What is dry-running of a pump? Dry-running protection

Dry-running occurs when the pump operates without sufficient fluid. In this situation, internal components such as the impeller continue to move, which generates a significant amount of heat. Normally, the fluid flowing through the pump serves as a cooling medium to dissipate the excess heat. Without cooling, the temperature in pumps quickly rises to levels that can be dangerous to their structure.

Elastomeric winding parts are particularly sensitive to high temperatures. As a result of dry running, the rubber components can degrade, leading to cracking, delamination or complete destruction. Damage to these components not only shortens the life of the pump, but can also lead to sudden pump failure.

Prolonged dry running can also damage other parts of the pump, such as seals, bearings and housings, which are not designed to withstand extreme temperatures. Consequences can include component seizure, fluid leakage and mechanical failure. It is therefore crucial that appropriate safeguards are in place, such as temperature monitoring systems and automatic pump shutdown.

What problems does temperature rise cause in cavitation pumps?

Our client, a manufacturer of cavitation pumps, approached us with a problem of regular pump failures caused by dry running. This type of pump consists of two main parts: a rotating impeller and a stationary stator. The impeller is like a rotating screw that moves the liquid through the pump. The stator, which is a flexible tube that surrounds the impeller, creates conveying spaces that carry the liquid from the inlet to the outlet of the pump. This ensures that it is efficiently pumped from one side to the other.

A temperature rise in the stator led to stator failure, resulting in frequent pump failures, production downtime and high repair costs. Our customer needed a solution that would protect the pumps from thermal damage and ensure reliability.

How to protect pumps against dry running? Monitoring the winding surface temperature?

We have implemented a solution at our customer, based on the JUMO miroTRON electronic thermostat with PID function, which effectively protects pumps against dry running. During pump operation, the stator surface temperature is continuously monitored by the protection system. When the temperature exceeds the setpoint, the thermostat sends a signal to the motor controller, which causes the pump to shut down immediately. A temperature rise, caused by dry running, is quickly detected, preventing damage to the impeller and stator. In addition, the system allows a second setpoint temperature to be set, providing additional protection. This is particularly useful during cleaning processes when the temperature of the medium can vary. With this solution, the pumps are protected from thermal damage, which increases their reliability and reduces repair and downtime costs.

For the early detection of drops in the level of water or another medium in the pump, we also recommend a level probe, in particular the JUMO ZELOS C01 capacitive level sensor designed, among other things, to prevent dry running.

About the author

My name is Ewelina Szmit and I have been working in content marketing for several years, combining my professional skills with my passion for writing. I am convinced that even the most technical topics can be presented in an interesting and accessible way for everyone. Outside of work, I unleash my creativity by creating newspaper collages. I like to spend my free time being active, walking my dog or running.

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