How to maintain and service submersible sewage pumps

Daily inspection and maintenance

Sealing inspection: After long-term use in sewage medium, the gap between the impeller and the sealing ring may increase, resulting in a decrease in the flow rate and efficiency of the water pump. At this point, the power switch should be turned off, the water pump lifted, the bottom cover removed, and the sealing ring taken off. The sealing ring should be matched with the actual size of the impeller mouth ring, and the gap is generally about 0.5mm.

Cable inspection: Cables should be inspected at least once a year. If any are damaged, they should be replaced.

Motor insulation and fastening screw inspection: Inspect the motor insulation and fastening screws at least once a year. If the motor insulation drops, please have it repaired by a professional. If the fastening screws are loose, please re-tighten them.

Engine oil inspection: The submersible sewage pump has been filled with an appropriate amount of engine oil before leaving the factory to lubricate the mechanical seal. This engine oil should be inspected once a year. If water is found in the engine oil, it should be drained, the oil replaced, the gasket replaced and the plug tightened. Three weeks later, a re-inspection is required. If the engine oil has become an emulsion again, the mechanical seal should be inspected and replaced if necessary.

Power supply voltage monitoring: During the operation of the submersible sewage pump, the operator should constantly monitor the power supply voltage value. If it is less than 10% lower than the extra voltage or more than 10% higher than the extra voltage, the motor should be stopped from working, the cause should be identified and the fault eliminated.

Current monitoring: Current monitoring during operation: The current of the water pump must not exceed the rated current indicated on the nameplate. The three-phase current unbalance degree should not exceed 10% under no-load conditions and 5% under rated load conditions. Voltage monitoring during operation: The deviation of the power supply voltage from the rated voltage shall not exceed ±5%, and the unbalance degree of three-phase voltage shall not exceed 1.5%.

Long-term maintenance out of service

When the submersible sewage pump is not in use for a long time, it should be cleaned, lifted and placed in a well-ventilated and dry area, and precautions should be taken against freezing. If placed in water, it should be operated for at least 30 minutes every 15 days (dry grinding is not allowed) to check its functionality and adaptability.

Inspection operation: During the long-term shutdown of the pump installed on the device, the pump should be started for inspection operation for about 5 minutes every one or three months to prevent rusting at the gap between the impeller and the pump body and to prevent sedimentation from forming inside the pump and around the pump inlet. When the water in the pump pit is intermittent, the time interval between two inspection runs should be shorter. Before each inspection operation, corresponding measures should be taken.

Regular maintenance

Bearing grease replacement: The replacement of bearing grease should be carried out at least once a year. Before filling in new grease, the original grease should be cleaned off to prevent the possible harm caused by mixing greases of different qualities. The recommended grease for use is lithium-based grease. When replacing a new bearing, if it is a single-sided bearing with a sealing ring or dust cover, the sealing ring or dust cover should be on the lower side to prevent grease loss.

Mechanical seal inspection and replacement: When disassembling and assembling mechanical seals, be extremely careful. Pay attention to protecting the mechanical seal and the surfaces that fit with it to ensure they are clean and undamaged. The friction pair materials of the mechanical seal on the pump side and the mechanical seal on the motor side are different. The friction pair of the mechanical seal on the pump side is silicon carbide/silicon carbide, while that of the mechanical seal on the motor side is graphite (dynamic ring)/silicon carbide (static ring). Be careful not to install them wrongly. When disassembling or assembling the retaining ring of the mechanical seal on the motor side, the opening groove of the retaining ring should be opened for disassembly and assembly. When installing mechanical seals, you can apply vaseline or soapy water to the holes where the static ring is installed and to the shaft where the dynamic ring is installed, but do not apply oil.

Whole machine air pressure test: After the pump is reinstalled, air pressure tests should be conducted separately for the motor and the entire machine to check the sealing performance. The air pressure is 0.2MPa and the duration is 5 minutes. During the test, the position of the motor and the entire machine should be like this: If there is a leakage in the mechanical seal, the escaping air bubbles should be observable. The pneumatic test of the entire machine should be conducted before the oil chamber is filled with oil.

Troubleshooting and professional maintenance

Troubleshooting: After a malfunction occurs during the operation of the submersible sewage pump, it should be eliminated according to the provided troubleshooting methods. If the problem still cannot be solved and the cause cannot be determined, do not disassemble or repair it randomly by yourself. Instead, immediately seek professional assistance for maintenance.

Pre-maintenance treatment: Before disassembling the pump for maintenance, it should be cleaned and disinfected if necessary to prevent harm to the health of personnel.