Effective Shovel Maintenance Blends Technology, Tools, and Technique

RUSSELL A. CARTER / WESTERN EDITOR

Coal Age, Jun 1, 2001

Maintaining a machine that weighs millions of pounds and contains thousands of electrical, mechanical, and structural parts would be a formidable assignment under any circumstances. When that machine is a mining shovel that spends more than 90% of its life ripping 100-ton chunks of dirt and rock from a pit wall, the job is even more challenging, but successful shovel maintenance teams find ways to even the odds.

CUTTING THE UNDECK

In addition to software, there are a number of jumbo-sized, specialized mechanical tools available to assist maintenance on massive machines. For example, when a shovel breaks down or is scheduled to undergo major repairs that involve the pinions, rollers, center pin, or swing rack, much of the downtime can be taken up simply by preparing the shovel for "undecking" - the process of raising the machine's upper assembly high enough to disengage the pinions from the ring gear and to clear the center pin extending from the lower unit, or carbody. A typical method employed is to stack wood cribbing under the shovel, detach and lift the upper unit with jacks to allow space for additional cribbing, and by repetition of the process, raise the upper section until it's clear of the carbody, which then can be removed. The process may then be reversed to lower the upper unit to a convenient working height for repairs; once the work is completed, the upper section must again be raised to allow positioning of the carbody for reassembly.

Each jacking/cribbing cycle will lift the assembly only about 8 inches or so - a fraction of the 5- to 6-foot (ft) elevation typically required for complete disengagement. The process is tedious and can add days to overall downtime. Raising the upper unit in longer lifts presents problems that can range from binding of the center pin in its sleeve due to tilting of the upper section as individual jacks are activated; to instability of the whole upper unit as it is tilted while being lifted. And, once the undecking is completed, the cribbing can hinder worker access to the shovel components that require service.

Quebec-based Megatraction Equipment Co. has developed a technique to speed this process and eliminate the lengthy delays involved in cribbing and jacking a shovel. The company's patented MegaLifter system comprises two computer-controlled lifting modules that attach at the front and back of the shovel, allowing the upper section to be lifted smoothly and evenly in a matter of hours for carbody removal, then lowered to allow convenient access for repairs.

According to company President Christian Belley, a prototype of the MegaLifter system was developed in the mid-90s and has since been used successfully in eastern Canadian mines; a larger unit was put into service last year and has been employed at western U.S. and Canadian mines to lift shovels as large as the P&H 4100 or Bucyrus 495B models. The system can also be used to lift all but the largest of hydraulic excavators, said Belley, using attachments specifically designed for various models.

Using a single crane, the MegaLifter's components can be assembled and installed on the shovel in one day, and the lift can then be completed during the same shift, saving as much as 6 to 7 days of downtime required for cribbing and jacking. The company recently developed additional attachments that allow a shovel to be raised with the boom and dipper attached.

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