Home / Services / Pump Encyclopedia / Pump Knowledge / Corrosion-resistant and wear-resistant centrifugal pumps have special requirements for pump shaft sealsAnalysis of the Causes of the Locking Failure of the Pump Shaft of the Horizontal Multi-stage Boo

Corrosion-resistant and wear-resistant centrifugal pumps have special requirements for pump shaft sealsAnalysis of the Causes of the Locking Failure of the Pump Shaft of the Horizontal Multi-stage Boo

07 Sep 2021Email

Horizontal multi-stage booster pumps are widely used in power plants, buildings, and life. Once the horizontal multi-stage booster pump fails, it may cause the entire production to stop, and corresponding inspection and maintenance work must be done. If the horizontal multi-stage booster pump emits a lot of noise during the operation period, the motor current increases sharply, the outlet pressure decreases, and the vibration of the drive end bearing greatly increases. How to check and repair the pump shaft lock failure of the stage booster pump?

multistage pump

Analysis of the cause of the lock-up failure of the pump shaft of the horizontal multi-stage pump:

1. There is a deviation in the shaft alignment of the pump and the motor, and the local anchor bolts are not properly installed and loose or the coupling connection is unreasonable. It is easy to cause a deviation in the shaft alignment of the pump and the motor. Once the motor is started, it will Cause the shaft to lock
2. Inadequate work of the heating pump and sudden acceleration of the load will cause the pump shaft to lock. If the machine is in a cold state, enough heat pump work is required when starting, because the temperature of the boiler water is high, if the heat pump does not work in place, it is very likely that the temperature difference between the inside and outside of the pump will increase during the flow of the boiler water, and the expansion will be uneven. . In addition, when the drum needs a lot of water, the replenishment speed of the pump should be uniform. If the replenishment flow is suddenly increased and the load is too heavy, it will have a greater impact on the pump shaft and cause the shaft to lock.
3. Stop the pump too early. When the pump is just stopped, due to long-term operation, the shaft is still in a hot state, the crank is not completely turned, and it is not yet in a cold state. Once it is stopped for a long time, the shaft is prone to bend and deform, so that the shaft locks up when restarting.
4. Impurities are blocked. Since it is the trial operation stage, there are many possible reasons for the locking of the rotating shaft. Blockage, causing the shaft to lock up
5. The rotor supporting parts are loose. If the bearing frame is relatively loose and the bearing is not fixed, the center of the shaft will be offset to a certain extent, which is inconsistent with the shaft of the motor, causing the bearing to be damaged and causing the shaft to lock. Affected by the structure, the damping and stiffness of the bearing in the vertical and horizontal directions are very different. When the motor and the rotating shaft are offset, the difference is even greater, but when the offset value reaches a certain level, the bearing will be changed. The working conditions make the shaft unstable.

Horizontal multi-stage booster pump shaft disassembly inspection:
Because the horizontal multi-stage booster pump shaft is locked, the horizontal multi-stage centrifugal pump cannot work normally and needs to be disassembled for inspection to further understand the fault condition.
1. For a failed pump, it is more difficult to turn the coupling by hand. Motors and pumps are facing the risk of being damaged. To ensure their safety and effectively suppress the spread of faults, the power switch should be disconnected in time and cannot be restarted. Remove the anchor bolts and send the centrifugal pump to the maintenance workshop for maintenance.
2. Read and study the product manual and manufacturing drawings in detail, and be familiar with the structure, working principle and performance of the pump, so as to prevent hasty disassembly. Next, prepare the required tools and thoroughly clean the site to facilitate the placement of various parts after disassembly
3. Remove the fastening bolts and carry out the disassembly work of the pump. The disassembly should be carried out in the correct order, starting with the auxiliary equipment, then the parts of the pump itself, and disassembling from the inside out: If the installation of some parts is restricted by the angle or position, it should be clearly marked before disassembly , Provide convenience for reinstallation work. In addition, when disassembling, the clearance of each component should be done well.
The recording work provides convenient conditions for reinstallation and retesting. The disassembly method should be reasonable, and the disassembled parts should be placed in classification.

4. Check the disassembled parts, remove the grease on the bearing, observe whether the cage is deformed and twisted, if the ball and outer ring track are not damaged, it indicates that the bearing can be used normally; check whether the sealing strip is damaged and whether the internal spring is deformed or twisted : The shaft is locked to see if it is bent or deformed; the inspection of the impeller found no scratches caused by hard impurities, cracks and traces of static and dynamic friction.
5. After careful inspection, only two of the four faulty centrifugal pumps had the shaft being scratched, but no other parts were damaged. This requires further analysis of the cause of the failure.


Treatment countermeasures and reinstallation of horizontal multi-stage booster pump shaft locking:
Fix the anchor bolts to prevent loosening. A high-precision level gauge is used to check the levelness of the pump and motor base. All elements are in compliance with the installation regulations, indicating that there is no problem with the installation work and no need to re-grouting. Because it is a horizontal multi-stage booster pump shaft lock failure, it is difficult to check the shaft alignment of the motor and pump, but the rechecked data shows that it is within the qualified range and the alignment is good. If the multi-stage pump is started in the cold state, it is easy to cause a temperature difference. For this reason, the maintenance personnel should adopt a suitable heating pump plan and do the heating pump work.
The reassembly work should be carried out strictly in accordance with the reverse steps of disassembly, especially the control of the dynamic and static clearance and the amount of shaft movement, which need to be paid more attention. After the reassembly work, put it in the working position, set up a dial indicator at the coupling, keep the coupling with the motor shaft in good alignment, and then tighten the anchor bolts and coupling bolts. Rotate the shaft by hand, if there is no jam, you can try the pump.

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