How To Judge The Quality Of The Sewage Pump Motor

Aug 09, 2025

As the "heart" of sewage treatment, the quality of the motor of the sewage pump directly determines the service life and operational stability of the equipment. It is crucial to master scientific testing methods when facing products with varying quality in the market. This article combines industry practice and professional testing standards to analyze motor quality judgment methods from six dimensions.

 

1, Appearance Structure: The First Line of Quality Defense

The high-quality sewage pump motor adopts integrated casting technology, and the shell has no splicing gaps, which can effectively prevent sewage infiltration. During inspection, it is important to focus on observing:

1.Protection level identification:

IP68 is the industry's minimum standard, indicating that the motor can operate in a water depth of 1 meter for a long time.
2.Material and process:

High quality pump bodies are made of 304 stainless steel or cast aluminum wrapped stainless steel structure, while inferior products are commonly coated with cast iron or plastic, which are prone to corrosion and perforation.

3.Sealing design:

Observe the isolation structure between the oil chamber and the motor chamber. High quality products use dual mechanical seals and skeleton oil seals, while inferior products may only use single-layer rubber seals.
 

2, Electrical Performance: Core Indicator Testing

1.Insulation resistance test：
Use a 500V megohmmeter to measure the insulation resistance between the winding and the casing, with a standard value of ≥ 2M Ω. If the reading is less than 0.5M Ω, it indicates that the insulation layer has been dampened or damaged. A case study of a sewage treatment plant shows that a motor with an insulation resistance of 0.3M Ω burned out after running for 2 hours.

2.Three phase balance detection：
Measure the resistance value of the three-phase winding with a multimeter, and the deviation of the resistance value of high-quality motors should be less than 5%. If the resistance value of a certain phase exceeds the average value by 20%, there may be a turn to turn short circuit. The actual test data of a certain brand of motor shows that the three-phase resistance values of qualified products are 12.3 Ω, 12.5 Ω, and 12.4 Ω, respectively, while the fault motors are 15.2 Ω, 8.7 Ω, and 12.6 Ω.

3.No load current test：
The no-load current at rated voltage should be 30% -50% of the rated current. If the current exceeds the standard by more than 50%, there may be bearing jamming or sweeping failure.

 

3, Running status: Key points for dynamic monitoring

1.Vibration noise analysis：
The vibration value of high-quality motors during operation should be less than 2.8mm/s (ISO10816 standard), and the noise should be ≤ 75dB (measured at 1 meter). A certain test showed that the vibration value of the motor with damaged bearings reached 8.2mm/s, accompanied by periodic metal friction sound.

2.Temperature rise control：
After continuous operation for 2 hours, the surface temperature of the motor should be ≤ 80 ℃ (when the ambient temperature is 25 ℃). A certain brand of H-grade insulated motor has a measured temperature rise of only 55K, while inferior motors can reach over 100K.

3.Turn verification：
Wrong steering can lead to a decrease in traffic of over 40%. Due to wiring errors, a 55kW motor at a certain sewage station ran idle and burned out, resulting in a direct loss of over 11,138.32 dollars.

 

4, Protection design: adaptability to special working conditions

1.overload protection:
High quality motors are equipped with PTC thermistors, which automatically cut off power when the temperature reaches 130 ℃. During the stall test of a certain brand of motor, the power was cut off within 15 seconds, while the inferior product continued to run until the coil melted.

2.anti-corrosive treatment:
The motor junction box should be made of 316L stainless steel material, and the cable entry device should have an IP68 protection level. A coastal sewage treatment plant used motors that had not undergone anti-corrosion treatment, and after 6 months, the terminal posts corroded and broke.

 

5, Maintenance and upkeep: Extend service life

1.Regularly change the oil:
Replace the 32 # mechanical oil every 2000 hours of operation.

2.Adjustment of impeller clearance:
After wear, the gap should be maintained at 0.15-0.3mm, and if it exceeds 0.5mm, the sealing ring needs to be replaced. A certain pump station experienced a 30% decrease in flow due to failure to adjust the gap in a timely manner.

 

Mastering these detection methods can systematically evaluate the quality of sewage pump motors.