Analysis of the cause of self-priming centrifugal pump
Sofa Sets Guangdong Widinlsa International Co.Ltd , https://www.widinlsamachine.com
The self-priming centrifugal pump has become a kind of water pump widely used in agriculture because of its simple structure, convenient use and maintenance, and high efficiency, but it is also troublesome because it is sometimes not lifted.
1. There is air in the inlet pipe and pump body.
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 high, 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 bend, and there is a slight gap between the inlet pipe and the pump, which may cause air to enter the inlet pipe.
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 bearing damage, 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, the wire diameter, the wiring method change during maintenance, or the failure to completely eliminate the fault during maintenance will also cause the pump speed to change.
Second, the suction 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 water absorption or no water at all. It is necessary 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 large allowable suction range, generally between 3-8.5 meters.
Some users have measured that although the vertical distance from the reservoir or water tower to the water surface is slightly smaller than the pump lift, the water is still small or not watered. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the flow loss of the water flow in the pipeline is too large. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the flow loss of the water flow in the pipeline is too large. 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.
Third, the impact of other factors
1. The bottom valve cannot be opened. Usually because the pump is left too long, the bottom valve gasket is stuck, and the bottom valve without the gasket may rust.
2. The bottom valve filter net is blocked; or the bottom valve may cause blockage of the filter in the sludge layer in the water.
3. The impeller wear is serious. Impeller blades wear over long-term use, affecting pump performance
4. The gate valve can be faulty or blocked by the check valve, which will reduce the flow or even the water.
5. The leakage of the outlet pipe will also affect the amount of water pumped by the self-priming pump.