Cavitation is a common issue that can have a detrimental impact on the efficiency and reliability of pumps. However, Danfoss variable frequency drives (VFDs) feature integrated condition-based monitoring (CBM) provides new avenues for detecting and avoiding cavitation in pump systems. By utilizing the "VFD as a sensor" approach and current signature analysis, condition monitoring can effectively identify cavitation-related faults and help prevent potential damage and wear-out.
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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 (VFDs) with older CBM licenses can be upgraded to feature cavitation monitoring through a software upgrade.
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 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 reduces pump efficiency by distorting the flow pattern.
The local implosions of cavitation bubbles can also alter the chemical properties of the liquid, producing free radicals, causing oxidation, and degrading chemical compounds. Although these effects occur in small amounts, they still result in changes to product quality—an important factor in the food and beverage or oil and gas industries.
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.
Detecting and avoiding cavitation is crucial for maintaining pump performance and preventing costly damage. Condition monitoring in the form of integrated CBM in the VFD offers an effective solution for achieving this. Cavitation detection can be achieved using current signature analysis in the VFD, enabling sensor-less detection. Cavitation produces turbulence, creating audible noise and a distinctive signature in the motor current. This turbulence is reflected in the motor current and become detected by the condition monitoring algorithm.
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.
The benefits of avoiding cavitation using condition monitoring are significant. With permanent monitoring using CBM integrated in the Danfoss VFD, both the detection and avoidance of cavitation become possible. This is a cost-effective solution that competes with traditional methods based on external sensors, such as sound, vibration, or pressure. 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.
Cavitation is one of the killers of pump performance. With condition-based monitoring integrated directly in the VFD, we’re giving our customers a proactive way to detect and prevent damage before it happens. It’s smarter, simpler, and far more cost-effective than relying on traditional sensor-based methods.
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 avoided, the function can be configured either to remain at the last speed that prevented cavitation, or to gradually attempt returning to the original speed reference—continuously checking whether cavitation has disappeared in the meantime. Additionally, the function provides all necessary status information, allowing the VFD to operate as a standalone unit or to be integrated with PLCs into a higher-level process control system. This avoidance function is turned off by default, and it is up to the user to decide whether 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.
With the edge computing solution, which enables faster insights by processing data at the VFD, data is collected several times per second—ensuring that any measurements outside the normal range trigger a warning quickly and in a timely manner, thus minimizing the risk of undetected abnormalities.
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Pump cavitation occurs when rapid pressure drops inside a pump cause vapor bubbles to form and collapse violently. This leads to micro-pitting, noise, vibration, and accelerated wear on impellers and other components. Left unchecked, cavitation can reduce efficiency, damage equipment, and shorten system lifetime.
Danfoss drives use current signature analysis to detect cavitation. When cavitation causes turbulence in the pump, it creates a unique fluctuation pattern in the motor current. The drive analyzes this signal and compares it against baseline values. If the deviation exceeds user-defined thresholds, the drive flags a cavitation event—no external sensors required.
Traditional methods rely on external sensors like microphones, accelerometers, or pressure transducers. In contrast, the Danfoss CBM solution is fully integrated in the VFD and uses internal data processing. It’s more cost-effective, easier to maintain, and enables continuous monitoring without extra hardware.
The integrated avoidance function automatically lowers the pump speed within preset limits to eliminate cavitation. Once resolved, the VFD can maintain the new speed or attempt to return to the original speed reference—continuously monitoring whether cavitation returns.
By catching cavitation early and automatically adjusting operation, condition-based monitoring helps prevent damage, reduce maintenance costs, and extend pump and system lifespan. It supports predictive maintenance strategies and helps improve process uptime.
Industries with critical pump systems—such as water and wastewater, food and beverage, oil and gas, and chemical processing—gain the most value. Cavitation detection is especially useful in remote or difficult-to-access locations, where traditional inspections may be delayed or impractical.
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