Well To Begin With, What Is Cavitation?
It is the formation of bubbles in liquid, developed in regions of low pressure around an impeller. The reason cavitation can become damaging is the way in which the bubbles implode by releasing a small stream of water which is powerful enough to cause micro cracks in material:
- Which over the course of several months to a few years can cause serious damage to the pump.
- Which can have a severe negative impact on the performance and lifespan of a pump.
To put it into perspective, cavitation is the most commonly encountered problem for all pumping applications.
Telltale Signs That Your Pump Is Cavitating?
- Rather than an occasional rattle cavitation sounds like popping bubbles or rocks passing through the system
- Excessive vibration affecting the shaft, bearing and seals
- Small bits of materials missing off the affected parts giving it a sponge-like look
- Decreased flow
- Higher power consumption
What Are The Most Common Reasons For Cavitation?
- Insufficient Net Positive Suction Head available (NPSHa)
- Excessive pump speed
- Pipe blockage on the suction side
How To Prevent This Phenomenon?
✓ Ensure that at a given flowrate with a particular impeller size the NPSHa > NPSHr (This is where our Engineers come in):
- Correctly sizing the most cost effective and optimal pump solutions for our customers
- Increase the size of the impeller
- Increase diameter of suction pipe
- Reduce length of suction pipe
✓ Alternatively using two lower capacity pumps in parallel
Vapor pressure – measure of tendency of a material to change to a gaseous or vapor state.
→The temperature at which the vapor pressure at the surface of a liquid = pressure exerted by the surroundings is called the boiling point. The lower the surrounding atmospheric pressure inside of the pump, the sooner the vapor pressure = surrounding atmospheric pressure and thus the lower the boiling point.