# Pump Performance Curve

The pumping performance of a centrifugal pump is expressed in the form of an H-Q curve, depicting the Flow Q (e.g. in m³/h) and the Head H (e.g. in m) of the pump.

The graph of the curve is shown dropping from top left to bottom right with increasing rate of flow. The slope of the curve is determined by the pump construction and particularly by the design of the impeller.

The characteristics of the pump duty curve is the inter-dependent relationship between capacity and head.

Each change of head effects a consequential variation in the rate of flow.

High rate of flow -> low head
Low rate of flow -> high head

Though it is the frictional resistance of the installed pipe system which determines a given pump capacity, the respective pump can take up only one duty point on its curve. This duty point is the intersection of pump H-Q curve with the system H-Q curve.

In addition to the Q-H performance curve, the following performance curves are often found for centrifugal pumps:

• Power
• Shaft power P2(Q)
• Electrical power consumption P1(Q)
• Efficiency
• Hydraulic efficiency ηhydr(Q)
• Total efficiency ηtot(Q)
• NPSH required NPSHreq(Q)
• Speed n(Q)

## More articles on this topic

The static head means that part of the system H-Q curve that is unrelated to the flow.

### Waste water drainage

Decisive for the design is the expected wastewater discharge.

### Rainwater drainage

The precipitation values are climatically conditioned and regionally very different. Depending on their frequency, the rainfall donations that occur are differentiated into:

### Speed – Affinity Laws

The affinity law describes the speed dependency of the delivery parameters of centrifugal pumps. It can be derived from the general similarity relationships as a special case.

### Pump Performance Chart

The pump performance chart is a summarized diagram containing multiple pump performance curves.

### Calculating the System H-Q Curve

The system H-Q curve depicts the dependency of the total head Hsystem on the Flow Q.