NPSH

A number of technical papers (1, 4, 7, 8) have shown that the maximum damage rate to centrifugal pumps, at least in water services, typically occurs when the NPSHA is in the range of two to three times the NPSHR3.
In 1982, Richard Dubner of Chevron developed a graph for use in establishing minimum continuous flow rates for centrifugal pumps.
If it is necessary to increase a system's NPSHA, one or more of the following steps may be employed.NPSH, net positive suction head, pump system optimization
The impact of pump wear ring clearance on pump efficiency.
It is common practice for the designer of a new centrifugal pump to model the new pump from an existing pump. Each dimension of the existing pump (except the shaft diameter) is multiplied by a modeling factor "F" to obtain each dimension of the new pump.
The Hydraulic Institute NPSHA Margin Work Group (1) recommended NPSH margins ranging from zero to four times the NPSHR (NPSHA÷NPSHR = 1 to 5).
The Hydraulic Institute NPSHA Margin Work Group (1) recommended NPSH margins ranging from zero to four times the NPSHR (NPSHA÷NPSHR = 1 to 5).
Sometimes running pumps faster can help avoid cavitation.

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