Prevention of pump cavitation using condition-based monitoring

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.

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.

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.