What is cavitation and how can you prevent it?
Cavitation is a common problem in pumps that can lead to serious damage and loss of performance. In this article, we explain what cavitation is, how it occurs, what the consequences are and how you can prevent it.
What is cavitation?
Cavitation occurs when the pressure in a liquid drops below the vapour pressure, causing vapour bubbles to form. These vapour bubbles are carried to areas of higher pressure, where they abruptly implode. These implosions generate powerful shock waves that can cause damage to the internal components of the pump, such as the impeller and pump casing.
How does cavitation occur?
Cavitation usually occurs on the suction side of the pump, where the pressure is lowest. This is where there is the greatest risk of the liquid starting to boil, which you want to prevent. Often, a combination of factors plays a role. Examples include insufficient pressure at the inlet, a liquid flowing at high speed through a pipe that is too narrow, or a temperature that significantly increases the vapour pressure of the medium. Obstructions in the system, such as dirty filters or an incorrect pipe diameter, can also disrupt the flow and thus promote cavitation. In short: it’s all about balance in the system. If one component is not right, you often pay for it with damage to your pump.
Consequences of cavitation
When vapour bubbles implode inside the pump, it is not a gentle process. The sudden collapse causes tiny shock waves that strike the inside of the pump with considerable force. This leads to damage to critical components such as the impeller and the pump housing. You will often notice this by a grinding or tapping noise, increased vibrations or a pump that suddenly delivers less than before. Efficiency deteriorates, energy consumption skyrockets and, in the long run, entire components can fail. What starts as a little cavitation can turn into serious damage and unexpected downtime, which always costs more than preventing it.
How can you recognise cavitation?
Cavitation often makes itself known early on — literally. One of the first signs is a rattling or crackling sound, as if marbles were flying through your pump. This sound is often accompanied by unexplained vibrations or fluctuations in pressure and flow rate. The pump suddenly delivers less than you are used to, without any immediate technical explanation. If you were to open the pump at that moment, you would often see the first signs of damage: pits, erosion or frayed edges on the impeller and other internal parts. These are signs that the vapour bubbles have already begun their destructive work.
How do you prevent cavitation?
Preventing cavitation starts with making the right choices in the design phase of your installation. A well-tuned system prevents a lot of trouble later on. For example, it is crucial that the available net positive suction head (NPSHa) is always higher than the minimum required by the pump (NPSHr). If this is not the case, you are already in the danger zone. You can also reduce the risk of cavitation by increasing the pressure at the pump inlet. You can do this, for example, by placing the pump as close as possible to the liquid source or by increasing the liquid level.
Temperature also plays a role: the warmer the liquid, the higher the vapour pressure and therefore the greater the risk. Furthermore, it helps enormously to use pipes with a sufficient diameter, avoid sharp bends and limit the number of fittings. Finally, keep your suction system clean and free of obstacles. A clogged filter or worn hose can be enough to cause the pressure to drop and cavitation to start.
Any questions? Just give us a call
At Van Tongeren Trading, we are happy to help you select the right pump and optimise your system to prevent cavitation. Contact us for tailored advice.