Coal Age

AUG 2016

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36 www.coalage.com August 2016 dragline maintenance continued will begin to fall away. A smarter approach to maintenance is certainly needed. Advances in technology are note- worthy and have certainly impacted the way in which maintenance departments operate. The tools that are available for engineers are getting faster and more ac- curate. While in the past, if there was a structural failure, it may have taken two to three weeks before a decision could be made as to whether to shut down produc- tion to fix the problem or continue oper- ating the machine, with today's structural modeling and analysis tools such as AN- SYS, Femap, IDEAS, LS-DYNA and Ab- aqus, these decisions can be determined much more effectively and efficiently. Applying New Techniques to Draglines BMT WBM has been involved with drag- line maintenance issues and improve- ment strategies for more than 40 years. Key areas of failure include boom, mast and roller circle. A more sophisticated approach to maintenance can, in some cases, reduce maintenance and inspec- tion workloads and extend the fatigue life of these structures. BMT WBM has com- pleted numerous Finite Element Analyses (FEAs) identifying high stress and fatigue prone areas of dragline structures. A map can then be created to guide maintenance inspectors on where to focus their atten- tion, ultimately reducing the time needed for the inspections. While maintenance planning in min- ing has been systematized for many years, techniques such as Reliability Centered Maintenance (RCM), which have been used over the last 40 years in other in- dustries including aerospace, are being increasingly applied to mining machin- ery maintenance. RCM techniques can help identify the component failures that impact availability most significantly and thereby, enabling appropriate solutions to be devised. One recent example where RCM prin- ciples have been followed to significantly improve the 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 out ongoing structural crack- ing issues. The cracking originated from large floor penetrations and propagated across the machine. The maintenance ef- fort required to keep up the repairs were onerous. The problem stemmed from a pre-existing deficiency of the OEM de- sign in this area and the accumulation of fatigue damage through a long service for the machine. Further, in an effort to increase production, the mine was in- tending to increase the suspended load and was concerned about further exac- erbating the problems in this area. BMT WBM used a combination of field mea- surements to obtain the actual working stresses and analysis to propose a sub- stantial design upgrade for the floor. The upgrade was implemented during a major maintenance shutdown for the machine. Currently, this upgrade has been in place for approximately six months. Working closely with Westmoreland Coal Co., BMT recently deployed its in- novative DuraCluster modification and repair scheme, which dramatically im- proves the fatigue performance of clus- ter joints on existing tubular dragline boom designs. This involved replacing a number of fatigued boom clusters with DuraCluster to demonstrate both ease of installation and operational suitability. Once implemented, this modification for tubular boom draglines significantly reduces maintenance and inspection work- loads and dramatically reduces the prob- lem of long-term fatigue cracking associ- ated with the existing cluster design. BMT was able to offer both reduced downtime and outage costs. Once installed, Dura- Cluster also reduces the risks to operators and maintenance teams in having to lower the boom and carry out complicated weld repairs with limited access. Installation for Westmoreland was successfully completed in the allocated timeframe and the dragline returned to duty. The long booms of draglines comprise a number of tubular chords with inter- DuraCluster installed on 1570 dragline boom. Finite Element Analysis (FEA) of DuraCluster prior to installation.

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