creating a shock wave or vibration which causes surface fatigue to metal components. This damage is specifically evident on a pumps intake valves.
Cavitation is perhaps one of the biggest problems faced by the high pressure pump, most issues can be avoided with regular checks and preventative maintenance.
WHEN DOES CAVITATION OCCUR?
When pressure drops, the fluid tends to expand in volume. This is the basic principle of any pumping system, so a fluid placed in two environments at different pressures tends by its very nature to expand to compensate for this Δ, moving from the higher-pressure environment to the lower-pressure environment. In practice, the Δ pressure generates a downward movement of the fluid, then a rise, and in short, pumping.
However, when the pressure is lowered beyond a certain threshold, the fluid expands so much that it passes from the liquid to the gaseous state, in the form of bubbles (real cavities) containing vapour. This can have very negative consequences on both the pump and the machine.
In a pumping system, the causes of cavitation can vary:
In case of cavitation, the vapour bubbles rise from the suction pipe towards the diaphragm pump, where they undergo a drastic increase in pressure (in practice they are crushed violently) and this causes a violent implosion, recognisable by a characteristic noise, i.e. as if gravel was passing through the pump.
These violent shocks lead to a significant erosion of the components of the pump, which can cause valve rupture, diaphragm tearing, and even real head fractures.
CAN CAVITATION BE AVOIDED?
Yes, to prevent cavitation it is necessary to ensure that the negative pressure on the suction line never exceeds the limits set by the pump. This is achieved:
Regular maintenance is always highly recommended to avoid problems and malfunctions, and to extend the life of your pumps.