What is Pump Cavitation?

If your pump is making strange and disturbing sounds, it might be a symptom of cavitation. The name "cavitation" comes from the vapor cavities (or bubbles) that form in liquid when changes in pressure occur in the flowing liquid. These liquid-free cavities or voids often form in low-pressure zones and burst during high pressure situations, sending shockwaves throughout your system and eroding the impeller surface. This can cause damage to the pump - leading to premature valve failure and decreased flow pressure.

Pump cavitation can result in unwanted noise, vibration, component damage and increased energy usage. It causes repetitive stress on critical pump parts, which shortens their overall lifespan and decreases efficiency over time, eventually leading to pump failure.

Two types of pump cavitation occur when using centrifugal pumps: suction and discharge.
Suction Cavitation

Suction cavitation occurs when a pump doesn't receive enough flow, either from being in a low-pressure environment or when there is a high vacuum. This causes bubbles or cavities to form on the eye of the impeller. As they move towards the discharge side of the pump, they compress into liquid and implode on the impeller's edge, causing low flow rates on the suction side and resulting in expansion and pressure decrease.

Suction cavitation is often caused by:

• Clogged filters or obstructed strainer
• Blockage of the pipes on the suction side
• Fluid that has been overly heated to the point of vaporization
• Bad piping design
• Pump running too far right on the pump curve
• Suction conditions not meeting NPSH (net positive suction head) requirements

Discharge cavitation

Discharge cavitation happens when the discharge pressure of the pump is too high, making it difficult for the fluid to move out of the pump. Instead it circulates at high velocities inside the pump, causing a vacuum and forming bubbles in the process. Much like suction cavitation, these bubbles can trigger shockwaves that can wear away at the impeller, even causing the impeller shaft to break completely.

Discharge cavitation is often caused by:

• Clogged filters
• Bockage of pipes on the discharge side
• Bad piping design
• Pump running too far left on the pump curve

It's essential to recognize the warning signs of cavitation and take immediate action. Here are some quick tips for troubleshooting cavitation problems:

1. Check your filters and strainers
Any clogs on either the suction or discharge side can create pressure issues inside the pump

2. Know your pump's curve
Make sure your pump is operating on its best efficiency point by using a pressure gauge or flow meter. If it operates too far left or right of its curve, cavitation will occur over time

3. Use the right pump for the application
Operate a pump best suited for the application, with the right pipe design to ensure the liquid flows correctly to and from your pump

4. Make sure the pump is not operating at high altitude
Altitude can affect pump operation - liquids boil at a lower temperature

5. Monitor fluid levels and temperature to prevent vaporization and suction

Cavitation is a common problem in pump systems but with proper sizing, design and care, damage to pumps and impellers can be avoided. If you'd like more information on how to prevent pump cavitation, call our toll-free number at 1-800- 367-4180. We have experts on hand to help you choose, install, and maintain a variety of equipment.

Sources:
https://www.mechlectures.com/cavitation-causes-prevention/
http://www.chemeurope.com/en/encyclopedia/Cavitation.html
https://www.fluidpowerworld.com/aeration-versus-cavitation/
https://news.thomasnet.com/featured/designing-equipment-to-avoid-pump-cavitation/
http://empoweringpumps.com/what-causes-cavitation-triangle-pump-components/
https://www.sciencedirect.com/topics/engineering/pump-volumetric-efficiency
https://www.flowcontrolnetwork.com/understanding-avoiding-pump-cavitation/