# Centrifugal Pumps - Speed Torque Curve

## Centrifugal pumps and the characteristic speed torque curve

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The speed torque curve characterize a centrifugal pump. The theoretical characteristic is a parabola starting from the origin and proportional to the square of the speed.

The torque can be expressed as

T = k n^{2}(1)

where

T = torque (Nm, lb_{f }ft)

k = constant

n = pump speed or velocity (rpm)

With the discharge valve closed the torque amounts to *30 - 50 % *of the nominal torque at full speed.

### Full Load Torque

The torque at full load can be calculated as

T = 30 P / (π n) (2)

where

T = torque (kN m)

P = power (kW)

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## Related Topics

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