What should I do if the bearing bush temperature is abnormal when the power plant is running?
The gas turbine power plant adopts the STAG-109FA-SS single-shaft combined cycle unit, which consists of a PG9351FA gas turbine, a two-cylinder two-flow steam turbine with a D10 three-pressure reheat system, a 390H hydrogen-cooled generator, and a triple-pressure reheat but with a condenser It is composed of a natural circulation waste heat boiler for deaeration. Except that the waste heat boiler is supplied by Hangzhou Boiler, the rest are provided by Harbin Power Equipment Co., Ltd. and General Electric Company of the United States. The entire shafting system is supported by 8 bearings, 2#, 1# bearings support the gas turbine, 3#, 4# bearings support high and medium pressure cylinders, 5#, 6# bearings support low pressure cylinders, 7#, 8# bearings support generators , Of which 1#, 2#, 3#, 4#, 5# bearings are tilting pad bearings, and the rest are elliptical pad bearings. Now we discuss the problem of high temperature of bearing bush during operation of 4# bearing.
The gas turbine unit has been shut down for a long time after inspection type A repairs. After the cold start-up, it was found that the temperature of the bearing bush metal of the unit 4# was high. When the unit is running at full load, real-time monitoring of 4# bearing bush, 5# bearing bush and lubricating oil inlet temperature is carried out. Through the monitoring data, it can be found that when the unit is operating at full load, the temperature measurement points of the two bushes of 4# bearing are near the high alarm value of the bearing bush temperature, while the temperature of the 5# bearing bush is basically below 100℃, and the 4# bearing bush is in operation. There is an abnormal phenomenon of high temperature, which threatens the safe and stable operation of the unit.
The 4# bearing of the power plant is a tilting pad bearing. The surface of the bearing pad is covered with a layer of babbitt alloy. When the temperature is high or the bearing pad is subjected to abnormal stress, the babbitt alloy will be deformed. In addition, the 4# bearing is adjacent to the shaft seal of the high and medium pressure cylinder, which does not rule out the influence of the large leakage of the shaft seal on the temperature of the bearing bush.
The oil quality of the lubricating oil affects the establishment of the oil film, and situations such as unqualified lubricating oil particles often occur during operation. After investigation, it was found that the factory would regularly sample and analyze the lubricating oil. At the same time, the unit used an external oil filter to filter the lubricating oil for a long time, and no problems with the lubricating oil quality were found.
During the operation of the unit, the operating personnel monitor the lubricating oil temperature at all times to ensure that the lubricating oil temperature is within the normal allowable range. At the same time, by looking at the two-day operating data, it can be seen that the lubricating oil inlet temperature has been around 41°C, which is within the normal operating range. When the temperature of the 4# bearing bush was high, the maintenance personnel of the plant repeatedly inspected the surrounding environment of the 4# bearing and used a spot temperature gun to measure the temperature of the shaft seal on the medium pressure cylinder side. No abnormal phenomenon was found.
The lubricating oil intake affects the quality of the oil film establishment. During the construction of the unit, the lubricating oil intake is specified by the Electric Power Design Institute and generally does not change. Checking the maintenance history of the unit, it was found that the unit had experienced high temperature of the bearing bush of 5# bearing. After communicating with the manufacturer, the inner diameters of the oil inlet holes of the 4# and 5# bearings were adjusted to increase the 5# bearing inlet. Oil quantity, reduce the oil intake of 4# bearing, try to reduce the temperature of 5# bearing bush, but the adjustment did not reach the expected effect. The follow-up investigation found that the bearing bush temperature measuring points of 4# and 5# of the factory were connected reversely.
The 5# bearing of this unit has been adjusted centrally and the 5# bearing is raised by 0.17mm. However, the unit operation found that the bearing bush temperature change is not as obvious as expected. It is suspected that the uneven distribution of the rotor load will cause the bearing bush to deform, resulting in poor quality of the oil film in the bearing. , The 4# bearing bush cannot be cooled effectively, resulting in high temperature of the 4# bearing bush.
After analysis, the maintenance plan was selected. The first item is to restore the 4#, 5# bearing orifice plate to the original design value, and the second item is to remove the 4#, 5# bearing and inspect it. Re-pouring the bearing bush if necessary. After dismantling the bearing, first check the appearance of the bearing bush. It is found that there are obvious indentations in the central area of the lowermost bush of the bearing. This area is in contact with the hard steel area on the inner surface of the bearing and is the main stress area of the bush. This phenomenon can be It is inferred that the pad has received a large load and the bearing pad is likely to be deformed. In order to further verify the appeal inference, the lower half of the bearing was subjected to the step of pressing the false shaft, and the contact between the bearing bush and the rotor was checked. After pressing the false shaft, the red lead on the bearing bush was unevenly distributed. It can be judged that the bearing bush has been deformed and needs to be returned to the factory for re-pouring. After the bearing bush is poured, the bearing is reinstalled into the unit, and the bearing and rotor Find the center and restore the relative position of the bearing and the rotor to the state before repair. After the unit is turned on, by checking the operating curve, the temperature of the 4# bearing bush has been significantly improved after overhaul. When the unit is fully loaded, the temperature of the bearing bush has dropped by about 10°C on average.