1. The pump cannot start or starts under load
The following are the possible causes and solutions:
(1) The prime mover or power supply is not functioning properly. Check the power source and the prime mover to ensure they are working correctly.
(2) The pump is jammed. Inspect the coupling manually, perform a disassembly check if necessary, and address any issues between the stationary and rotating parts.
(3) The packing is too tight. Loosen the packing to reduce resistance.
(4) The discharge valve is not closed. Close the valve before restarting the pump.
(5) The balance pipe is clogged. Clear the balance pipe to restore normal operation.
2. The pump fails to prime
The following are the possible causes and solutions:
(1) The pump is not primed properly or there is air in the system. Re-prime the pump to remove air from the suction side.
(2) The pump is not rotating in the correct direction. Verify the rotation direction and adjust if needed.
(3) The pump speed is too low. Check the speed and increase it to the required level.
(4) The filter is clogged or the valve is malfunctioning. Inspect and clean the filter, and ensure the valve is operating properly.
(5) The suction height is too high or the suction tank is under vacuum. Lower the suction height and check the pressure in the suction tank.
3. The pump primes but then loses prime
The following are the possible causes and solutions:
(1) There is a leak in the suction piping. Inspect all connections and the stuffing box for leaks and seal them if necessary.
(2) Air has not been fully removed from the suction side. Repeat the priming process to ensure all air is expelled.
(3) Foreign material has blocked the suction side. Stop the pump and remove the obstruction.
(4) A large amount of gas is entering the pump. Check the inlet whirlpool and ensure the submerged depth is sufficient.
4. Low flow rate
The following are the possible causes and solutions:
(1) Similar issues as in points b and c. Take appropriate corrective actions based on the specific situation.
(2) The system static head has increased. Check the liquid level and system pressure to identify and resolve the issue.
(3) Friction losses have increased. Inspect the pipeline, check valves, and other obstructions that may be causing resistance.
(4) The wear ring between the casing and impeller is excessively worn. Replace or repair the affected components.
(5) There are leaks elsewhere in the system. Inspect the seals and other potential leakage points.
(6) The impeller is clogged, damaged, or corroded. Clean, inspect, and replace the impeller if necessary.
5. Insufficient head
The following are the possible causes and solutions:
(1) Same as previous issues (1), (2), (3), (4), and (6). Take appropriate measures to address the root cause.
(2) The impeller is mounted incorrectly (e.g., double-suction wheel). Check the impeller installation and correct it if needed.
(3) The liquid’s density or viscosity does not match the design conditions. Verify the physical properties of the liquid and adjust accordingly.
(4) The operating flow rate is too high. Reduce the flow to bring it within the design limits.
6. Excessive power consumption
The following are the possible causes and solutions:
(1) The impeller is rubbing against the wear ring or casing. Inspect and repair the affected areas.
(2) Similar to issue e(4). Reduce the flow rate to lower power consumption.
(3) The liquid density has increased. Check and verify the liquid properties.
(4) The packing is too tight or dry friction is occurring. Loosen the packing and check the water seal system.
(5) Bearings are damaged. Inspect and replace the bearings if necessary.
(6) The speed is too high. Check the driver and power supply to ensure the speed is within acceptable limits.
(7) The shaft is bent. Correct the shaft alignment to eliminate vibration and inefficiency.
(8) The axial force balance is failing. Check the balance hole and return pipe for blockages and clear them.
(9) Coupling misalignment or insufficient axial clearance. Check the alignment and adjust the clearance as needed.
7. Pump vibration or abnormal noise
The following are the possible causes and solutions:
(1) Similar issues as in c(4), f(5), (7), and (9). Take appropriate corrective actions.
(2) Vibration occurs at 0–40% of the operating speed. This may be due to excessive bearing clearance, loose bearings, impurities in the lubricant, poor oil quality, or cavitation. Inspect and take corrective measures such as adjusting the bearing clearance or replacing the oil.
(3) Vibration occurs at 60–100% of the operating speed. This could be caused by similar bearing issues as in (2), or by a large seal gap, loose rings, or seal wear. Inspect and adjust or replace the seal as needed.
(4) Vibration occurs at twice the operating speed. This may be due to coupling misalignment, loose coupling, seal friction, casing deformation, bearing damage, or resonance. Inspect and repair or replace the affected components.
(5) Vibration occurs at n times the operating speed. This can be caused by pressure pulsations, misalignment, casing deformation, seal friction, foundation or piping resonance, or machine resonance. Strengthen the foundation or piping and address the underlying issue.
(6) Vibration occurs at very high frequencies. This may be due to shaft friction, seal or bearing wear, improper fit, or bearing jitter. Address these issues similarly to those in point (4).
8. Bearing overheating
The following are the possible causes and solutions:
(1) The bearing pad scraping does not meet specifications. Repair or replace the bearing pads as needed.
(2) The bearing clearance is too small. Adjust the clearance or re-scrape the bearing.
(3) There is insufficient oil or poor-quality oil. Add more oil or replace the oil with new lubricant.
(4) The bearing assembly is incorrect. Check the assembly requirements and make necessary adjustments.
(5) The cooling water circuit is faulty. Inspect and repair the cooling system.
(6) The bearing is worn or loose. Repair or replace the bearing. If bolts are loose, tighten them appropriately.
(7) The shaft is bent. Correct the shaft alignment to prevent further damage.
(8) The oil slinger is deformed or not rotating properly, leading to no lubrication. Replace the oil slinger.
(9) Coupling misalignment or insufficient axial clearance. Check the alignment and adjust the clearance as required.
9. Shaft seal overheating
The following are the possible causes and solutions:
(1) The packing is too tight or experiencing friction. Loosen the packing and check the water seal tube.
(2) The water seal or water seal tube is misaligned. Realign the components to ensure proper function.
(3) The flushing or cooling system is not working. Inspect the circulation tube and ensure it is functioning correctly.
(4) The mechanical seal is faulty. Inspect and replace the mechanical seal if necessary.
10. Excessive rotor movement
The following are the possible causes and solutions:
(1) Improper operation or running outside the design conditions. Ensure the pump operates within its designed parameters.
(2) The balance line is not smooth. Clear the balance tube to restore proper function.
(3) The balance plate and seat are made of unsuitable materials. Replace them with materials that meet the required standards.
11. Water hammer occurred
The following are the possible causes and solutions:
(1) Sudden power failure causes pressure fluctuations, creating negative pressure in the system. Dissolved gases escape, leading to air pockets in the pump or pipes. Purge the air from the system.
(2) A sudden power outage causes a high-pressure liquid column to rush in, striking the outlet check valve. Reconfigure the pipeline layout and discharge system to avoid this issue.
(3) The discharge valve is closed too quickly. Slowly close the valve to prevent pressure surges.
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