Selection Of Pump Head

Feb 08, 2025

High head water pumps are used for low head pumping. Many operators believe that the lower the pumping head, the lower the motor load. Under this misconception, when choosing a water pump, the head of the pump is often chosen to be very high. In fact, for centrifugal water pumps, once the pump model is determined, the power consumption is directly proportional to the actual flow rate of the pump.
The flow rate of the water pump will decrease with the increase of the head, so the higher the head, the smaller the flow rate, and the lower the power consumption. On the contrary, the lower the head, the greater the flow rate, and the greater the power consumption. Therefore, in order to prevent motor overload, it is generally required that the actual pumping head of the water pump should not be less than 60% of the calibrated head.
So when high head is used for low head pumping, the motor is prone to overload and heat generation, and in severe cases, it can burn out the motor. If emergency use is required, a gate valve must be installed on the outlet pipe to adjust the water flow rate (or a small outlet must be blocked with wood or other materials), in order to reduce the flow rate and prevent motor overload. Pay attention to the temperature rise of the motor. If the motor is found to be overheated, the outlet flow rate should be reduced or the machine should be shut down in a timely manner.
This can also easily lead to misunderstandings. Some operators believe that blocking the water outlet and forcibly reducing the flow rate will increase the motor load. In fact, on the contrary, the outlet pipes of regular high-power centrifugal pump irrigation units are equipped with gate valves. In order to reduce the motor load during unit startup, the gate valves should be closed first, and gradually opened after the motor starts. This is the principle.