Causes and preventive measures for oil leakage of

2022-07-25
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Causes and preventive measures for oil leakage of turbine oil baffle in thermal power plants, in order to prevent the lubricating oil in the turbine bearing chamber from leaking outward and maintain the tightness of the dynamic and static parts, oil baffle seals are generally used now. The oil baffle consists of two groups of internal and external oil seal teeth and oil return grooves. Each group of oil baffle teeth has 2 ~ 4 copper or aluminum strips embedded on the oil baffle body, which is used to prevent the leakage of lubricating oil and the entry of external steam in the bearing chamber. The millions of dollars invested in the oil baffle include the construction of a new production facility in the United States, which is installed at the axial ends of the bearing chamber by means of assembly slots or screws. This sealing technology is widely used in in-service units

at present, the oil baffle clearance is adjusted to the specified range (left and right sides: 0.15 ~ 0.2 mm; lower part: 0.05 ~ 0.10 mm; upper part: 0.20 ~ 0.25 mm) in strict accordance with the requirements of turbine maintenance process and quality standard for each major and minor repair. However, after the unit operates for a period of time, the oil baffle will still leak. On the one hand, it will pollute the surrounding environment. On the other hand, if leakage is thrown onto the insulation of high-temperature pipelines, unsafe phenomena such as smoking, fire and burning of adjacent protective cables will occur, threatening the normal operation of the unit and even causing forced shutdown in serious cases. Therefore, the oil leakage prevention of steam turbine oil has become a "chronic problem" that affects the safety and civilized production of thermal power plants

1 cause analysis

(1) the layout of local oil return pipeline is unreasonable, which makes the oil return not smooth, the formation of micro negative pressure in the bearing chamber is blocked, and the oil leakage of the bearing bush is unstable and leaks outward along the shaft through the oil baffle clearance

(2) the blast generated by the high-speed rotation of the coupling destroys the micro negative pressure state of the bearing chamber, resulting in the pressure in the bearing chamber being greater than the external pressure, which is prone to oil leakage of the oil baffle

(3) during operation, the suction generated by the fan blades on the generator rotor is enough to lead out the oil smoke in the bearing chamber, gather it into oil drops, and throw it out under the action of centrifugal force

the proportion of cobalt in the used hand motor pool is 60% (4) when the steam turbine is in unsteady speed, the rotor rotation track is non-circular, causing the shaft to rub against the oil baffle teeth, the oil baffle clearance increases destructively, and serious oil leakage occurs

2 preventive measures

2.1 improve the understanding of the harm of oil leakage from the oil baffle

the oil leakage from the oil baffle is easy to cause unsafe phenomena such as smoke, fire and burning of adjacent protective cables, which should be highly valued by the functional departments. Each thermal power plant shall conscientiously implement the requirements of "fire prevention of steam oil system" in item 1.2 of the twenty five key requirements for preventing major accidents in power production, focus on prevention of key parts, and eliminate hidden dangers of equipment, so as to prevent accidents from happening and prevent the expansion of accidents; The system of investigation for work safety shall be implemented to ensure the safety and stability of power production

2.2 strengthen regular patrol inspection and daily inventory of equipment

regularly carry out safety patrol inspection and daily cleaning and inspection of the oil baffle by using phenol based main antioxidant and phosphite based auxiliary antioxidant, mainly including: whether there is oil stain on the oil baffle facade, thermal insulation on high-temperature pipelines, adjacent protective cables and exciter carbon brushes. Once oil leakage is found, it should be eliminated in time. If it cannot be solved at the moment, it should develop plans and preventive measures; In case of smoke and fire due to oil leakage from the oil baffle, personnel shall be organized to put it out immediately and a special person shall be assigned to carry out 24-h monitoring to prevent the recurrence of the ignition point and the expansion of the accident. At the same time, the "four don't let go" that will affect the service life of the device shall be done carefully. It is strictly prohibited to conceal the dereliction of duty

2.3 improve the reliability of the equipment through technical transformation

(1) select efficient smoke exhaust fan to improve the negative pressure of the bearing room, which is usually controlled at 49.5 ~ 98 PA

(2) adjust the declination angle of the oil return main pipe, appropriately increase the pipe diameter, so that the oil discharged from the bearing bush can smoothly return to the main oil tank or sealed oil tank

(3) install a cover on the coupling to reduce the interference of air blast on the oil drainage of bearing bush and maintain the relatively stable micro negative pressure in the bearing chamber

(4) the bearing chamber close to the generator shall be equipped with an oil fume exhaust pipe, which shall be connected to the inlet of the smoke exhaust fan to reduce the impact of suction on the micro negative pressure of the bearing chamber

(5) using a new non leakage floating oil baffle instead of the traditional oil baffle can effectively control the outward leakage of lubricating oil in the bearing chamber. (gengjun)

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