1. How to Maintain and Disassemble a Self-Priming Pump
Self-priming pumps are characterized by their simple, reliable structure and long service life, making them widely used in industrial production. Under normal conditions, frequent disassembly for maintenance is generally unnecessary. However, when malfunctions occur, prompt resolution is essential. Below, we share methods for maintaining self-priming pumps and the proper sequence for disassembly and reassembly.
1. Maintenance Methods for Self-Priming Pumps
(1) Rolling Bearing Maintenance: After prolonged operation, replace bearings when wear reaches a certain level.
(2) Front and Rear Seal Ring Maintenance: Replace seal rings when wear reaches a certain level.
(3) Mechanical Seal Maintenance: Generally, mechanical seals should not be disassembled for inspection unless leakage occurs. If leakage appears at the lower end of the bearing housing or severe leakage occurs, the mechanical seal must be disassembled and inspected. When installing or removing the mechanical seal, handle components gently, ensure mating surfaces are clean, avoid striking or colliding with parts, and protect the mirror surfaces of both the stationary and rotating rings.
2. Self-Priming Pump Disassembly Sequence
(1) Disengage the coupling or remove the motor.
(2) Remove the bearing housing assembly. Inspect the front seal ring, impeller, and radial clearance. Also check for any loosening of the impeller nuts.
(3) Remove the impeller nut, then inspect the rear seal ring, impeller, and radial clearance.
(4) Loosen the mechanical seal set screws, then pull out the mechanical seal's rotating ring. Simultaneously check the fit between the stationary and rotating ring end faces, then inspect the O-ring seal condition.
(5) Loosen the coupling set screws, then pull out the coupling from the self-priming pump.
(6) Remove the bearing end cover of the self-priming pump and disassemble the pump shaft and bearings.
(7) Reassembly follows the reverse sequence of disassembly.
The above outlines the maintenance and disassembly procedures for self-priming pumps. Only through regular maintenance can the service life of self-priming pumps be extended.
2.Six Common Failures of Self-Priming Pumps and Their Solutions
A self-priming pump is a type of centrifugal pump capable of drawing gas under suction conditions. It primarily achieves gas extraction by combining the gas-liquid mixing principle with the pump's specialized structure. This enables the creation of a certain degree of vacuum within the pump's suction piping, thereby facilitating centrifugal operation.
1.Causes of Loud Noise in Self-Priming Pumps:
Cause: Insufficient head of the self-priming pump prevents it from drawing water from the well, resulting in excessive noise.
Solution: Replace the pump with one that has sufficient actual head and adequate power to resolve the loud noise issue.
Cause: Air ingress or leakage at pipe connections between the well water level and the pressure tank allows air to enter, causing pump noise.
Solution: Re-inspect the pipe section and connections from the well water level to the pressure tank for air leaks, then reconnect them properly.
2. If the self-priming pump fails to start, first inspect the power supply:
Check if the connectors are securely fastened;
Verify if the switch contacts are properly engaged;
Examine if the fuse has blown;
For three-phase power, check for missing phases.
If an open circuit, poor contact, blown fuse, or missing phase is detected, identify the cause and repair promptly. Next, inspect for mechanical faults within the pump itself.
Common causes include: packing too tight or debris blocking the impeller-to-housing clearance; rusted pump shaft, bearings, or wear rings; severely bent pump shaft.
Troubleshooting methods: Loosen packing and clear the water guide groove; disassemble the pump housing to remove debris and rust; remove the pump shaft for straightening or replace it with a new one.
3.Causes of Self-Priming Pump Overheating:
Bearing damage;
Insufficient clearance between rolling bearings or bracket covers;
Pump shaft bending or misalignment between shafts;
Excessively tight belt tension; insufficient lubrication or poor oil quality;
Blocked balance holes on the impeller causing imbalance and increased thrust on one side.
Troubleshooting Methods:
Replace bearings;
Remove rear cover and install shims between bracket and bearing housing;
Inspect pump shaft or adjust shaft alignment;
Loosen belt tension appropriately;
Add clean grease filling approximately 60% of bearing cavity;
Clear obstructions from balance holes.
4.Motor Section Issues:
Issue: No response after power connection.
Cause: Mostly due to short circuits in the power plug, power lead wires, or motor windings.
Issue: Difficult or failed start-up accompanied by a “humming” sound.
Troubleshooting: During inspection, use a small bamboo stick to quickly flick the fan blades in the direction of rotation. If the motor spins rapidly, this indicates a faulty start capacitor or start winding; replace with a capacitor of identical capacity or repair the start winding. If the motor seizes, it is often due to mechanical failure between the motor and pump head, such as damaged bearings or a jammed impeller.
Issue: Motor runs but at low speed, with overheating housing and a burning odor.
Troubleshooting: This is usually caused by a short circuit in the motor windings. Disassemble the motor and repair using appropriate methods based on the damage, such as welding, jumpering, isolation, or rewinding.
Issue: Excessive noise and vibration during operation.
Troubleshooting: This is usually caused by bearing damage or improper bearing-to-housing fit. Disassemble the motor for inspection. Replace damaged bearings. If the bearing outer race is worn, apply knurling to the mating surface of the pump housing. If the bearing inner race is worn, apply knurling to the worn section of the motor shaft. For severe wear, repair by first performing weld overlay followed by turning.
5. Causes of Insufficient Flow in Self-Priming Pumps:
Mismatched motor speed or belt slippage resulting in low rotational speed;
Insufficient blade installation angle in axial flow pumps;
Inadequate head due to excessively long piping or sharp bends;
Excessive suction lift;
Partial blockage in foot valves, piping, or impellers, or impeller damage;
Severe leakage in discharge pipes.
Troubleshooting Methods:
Restore rated speed; clean oil residue from belts and adjust tension;
Adjust impeller angle; lower pump installation height; shorten piping or modify bends;
Seal pump air leaks and tighten packing;
Clear obstructions and replace impeller; replace leak-reducing ring and seal leaks.
6.Reasons for Self-Priming Pump Failure to Draw Water:
Air trapped inside the pump body or in the inlet pipe, or an improperly sealed foot valve preventing sufficient priming water. Severe air leakage from the vacuum pump packing, or improper sealing of gate valves or flap valves.
Troubleshooting: First, increase water pressure, then fill the pump casing with water before starting the pump. Simultaneously inspect the check valve for tightness and check the piping and joints for air leaks. If leaks are found, disassemble the joints, apply lubricating oil or enamel paint, and tighten the screws. Inspect the oil seal ring on the pump shaft; replace it if severely worn. Leaks in the piping may be due to water or air. Possible cause: Nuts were not sufficiently tightened during installation. For minor leaks, apply cement or a mixture of asphalt oil and cement paste to the affected area. For temporary repairs, apply wet clay or soft soap. If leakage occurs at joints, tighten nuts with a wrench. For severe leaks, disassemble and reassemble the system, replacing cracked pipes. Reduce the lift height and submerge the pump outlet pipe 0.5 meters below water level.
