If you’ve ever heard what sounds like gravel running through your pump, you’ve probably experienced the problems that come from cavitation.
Cavitation, the formation and implosion of bubbles inside the pump head, causes more than just an obnoxious noise. Those tiny bubbles can result in thousands of dollars in repairs due to pitting on the impeller and casing, or collateral damage from the vibration of the pump. Meanwhile, the pump’s efficiencies plummet, and head pressures decrease, resulting in suffering production numbers.
In most situations, cavitation can be prevented before it ever starts. A well-designed system can ensure that the pump always has adequate NPSHA (net positive suction head available). How to you ensure a good design? The more information you have available when designing a system and selecting a pump, the better. By paying proper attention to the design of the system, particularly on the supply side, you can help avoid the leading cause of cavitation—NPSHA at the suction side of the pump. Also, by allowing for a safety margin when calculating the requirements of the system, you can prevent numerous problems.
This photo shows the impeller of an Alfa Laval LKH certifugal pump
However, even a well-designed system can fall victim to cavitation problems as unexpected variables pop up or processes change. What then?
Cavitation can be stopped by:
- Increasing the head pressure on the supply side of the pump
- Decreasing the head pressure that your pump needs, or
- Lowering the vapor pressure of the fluid you are pumping
Here is a list of suggestions:
- Raise the level liquid in the tank
- Raise the tank
- Pressurize the tank
- Lower the pump
- Reduce supply line friction losses by:
- Increasing line size coming from the tank
- Simplifying inlet piping by eliminating excess tubing and elbows
- Ensuring that supply line is unobstructed by gaskets or other debris
- Ensuring that all valves are fully open
- Lower the product temperature prior to pumping
- Install a booster pump
- Increase size of pump inlet port
- Install an inducer
- Replace high speed pump with slower speed pump
- Replace pump with higher efficiency, low NPSHR pump
Of course, every pump application is different, and cavitation can have a number of causes. If you’re still having problems, contact your pump supplier for technical support.
