Deep well pump, a type of vertical multistage centrifugal pump, which can draw water from deep well . With the drawdown, deep well pumps are widely used than centrifugal pumps. However, due to the wrong choice of some customers, it came out some problems, such as the pump doesn’t fit the well diameter, the insufficient water yield, the water can’t be pumped out, even the motor-pumped well be damaged. That’s why it seems so significant about how to choose deep well pumps.
（1） According to the well diameter and water quality , choose the pump type preliminary. Different types of pump have certain requirements about the dimension of well diameters, the maximum dimension of pump has to be 25~50mm less than the well diameter. If the well hole is askew, the maximum dimension of pump should be smaller. In a word, the pump body cannot be closed to the inner wall of well, to avoid the well being damaged by the pump.
（2） Based on the water yield, select the capacity of pumps. Every well has the optimal economic water yield, the capacity of pump should be equal to or less than the water yield when the water level of motor-pumped well drop to the half of depth of water. When the water pumpage is greater than the water yield of motor-pumped well, it will brought borehole wall sloughing and silting up, which will affect the lifespan of well. On the contrary, if the water pumpage is too little, the well can’t be fully effective. So, the best way is having a pumping test and find out the maximum water yield of well to select the capacity of pumps. The capacity of pumps are subject to the factory plate model and the number marked on the instruction.
（3） In accordance with the depth of decline of well water level and head loss of hydraulic permeability pipeline, make sure the actual needed dynamic head of well pump, which is equal to the vertical distance from the surface of outlet sump to the water level of well (net head) plus head loss. Head loss is about 6~9% of net head, usually around 1~2m.The depth of the primary impeller which is on the nethermost of the pump should be around 1~1.5m.The total length of tube well can’t exceed the maximum immersion marked on the instruction.
（4） Those pumping wells, whose sand content is more than ten thousandth, are not suitable to use submersible pumps. With high sand content , for example ,when the sand content is beyond 0.1%, it will speed up the wear of rubber bearing, leading to pump vibration and shorten the lifespan of pump.
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