Although pump cavitation is a common occurrence in industrial pumps, avoiding this phenomenon and the destruction it causes is easily avoidable.
Cavitation can be extremely destructive to a pump’s internal components, prematurely shortening the lifespan of your equipment and hindering its productivity.
Learn more about what causes pumps to cavitate and how you can maximize the investment of your industrial pump by preventing cavitation with our tips.
What causes pump cavitation?
Pump cavitation is essentially the accumulation of bubbles around an industrial pump’s impeller (the rotary component which increases or decreases the pressure of the liquids). This happens while liquid is moving through the pump. During this movement, when the liquid’s bubbles burst or collapse, it creates a small energy shock wave in the liquid.
Over time, this causes the pump’s impeller, and/or other components to become eroded.
Pump cavitation occurs when a pump is unable to keep up with the incoming flow of collapsing bubbles, which causes pumping capacity to decrease and the potential for overflow.
Cavitation degrades the pump’s performance, resulting in flow rates and discharge pressures that fluctuate. Not only does this affect productivity, its extremely destructive to a pump’s internal components.
The cumulative effect of the pits created by the collapsing bubbles weakens and destroys a pump’s impeller. It can also cause excessive pump vibration, which damages the pump’s bearings, wearing rings, seals and other components.
Cavitation should not be confused with another phenomenon called air entrainment.
Air entrainment occurs when air is allowed to enter the pump on its suction side and expands as it enters the impeller’s eye. This often reduces the flow of the pump, causing vibration and leading to damage to bearings and seals.
Unlike cavitation, this problem can be easily fixed by identifying air leaks and fixing them.
Types of pump cavitation
There are five types of pump cavitation, and each type occurs in a unique way. It is important to understand the cause of each type of cavitation so you can prevent it from damaging your industrial pump.
The five types of pump cavitation include:
- Turbulence – If components of your pump system such as pipes, filters or valves aren’t adequate for the type or amount of liquid you’re pumping, vortexes are created, causing the liquid to become turbulent, due to the different pressures within the pump.
- Vaporization – This is known as the classic type of cavitation, and happens when the pump imparts velocity to the liquid when it passes through the eye of the impeller. If the impeller isn’t working correctly, the liquid becomes vaporized, which creates shock waves in the pump’s components.
- Vane syndrome, or “Vane passing syndrome” – This occurs when the impeller’s diameter is too large, or the coating on the housing is too thick. Both of these occurrences create less space in the housing. The small amounts of free space within the housing increases the velocity in the liquid, lowering the pressure. The lowered pressure then heats the liquid, which creates cavitation bubbles.
- Air aspiration cavitation – If the pump has failing valves, air can be sucked in through the faulty valves or joint rings. As the liquid moves through the pump, air bubbles form, which in turn pop and create shock waves within the pump. This is a very common form of cavitation.
- Internal re-circulation – When this form of cavitation occurs, the pump is not able to discharge at the proper rate, causing the liquid to be re-circulated around the impeller. This causes the liquid to travel through low and high-pressure zones, resulting in heat and high velocity, causing vaporized bubbles. A common culprit of this form of cavitation is when a discharge valve has been closed while the pump is running.
How can I tell if my pump is cavitating?
There are a few telltale signs that your industrial pump is cavitating. Some of them include:
- Vibrations that cause noise
- A fluctuating discharge in pressure, flow rate, or pump motor current
- Movement of pump
- Irregular power consumption
How can I prevent pump cavitation?
Several changes in the pump’s system design may need to occur to avoid cavitation. One common fix is to increase the Net Positive Suction Head Available (NPSHA) above the Net Positive Suction Head Required (NPSHR).
To do this, you must increase the suction to the pressure of the pump.
For example, if the pump is taking suction from an enclosed tank, either raising the level of the liquid in the tank or increasing the pressure in the space above the liquid increases suction pressure.
The NPSHA should always be one to two feet above the SPSHR.
Other tips to consider to avoid pump cavitation include:
- Pumping water at the appropriate level, as pumping water too high can create cavitation issues
- Sizing the pump to the application is critical – Axiom’s experts can help you choose the right size
- The right size of suction screen is very important – a partially clogged screen can cause cavitation
Check out our YouTube channel for more tips on maintaining and getting the most out of your industrial pump.
At Axiom Equipment Group, we offer customers the option to trade and/or return your equipment as you need, and offer several industrial pump sizes and combinations to fit your application’s needs.
Our experienced team has decades of combined experience in equipment rental, sales and service.
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