How to determine whether a vertical long shaft multi-stage drum bag pump needs major repairs?

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1. To determine whether a vertical long shaft multi-stage cylindrical bag pump needs major repairs, a comprehensive evaluation can be conducted based on the following core standards:




2. 1、 Serious damage or wear of critical components




3. Pump body rupture or deformation: If there are cracks, perforations, or severe deformation in the pump body, resulting in seal failure or medium leakage, it is necessary to immediately shut down for major repairs.




4. Shaft bending or fracture: Measure the radial runout of the pump shaft using a dial gauge. If it exceeds the allowable value (usually ≤ 0.05mm), or if the shaft cracks or fractures, a new shaft needs to be replaced.




5. Wear of impeller and guide vanes: Check the wear of the impeller mouth ring and guide vanes. If the wear exceeds 50% of the design clearance (such as the mouth ring clearance was originally 0.5mm, but after wear it is ≥ 0.75mm), the impeller or guide vanes need to be replaced.




6. Bearing damage: If there is abnormal noise, increased vibration, or high temperature (exceeding the ambient temperature of 35 ℃ or the maximum temperature ≥ 80 ℃) in the bearing, it needs to be replaced.




7. 2、 Significant performance decline




8. Insufficient flow and head: At rated speed, if the flow or head of the pump is lower than 50% of the design value, it may be caused by impeller wear, cavitation, or internal leakage, requiring major repairs to restore performance.




9. Efficiency reduction: Through power monitoring, it was found that the input power of the pump had significantly increased, but the output flow rate and head did not meet expectations, indicating serious friction or leakage inside the pump and requiring major repairs.




10. Severe cavitation: If the pump experiences severe vibration, increased noise, or a sharp decline in performance during operation, it may cause damage to the impeller due to cavitation, and the cavitation area needs to be inspected and repaired.




11. 3、 Deterioration of operational stability




12. Vibration exceeding the standard: The vibration value of the pump is monitored by a vibration sensor. If it exceeds the standard value (such as the vibration intensity specified in ISO 10816-3 ≥ 7.1mm/s), the machine needs to be stopped for inspection and major repairs.




13. Abnormal noise: If the pump produces harsh noise or metal friction sound during operation, it may be caused by loose, worn or corroded components, and requires major repairs to investigate the cause.




14. Sealing leakage: If there is a serious leakage in the mechanical seal or packing seal (such as a leakage rate of more than 20 drops/minute at the packing box), the sealing element needs to be replaced or the sealing surface needs to be repaired.




15. 4、 Increased security risks




16. Electrical failure: If the motor insulation is aging, the winding is short circuited, or the control cabinet is faulty, causing the pump to malfunction or posing a safety hazard, the electrical system needs to be overhauled.




17. Structural looseness: If the pump body, base, or connecting pipes become loose or cracked, it may cause the pump body to overturn or the medium to leak, and the components need to be tightened or replaced.




18. Failure of protective devices: If the protective cover, safety valve, or other safety devices of the pump are damaged or fail, they must be repaired or replaced immediately to ensure safe operation.




19. 5、 Suggestions for overhaul cycle




20. Regular overhaul: Based on the operating time and working conditions of the pump, it is recommended to conduct a comprehensive overhaul every 4-7 years, replacing vulnerable parts, inspecting and repairing potential faults.




21. Condition monitoring overhaul: Through vibration analysis, oil detection, infrared temperature measurement and other condition monitoring technologies, real-time evaluation of the pump's operating status, early detection of potential faults, and reasonable arrangement of overhaul time.

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