At present, the problem of oil leakage in the bearing box of the feed pump motor in domestic thermal power plants is widespread. Analysis of the reasons can be roughly divided into two types: the motor oil block is poorly sealed or the oil block is damaged after long-term operation; the original casting bearing box has casting defects such as sand holes, pores, cracks, shrinkage porosity, etc. due to poor casting technology, which occurs after long-term operation. leakage.
(1) Problems
A power plant 8#, 9# unit electric feed pump motor bearing box, after long-term operation, oil leakage occurs, the turbine oil loss is serious, the oil replenishment is frequent, the output of the feed pump is affected, and the environment is also affected to a certain extent. Pollution.
(2) Cause analysis
The 8# and 9# units of the power plant are two old units, which were put into production in 1985 and 1990 respectively. The bearing seat of the feed pump motor adopts the casting process, and there are inevitably some defects such as blisters, pores, cracks, shrinkage porosity and so on. In the past, due to the short operation time, these shortcomings could not be exposed quickly. After 10 or even 20 years of operation, oil leakage occurred in the bearing seat of the feed pump motor.
(3) Improvement plan
Consult a large number of relevant materials, and formulate this plan on the basis of sufficient research and in combination with the actual situation on site. The HT series products produced by the domestic Huitian Rubber Industry are used for leakage coating treatment. Generally, it is difficult to confirm the leakage location due to leakage caused by casting defects. Therefore, the entire inner surface is coated with an anti-leakage coating to completely eliminate leakage. . The operation process is as follows: first clean the inner surface of the bearing housing, then clean it and dry it, and then infiltrate the inner cavity of the bearing housing with special impregnating glue. Corrosion-resistant repair agent is used for outer anti-corrosion and anti-leakage treatment.
The specific operation method is as follows.
①First, use the high-efficiency cleaning agent HT755 to clean the surface oil, and use the scavenger HT790 to remove the surface paint.
②Use acetylene flame to drive out the oil stains in the dead corners and cracks.
③Use abrasive cloth, wire brush and other tools to polish to the casting body, clean and dry.
etc.; the upper bearing (deep groove ball bearing) is basically not bad; the lower bearing is broken and the bearing and bearing cavity are filled with cinder, sand and water.
According to the analysis, the life of the upper bearing is longer than that of the lower bearing, and the electric pump cannot be operated due to the fragmentation of the lower bearing; the cinder, sand and water filled in the lower bearing and bearing cavity are the direct and main reasons for the rapid failure of the lower bearing; The cinder, sand and water filled in the cavity come from the motor cavity, and the cinder, sand, etc. in the motor cavity also come from the working water. The reason is that the skeleton oil seals 5, 10, 14, etc.
(4) Problem solving
In response to the above analysis, a QS20-75/5-7.5 submersible deep well pump was improved and processed in October 2002. The improvements are as follows: The skeleton oil seal 5 is modified with a single-end mechanical seal to prevent water and other debris in the motor cavity from entering Bearing, accelerated bearing wear failure; bearing cavity 7 is filled with oil, the purpose is to lubricate the bearing, lubricate and cool the mechanical seal, and improve the working environment of the lower bearing. The improved prototype was put into test use in a coal mine on October 15, 2002. After running for a total of 75 days, there were ## failures - the upper bearing was broken. factory. ##The lifespan is 2.5 times that of the original, and it has achieved initial success. After inspection and dissection, it was found that: the motor is good; the upper shaft is willing to break and the bearing and bearing cavity are full of cinder, sand, etc.; the skeleton oil seal 2 is seriously worn, and the cinder and sand enter the upper bearing from the gap between the skeleton oil seal and the shaft. ; The lower bearing has been used for a total of 105 days (3 to 4 times before the improvement) in good condition. There is no cinder and sand in the bearing cavity, and there is a small amount of water in the single oil.
In this way, the problem has been transformed into how to extend the life of the upper bearing to be consistent with the lower bearing. Since the problem of the lower bearing has been solved, a similar solution is adopted to solve the problem of the life of the upper bearing; the skeleton oil seal 2 is modified into a single-end mechanical seal that can be installed on the shaft to prevent cinder, sand, etc. from entering the upper bearing, improving the upper bearing. operating environment, thereby increasing its lifespan.
(5) Summary
Since February 2003, more than 70 improved QS pumps have been put on the market, which are used for deep well water lifting and mine drainage (the main ones), and the longest use time is 5 months. , so far only one has failed, but it is not a bearing problem. According to this method, the bearing life problem of the QS type submersible electric pump can be completely solved