Cavitation can occur when the pump suction contains air or when the pump is running faster than the designed speed
Cavitation is the formation and accumulation of bubbles around a pump impeller. This tends to form in liquids of any viscosity as they are being transported through and around a pump system. When each of these tiny bubbles collapses or bursts, it creates a high energy shock wave inside the liquid. These shock waves hit the impeller and other pump components which cause erosion over time.
Causes
> Air leakage to suction side
> Pressure in the suction side is less than the vapour pressure of that pumping liquid
> High temperature
> Throttled suction valve
> Pump running faster than the designed
> Pump taking suction lower than designed
Indication
> Decreased Flow or Pressure
> Erratic Power Consumption
> Pitting
> Noise
> Vibration
> Decrease in the pump efficiency.
How to Prevent Cavitation
> Reduce motor speed (RPMs). Note: Slowing the pump down will reduce flow rate and head pressure.
> Incorporate a booster pump into your pump system. This will take some of the stress off of your primary pump.
> If possible, reduce the temperature of your pump, liquid, and/or other components.
> Increase liquid level around the suction area.
> Always keep NPSHA greater than NPSHR