Pump Performance Curve – Centrifugal Pumps

Pump Characteristic Curve

Pump characteristic curve (or pump performance curve) determines the range of flows and energy produced for a fixed speed, size, design and suction conditions of the pump. The head / pressure (energy) produced by a pump must equal to or exceed the net head / pressure (energy) required by the system so that the pump is able to move a liquid from a lower pressure level to a higher pressure level. In addition, the net pressure (energy) available on the suction side of the pump system must be greater than the liquid vapor pressure to assure that liquid enters the pump without potential deterioration of performance or mechanical damage.

Centrifugal Pump Curve

Figure 9. A typical centrifugal pump performance curve

Figure 9 illustrates the characteristic curve for a centrifugal pump. A centrifugal pump performance characteristics are outlined for a ranged of capacity and head produced for fixed impeller geometry and a variety of impeller diameters.

The limits of the centrifugal pump curve

The centrifugal pump curve has minimum allowable flow and flow exceeding end of curve (maximum flow) limits which can result in significant mechanical damage to the pump if not avoided. If the rated flow is operated below the minimum allowable flow, flow recirculation can damage a pump while at the rated flow exceeding the end of curve, excessive NPSHr, horsepower and choke flow can cause mechanical damage to impellers, casing, shaft, bearings and seals.