Application of a Model-Based Method for Balancing a Large Steam Turbo-Generator Unit

The operators of electric power plants are interested in having at its disposal a rapid and reliable tool that provides condition monitoring as well as fault detection (unbalance, bow, cracks, etc.) and diagnostics for its rotating machinery. Monitoring machine vibrations is a major concern for any operator in order to ensure safety by preventing machine failure and scheduling any necessary maintenance. In the present paper a model based approach is used to balance a large steam turbo-generator unit experiencing high amplitude vibration levels. Such approach combines a finite element model for the shaft-bearing-support system and vibration measurement acquired on the real machine in order to identify the appropriate solution for balancing. Rotor lateral position is monitored using displacement probes mounted close to the bearings location combined to seismic transducers mounted on the bearing casing. Several vibration datasets, measured by the displacement probes and corresponding to different operating regimes of the machine, are used for fault detection. The results obtained from these analyzes are then used to balance the machine and thus reduce vibration levels.