2 types of powers are associated with a pump : the hydraulic power and the shaft power.
In order to size properly the motor of the pump, it is necessary to know the power to be transmitted to the shaft. The shaft power is dependent on the hydraulic power, the power to be transmitted to the fluid, and the efficiency of the pump which takes into account all the losses that happens when converting the shaft power to the hydraulic power.
The pump efficiency is given by the manufacturer, as a function of the pump capacity and can be determined from the pump characteristic.
How to calculate the pump power.
Calculation of the hydraulic power
Equation 1 : Pump Hydraulic Power
Q : pump capacity (m3/h)
H : pump head(m)
spgr4t : specific gravity of the liquid processed
Hydraulic Power : (kW)
Calculation of the shaft power
Equation 2 : Pump Shaft Power
The shaft power is used to calculate the motor required for a pump. To calculate the electrical power, the shaft power should be divided by the electrical effiency of the motor chosen.