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    Home > Active Ingredient News > Drugs Articles > Analysis of the reason why the self-priming centrifugal pump can not lift water

    Analysis of the reason why the self-priming centrifugal pump can not lift water

    • Last Update: 2017-10-14
    • Source: Internet
    • Author: User
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    The self-priming centrifugal pump is widely used in agriculture because of its simple structure, convenient use and maintenance, and high efficiency However, it is also very troublesome because it can not lift water sometimes 1、 There is air in the water inlet pipe and pump body 1 Some users did not fill enough water before the start of the pump, sometimes it seems that the filled water overflowed from the vent hole, but did not rotate the pump shaft to make the air completely discharged, resulting in a little air remaining in the water inlet pipe or pump body 2 The horizontal section of the water inlet pipe in contact with the self-priming centrifugal oil pump shall have a gradient of more than 0.5% against the water flow direction, and the end connected to the water pump inlet shall be Zui high, not completely horizontal If it is raised up, air will remain in the water inlet pipe, which reduces the vacuum degree in the water pipe and water pump and affects water absorption 3 The packing of the self-priming pump has been worn or pressed too loose due to long-term use, resulting in a large amount of water ejecting from the gap between the packing and the pump shaft sleeve As a result, the external air enters the inside of the pump from these gaps, affecting the water extraction 4 Due to the long-term potential underwater, the water inlet pipe has holes due to the corrosion of the pipe wall After the water pump works, the water surface continues to drop When these holes are exposed to the water surface, the air enters the civil water inlet pipe from the holes 5 There are cracks at the elbow of the water inlet pipe, and there is a small gap at the connection between the water inlet pipe and the water pump, which may cause air to enter the water inlet pipe Pump speed too low 1, human factors Because of the damage of the original electric motor, quite a number of users randomly equipped with another electric motor to drive, resulting in small flow, low head or even no water 2 The drive belt is worn There are many large centrifugal pumps with belt transmission, because of long-term use, the transmission belt is worn and loose, resulting in slipping, thus reducing the speed of the pump 3 Improper installation If the center distance between the two pulleys is too small or the two shafts are not parallel, if the drive belt is too tight and installed on it, the wrap angle is too small, the calculation error of the diameter of the two pulleys and the eccentricity of the two shafts of the water pump driven by the coupling are too large, the speed of the water pump will change 4 Mechanical failure of self-priming pump itself If the fastening nut between the impeller and the pump shaft is loose or the pump shaft is deformed and bent, the impeller will move more, directly rub with the pump body, or the bearing is damaged, the speed of the pump may be reduced 5 The maintenance of the power machine is poor The loss of excitation of motor due to the burning of winding, the change of winding turns, wire diameter and wiring method in the maintenance, or the failure in the maintenance is not completely eliminated, will also change the speed of water pump 2、 The suction head is too large, some water sources are deep, some water sources are relatively flat, and the allowable suction head of the pump is ignored, resulting in less water absorption or no water at all It is necessary to know that there is a limit to the degree of vacuum that can be established at the water intake of the pump The suction head of the vacuum is about 10 meters of water column high, and the vacuum that can not be established by the pump And the vacuum is too large, it is easy to make the water in the pump gasified, which is not good for the work of the pump Therefore, each centrifugal pump has its Zui large allowable suction head, 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 of the water source is slightly less than the head of the water pump, the water volume is still small or cannot be lifted The reason is often that the pipeline is too long, there are many bends in the pipeline, and the resistance loss of water flow in the pipeline is too large The reason is often that the pipeline is too long, there are many bends in the pipeline, and the resistance loss of water flow in the pipeline is too large In general, the resistance of 90 degree bend is greater than that of 120 degree bend The head loss of each 90 degree bend is about 0.5-1 m, and the head loss of each 20 m pipe can be about 1 m In addition, some users are also free to pump in and out of the pipe diameter, which also has a certain impact on the lift 3、 Influence of other factors 1 The bottom valve cannot be opened It is usually because the water pump has been used for a long time, the bottom valve gasket is stuck, and the bottom valve without gasket may rust 2 The filter net of bottom valve is blocked; or the filter net is blocked in the potential water sludge layer of bottom valve 3 Impeller is seriously worn Impeller blades wear after long-term use, which affects the performance of water pump 4 Failure or blockage of gate valve check valve will cause flow reduction or even water pumping failure 5 The leakage of the outlet pipe will also affect the water extraction of the self-priming pump.
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