As indicated in the sample pump performance curve above, the plot of pump efficiency against volumetric flow rate is also commonly reported on the pump performance curves. When the theoretical pumping power requirement is divided by this efficiency for the corresponding flow, the result is pump shaft power requirement. For more information on pump power calculations using efficiency, refer to EnggCyclopedia’s solved sample problem. The calculated pump shaft power has to be provided by an electric motor.
The efficiency curve typically has a maximum within the allowable operating range. This maximum is also known as the Best Efficiency Point (BEP) as indicated in the sample curves. The normal operation should be preferably done close this best efficiency point for minimum power requirements.
Sometimes a plot of Pump Shaft Power requirement is also done against the volumetric flow rate on the performance curves. This curve readily gives the value of power requirement for a particular flow rate