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Engineering ToolBox > Discharge Regulation of Centrifugal Pumps
It is often necessary to adapt the pump capacity to a temporary or permanent change in the process demand.
The capacity of a centrifugal pump can be regulated either at
Speed regulating is energy efficient since the energy to the pump is reduced with the decrease of speed.
The speed of the pump can be varied with
The change in power consumption, head and volume rate can be estimated with the affinity laws.
Capacity can be regulated at constant speed by
Throttling can be carried out by opening and closing a discharge valve.
Throttling is energy inefficient since the energy to the pump is not reduced. Energy is wasted by increasing the dynamic loss.
The discharge capacity can be regulated by leading a part of the discharge flow back to the suction side of the pump. Bypassing the flow is energy inefficient since the energy to the pump is not reduced.
Reducing the impellers diameter is a permanent change and the method can be used where the change in process demand is temporary. The method may be energy efficient if the motor is changed and the energy consumption reduced.
The change in power consumption, head and volume rate can be estimated with the affinity laws.
The flow rate and the head can be modulated by changing the pitch of the blades. Complicated and seldom used.
Power consumption of some of the regulating methods are compared in the figure below:
