Pump Cavitation Case Study

Cavitation occurs when the “NPSH available” falls below the “NPSH required” for a pump (i.e. liquid's pressure drops below its vapor pressure). This low pressure causes bubbles to form in a liquid, which then collapse violently & generate intense shockwaves, leading to erosion of nearby surfaces and producing noise. It can also induce damaging oscillations within pump, contributing to premature wear and tear of internals (i.e. impeller, partition plate & volute casing), decreased efficiency, and potentially catastrophic failure if left unchecked.
In the vibration spectrum, the presence of cavitation induced vibrations can be identified by observing hump at higher frequency peaks with raised noise floor. These peaks may also appear at frequencies corresponding to blade passing frequencies or other characteristic frequencies of the rotating components. In waveform analysis, impacting signs with random burst of energy will be observed. Additionally if you listen to vibration, it will appear like gravel in the pump.