Specific Speed - Net Suction Specific Speed

Net Suction Specific Speed

The net suction specific speed is mainly used to see if there will be problems with cavitation during the pump's operation on the suction side. It is defined by centrifugal and axial pumps' inherent physical characteristics and operating point. The net suction specific speed of a pump will define the range of operation in which a pump will experience stable operation . The higher the net suction specific speed, then the smaller the range of stable operation. The envelope of stable operation is defined in terms of the best efficiency point of the pump.

The net suction specific speed is defined as:


N_{ss} = \frac{N\sqrt{Q}} {{NPSH}_R^{0.75}}

where:

net suction specific speed
rotational speed of pump in rpm
flow of pump in US gallons per minute
Net positive suction head (NPSH) required in feet at pump's best efficiency point

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