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Why does the self-priming sewage pump appear to be unable to absorb water

Author: Source: Posted On: 2019/3/1 15:50:04

  A friend who often uses a self-priming sewage pump will find that the pump does not catch water. What is the reason for this? It may be that the inlet pipe and the pump body have air or the pump speed is too low, and there is self-priming. The pump suction stroke is too large, as follows:

  First,Self-priming pump inlet pipe and pump body have air

  1. Some users do not fill enough water before the pump starts. Sometimes it seems that the water has overflowed from the venting hole, but the air is not completely discharged from the pump shaft, so that a little air remains in the inlet pipe or pump body.

  2. The horizontal section of the inlet pipe that is in contact with the self-priming centrifugal oil pump applies a downward slope of more than 0.5% in the direction of the water flow, and the end of the inlet of the water pump is the highest, not completely horizontal. If it is lifted up, air will remain in the inlet pipe, which will reduce the vacuum in the water pipe and the water pump and affect the water absorption.

  3. The packing of the self-priming pump has been worn out due to long-term use or the packing is too loose, causing a large amount of water to be ejected from the gap between the packing and the pump shaft bushing. As a result, external air enters the inside of the pump from these gaps. , affecting the water.

  4. Because the inlet pipe is exposed to water for a long time, the hole in the pipe wall is corroded. After the pump works, the water surface continuously drops. When these holes are exposed to the water surface, the air enters the water inlet pipe from the hole.

  5. Cracks appear at the inlet pipe bends, and small gaps appear at the connection between the inlet pipe and the pump, which may cause air to enter the inlet pipe.

  Second, self-priming pump water pump speed is too low

  1. Artificial factors. A considerable number of users are randomly equipped with another motor to drive the original motor, resulting in low flow, low lift or even no water.

  2. The belt is worn. There are many large centrifugal pumps that use belt transmission. Due to long-term use, the belt is worn out and slacks, resulting in slipping, which reduces the speed of the pump.

  3. Improper installation. The center distance between the two pulleys is too small or the two shafts are not parallel. The transmission belt is tightly mounted to the top, causing the wrap angle to be too small, the calculation of the diameter of the two pulleys and the eccentricity of the two shafts of the coupling drive are large, etc. The change in pump speed.

  4. The mechanical failure of the self-priming pump itself. The impeller and the pump shaft fastening nut are loose or the pump shaft is deformed and bent, causing the impeller to move more, directly rubbing against the pump body, or the bearing is damaged, which may reduce the rotation speed of the pump.

  5, power machine maintenance is not working. The motor is de-excited due to the burning of the windings. The number of winding turns, wire diameter, wiring method changes during maintenance, or failure to completely eliminate the fault during maintenance will also cause the pump speed to change.

  Third, the self-priming pump suction path is too large

  Some water sources are deeper, and some of the water sources have a flatter outer surface, ignoring the allowable suction of the pump, resulting in less or no water absorption. It is important to know that the vacuum that can be established at the suction port of the pump is limited. The absolute vacuum suction is about 10 meters high, and the pump cannot establish an absolute vacuum. Moreover, the degree of vacuum is too large, which makes it easy to vaporize the water in the pump, which is detrimental to the operation of the pump. Therefore, each centrifugal pump has its maximum allowable suction stroke, generally between 3-8.5 meters.

  Some users have measured that although the vertical distance from the reservoir or water tower to the water source is slightly smaller than the pump lift, it is still small or impossible to lift. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the water flow is excessively lost in the pipeline. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the water flow is excessively lost in the pipeline. Under normal circumstances, the 90 degree bend is more resistant than the 120 degree bend, and the loss of each 90 degree bend is about 0.5-1 meters. The resistance of each 20 meter pipeline can cause the head loss to be about 1 meter. In addition, some users also arbitrarily pump the diameter of the pipe into and out of the pipe, which also has a certain impact on the lift.

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