1、PDF外文：http:/ 5400 字 出处： Engineering Failure Analysis, 2010, 17(5): 1188-1194 附录 A Investigation of causes of fan shaft failure M. Ristivojevic, R. Mitrovic and T. Lazovic Belgrade University, Faculty of Mechanical Engineering, Kraljice Marije 16, Belgrade 11120, Serbia Abstract Ene
2、rgy efficiency of thermal power plants depends on the vital plant elements reliability levels. In order to preserve high level of energy efficiency, the vital elements operational capability is continually monitored via observing the working temperature, vibration and noise levels. Yet, however, in
3、spite of this, and usually due to inadequate maintenance, inadequate assembly, errors in the design or manufacturing processes, or due to accidents, abrupt failures of the plants vital elements can occur. An example for this is the volumetric destruction of the fresh air fan shaft due to melting of
4、the shaft at the shafts stationary support. In addition to shaft destruction, the fan bearing and wheel blades have undergone destruction as well. This breakdown has occurred in the course of continual monitoring of the bearing service temperature and vibrations levels. Former studies, aimed at dete
5、rmining the breakdown causes, were based on the detailed examination of the damaged elements materials and detailed analysis of the bearing setting arrangement. Considering the fact that the shaft stationary support was realized by means of a double-pressed joint, a thorough analysis has been made i
6、n this paper of the pressed joint operational capability in the boundary service conditions, in order to determine the extent to which the pressed joint participated in the breakdown. Keywords: Fan； Shaft； Ball bearing； Pressed joint； Temperature Article Outline 1. Introduction 2. Setting arrangemen
7、t analysis in fixed shaft support 3. Bearing setting arrangement breakdown condition description 4. Double-pressed joint analysis vs. bearing setting operational capability 5. Conclusion References 1. Introduction Fresh air fan feeds fresh air into the thermal power plant boiler. The fan uses a high
8、-voltage AC electric motor as the driving machine, to which it is connected by way of a flexible coupling. The fan consists of a pre-wheel, 13-blade working wheel and a shaft. Fan shaft is embedded on two double-row, self-adjusting barrel-shaped bearings of the 22340 CC/W33 type, with steel cages, f
9、itted on four cast concrete foundations, made especially for this purpose. The shafts technical characteristics are presented in Fig. 1. Fig. 1. Fan shaft Bearings rotation operational frequencies at the shaft supports, placed in separate housings, are close to boundary values (operational fr
10、equency is 740 min1, and the boundary one is 850 min1, for the permanent grease-lubrication solution). In order to compensate for errors in the bearing setting arrangement and in order to ensure the shafts axial movement due to thermal deformations, the outer bearing is axially movable and fitted ne
11、xt to the electric motor, while the inner bearing is axially immovable. In service conditions, proper fan operation is ensured by continual monitoring of the electric motor service temperature, as the driving machine, and of both bearings on the fan shaft. Due to high operating temperatures, the pla
12、nt components cooling has been provided for.The electric motor is air cooled, while the initial structural solution of water cooling was replaced by air cooling. Yet, however, in spite of the continual monitoring of the fresh air fan assemblys vital elements operational capability, a major breakdown
13、 occurred, i.e. the volumetric shaft destruction. In order to establish the causes of the breakdown, a thorough examination of the quality of materials was undertaken (micro-structure examining and determining the shaft materials chemical and mechanical properties) 1 and design solution for the bear
14、ing setting arrangement was analyzed 2. Literature 1 provides images of the breakdown status of the fixed supports bearing assembly setting arrangement. Literature 2 provides proposed optional solutions, aimed at improving the actual structural design of the shaft setting arrangement at the immovabl
15、e support. Bearing in mind that the bearing setting arrangement in the shafts fixed support is realized by means of a double-pressed joint: shaftbushing and bushingbearing inner ring, this paper depicts a thorough analysis of the pressed joints operational capability in the extreme service and desig
16、n conditions. Based on the performed analysis, the contribution of the pressed joints to the fan shaft breakdown in thermal plants has been recognized. 2. Setting arrangement analysis in fixed shaft support The fan shaft sleeve was fitted with a bushing to which a self-adjusting barrel-shaped bearing was positioned as well as a disk. The axial movement of the inner bearing ring at the sleeve was prevented by a nut, while axial movement of the outer ring in the housing was prevented by the hood. A cylindrical bushing was positioned between the shaft sleeve and inner bearing ring (Fig. 2).
