# Calculating the load torque on a turbine pump

How is the load torque on a turbine pump handled. Generally, with motors, there is a load attached to the shaft which resists the output torque of the motor however, with a pump increasing the flow rate of water, I assume the water should act as a smaller load.

Currently, I am calculating this load torque using the approach of a point load at the end of a cantilever beam. I know in a more realistic sense, the water would be a distributed load but I am going for a simplistic answer and I'm wondering if this is a valid approach to calculating this load.

• Do you specifically mean the torque required by the pump to pump the water? – mechcad Feb 17 at 20:04
• Essentially, yes – Pelumi Feb 18 at 3:34

## 1 Answer

Pump torque can be calculated via the power consumed and the rotational speed in rpm:

Power = Torque * Rotational Speed


Rearranging this equation, the torque is

Torque = Power/Rotational Speed


Without details about the type of pump, this may be the most straightforward calculation to determine the torque. If you know more about the type of pump (i.e. centrifugal, positive displacement, etc), there are specific pump type equations you can use to estimate the power and then the torque (if you have pump rpm). Even easier than that, if you have the pump characteristic curves you may be able to find the power as a function of another parameter, like flow rate or rpm.

I would advise against using the method you suggested if you're simply looking for pump torque (unless you know more about the shaft and applied force). The methods I listed above are more conventional for pump analysis/selection.

• I see. The applied force is unknown so I'll be better off using the generated motor torque as suggested. Thank you! – Pelumi Feb 18 at 17:39