BE 1370 Dragline, Drag Drive Gearbox, Intermediate Shaft Bearing.
BE1370 Dragline
BE1370 Dragline
1) Background
This dragline has been monitored by VA for 12 years during which time many bearing and gear faults have been successfully detected.
2) Monitoring History
During the first monitoring survey following a major shutdown, VA detected a significant fault in an intermediate shaft taper roller bearing. This bearing had not been inspected during the shutdown. A special VA survey 2 weeks later confirmed the fault and WDA on the grease indicated severe spalling was occuring. A bearing changeout was then scheduled.
Vibration Spectrum with Bearing Fault
3) Machine Overhaul Report
Bearing Inner Race Flaking
Subsequent inspection of the failing bearing indicated that severe flaking had progressed around 180° of the inner race. The other bearing components had suffered some consequential damage from the flaking wear debris.
4) Failure Analysis
There was some indication that the initial flaking damage occured at sites coincident with roller spacing around the inner race. As there had been no bearing damage indication before the major overhaul, it was postulated that static overload had ocurred during the shutdown causing brinelling and subsequent in-service flaking. It is often the case that “preventive” maintenance procedures lead to failure and one of the advantages of performing maintenance-on-condition is that the number of maintenance interventions are minimised.
5) Cost Savings Calculation
SAVINGS ESTIMATION Cost of Lost Production Cost of Repair A planned changeout would take 8 hrs versus 16 - 24 hrs for an unplanned changeout due to sudden breakdown. An in-service failure typically results in consequential damage which requires an additional $100,000 to $300,000 for repair. Mid-Range Savings $60,000 $200,000 TOTAL SAVINGS $260,000
This results in a savings of between $40,000 to $80,000.
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