Cavitation is one of the most common problems for centrifugal pumps. If you’ve been hearing excessive noises from your pump during use, chances are high that the reason is cavitation. Cavitation can be costly and destructive as it results in high energy consumption and damage to the pump when not controlled.
What is pump cavitation?
Cavitation is simply the creation and buildup of bubbles or cavities in a liquid being transported through or around a pump system. The bubbles form in areas of relatively low pressure around the pump’s impeller, and when these tiny bubbles burst, they trigger intense shockwaves that cause vibrations in the pump. Due to the sheer number of bubbles that create these shockwaves, significant damage and premature wear can occur to the impeller and other parts of the pump, such as its housing and seals.
Types of pump cavitation
There are several common ways pump cavitation occurs, so it’s important to look at them when considering ways to reduce the problem.
This is the most common form of pump cavitation. It is also known as “classic cavitation” and happens when a pump exerts velocity on a liquid as it goes through the eye of an impeller that isn’t functioning well. When this happens, some of this liquid is vaporized and results in the creation of cavitation shockwaves.
2. Vane Syndrome
This type of cavitation also is referred to as Vane Passing Syndrome. It occurs when an impeller has a much larger diameter than required or when the housing has a very thick coat. Both of these conditions create less space within the housing, and this results in increased liquid velocity. The high liquid speed then leads to low pressure, which heats up the fluid and causes the formation of cavitation bubbles.
If parts of the system such as valves, pipes, and filters are inadequate or unfit for the type of fluid you are pumping, the liquid can become unstable because of pressure differences throughout the system. This turbulence leads to the creation of shockwaves and vibrations that can eat away at solid materials over time.
4. Internal re-circulation
In this type of cavitation, a pump cannot discharge at the required rate, and this results in the liquid re-circulating around the impeller. The liquid encounters pressure differences in the system, leading to heating and high velocity that cause the formation of vaporized bubbles.
5. Air aspiration cavitation
This form of cavitation occurs when air is sucked into the pumping system through weak points such as joint rings or worn out valves. When the air gets into the system, it has no other way of getting out and ends up forming bubbles in the liquid. When the bubbles burst due to pressure from the impeller, cavitation occurs.