Successful elimination of a pad-fluttering phenomenon

Abstract

Tilting pad journal bearings counteract the occurrence of possible unstable vibrations of rotating machines. However, lightly loaded shoes can be the source of subsynchronous oil-film forces that, in turn, cause subsynchronous vibrations of some pads. This pad-fluttering phenomenon can cause high level vibrations of the shaft, especially when the subsynchronous oil-film forces excite a flexural normal mode of the rotor system. Some basic measures can be implemented to prevent this serious phenomenon. The experimental findings detected during the performance tests of two identical centrifugal compressors that have been affected by pad-fluttering onsets are shown and analysed. Besides, the satisfactory results obtained with a suitable corrective action are shown and discussed.