Common 8 Fault Diagnosis Guidelines for Pumps
Common Faults Corresponding to Diagnoses (Symptoms → Possible Causes → Inspection Items)
A. Pump fails to start / immediately trips.
Possible causes: Electrical failure, bearing jamming, impeller blockage, severe cavitation/vibration
Check items:
1. Check the motor wiring, overload settings and voltage to ensure they are normal;
2. Listen for any friction sounds from the equipment (refer to vibration readings for auxiliary judgment);
3. Check for any blockages in the filter, suction pipe, and impeller;
4. Verify the rotation direction of the pump and the alignment of the connection points.
B. Low flow rate / Low discharge pressure
Possible causes: Air intrusion, cavitation, blockage of the suction pipeline, component wear (impeller/liner), incorrect operating point
Check items:
1. Inspect the suction pipe: Confirm whether the filter is clogged, and whether the valve is partially closed; Check if the suction pipe is too small/long/irrationally laid out; Verify if the suction pressure is lower than the required net positive suction head; Check if there is any leakage at the suction point (caused by vacuum, resulting in air intake);
2. Confirm whether the system curve matches the pump curve, and check if the operating speed of the pump meets the requirements;
3. Inspect the worn components (impeller diameter, throat bushing, liner), as wear will directly lead to a decrease in head.
C. Corrosion (accompanied by noise, vibration, and dents; the exhaust port may show a "rusty" appearance)
Possible causes: Insufficient necessary suction head margin, excessive suction loss, excessively high temperature, flash evaporation
Check items:
1. Measure the suction pressure and calculate the available net positive suction head;
2. Increase the available necessary suction head: raise the liquid level of the feed tank; reduce suction loss (replace large-diameter pipes, clean filters, reduce elbows); try to lower the pulp temperature; reduce the flow rate to stay away from the cavitation area;
3. Check for any air leakage at the seals and flanges.
D. Excessive vibration/friction
Possible causes: non-parallel axes, bearing wear, imbalance (solid accumulation), shaft bending, unstable suction
Check items:
1. Conduct alignment checks (preferably using laser alignment method);
2. Inspect the condition of the bearings and the lubrication status (confirm the type of lubricant, the oil level, and whether the lubrication frequency is reasonable);
3. Check for any axial offset of the shaft and troubleshoot any issues related to shaft bending;
4. Clean the impeller and inspect for any uneven solid deposits.
E. Rapid wear of the impeller/sleeve (short service life)
Possible causes: improper setting of slurry parameters, operation under non-design conditions, mismatch in material selection, incorrect gap setting, poor solid control
Check items:
1. Check the mud parameters: particle size distribution, hardness, concentration; investigate erosion phenomena caused by large particles;
2. Ensure the correct gap (between the throat liner/liner and the impeller) is maintained; improper gap will accelerate wear;
3. Check if the inlet pipeline causes erosion to the impeller: avoid direct water jetting into the center of the impeller; use appropriate suction pressure reducers/bends; consider using wear-resistant materials (hard alloy coating, high chromium material, rubber/ceramic lining, etc., select based on operating conditions).
F. Sealing Issues (Leakage, overheating of sealing components, poor cleanliness of sealing surfaces)
Possible causes: improper cleaning method for the sealing surface, unreasonable pressure in the sealing chamber, intrusion of solid substances, incorrect selection of sealing surface material
Check items:
1. Verify the sealing flushing system: Check the flushing flow rate, pressure (usually higher than the slurry pressure at the sealing point) and cleanliness; Confirm the compatibility and filtering effect of the flushing fluid;
2. Check the layout and direction of the sealing chamber (if applicable);
3. Check if the sealing package (if used) is properly adjusted and has been lubricated.
G. Bearing overheating / Increase in motor load
Possible causes: Bearing damage, misalignment, wear of the impeller leading to increased hydraulic loss, friction of the seals, cavitation.
Check items:
1. Check the temperature trend and lubrication condition of the bearings;
2. Reconfirm the alignment and connection status of the equipment;
3. Inspect the worn rings/wheel and the gap condition;
4. Monitor the motor current and compare it with historical data for analysis.
H. Pipe blockage / obstruction / sudden performance decline
Possible causes: Excessive slurry concentration, presence of fibrous particles, oversized solid particles, incorrect setting of screens/filters
Check items:
1. Check for any buildup or blockage in the inhalation filter and the inhalation pipeline.
2. Adjust the solid handling method: Replace the appropriate impeller type (such as vortex type, free flow type, etc.); adjust the screen opening position; optimize the feeding strategy (avoiding blank periods of feeding and preventing particle deposition).
