Analysis And Modification Of Failure Problems Of Hydro-modified Air-cooled Fans

Air cooling fan, as the main component in the diesel hydrogenation modified system owned to Karamay Petrochemical Company, whose production capacity is around 1.2 million tons per year, has appeared various strength failures frequently since it was put into production in November 2012. Security and stability of the device have been affected seriously by such problems like U-shaped bolt fracture, fracture of the blade shaft, blade fracture, a fan shaft wear, and etc. In view of above problems, a series of researches and analysis were carried out in this paper. Firstly, the strength of the fan blade shaft were checked by relevant mechanics theories, and static analysis of the wind turbine blade, a blade shaft and a U-shaped bolt was performed using the finite element software ABAQUS. We found there were high stress concentration areas in its internal, and these high stress areas were consistent with engineering fault failure. Then, modal analysis indicated that the fourth-order natural frequency approaches to the fan rotational excitation frequency was one of reasons, causing the acceleration failure of fan blade resonance. U-bolt fracture was mainly caused by fatigue fracture, resulting from working in a relaxed state due to inadequate preload of U-bolt when the blade was mounted, while some external factors, such as the high stress areas presenting inside of the U type bolt, fan blade resonance problem and etc., accelerated the fracture process. The thin design of wind shaft system, blade resonance, insufficient preload of shaft bolt, bearing bolt loosening caused by blade impacting duct wall was the main reason for the broken of blade and the fan blade shaft. The insufficient bearing design height and the design of thin bearing seat, were also the main reason of fan bearing inner ring and shaft wear away. Finally, several measures, including replacing the U-shaped bolts diameter 3658mm fan with splint fixing bolt, transforming the first-order axis positioning with the second-order bidirectional positioning, and strictly regulating the blade installation angle and the bolt preload, were taken to solve the diameter 3658mm fan U-shaped bolt fracture problems effectively. Moreover, the bearing inner race run, the fracture problems of blade and the blade shaft were optimized effectively by dividing split bearings into type bearing for the whole container type shaft system. The wind machine, ?3658mm, avoided resonance frequency by increasing frequency, which makes the running state of the fan better. According to the above fault analysis, shaft transformation is the core measure to solve all the problems. Through technological innovation, the air cooling fan running major hidden safety problems would be solved timely, which has laid a good foundation for the safe and stable operation of air-cooled units and achieved good construction.