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What are the Misunderstandings in the Use of Centrifugal Water Pumps?

Apr. 26, 2021

As a Centrifugal Water Pump Manufacturer, share with you.

High-lift water pump for low-lift pumping

Many operators believe that the lower the pumping head, the smaller the motor load. Under the misleading of this kind of misunderstanding, when purchasing a water pump, the head of the water pump is often selected very high. In fact, for centrifugal water pumps, when the pump model is determined, its power consumption is 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 and the lower the power consumption. Conversely, the lower the head, the greater the flow, and the greater the power consumed. 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 water with a low head, the motor is easy to be overloaded and generate heat, 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 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. This is also easy to misunderstand. Some operators think that blocking the water outlet and forcibly reducing the flow will increase the motor load. In fact, the opposite is true. The outlet pipe of the regular high-power centrifugal pump drainage and irrigation unit are equipped with a gate valve. In order to reduce the motor load when the unit starts, the gate valve should be closed first, and then the gate valve should be gradually opened after the motor starts.

Centrifugal Water Pump

Centrifugal Water Pump

Large-caliber water pump with small water pipe for pumping water

Many pilots think that this can increase the actual head. In fact, the actual head of the water pump = total head ~ loss head. When the pump model is determined, the total head is fixed; the loss head mainly comes from the pipeline resistance. The smaller the pipe diameter is, the greater the resistance is, and the greater the loss head. Therefore, after the pipe diameter is reduced, the actual head of the water pump cannot be increased. , On the contrary, it will decrease, resulting in a decrease in the efficiency of the pump. In the same way, when a small-diameter water pump uses a large water pipe to pump water, the actual head of the pump will not be reduced. On the contrary, the loss of the head will be reduced due to the decrease in the resistance of the pipeline, and the actual head will be increased. They also think that when a small-diameter water pump uses a large water pipe to pump water, it will inevitably increase the motor load. They believe that as the pipe diameter increases, the water in the outlet pipe will exert greater pressure on the pump impeller, which will greatly increase the motor load. As everyone knows, the size of the liquid pressure is only related to the height of the head, and has nothing to do with the cross-sectional area of the water pipe. As long as the head is constant, the size of the impeller of the pump remains the same, and the pressure acting on the impeller is constant regardless of the pipe diameter. Only after the pipe diameter increases, the water flow resistance will decrease, and the flow will increase, and the power consumption will also increase appropriately. But as long as it is within the rated head range, the pump can work normally no matter how the pipe diameter is increased, and it can also reduce the pipeline loss and improve the pump efficiency.

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