CALCULATION OF BEARING PRELOAD TO EXTEND BEARING LIFE USING ROTOR LIFT AND AXIAL ENDPLAY METHOD

Abstract

This research examines the application of bearing preload techniques on the Primary Air Fan Fluid Coupling at the Indramayu Power Plant to enhance operational reliability and reduce vibrations caused by improper bearing preload adjustments. The Primary Air Fan functions to circulate primary air for combustion, while the fluid coupling transmits power from the motor to the fan. Damage to the four-point contact ball bearings of type NU 226 ECJ and QJ 322 N2MA frequently occur due to inadequate preload adjustments, resulting in high vibrations and operational disturbances. The research approach includes measuring bearing stiffness and adjusting shaft-housing fits & tolerances using rotor lift and axial endplay techniques, which allow for measurements without disassembling components. Prior to the repairs, the radial internal clearance values for bearing NU 226 ECJ were 0.08 mm and 0.04 mm for QJ 322 N2MA. After the application of appropriate preload, the clearance for QJ 322 N2MA was reduced to 0.03 mm. The results of the vibration analysis indicate a significant improvement in the peak vibration value from 18.58 mm/s before the repair to 2.24 mm/s after the adjustment of preload and other parameters. The application of this technique extends the service life of the bearing and reduces the risk of mechanical failure. These findings provide guidance for the maintenance and optimization of systems in power plants, as well as underscore the importance of attention to preload in the design and maintenance of mechanical systems.