What are the effects of multistage centrifugal pumps working under low flow and low head conditions?
When the multi-stage centrifugal pump is designed, the flow head is a curve, and the flow head has the minimum and maximum limits. If the limit is exceeded, the performance of the multi-stage pump will decrease. When selecting a multi-stage centrifugal pump, the selected flow and head are best to be the rated flow head of the pump design or a similar pump, so as not to affect the efficiency of the pump.
D type multistage centrifugal pump
Many customers usually think that the lower the head of the centrifugal pump, the lower the motor load. Under the misleading misunderstanding of this kind of misunderstanding, when buying a water pump, they often choose a high head. In fact, for centrifugal pumps, when the pump model is determined, the power consumption is proportional to the actual flow 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 and the lower the power consumption. Conversely, the lower the head, the greater the flow and the greater the power consumption. Therefore, in order to prevent the motor from overloading, it is generally required that the actual pumping head of the pump should not be less than 60% of the calibrated head. Therefore, when the high head is used for pumping with a low head, the motor is easily overloaded and heats up, and it can burn the motor in severe cases. In case of emergency use, a gate valve for adjusting the amount of water must be installed on the outlet pipe (or block the small outlet with wood, etc.) to reduce the flow and prevent the motor from overloading. Pay attention to the temperature rise of the motor. If the motor is overheated, turn off the water outlet flow or shut down in time.
It can be seen from the above, why the multi-stage centrifugal pump needs to close the outlet gate valve when starting and stopping, just to prevent the motor from overcurrent, causing the motor to burn out.
