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Analysis of centrifugal pump without water
- Jul 13, 2018 -

The centrifugal pump has become the most widely used type of water pump in agriculture because of its simple structure, convenient use and maintenance, and high efficiency. However, it is also troublesome because it is sometimes not lifted. Now I will analyze the reasons for not mentioning the water barrier.

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, centrifugal pump 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 water pump applies a downward slope of 0.5% or more 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 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. Affected the lifting of water.

(4) Due to the long-term potential of the inlet pipe, there is a hole in the corrosion of the pipe wall. After the pump works, the water surface continuously drops. When these holes are exposed to the water surface, the air enters the inlet pipe from the hole.

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

Pump speed is too low

(1) Human factors. centrifugal pump A considerable number of users are randomly equipped with another motor to drive the original motor, resulting in less flow, low lift or even water.

(2) The belt is worn. There are many large-sized off-water pumps that use belt transmission. Due to long-term use, the belt is worn and loose, and slippage occurs, 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. centrifugal pump The tight side of the transmission belt is mounted on the upper side, 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) Mechanical failure of the 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) The maintenance of the power machine is not recorded. The motor is de-excited due to the burning of the windings. The number of winding turns, centrifugal pump 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.


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