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BE1570W Drag Drum Case Study
Background
The gearcase is monitored on a 13-week cycle. It is a direct drive, reversing, variable speed gearcase utilizing helical cut gears and a dual load path. The production cost of dragline downtime is $3,600 per hour and the dragline utilization is 7,000 hours per year. |
Detection
The first survey on the dragline revealed a No.4 Swing Gearcase input shaft outer race defect on the non-drive end bearing. The vibration spectrum from the input shaft NDE measurement location is illustrated on the right and the input shaft bearing outer race defect harmonic series is superimposed on the figure. Due to the severity of the defect indication, a recommendation was made to change out the bearing at a suitable maintenance opportunity. |
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Strip Down Inspection
Five months after detection, the bearing was replaced in conjunction with a scheduled outage. Inspection of the bearing revealed spalling of the outer race and rolling elements shown on the right. |
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| Cost Benefit Analysis |
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Production Downtime Saving |
Repair Cost Saving |
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The planned change out without any secondary damage is typically 24 hours and an unplanned change out is 48 to 60 hours depending on the secondary damage. Thus savings in the range $86,400 to $172,800. |
In service failure would have resulted in a combination of input shaft, input shaft top bearing, and the "Y" and "Z" intermediate shafts and intermediate shaft bull gears. |
| Mid Range Savings |
$USD 129,600 |
Component costs unknown. |
| ROI |
1191% (based on production savings only for 1 incident every 5 years) |
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