There is a grinding sound inside the water pump while it is running
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When the pump on site is in operation, there is a sound as if gravel were rolling inside it. But the vibration is normal. The inspectors said that cavitation is occurring, but doesn’t vibration also increase when there is cavitation?
It’s cavitation; first, run water to open the bypass and remove the air from the pipeline, then close the bypass valve – once it operates normally, there will be no problem. Generally, air needs to be exhausted before a pump is started.
It might be the sound of bubbles breaking, with gas being released; the inlet pipe needs to be fully open to avoid restricting the flow rate
Cavitation generally has an impact on vibration, but the extent of this impact varies depending on the degree of cavitation
Who says that the vibration of a pump must exceed limits when cavitation occurs? Whether vibration levels exceed the acceptable limits when cavitation occurs is related to the pump’s design, installation, and operating conditions. Although in most cases cavitation is accompanied by increased vibration, in some situations—such as when the pump has a high degree of stiffness and its foundation is relatively large compared to the pump body, or when the cavitation itself is not particularly severe—vibration may not increase significantly. Moreover, vibration testing instruments generally have their own frequency range, so if the frequency of cavitation is very low, it may not be possible to detect it.
The sound of gravel suggests that there is air inside the pump; check whether the mechanical seal and the volute are leaking, as well as whether the air within the pump has been properly removed