Cavitation margin issue
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Do centrifugal pumps all have specified NPSH?
Centrifugal pumps all require a net positive suction head, which is determined by the operating characteristics of the pumps themselves.
When the pressure at the inlet of a centrifugal pump impeller is lower than the saturation pressure of the working fluid, part of the liquid evaporates (i.e., vaporizes). When these vapor bubbles reach areas with higher pressure, they condense suddenly due to the increased pressure; as a result, the surrounding liquid flows in to fill that space, creating a hydraulic shock. This phenomenon is known as cavitation
When the pressure at the inlet of a centrifugal pump impeller is lower than the saturation pressure of the working fluid, part of the liquid evaporates (i.e., vaporizes). When these vapor bubbles reach areas with higher pressure, they condense suddenly due to the increased pressure; as a result, the surrounding liquid flows in to fill that space, creating a hydraulic shock. This phenomenon is known as cavitation
This is an inherent characteristic of the pump; the NPSHR value indicated in most manuals refers to the required net positive suction head, and the higher this value, the easier cavitation occurs