Malhaty Pump - Pioneer of centrifugal pumps and customized pumps for special liquids transfer

It is an extreme pressure fluctuation that occurs when the flow of liquid in piping is rapidly changed.

More specifically, when a valve at the end or middle of a long pipeline is suddenly opened or closed, or when the operating condition of a pump in the middle of pumping water suddenly changes, a significant pressure rises or drops by the compressed water occurs, which results in extreme pressure fluctuations. This is the mechanism of how the water hammer occurs. Water hammer may damage piping. 

Yes. The rotation speed is different between 50Hz and 60Hz frequencies. The rotation speed for 60Hz is 20% faster than 50Hz. This affects the pump performance in the way mentioned below. Here we take centrifugal pumps as an example.

The discharge volume is directly proportional to the increase or decrease in rotation speed. In other words, if the frequency changes from 50Hz to 60Hz, the discharge volume increases by 20%. Similarly, the head is proportional to the square of the rotation speed. The required power is proportional to the cube of the rotation speed.

When the pressure at the impeller's inlet of the pump drops below the liquid's saturated vapor pressure, vaporizes, and forms vapor bubbles, and subsequently, these bubbles collapse. The shock waves generated by this phenomenon make extreme noise and vibration, which eventually erode and damage the impeller. This phenomenon is called cavitation.