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Suction characteristics

A centrifugal pump's suction characteristics describe the pump's reaction to changing NPSHa values (NPSH of the system) at the operating point and are determined by cavitation on the pump system's suction side and in the pump itself. A centrifugal pump can be operated continuously at the rotational speed (ncontract), flow rate (Qcontract) and head (Hcontract) and with the fluid specified in the supply contract if NPSHa is greater or equal NPSHr (= NPSH required by the pump), i.e. if

Saugverhalten_Formel_1

In a pump operating at a given operating point characterised by a flow rate (kept at a constant value) and a pump speed (kept at a constant value), a decrease in NPSHa is accompanied by a more or less pronounced decrease in head as a result of cavitation. 

A common method of evaluating the suction characteristics is to plot the flow rate or pump efficiency (η) against NPSHa.

Suction characteristics