Centrifugal Pumps - Speed Torque Curve

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 n²                                   (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)