Study of solid contamination in ball bearings through vibration and wear analyses

In rolling bearings, contamination of lubricant oil by solid particles is one of the main reasons for early bearing failure. In order to deal with this problem, it is fundamental not only the use of reliable techniques concerning detection of solid contamination but also the investigation of the effects of certain contaminant characteristics on bearing performance. Nowadays, non-invasive techniques, such as vibration measurements, are being increasingly used for on-time monitoring of machinery performance. In this context, the present work investigates the effect of lubricant contamination by solid particles on the dynamical behavior of rolling bearings, in order to determine the trends in the amounts of vibration affected by contamination in the oil and by the bearing wear itself. Experimental tests were performed with radial ball bearings lubricated by oil bath. Quartz powder in three concentration levels and different particle sizes was used to contaminate the oil. Vibration signals were analyzed in terms of the root mean square (rms) values. The results show that changes in the rms values of vibration in the high-frequency band, from 600 to 10,000 Hz, were associated to the changes in oil lubrication in the bearing contacts, caused by oil contamination and wear damage on the bearing surfaces.