A pump that vibrates or produces a grinding noise is almost never just a minor inconvenience. In many cases, this indicates cavitation: the formation and collapse of vapor bubbles in the impeller. Cavitation not only causes noise and vibration but can also lead to damage to impellers, bearings, and seal faces within a short period of time. In technical installations, we frequently observe this as a result of unfavorable piping configurations or an incorrect NPSH balance.
Cavitation occurs when the pressure on the suction side becomes too low. As a result, the fluid begins to boil locally, even though the temperature is well below the boiling point. The vapor bubbles that form implode inside the pump, causing the typical “rattling” or “dragging” sound.
\n\nIn technical systems, we see that this is primarily caused by:
\n\n\n\nA pump that originally ran quietly but later begins to vibrate is almost always experiencing one of these situations.
Vibrations in a pump are often attributed to cavitation, whereas in reality they may also be caused by mechanical imbalance. Both produce an abnormal vibration pattern, but their behavior differs clearly:
\n\n\n\nIn overhaul work, we see that cavitation damages the pump much more quickly than mechanical imbalance. The characteristic damage is erosion on impeller edges and face plates, often already visible after a relatively short operating period.
For technical services and installers, the most important measures are:
\n\n\n\nInstalling pressure gauges on both the suction and discharge sides is strongly recommended. This makes it immediately clear whether the pump is operating within its operating range (pump curve).
\n\nIf in doubt about system pressures or NPSH conditions, a quick check can prevent significant damage.
For technical services and installers, the most important measures are:
\n\n\n\nIn the event of abnormal vibration levels or a sudden increase in noise, a brief mechanical inspection is often sufficient to detect incipient imbalance in a timely manner.
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