Liquid ring pump cavitation happens when pressure inside a liquid ring pump becomes low enough for the service liquid to vaporize. Those vapor pockets can then move into higher-pressure regions, collapse, and strike internal surfaces. The result may be noise, vibration, reduced vacuum performance, and eventual cavitation damage.
At Provac Sales, Inc., we approach cavitation in liquid ring equipment by looking closely at operating conditions. A liquid ring vacuum pump depends on the relationship between suction pressure, vapor pressure, service liquid supply temperature, flow rate, and the pump's load. When those conditions move outside the intended operating range, cavitation can develop.
Facilities operating this equipment can explore our liquid ring vacuum pump selection or review our broader vacuum pump inventory when evaluating equipment for a process.
How Does Cavitation in a Liquid Ring Pump Develop?
A liquid ring pump uses an eccentrically positioned impeller inside a casing containing service liquid. As the impeller rotates, centrifugal action creates a liquid ring around the casing. The changing spaces between the impeller blades and liquid draw process gas through the pump's suction, compress the resulting mixture, and move gas and liquid toward the pump discharge connection.
Our guide to how liquid ring pumps work explains this operating principle in more detail.
Cavitation begins when local pressure drops below the vapor pressure of the liquid. Vapor cavities form and travel toward higher pressure regions, where they collapse back into liquid. This cyclic action can produce noise and erosion damage.
In a liquid ring vacuum pump, flashing inside the compression process can become especially important because the service liquid itself is part of the vacuum-generating mechanism.
Why Does Service Liquid Temperature Affect Cavitation?
Service liquid supply temperature directly affects vapor pressure. As water temperature increases, its vapor pressure also increases. NIST vapor-pressure data demonstrates this temperature-dependent relationship.
Water is a common service liquid and, in many applications, the most common service liquid. When warmer water is used, the pump reaches the service liquid's boiling point at a higher absolute pressure. This reduces the margin between the pump's suction pressure and the vapor point.
That explains why the hottest month of the year can reveal pump cavitation that was not apparent during cooler conditions. Colder service liquid can provide more operating margin before vaporization begins.
The service liquid utilized must still match the application. Some systems utilize water, while properly configured processes may utilize oils or other fluids. Vapor pressure, chemical compatibility, viscosity, temperature, and equipment requirements all need consideration.
You can also review our liquid ring vacuum pump overview for additional information about seal fluid and liquid ring operation.
What Are the Leading Causes of Liquid Ring Pump Cavitation?
Several conditions can contribute to cavitation in liquid ring operation:
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Service liquid inlet temperature that is too high
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Incorrect service liquid supply or insufficient flow rate
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Pump's suction pressure approaching the service liquid's vapor pressure
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Very low suction load that allows the pump to pull an excessively deep vacuum
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A recycle line returning hot service liquid without adequate cooling
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Restrictions that create abnormal pressure drops at the pump's suction
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Incorrect seal fluid for the operating pressure and temperature
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Process changes that reduce non-condensable gas entering the pump
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Restrictions around the pump discharge connection or the pump's ports
The pump's discharge temperature and pump outlet temperature are also useful measurements. Rising outlet temperatures may indicate that the pump's service liquid is accumulating heat.
Noise is another warning sign. Our vacuum pump noise and cavitation troubleshooting guide covers symptoms such as crackling, vibration, pressure changes, and internal erosion.
How Can You Prevent Cavitation in Liquid Ring Vacuum Systems?
The goal is to prevent the service liquid from reaching conditions where it can vaporize inside the pump.
Important operating checks include:
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Measure supply temperature at the service liquid inlet.
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Confirm the required service liquid flow rate.
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Monitor the pump's suction pressure.
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Track the pump's discharge temperature and outlet temperatures.
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Check the pump's suction load at normal and lowest load conditions.
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Inspect the recycle line and cooling system.
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Verify that the pump discharge connection is unrestricted.
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Compare operating pressure with the pump's specified operating range.
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Maintain an appropriate safety factor between operating conditions and the corresponding boiling point of the service liquid.
In certain properly engineered systems, an air bleed or another non-condensable gas source may be used to prevent the pump from reaching an unnecessarily deep suction pressure when suction load becomes very low. Because adding air or other gases changes the pump's load and vacuum performance, this approach should only be applied when appropriate for the process.
Proper maintenance is equally important. Our vacuum pump maintenance guide provides additional guidance for maintaining reliable pump operation.
What Does a Simple Cavitation Example Look Like?
In the example below, consider a water ring system operating correctly during cooler weather.
The service liquid supply temperature increases as seasonal temperatures rise. At the same time, the suction load decreases. Because the pump pulls toward its deepest suction pressure at the lowest load, internal pressure approaches the warmer service liquid's corresponding boiling point.
The liquid begins to vaporize inside the pump. Vapor pockets develop as the impeller moves through the low-pressure portion of the process. Those pockets then enter higher-pressure regions and collapse.
The process repeats, creating cavitation.
Depending on the system, correction might involve colder service liquid, restored seal liquid flow, improved cooling, changes to the suction load, or a correctly designed air bleed.
How Can You Tell Cavitation From Other Pump Problems?
Cavitation symptoms may resemble other failure mechanisms. Bearing wear, restrictions, alignment problems, foreign material, inadequate liquid supply, and mechanical damage can also produce noise or vibration.
Before changing operating conditions, record:
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Vacuum or suction pressure
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Service liquid temperature
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Seal fluid flow
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Suction load
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Pump discharge pressure
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Pump's discharge temperature
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Outlet temperatures
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Process conditions when the noise occurs
Evaluating cavitation with operating data helps determine whether vapor pockets are actually forming or whether another failure mechanism is responsible.
If internal damage is suspected, our pump repair services can help assess the equipment. You can also request a pump repair evaluation or use our repair authorization portal when equipment needs to be sent to Provac.
How Can Provac Help Protect Your Liquid Ring Pump?
At Provac, our goal is to help customers keep vacuum equipment operating reliably instead of simply addressing symptoms after damage occurs.
If a liquid ring pump begins producing unusual noise, losing vacuum performance, or showing signs of cavitation damage, we can help evaluate the operating conditions and equipment. Inspection can determine whether the impeller, internal surfaces, bearings, seals, or other components require attention.
Correcting the root operating condition is just as important as repairing damaged parts. Monitoring vapor pressure, service liquid temperature, suction pressure, flow, and pump load can adequately protect the equipment and reduce the chance that the same cavitation process repeats.
What Are the Most Common Questions About Liquid Ring Pump Cavitation?
What Does Liquid Ring Pump Cavitation Sound Like?
Cavitation often produces crackling, popping, or gravel-like noise as vapor pockets form and collapse. Increased vibration and unstable vacuum performance may occur at the same time.
Can Hot Service Liquid Cause Pump Cavitation?
Yes. Higher service liquid temperature increases vapor pressure, reducing the pressure margin before the liquid begins to vaporize. Maintaining the correct supply temperature is therefore an important part of cavitation prevention.
Can Low Suction Load Cause Cavitation?
Yes. When the pump's suction load becomes very low, a vacuum pump may pull toward a deeper vacuum. If suction pressure approaches the service liquid's vapor point, cavitation becomes more likely.
Can Colder Service Liquid Prevent Cavitation?
Colder service liquid can increase the margin between operating pressure and the liquid's boiling point. However, temperature, flow rate, process compatibility, and the pump's specifications must all remain within the correct operating range.
Can Cavitation Permanently Damage an Impeller?
Repeated vapor-pocket collapse can cause cavitation damage such as pitting and erosion on internal surfaces. Impeller tips and other areas exposed to repeated bubble collapse may eventually require repair or replacement if cavitation continues.
Which Organizations Support These Technical Principles?
Hydraulic Institute. “What Is Cavitation?” 6 May 2024. Accessed 24 Aug. 2026.
National Institute of Standards and Technology. “Water: Antoine Equation Parameters and Vapor Pressure Data.” NIST Chemistry WebBook. Accessed 24 Aug. 2026.
