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God Bless America 09/11/2001
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As the mining industry continues to look for the 100% availability of equipment, some mining companies are looking for new technologies to help them achieve their goals. Vibration analysis is an excellent predictive maintenance tool, and a proactive maintenance tool that can help design equipment to last longer. 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 mining industry. All newsletters pertain to real case histories, as the one that follows. CASE HISTORY #31 (Bearing defect Gsenv) by Larry Massey During October 2002, while completing our monthly check on a coalmine longwall operation, we discovered a bearing defect on the coal side of the belt tail roller. The bearing outer race was spalled and cracked along with the rollers being pitted. The Enveloped Gs spectrum below shows the evidence of these forces.
The picture below shows the outer race cracked and destroyed two weeks later. The bearings on the roller were 22238 bearings.
Enveloped Gs is a very important tool in early detection of bearing problems. I have also found it to be an excellent tool in determining which bearing is bad on a two bearing pulley. Low frequency travels very well through the shaft from bearing to bearing, however high frequency does not travel as well. The first spectrum overlay below shows both bearings in velocity. The second spectrum shows both bearings in Enveloped Gs (Gsenv). The enveloped Gs spectrum definitely shows which bearing has the defect. Blue is the right bearing and green is the left bearing. Both bearings were replaced, but our customers wanted to know which bearing was bad. Enveloped Gs is a positive check. I have also used SKF Enveloped Gs to determine which bearing is bad on a gear case shaft. Please don't forget to use the correct filter band for the running speed rpm. An incorrect filter band will not provide the best results.
This is one of many examples of vibration analysis uncovering a problem. In the next newsletter I will illustrate a different case study of vibration analysis that detects a problem and verifies the problem when investigated. If you have any questions please call. Feedback is very important to us |
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