Engineering & Mining Journal

JAN 2017

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REBUILDS JANUARY 2017 • E&MJ; 27 www.e-mj.com nance costs, with Liebherr offering its customers a variety of component repair and exchange programs to provide main- tenance budget flexibility. The most basic of these, the Repair program, is based on a minimum standard repair scope, which is expanded depending on the condition of the returned component. It provides users with transparency into the cost of repair as well as the lowest upfront repair cost on first-turn components, Lieb- herr said, with operators maintaining their own inventory of swing components in order to minimize machine downtime while com- ponents are being repaired. More comprehensive, the company's Fixed-price Exchange system offers users the delivery of an exchange component ahead of removing and returning of the defective part, hence reducing swing-com- ponent inventory requirements. Exchange parts come with a full new component war- ranty, with users receiving the latest tech- nical version of the component involved. The top of Liebherr's program range, the Cost Cap exchange program provides an extended pro-rata warranty that guar- antees the component cost per hour, thereby providing users with the highest degree of certainty when planning com- ponent maintenance budgets, and the lowest risk for costs of early failures. Of the three programs, the basic Re- pair approach provides the lowest upfront repair cost but high variability in repair costs, while Cost Cap exchange offers guaranteed costs per hour albeit at the expense of higher upfront exchange costs. Taken as a percentage of the full cost of a new component, Liebherr suggested that the Repair approach may cost around 10%, fixed-price exchange of 30% and Cost Cap exchange of 40%. Where reman is concerned, Liebherr offers a comprehensive service covering its mining trucks and shovels. Here, used components returned to the company are completely disassembled, with potentially reusable parts stripped of paint, cleaned and appraised for reconditioning to as-new quality. For mining trucks, this covers com- ponents such as diesel engines, hydraulic pumps, motors and cylinders, electronic control elements, electric motors, radia- tors, wheel drives and front suspension. While for excavators, Liebherr can reman- ufacture parts such as displays and mon- itors, rotary joints, travel drives, hydraulic pumps, motors and cylinders, splitter box- es and swivel drives, with engine reman available for some machine models. Taking an Opportunity As reported in detail in the March 2015 edition of Coal Age (pp.37-40), between 2012 and 2014 Cabot Corp., North Amer- ican Coal and the mining division of the industrial construction and fabrication firm CCC Group, took down a Page 757 dragline at the Jim Bridger coal mine in Wyoming, moved it in pieces nearly 2,100 km (1,300 miles) and rebuilt it at its new workplace in Texas. Its new owner, North American Coal subsidiary Caddo Creek Resources, took the opportunity to make some significant changes to the machine, which already had 27 years of work under its belt. According to Rob Davies, vice presi- dent of global manufacturing at Cabot Norit Activated Carbon, planning for the company's new Marshall mine had always assumed that a dragline, particularly a pre-owned and rebuilt unit, would be at the heart of its operations. "An economic analysis showed this to be the lowest-cost option over the life of the mine," he said. Major rebuild modifications included an improved design of truss to minimize cracking at high-stress points, and on- board transformers, which were deemed to be less costly and more reliable while altering the input supply from 8 kilovolts (kV) to 25 kV. The revolving frame deck was extended to house these, while the machine's ballast was recalculated to take the weight of the transformers into ac- count. Cabot chose, however, to stay with the machine's original DC system rather than upgrading to AC, citing cost-effec- tiveness constraints. All of the dragline's gear cases were rebuilt, with thicker baseplates installed under the hoist and drag drums, with new hoist and drag pads. A completely new upper superstructure provided an improved operator's cab, with electrical upgrades including LED lighting and a PLC-based operating system. Sandvik Rebuilds Underground Machines While wear and tear take their toll on surface-mining equipment, the situation for LHDs, mine trucks and drill rigs underground can be even more challenging. Not surprisingly, then, the man- ufacturers of these machines often offer rebuild services to en- sure that operators get the best from their investments. As Sandvik pointed out, in these cost-conscious times, replac- ing an exhausted asset with new equipment often isn't feasible, so a manufacturer's rebuild can be the most cost-effective solution. The company offers a three-tier approach to rebuilds, starting with life extension work and then ranging upwards in complexity to a full-scope rebuild plus upgrades to the latest technology. Sandvik suggested that its life-extension solutions offer cus- tomers flexibility, from customized scopes targeted toward ex- tending the units life for a specified period, to a more modular approach targeting only a system or range of systems that are currently reducing reliability. The company's "Reborn" option aims at providing customers with essentially a second life from their unit from a fixed-priced package that can save up to 35% on investment costs against a new piece of equipment. Rebuilt machines contain the latest safety and product updates as standard and are offered with "as new" full warranty terms and conditions. In addition, Sandvik's "+" solutions contain productivity, safety and operator comfort upgrades on top of this. Sandvik cited the example of rebuilding one of its DL420- 10C production drill rigs from the Frog's Leg gold mine in West- ern Australia, following reduced productivity being caused by hydraulics and electrical issues. The machine was stripped, sandblasted and subjected to NDT crack testing and repair. It received a completely new drivetrain, with the hydraulic lines re- hosed back to factory specifications. A 24-volt rewire, including the operator consoles, was undertaken, with upgraded drilling control modules to provide improved reliability and functionality. Also in Australia, Sandvik rebuilt a seven-year-old develop- ment drill rig that was destined for a change of location, where it is expected to perform for a further seven years at least. The machine was stripped to its base chassis and individual compo- nents. After thorough crack tests and inspections to detect any fatigue, specified parts and components were replaced by new or rebuilt versions. The result was a completely overhauled and updated unit, in compliance with today's standards, and covered by Sandvik Australia's 12-month/1,500-hour warranty.

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