Analysis of common failure causes of pumps and corresponding measures

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Fault symptoms, causes, and treatment methods:
1. Overload of the prime mover
(1) The pump is not assembled properly, resulting in friction or jamming between the moving and stationary parts.
(2) The outlet valve is fully open when the pump starts, resulting in low resistance in the outlet pipeline.
(3) The balance pipe is blocked.
(4) The packing is tightened too much, or the packing gland is jammed.
(5) One phase of the three-phase power supply is missing.
Treatment:
(1) Reassemble the pump to eliminate friction or jamming between the moving and stationary parts.
(2) Close the outlet valve; slowly open it after the pump starts.
(3) Clear the blockage in the balance pipe.
(4) Loosen the packing gland, adjust it properly, and tighten the nuts symmetrically – but not too tightly.
(5) Reconnect the three-phase power supply properly.

2. Insufficient flow rate
(1) The suction pipe or the pump inlet is blocked, resulting in high resistance in the suction pipe.
(2) The wear ring at the impeller’s suction inlet is damaged, causing an excessive gap.
(3) The pump is rotating in the wrong direction (or the impeller is installed backwards).
(4) The outlet valve is not open or is not opened enough.
(5) The speed of the drive motor is insufficient.
Treatment:
(1) Remove any blockages.
(2) Replace the wear ring to ensure that the gap is within the specified range.
(3) Change the direction of rotation (or reinstall the impeller).
(4) Open the outlet valve fully.
(5) Increase the speed of the drive motor to the pump’s rated speed.

3. Vibration
(1) The pump rotor or the drive motor rotor is unbalanced.
(2) The alignment of the unit is incorrect.
(3) The bearings are worn, with excessive gaps.
(4) The foundation bolts are loose.
(5) The foundation is not solid enough.
(6) The shaft is bent.
(7) The pipe supports are not secure, causing vibration in the pipes.
(8) There is internal friction inside the pump.
(9) The rotor components are loose or damaged.
Treatment:
(1) Rebalance the rotor.
(2) Realign the unit carefully.
(3) Repair or replace the bearings.
(4) Tighten the foundation bolts.
(5) Strengthen the foundation.
(6) Straighten the shaft or replace it with a new one.
(7) Strengthen the pipe supports.
(8) Disassemble the pump to check for internal friction and eliminate it.
(9) Tighten the rotor components and take measures to prevent them from becoming loose again. If a part is damaged, replace it. (10) Remove foreign objects. 4. Water hammer occurs: (1) A sudden power outage creates pressure waves in the system, resulting in negative pressure in the discharge system; gases dissolved in the liquid escape, leaving gas inside the pump or pipes. (2) The high-pressure liquid column rushes back due to the sudden power outage, striking the valve plate of the check valve at the pump outlet. (3) The valve at the outlet pipe closes too quickly. (1) Drain all the gas. (2) Revise the layout of the pipes and pipe fittings in the discharge system to ensure proper functioning of the pump. (3) Close the valve slowly. 5. High bearing temperature: (1) The bearing shells are not properly lapped. (2) The bearing clearance is too small. (3) The bearings are not installed correctly. (4) The bearings are worn or loose. (5) If the oil slinger is deformed, it cannot rotate and thus cannot transfer oil. (6) There is insufficient or excessive oil, or the oil quality is poor. (1) Repair the bearing shells or replace them. (2) Lap them again as required. (3) Check the installation of the bearings to eliminate any issues. (4) Repair the bearings or discard them. If loose, retighten the relevant bolts. (5) Replace the oil slinger. (6) Apply an appropriate amount of qualified lubricant or change the oil completely. 6. Packing overheating: (1) The packing is compressed too tightly; (2) Friction between the shaft and the packing gland; (3) Lack of lubrication for the packing. Cooling fluid: (1) Slightly loosen the packing gland; (2) Adjust the gap between the gland and the shaft so that the gaps in all directions are similar; (3) Check and adjust to ensure that there is an appropriate amount of leakage from the packing seal. 7. Rapid wear of the packing: (1) Poor quality of the packing; (2) The packing is compressed too tightly and not properly lubricated. (1) Replace it with qualified packing; (2) Slightly loosen the packing gland to allow an appropriate amount of leakage from the packing seal. 8. Excessive rotor play: (1) Improper operation, with operating conditions far from those designed for the pump; (2) Blocked balance tubes; (3) The material of the balance disc and its seat does not meet the requirements. (1) Operate the pump carefully to keep it running within the designed operating conditions; (2) Clear the balance tubes; (3) Replace the balance disc and its seat with materials that meet the requirements. Analysis of fault characteristics and preventive measures: 1. Bearings turning blue or black: 1. Damaged due to excessive temperatures during operation ； 2. When installing bearings using the heating method, excessive heating can cause the bearings to anneal, resulting in a reduction in their hardness by 1. Pay attention to the quality of installation. 2. When using heating to install bearings, the heating temperature must be controlled in accordance with regulations. 2. If the temperature of the bearings rises too much, 1. Impurities or contaminants may get inside during installation or operation ； 2. Using inappropriate lubricants or insufficient lubrication for the shaft ； 3. Friction occurs due to friction between sealing devices, gaskets, bushings, etc., or due to loose fit between them ； 4. Incorrect installation, such as skewing of the inner and outer rings, misalignment of the mounting hole, deformation of the raceways, and improper adjustment of gaps ； 5. Incorrect selection: Using an inappropriate bearing as a substitute can lead to overheating due to overload or excessive speed. 1. Pay attention to the quality of installation ； 2. Strengthen maintenance ； 3. Replacement bearings should be selected based on available data. 3. Abnormal noises occur during operation. 1. The rolling elements or raceways are damaged, resulting in an uneven surface ； 2. The bearing components are not installed properly; there is looseness and friction in the bearing accessories ； 3. Lack of lubricant ； 4. There are iron shavings or dirt inside the bearing. 1. Pay attention to the quality of installation ； 2. Lubricant should be added at regular intervals as specified. 4. The rolling elements are severely worn. 1. The bearing is subjected to improper axial loads ； 2. The rolling elements are installed at an angle ； 3. The lubricant is too thick ； 4. The rolling elements do not roll, resulting in sliding friction that causes wear ； 5. Excessive bearing temperature rise leads to damage to the rolling elements ； 6. Mechanical vibration or improper bearing installation causes the rolling elements to be crushed ； 7. The bearing manufacturing precision is not high; heat treatment is inadequate, resulting in low hardness, and the rolling elements become polyhedral in shape. 1. Ensure proper installation quality as required ； 2. Use lubricant as specified, or replace it regularly ； 3. Pay attention to usage and maintenance. 5. Pits and scars appear on the raceway; metal peeling and rusting occur ； 2. Lack of lubricant ； 3. Improper use of materials ； 4. The bearing withstands impact loads ； 5. Current passing through the bearings generates localized high temperatures, causing the metal to melt. 1. Select the bearings appropriately based on their performance characteristics ； 2. Add lubricant at regular intervals as specified ； 3. Electrical equipment must not leak electricity; machines should be equipped with grounding devices. 6. Cracks in the inner and outer rings of bearings. 1. Poor contact between the shaft journal and the bearing seat hole, gaps appearing in the areas of the raceways that are under stress; the bearings experience uneven stress, which leads to fatigue cracks ； 2. Improper disassembly and assembly. It was struck during installation ； 3. Increased bearing clearance leads to shock vibrations ； 4. Poor quality in bearing manufacturing; cracks present inside. 1. Ensure proper installation quality as required ； 2. Replace worn bearings in a timely manner ； 3. Thoroughly inspect the manufacturing quality of the bearings. 7. Metal flaking from the bearings. 1. The bearings are subjected to impact forces and alternating loads, as well as repeated changes in contact stress on the surface of the rolling elements ； 2. The inner and outer rings are installed at an angle; the axial fit step surfaces are not perpendicular; the shaft is bent; and the shaft holes are not aligned ； 3. The bearing clearance is adjusted too tightly ； 4. Iron shavings or hard debris falling between the bearing mating surfaces ； 5. The journal or bearing seat hole is oval in shape, resulting in excessive local loading on the raceways ； 6. The selected alternative or replacement bearing model does not meet the requirements. 1. Ensure proper installation quality as specified ； 2. Use the bearing properly ； 3. Be careful not to let iron shavings and other contaminants fall into the bearings ； 4. Select the bearing properly. 8. The rolling elements are crushed, often in thrust ball bearings. 1. The installation clearance is too small, resulting in excessive compressive force ； 2. Subject to severe shocks during use ； 3. Contamination such as hard iron shavings in the lubricant ； 4. The rolling elements originally had cracks or the bearing has been in use for too long. 1. Adjust the clearance properly. 2. Pay attention to the cleanliness of the lubricant ； 3. Replace or service the bearing at the specified time. 9. It cannot be rotated by hand after installation. 1. The bearing is not cleaned properly; there are sand particles or metal shavings between the rolling elements and the raceways ； 2. Deformation of the cage, with the rolling elements coming into contact with the bearing rings ； 3. The fit between the bearing and the shaft (or housing bore) is too tight (excessive interference, reduced bearing clearance), or the original bearing clearance is too small. 1. Pay attention to the cleaning quality ； 2. Pay attention to the installation quality ； 3. Grind the shaft diameter (or shell bore diameter) so that the fit interference is appropriately reduced ； 4. The original clearance of the bearing is too small to be repaired; it must be replaced. 10. Scratches are present on the bearing raceways. 1. The upper and lower rings of the bearing are not parallel ； 2. Excessive rotation speed ； 3. The rolling elements slide on the raceways ； 4. The lubricant is not clean. 1. Ensure proper installation quality as required ； 2. Select the bearings appropriately according to the usage requirements ； 3. Strengthen lubrication management