Prevention of pump cavitation using condition-based monitoring

Cavitation is a common issue that can have a detrimental impact on the efficiency and reliability of pumps. However, Danfoss drives feature integrated condition-based monitoring (CBM) which provides new avenues for detecting and avoiding cavitation in pump systems. By utilizing the "drive as a sensor" approach and current signature analysis, condition monitoring can effectively identify cavitation-related faults and help prevent potential damage and wear-out.

Like other CBM functions, such as stator winding fault detection, cavitation detection is now considered part of the CBM family. This means that the same CBM infrastructure can be utilized to implement cavitation detection systems. Even drives with older CBM licenses can be upgraded to feature cavitation monitoring through a software upgrade.

Cavitation on a pump impeller
Shock waves originating from burst air bubbles create micro-pits in the metal of the pump impeller, leading to accelerated wear-out. This image shows cavitation of a pump impeller.

What causes pump cavitation?

So, how does cavitation occur and what makes it a concern for pump systems?

Cavitation happens when rapid pressure changes in a liquid medium cause vapor-filled bubbles to form. These bubbles can collapse under higher pressure, generating shockwaves that create micro-pits in the metal of the pump impeller. This leads to accelerated wear-out and erosion of the rotating blades. Additionally, the collapse of bubbles generates additional noise, knocking, and vibration, which further reduce pump efficiency by distorting the flow pattern.

It is important to note that cavitation can also impact other system components in contact with high-velocity moving fluids, including piping systems, pump components, engine housing, cylinder sleeves, HEX components, and hydro turbine components. So, early detection of cavitation in the pump along with fast remedial action can protect and extend lifespan of a whole system of components.

Cavitation signature level graph
Cavitation signature level shown as fault level versus motor speed. When cavitation occurs, it displays a characteristic "striking cobra" type curve.

How does condition monitoring protect pumps against cavitation?

Detecting and avoiding cavitation is crucial for maintaining pump performance and preventing costly damage. Condition monitoring in the form of integrated CBM in the drive offers an effective solution for achieving this. Cavitation detection can be achieved using current signature analysis in the drive, enabling sensor-less detection. Cavitation produces turbulence, creating audible noise and a distinctive signature in the motor current. By analyzing the variation in load torque, shaft speed, and motor current, condition monitoring algorithms can identify the presence of cavitation.

The algorithm compares the actual cavitation signature against user-defined threshold levels. If the values exceed the set thresholds for a predefined time, the event is flagged as cavitation.

A room of pumps
Danfoss drives with integrated CBM give you the power to detect cavitation early, and optimize the energy efficiency of pumping operations

Benefits of condition monitoring and predictive maintenance

The benefits of avoiding cavitation using condition monitoring are significant. With permanent monitoring using CBM integrated in the Danfoss drive, both the detection and avoidance of cavitation become possible. This cost-effective solution surpasses traditional sound vibration detection methods. By preventing pump wear-out and damage caused by cavitation, productivity is optimized, and component lifetimes can be extended. It becomes possible to perform predictive maintenance and this ultimately leads to a reduction in service and replacement costs.

Avoiding pump cavitation using condition-based monitoring functionality

To avoid cavitation, the flow can be reduced by lowering the pump speed in small increments. Condition monitoring enables this through an avoidance function. The motor speed is automatically lowered within predefined limits when cavitation is detected. Once cavitation is no longer detected, the function attempts to return to the set point. This avoidance function is turned off by default, and it is up to the user to decide to activate it based on their specific needs.

In summary, preventing pump cavitation is crucial for maintaining pump efficiency and reducing potential damage and wear-out. Condition monitoring, using advanced techniques such as current signature analysis, provides a reliable and cost-effective solution for detecting and avoiding cavitation. By implementing condition monitoring systems, industrial processes can benefit from improved production, extended component lifetimes, and reduced maintenance costs, ultimately leading to smoother and more reliable operations.

VLT AQUA Drive FC 202 and a pump

Edge computer based real-time motor and pump analytics

With the edge computing solution, data is collected several times per second, ensuring that any measurements outside the normal range trigger a warning, quickly and timely, thus minimizing the risk of undetected abnormalities.

Drives for pump applications

More condition-based monitoring topics

Danfoss products using condition-based monitoring

Real-world case stories using condition monitoring

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    ITALY: At Rivoira Group, VLT® drives with built-in condition-based monitoring help preserve fruit perfectly by ensuring utterly reliable refrigeration.

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  • if (isSmallPicture) { Brewing up real change at HEINEKEN; } else if (isBigColumns) { Brewing up real change at HEINEKEN } else { Brewing up real change at HEINEKEN }
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    NETHERLANDS: HEINEKEN understands that to meet demand, its production line must always be up to the task – with all assets expected to deliver a consistently reliable and excellent performance. At Den Bosch brewery, the tough working environment posed several challenges. The solution was an upgrade using drives with integrated condition-based monitoring.