Development of a degradation index for machinery condition monitoring using the fictitious frequency response function and its application to a centrifugal compressor

  • K. Shin Andong National University
Keywords: Machinery condition monitoring, Condition-based maintenance (CBM), Time-based maintenance (TBM), Degradation index, Fictitious frequency response function, Vibration signal


Recently, many sophisticated machinery diagnosis techniques have been developed and incorporated to the condition-based maintenance (CBM) method for cost effective and reliable operation of machinery. However, many companies are still reluctant to change their maintenance strategy completely from the traditional time-based maintenance (TBM) method to the CBM method due to their conservative approach. Instead, they often want to reduce the maintenance cost by increasing the time between overhaul (TBO) provided that a machine under inspection has not been degraded too much. In order to meet this need, in this paper, a degradation index is suggested as a measure to evaluate how much a machine has been degraded since its last overhaul service. The proposed degradation index is based on the fictitious frequency response function method. It is simple to interpret, and has a clear physical meaning. It is applied to an integrally geared centrifugal compressor and validated its usefulness. The results show that the suggested degradation index can be used as a good complement to both the TBM and CBM methods.