Water pump fault diagnosis and remedial measures

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During maintenance, the diagnosis of pump failures is a crucial step. The following outlines several common faults along with measures to address them, to help in carrying out effective diagnoses of pump failures. 1. No liquid is available, or the supply of liquid is insufficient or the pressure is low. 1) The water pump is not filled with water or is not properly vented. Remedy: Check whether the pump casing and inlet pipes are completely filled with liquid. 2) The water pump speed is too low. Remedial measures: Check whether the motor wiring is correct, whether the voltage is normal, or whether the steam pressure of the turbine is normal. 3) The head pressure in the water pump system is too high. Remedy: Check the head pressure of the system (especially friction losses). 4) The water pump’s suction head is too high. Solution: Check the existing net head (very small or long inlet pipes can cause significant friction losses). 5) Clogging of the water pump impeller or pipelines. Remedy: Check for any obstructions. 6) The pump is rotating in the wrong direction. Solution: Check the rotation direction. 7) Air is generated by the water pump or there is a leak in the inlet pipeline. Remedy: Check the inlet pipeline for cavitation and/or air leaks. 8) Wear of the packing or seal in the pump’s stuffing box allows air to leak into the pump casing. Remedial measures: Check the packing or seal and replace it as necessary, and check whether the lubrication is proper. 9) Insufficient suction head when the water pump pumps hot or volatile liquids. Solution: Increase the suction head; consult the manufacturer. 10) The bottom valve of the water pump is too small. Solution: Install a bottom valve of the correct size. 11) The submergence depth of the water pump’s bottom valve or inlet pipe is insufficient. Solution: Consult the manufacturer for the correct submergence depth. Use baffles to eliminate vortices. 12) The clearance of the water pump impeller is too large. Remedy: Check whether the clearance is correct. 13) Damaged water pump impeller. Remedy: Inspect the impeller and replace it as required. 14) The diameter of the water pump impeller is too small. Solution: Consult the manufacturer for the correct impeller diameter. 15) The water pump pressure gauge is in the wrong position. Remedy: Check whether the position is correct, and inspect the outlet nozzle or pipe. 2. The water pump stops operating after running for a while. 1) The suction lift is too high. Solution: Check the existing net head (very small or long inlet pipes can cause significant friction losses). 2) Clogging of the impeller or pipeline. Remedy: Check for any obstructions. 3) Air is generated or there is a leak in the inlet pipeline. Remedial action: Check the inlet pipeline for cavitation and/or air leaks. 4) Wear of the packing or seal in the stuffing box allows air to leak into the pump casing. Remedial measure: Inspect the packing or seal and replace it as necessary. Check whether the lubrication is normal. 5) Insufficient suction head when pumping hot or volatile liquids. Solution: Increase the suction head; consult the manufacturer. 6) Insufficient immersion depth of the bottom valve or inlet pipe. Solution: Consult the manufacturer for the correct immersion depth, and use baffles to eliminate vortices. 7) Damaged pump casing gasket. Remedy: Check the condition of the gasket and replace it as required. 3. Excessive power consumption by the water pump 1) Incorrect rotation direction. Solution: Check the rotation direction. 2) Impeller damage. Remedy: Inspect the impeller and replace it as required. 3) Seized rotating parts – Remedy: Check whether the clearance of the internally worn parts is normal. 4) Shaft bending – Remedy: Straighten the shaft or replace it as required. 5) Too high speed. Countermeasure: Check the winding voltage of the motor or the steam pressure supplied to the turbine. 6) The head is below the rated value, and too much liquid is being pumped. Remedy: Consult the manufacturer. Install the throttle valve and cut the impeller. 7) The liquid density is higher than expected. Countermeasure: Check the density and viscosity. 8) The stuffing box does not have proper packing (insufficient packing, not properly inserted or worn out, packing that is too tight). Remedial action: Check the packing and refill the stuffing box. 9) Incorrect bearing lubrication or bearing wear. Remedy: Inspect and replace as required. 10) The operating clearance between the wear rings is incorrect. Remedy: Check whether the clearance is correct. Replace the pump casing and/or impeller wear rings as required. 11) The stress on the pipes on the pump casing is too high. Remedy: Relieve the stress and consult the manufacturer’s representative. After stress relief, check the alignment. 4. Excessive leakage in the pump’s stuffing box. 1) Bent shaft. Remedial measure: Straighten the shaft or replace it as required. 2) Misalignment of the coupling or between the pump and the drive unit. Remedial measure: Check the alignment; realign if necessary. 3) Incorrect bearing lubrication or bearing wear. Remedy: Inspect and replace as required. 5. Bearing temperature is too high. 1) Shaft bent. Remedy: Straighten the shaft or replace it as required. 2) Misalignment of the coupling or between the pump and the drive unit. Remedial measure: Check the alignment; realign if necessary. 3) Incorrect bearing lubrication or bearing wear. Remedy: Inspect and replace as required. 4) The stress on the pipes on the pump casing is too high. Remedy: Relieve the stress and consult the manufacturer’s representative. After stress relief, check the alignment. 5) Excessive lubricant. Remedy: Remove the plug to allow the excess grease to flow out automatically. If it is an oil-lubricated pump, drain the oil to the correct level. 6. Overheating of the water pump stuffing box 1) The packing or seal in the water pump stuffing box is worn, allowing air to leak into the pump casing. Solution: Inspect the packing or seal and replace it as necessary. Check whether the lubrication is normal. 2) The water pump stuffing box does not have the proper packing (insufficient packing, not properly inserted or adjusted, or the packing is too tight). Remedial action: Check the packing and refill the stuffing box. 3) There are design issues with the water pump packing or mechanical seal. Remedy: Consult the manufacturer. 4) Damage to the mechanical seal of the water pump. Remedy: Inspect and replace it as required. Consult the manufacturer. 5) Scratches on the water pump shaft sleeve – Remedial measures: Repair, re-machine, or replace as required. 6) The pump packing is too tight or the mechanical seal is not properly adjusted. Remedy: Check and adjust the packing, and replace it as required. Adjust the mechanical seal (refer to the manufacturer’s instructions provided with the water pump or consult the manufacturer). 7. Difficult rotation or friction in rotating components 1) Bent water pump shaft. Remedy: Straighten the shaft or replace it as required. 2) The operating clearance between the wear rings of the water pump is incorrect. Remedy: Check whether the clearance is correct. Replace the wear rings of the pump casing or impeller as required. 3) The stress on the pipes on the water pump casing is too high. Remedy: Relieve the stress and consult the manufacturer’s representative. After stress relief, check the alignment. 4) Excessive swinging of the water pump shaft or impeller ring. Remedy: Inspect the rotating parts and bearings, and replace any worn or damaged components as required. 5) There is dirt between the water pump impeller and the wear ring of the pump casing, as well as inside the wear ring of the pump casing. Remedial action: Clean and inspect the wear rings, and replace them as required. Isolate and eliminate the source of dirt.