The centrifugal water pump is widely used in agriculture because of its simple structure, convenient use and maintenance, and high efficiency, but it is also annoying because it can't carry water. The reason for not deliberately obstructing Sheung Shui is analyzed.
1. There is air in the water inlet pipe and the pump body
1. Some users have not filled enough water before starting the pump; it seems that the irrigation water has overflowed from the vent hole, but the air is completely discharged without rotating the pump shaft, causing a little air to remain in the water pipe or the pump body.
2. In contact with the pump, the horizontal section of the inlet pipe should be lowered by more than 0.5% against the direction of water flow. The end connected to the pump inlet is high, not completely horizontal. If it is tilted upward, air will remain in the water inlet pipe, which reduces the vacuum in the water pipe and the pump and affects water absorption.
3. The pump packing has been worn out for a long time or the packing is too loosely pressed, causing a large amount of water to be ejected from the gap between the packing and the shaft sleeve of the pump. As a result, external air enters the pump from these gaps, which affects the water extraction.
4. Due to the long-term diving, the inlet wall has holes due to corrosion of the pipe wall. After the pump works, the water surface continues to decline. When these holes are exposed, the air enters the inlet pipe through the holes.
5. There are cracks at the inlet pipe bend, and there is a slight gap at the connection between the inlet pipe and the pump, which may cause air to enter the inlet pipe.
Second, the pump speed is too low
1. Human factors. A considerable number of users are randomly equipped with another motor to drive due to the damage of the original motor. As a result, the result is less flow and low head.
2. The drive belt is worn. Many large water pumps use belt transmission. Due to long-term use, the transmission belt wears and loosens, slipping occurs, reducing the pump speed.
3. Improper installation. If the center distance of the two pulleys is too small or the two shafts are not parallel, the tight edge of the transmission belt is installed on the top, resulting in a too small wrap angle. The calculation error of the diameter of the two pulleys and the larger eccentricity of the two shafts of the coupling drive pump will cause the pump Speed ​​changes.
4. The mechanical failure of the pump itself. The loosening of the fastening nuts of the impeller and the pump shaft or the deformation and bending of the pump shaft cause the impeller to move more, directly rub against the pump body, or damage the bearings, which may reduce the speed of the pump.
5. Power machine maintenance is not recorded. The motor is demagnetized due to the burning of the winding. The number of winding turns, wire diameter, wiring method during maintenance, or failure to completely eliminate the factors during maintenance will also change the speed of the pump.
Third, the suction stroke is too large
Some water sources are deeper, and some water sources are flatter on the periphery, ignoring the allowable suction range of the pump, resulting in little or no water absorption. It is necessary to know that there is a limit to the degree of vacuum that can be established at the suction port of the pump. In absolute vacuum, the suction stroke is about 10 meters of water column height, and it is impossible for the pump to establish absolute vacuum. If the vacuum is too large, it is easy to vaporize the water in the pump, which is not good for the pump. Each centrifugal pump has its large allowable suction stroke, generally between 3 and 8.5 meters. When installing the pump, it is not necessary to be simple and convenient.
4. The resistance loss of water flowing into and out of the water pipe is too large
Some users have measured that the vertical distance from the reservoir or water tower to the source water surface is slightly smaller than the pump head, but the amount of water lifted is small or the water cannot be lifted. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the resistance loss in the water flow pipe is too large. Under normal circumstances, 90-degree elbows have greater resistance than 120-degree elbows. Each 90-degree elbow has a head loss of about 0.5 to 1 meter, and every 20 meters of pipe resistance can cause a head loss of about 1 meter. In addition, some users are also free to pump the inlet and outlet pipe diameters, which also have a certain impact on the head.
1. There is air in the water inlet pipe and the pump body
1. Some users have not filled enough water before starting the pump; it seems that the irrigation water has overflowed from the vent hole, but the air is completely discharged without rotating the pump shaft, causing a little air to remain in the water pipe or the pump body.
2. In contact with the pump, the horizontal section of the inlet pipe should be lowered by more than 0.5% against the direction of water flow. The end connected to the pump inlet is high, not completely horizontal. If it is tilted upward, air will remain in the water inlet pipe, which reduces the vacuum in the water pipe and the pump and affects water absorption.
3. The pump packing has been worn out for a long time or the packing is too loosely pressed, causing a large amount of water to be ejected from the gap between the packing and the shaft sleeve of the pump. As a result, external air enters the pump from these gaps, which affects the water extraction.
4. Due to the long-term diving, the inlet wall has holes due to corrosion of the pipe wall. After the pump works, the water surface continues to decline. When these holes are exposed, the air enters the inlet pipe through the holes.
5. There are cracks at the inlet pipe bend, and there is a slight gap at the connection between the inlet pipe and the pump, which may cause air to enter the inlet pipe.
Second, the pump speed is too low
1. Human factors. A considerable number of users are randomly equipped with another motor to drive due to the damage of the original motor. As a result, the result is less flow and low head.
2. The drive belt is worn. Many large water pumps use belt transmission. Due to long-term use, the transmission belt wears and loosens, slipping occurs, reducing the pump speed.
3. Improper installation. If the center distance of the two pulleys is too small or the two shafts are not parallel, the tight edge of the transmission belt is installed on the top, resulting in a too small wrap angle. The calculation error of the diameter of the two pulleys and the larger eccentricity of the two shafts of the coupling drive pump will cause the pump Speed ​​changes.
4. The mechanical failure of the pump itself. The loosening of the fastening nuts of the impeller and the pump shaft or the deformation and bending of the pump shaft cause the impeller to move more, directly rub against the pump body, or damage the bearings, which may reduce the speed of the pump.
5. Power machine maintenance is not recorded. The motor is demagnetized due to the burning of the winding. The number of winding turns, wire diameter, wiring method during maintenance, or failure to completely eliminate the factors during maintenance will also change the speed of the pump.
Third, the suction stroke is too large
Some water sources are deeper, and some water sources are flatter on the periphery, ignoring the allowable suction range of the pump, resulting in little or no water absorption. It is necessary to know that there is a limit to the degree of vacuum that can be established at the suction port of the pump. In absolute vacuum, the suction stroke is about 10 meters of water column height, and it is impossible for the pump to establish absolute vacuum. If the vacuum is too large, it is easy to vaporize the water in the pump, which is not good for the pump. Each centrifugal pump has its large allowable suction stroke, generally between 3 and 8.5 meters. When installing the pump, it is not necessary to be simple and convenient.
4. The resistance loss of water flowing into and out of the water pipe is too large
Some users have measured that the vertical distance from the reservoir or water tower to the source water surface is slightly smaller than the pump head, but the amount of water lifted is small or the water cannot be lifted. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the resistance loss in the water flow pipe is too large. Under normal circumstances, 90-degree elbows have greater resistance than 120-degree elbows. Each 90-degree elbow has a head loss of about 0.5 to 1 meter, and every 20 meters of pipe resistance can cause a head loss of about 1 meter. In addition, some users are also free to pump the inlet and outlet pipe diameters, which also have a certain impact on the head.
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