The Asia Miner

OCT-DEC 2016

The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region

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Page 66 of 75

Volume 13 • Issue 4 | 2016 | ASIA Miner | 65 Supplier News The BMT DuraCluster modification and repair scheme improves the fatigue performance of cluster joints. years . Key areas of failure include boom, mast and roller circle . A more sophisticated approach to maintenance can, in some cases, reduce maintenance and inspection workloads and extend the fa- tigue life of these structures . BMT WBM has completed numerous Finite Element Analyses identifying high stress and fatigue prone areas of dragline struc- tures . A map can then be created to guide maintenance inspectors on where to focus their attention, ultimately reducing the time need- ed for inspections . While maintenance planning in mining has been systematised for many years, techniques such as Reliability Centred Maintenance (RCM) which have been used over the last 40 years in other indus- tries including aerospace, are being increasingly applied to mining machinery maintenance . RCM techniques can help identify com- ponent failures that impact availability most significantly and thereby, enabling appropriate solutions to be devised . One recent example where RCM principles have been followed to significantly improve reliability of mining machine operation on a Marion 8200 Dragline is where a substantial revolving frame floor upgrade was carried out in order to design ongoing structural cracking issues. The cracking originated from large floor penetra- tions and propagated across the machine . The maintenance effort required to keep up the repairs were onerous . The problem stemmed from a pre-existing deficiency of the OEM design in this area and the accumulation of fatigue damage through a long service for the machine . Further, in an effort to increase pro- duction, the mine was intending to increase the suspended load and was concerned about further exacerbating the problems in this area . BMT WBM used a combination of field measurements to obtain the actual working stresses and analysis to propose a substantial floor design upgrade. The upgrade was implemented during a ma- jor maintenance shutdown for the machine and this upgrade has been in place for approximately six months . Working closely with Westmoreland Coal Company, BMT recently deployed its innovative DuraCluster modification and repair scheme which dramatically improves the fatigue performance of cluster joints on existing tubular dragline boom designs . This involved replacing a number of fatigued boom clusters with DuraCluster to demonstrate ease of installation and operational suitability . Once implemented, this modification for tubular boom draglines significantly reduces maintenance and inspection workloads and dramatically reduces the problem of long-term fatigue cracking as- sociated with the existing cluster design . BMT was able to offer reduced downtime and outage costs . Once installed, DuraCluster also reduces the risks to operators and maintenance teams in hav- ing to lower the boom and carry out complicated weld repairs with limited access . Installation for Westmoreland was completed in the allocated time frame and the dragline returned to duty . The long booms of draglines comprise a number of tubular chords with interconnecting lacings welded to the chords at cluster joints. Stresses are concentrated at the cluster joint weldments and over time, fatigue cracking becomes endemic . This methodology pre- vents the need to cut and replace windows in lacings by removing the problematic design detail and improving load paths . Further- more, DuraCluster can dramatically extend the fatigue life of dragline booms by reducing stress concentrations . A boom replacement can cost around $20 million and require a three-month machine outage. With BMT's modification and re- pair, the cluster design can be upgraded in around one week per cluster, depending on the extent of chord repair required, while multiple clusters can be modified simultaneously. With equivalent repair costs reduced to approximately $2 million, this is an attractive incentive for mining companies . While DuraCluster provides a step change in life to cracking for tubular boom construction, it is equally applicable to tubular masts . The innovative design allows lacings to be cut away from the chord, providing easy access to remove damaged or previously repaired material . The exposed chord can then be inspected and fully weld repaired before installing the plate . Another area of significant technological advance made over the past 20 years is dragline slew bearing, also known as the roller circle . The roller circle and the supporting structures above and be- low are vital mechanical and structural components of the dragline . Installation and maintenance activities in these areas carried out to a poor standard can lead to large amounts of cracking in the tub and revolving frame, and very poor bearing life . BMT WBM has developed supporting and repair techniques en- suring that the welding and machining of the upper and lower rail pads are done to a very high standard resulting in good bearing load distribution and long roller circle service life . Although there is optimism for the future of mining as a whole, mining companies are focusing heavily on cost efficiencies and productivity gains in the short to medium term . Pushing innovation and embracing the available technologies can play an integral role in realising these efficiencies but this is only one part of the jigsaw. Effective maintenance strategies which consider tools and tech- niques such as RCM and simultaneously align with the need to be production focused will create a step change in maintenance management, helping improve productivity and availability of critical assets and in many cases, reduce the overall cost of maintenance in the long-term .

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