Vibration Monitoring of the Gradual Worn in Journal Bearings

Direct surface contact between a journal and a bearing or surface fatigue wear can happen although the surfaces are well finished and their materials are made from low coefficients of friction. Especially, operation conditions are one of the most important factors that accelerate wear, such as low rotational speed, high load, and low lubricant viscosity. The rate of wear often increases gradually with its lifetime in which the quality of lubricant deteriorates. In this paper, vibration signal analysis is used to diagnose two stages of wear evolution in journal bearings. The first is the detection of early wear created by increasing direct contact between the shaft and the bearing and the other is the wear progress caused by adding micro-particulates in the oil. Based on the generation mechanisms of journal bearing vibrations, it has found that modulation signal bispectrum (MSB) is particularly suitable to characterize the noisy vibrations in which the high-frequency broadband signals are modulated by the low-frequency shaft harmonics. The diagnostic results show that MSB magnitude allows these two stages of wear to be differentiated across a wide range of operation conditions, showing the effectiveness of the vibration technology on the monitoring.