Preventing Undetected Train Torsional Oscillations

Abstract

In the past few years the authors have encountered numerous problems and coupling failures related to unexpected torque fluctuations on applications with reciprocating compressors and on VFD, synchronous motor, and gas engine driven trains. In some cases, dangerous coupling failures have resulted causing significant lost uptime, and requiring a tremendous amount of engineering resources to discover the root problem and the corrective action. Since almost all modern turbomachinery is outfitted with proximity probes to detect lateral vibrations, but not with probes or systems to detect torsional oscillations, these failures occurred suddenly and, in some instances, without warning. In this paper, some of these cases and the work done to deduce the causes of these failure and discussed. The various methods used to measure the oscillations and the advantages and disadvantages of each are presented.