Establishing vibration threshold for effective health monitoring of SL20-5 motor compressor set

SL20-5 motor compressor set (MCS) is one of the critical subsystems in the train assemblies as it supplies compressed air to support other subsystems in the train. Besides conducting visual and audible inspections on MCS in North East Line depot, which can be subjective, tedious, and time-consuming, technicians do not have any concrete method to objectively determine the health of MCS. This paper, therefore, proposes vibration measurement and analysis as a form of condition monitoring to assist technicians in effective monitoring the health of MCS. Experiments with ten MCSs, before and after overhaul, were conducted to analyze and correlate vibration signals with MCS health, as well as to establish reliable vibration threshold that can distinguish between healthy and unhealthy MCSs. Results from various statistical analyses, such as notched box plots, support vector machine, and receiver operating characteristic curves, consistently show the feasibility of monitoring and classifying healthy and unhealthy MCSs through vibration measurement and analysis, thereby enabling timely maintenance intervention before MCS malfunctions.