Research and analysis on the solution to oil leakage of sliding bearings in large high-speed motors
Abstract: The purpose of this research is to improve the sealing effect of motor bearings, solve the problem of oil leakage in large high-speed motor bearings, enhance the overall manufacturing quality of the motor, reduce the additional cost of the motor, and improve the market competitiveness of the product. This article proposes structural improvements from two aspects: increasing the sealing performance of the bearing shell and balancing negative pressure, and conducts experiments and analysis.
Keywords: large high-speed motor; Sliding bearings; Oil leakage; Bearing seal; Balance negative pressure; Experiment; economic analysis
Preface
The problem of oil leakage in the sliding bearings of large high-speed motors often exists, which has a significant impact on product quality and indirectly increases the user's operating costs. Four prototypes, YKK800-44500kW, YAKS710-23600kW, YZYKS2900-410500kW, and YPT800-62500kW, were selected for oil leakage testing. Prior to the testing, advanced motor companies such as Siemens and ABB were fully collected for bearing seal data. Communication was made with well-known domestic bearing manufacturers such as Shenke and Zhuji to solve the bearing seal problem, and sealing material manufacturers such as Kent were discussed for sealing structure issues. Based on the characteristics of each manufacturer and the trial production of products, a bearing oil leakage treatment plan was developed.
1. Oil leakage location and causes of sliding bearing motor bearings
1.1 Oil leakage location:
The penetration point of the inner cover shaft of the bearing shell.
The joint between the upper and lower covers of the bearing shell.
The connection points of various interfaces on the bearing shell.
Analysis of the causes of bearing oil leakage:
Negative pressure generated inside the motor causes oil leakage from the bearing shell (this study mainly focuses on this type of problem).
Poor sealing of the upper and lower interfaces of the bearing shell leads to oil leakage.
2. Design scheme and analysis of experimental results
2.1 Solution: Add a balanced negative pressure fan at the inner cover of the motor bearing to counteract the negative pressure generated by the inner fan, as shown in structural diagram 1:
Analysis of the experimental results of the proposed scheme: Trial production of YKK800-44500kW motor was carried out, and during motor operation, the balance pressure hole of the bearing shell was negative pressure. The motor ran for 2 hours, and after disassembly and inspection, it was found that there was oil leakage at the through point of the bearing shaft. The positive pressure generated by the added axial fan cannot offset the negative pressure generated by the fan inside the motor, resulting in the failure of the experiment.
2.2 Second option: Introduce the positive pressure generated by the fan into the interior of the bearing shell to balance the negative pressure, as shown in structural diagram 2.
Analysis of test results for the second option: Trial production of YPT800-62500kW motors was carried out. During motor operation, the pressure in the bearing balance air pressure hole was 0, and the motor ran for 2 hours without any oil leakage after disassembly and inspection. The positive pressure generated by the motor fan can effectively resist negative pressure, the pressure inside the bearing shell is balanced, and the test is successful.
2.3 Third option: Increase the number of sealing rings in the bearing shell and add balance pressure holes in the bearing shell, as shown in structural diagram 3:
Analysis of test results for the third option: Trial production of YAKS710-23600kW motor was carried out. During motor operation, the pressure in the balance pressure hole of the bearing shell was slightly positive. After 2 hours of operation, there was no oil leakage after disassembly and inspection. The newly added sealing structure and introduced positive pressure gas can effectively overcome negative pressure, and the pressure inside the bearing shell is slightly positive, indicating successful testing.
2.4 Fourth option: Add a curved structure and fill it with lubricating grease to form a closed cavity, as shown in Figure 4:
Result analysis of the fourth option: Trial production was conducted on the YZYKS900-410500kW motor. During motor operation, the pressure in the bearing balance air pressure hole was 0, and the motor ran for 2 hours without any oil leakage after disassembly and inspection. The added curved structure has good sealing performance and can withstand negative pressure inside the cavity, indicating successful testing.
3. Technical and economic analysis of scientific research achievements
Oil leakage in high-voltage three-phase asynchronous motors undoubtedly reduces the operating costs for users. Taking motor lubricating oil L-TSA32 as an example:
The price of L-TSA32 turbine oil is 2100 yuan for 200L. According to user feedback, the H900 center high asynchronous motor has an oil leakage of about 1 barrel per 5 months in its original structure.
The annual lubricant usage fee for users is 5040 yuan, which is calculated as 12 ÷ 5 × 2100.
It can be seen that through the structural transformation of the motor bearing shell, our company's product quality has been improved, and we can also save users 5000 yuan/year in oil costs.
4. Conclusion
Through testing the YKK800-44500kW, YAKS710-23600kW, YZYKS900-410500kW, and YPT800-62500kW motor prototypes, it was confirmed that the sealing structures of the second, third, and fourth schemes are completely feasible. This sealing structure not only improves the quality of the motor, but also saves operating costs for users and enhances the competitiveness of the product in the market.
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