Vibrations in Turbo Machinery

Motor-Generator Vibration Problems Encountered When Restaging an FCCU Turboexpander

Paper No. 64

F. R. Szenasi, 2nd International Turbo-Expander Users’ Council, Houston, TX, May 24-27, 1993.

This paper describes the solution of a vibration problem which resulted from the conversion of a single-stage power-recovery turbo expander train in an FCCU to a two-stage turbo expander. Details of the equipment rain and operating speeds are given in Figure 1. During the startup of the upgraded expander train, high vibrations (in excess of 10 mils peak-peak) were experienced by the motor-generator. These high vibrations caused the unit to shut down as soon as it reached rated speed. Because of high vibrations, the train was not able to operate for any length of time; however, it was operated long enough to obtain data to balance the motor-generator to allow further investigation of the problem. Accelerometers and permanently installed proximity probes were used to obtain the vibration data to determine the location of the critical speeds of the motor, one of which was near the operating speed. The motor-generator was field balanced to allow operation until a long-term solution could be developed.


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