Coast Down Time analysis for condition monitoring: An experimental investigation to study the effects of bearing lubrication and shaft misalignment in rotating machinery

The inherent behavior of any rotating system after the power cut-off is termed as the Coast down Phenomena (CDP). Coast Down Time (CDT), which is the exact time elapsed during deceleration period, can be effectively used to monitor the tribological behavior and mechanical degradation of rotating machinery. This paper presents results of an experimental investigation on a Centrifugal Blower test setup supported with full journal bearing to study effects of lubricants and influence of shaft misalignment on CDT under different operating conditions. Extensive experimental work has been carried out with different oils (different grades of both fresh and used oils) under various shaft misalignment conditions at different cutoff speeds to study the tribological behaviour of lubricants and to study the effect of oil degradation on CDT. Further, an attempt is made to understand effectiveness of lubrication using CDT as performance parameter in comparison with steady state vibration which can be used as tool for selection and optimization of the lubricants for a given application. The result shows that higher order of shaft misalignment condition has considerable effect on CDT at lower cut-off speed.