Vibration Reduction Or Large Steam Turbine Generator Through Bearing Analysis/Modification.

LecturePg. 1-6Large utility steam turbines have experienced very high vibration levels on their generator exciter bearings. Units where the exciter rotor is supported by a single bearing are particularly susceptible. This synchronous vibration, measured as high as 14 mils (pk/pk), is typically unresponsive to balancing attempts. Vibration levels of this magnitude can lead to bearing or bearing support damage and higher scrutiny by insurers. Exciter and generator rotors are direct coupled, but differ significantly in mass. As the generator is loaded, it grows vertically, drawing the smaller exciter rotor with it. If adequate loading of the exciter journal bearing has not been established during generator to exciter alignment, the bearing becomes unloaded, affecting its stiffness and damping properties. These changes affect the exciter's vibration response and balance characteristics. Bearing modifications can enhance bearing stiffness and damping properties, reduce the effect of the exciter rotor's radial growth, and improve balancing characteristics