Centrifugal water pump has become a widely used water pump in agriculture because of its simple structure, convenient use and maintenance, and high efficiency. However, it is also annoying because it can't carry water. The reason for the deliberate obstacle that cannot be mentioned is now analyzed.
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　　 1. There is air in the water inlet pipe and pump body
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　　 1. Some users have not filled enough water before starting the pump; it seems that the water has overflowed from the vent, but the pump shaft has not been rotated to completely exhaust the air, resulting in a little air remaining in the inlet pipe or pump body.
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　　2. The horizontal section of the inlet pipe in contact with the water pump should have a downward slope of more than 0.5% in the reverse direction of the water. The end connected to the inlet of the water pump is high, not completely horizontal. When tilted upwards, air will remain in the water inlet pipe, which reduces the vacuum in the water pipe and the water pump and affects water absorption.
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　　3. The water pump packing has worn out due to long-term use or the packing pressure is too loose, causing a large amount of water to be sprayed from the gap between the packing and the pump shaft sleeve. As a result, external air enters the water pump from these gaps, affecting the water lifting.
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　　4. Holes appeared in the inlet pipe due to long-term diving, and the pipe wall was corroded. After the pump worked, the water surface continued to drop. When these holes were exposed to the water surface, air entered the inlet pipe from the holes.
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　　 5. There are cracks in the elbow of the inlet pipe, and there is a small gap between the inlet pipe and the water pump, which may cause air to enter the inlet pipe.
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　　 2. The pump speed is too low
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　　 1. Human factors. A considerable number of users arbitrarily equipped with another motor to drive because the original motor was damaged. As a result, the flow rate was low, the head was low, and the water was not pumped.
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　　2, the transmission belt is worn. Many large-scale water separation pumps use belt transmission. Due to long-term use, the transmission belt is worn and loose, and slipping occurs, which reduces the pump speed.
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　　 3. Improper installation. The center distance between the two pulleys is too small or the two shafts are not parallel, the tight side of the transmission belt is installed on it, resulting in too small wrap angle, the calculation of the diameter of the two pulleys, and the large eccentricity of the two shafts of the coupling drive water pump will cause the pump Speed ​​changes.
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　　 4. The water pump itself has a mechanical failure. The impeller and pump shaft tightening nut is loose or the pump shaft is deformed and bent, causing the impeller to move too much, directly rubbing against the pump body, or bearing damage, which may reduce the pump speed.
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　　 5. Power machine maintenance is not recorded. The motor loses its magnetism due to the burning of the windings. Changes in the number of winding turns, wire diameters, and wiring methods during maintenance, or failure to completely eliminate factors during maintenance will also cause the pump speed to change.
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　　 3. The suction range is too large
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　　Some water sources are deeper, and some water sources have a relatively flat periphery. The allowable suction stroke of the pump is ignored, resulting in little or no water absorption. It is necessary to know that the degree of vacuum that can be established at the suction port of the water pump is limited, and the suction range is about 10 meters water column height in absolute vacuum, and it is impossible for a water pump to establish an absolute vacuum. If the vacuum is too large, it is easy to vaporize the water in the pump, which is unfavorable for the operation of the pump. Each centrifugal pump has a large allowable suction stroke, generally between 3 and 8.5 meters. When installing the pump, it must not be convenient and simple.
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　　 Fourth, the resistance loss in the water flowing in and out of the water pipe is too large
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　　 Some users have measured that the vertical distance from the reservoir or water tower to the water surface is slightly less than the pump lift, but the water lift is small or unable to lift the water. The reason is often that the pipe is too long, the water pipe has many bends, and the resistance loss in the water flow pipe is too large. In general, the resistance of a 90-degree elbow is greater than that of a 120-degree elbow. The head loss of each 90-degree elbow is about 0.5 to 1 meter, and the resistance of every 20 meters of pipe can cause a head loss of about 1 meter. In addition, some users also arbitrarily pump inlet and outlet pipe diameters, which also have a certain impact on the head.