MASSEY TECHNICAL SERVICE LLC 10-Millbrook Rd. Bridgeport WV. 26330 Phone:304-842-6948

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 Bearing Outer Race Defects

As industry continues to look for the 100% availability of equipment, some companies are looking for new technologies to help them achieve their goals. Companies are also looking for cost savings from outside services.

Vibration analysis has been used for years for industrial applications, but only in the last few years, with the MSHA approval of the SKF data logger has the technology migrated to underground longwall mining. Vibration analysis is an excellent predictive maintenance tool, and a proactive maintenance tool that can help design equipment to last longer. Also by the use of oil analysis in conjunction with vibration analysis a new security can be realized with load changing heavy equipment, that is utilized daily in the global industry.

I will try to update the readers of this newsletter with new information as we discover and solve machine maintenance problems. I will accomplish this with newsletters that pertain to real case histories, as the one that follows.

CASE HISTORY #26- Ventilation Fan Bearing

During January 2000, while completing our monthly vibration check on a 1000 HP ventilation fan we found definite held bearing outer race defect frequencies. We rechecked the vibration in two weeks, and found the same readings. The ventilation fan's vibration system had not shown any excessive increase in vibration. The spectrum of the held bearing is shown below with outer race defects and sidebands at running speed. When the sidebands were present, which is an indication of a serious problem, we recommended replacement of the bearing. Management decided based on the waterfall trending and our recommendation to schedule a bearing change.

The waterfall trend diagram below shows the bearing outer race defect and the spectrums after replacement of the bearing.

The bearing was removed and a spalled area, shown in the picture below,  about 40mm long was found on the outer race. If the bearing had not been replaced it is possible the spalled area would have increased in size and caused to bearing to fail , which would lead to possible catastrophic failure of the ventilation fan.

This is one of many examples of vibration analysis uncovering a problem before the unit is near failure and giving management the time to schedule preventative maintenance work. In the next newsletter I will illustrate a different case study of vibration analysis, which detects a problem and verification of the problem when investigated. If you have any questions please contact us. Feedback is very important to us, and our mission to our customers.


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Last modified: May 19, 2015