Deere Loader Displays Long
In the world of highwall coal mining, success or failure is measured in high dollars per hour. A US$6 million mining machine can pull coal out of a mountain at a rate of 2500 t/day, so the wheel loader that supports that big miner had better be the most reliable and productive machine available.
Contour Highwall Mining Inc. in Summersville, West Virginia, found the perfect solution: a John Deere 724J Loader. Contour Highwall Mining uses the 724J to add or remove the 60 m long, 4,5 t push-beams that join end-to-end and extend under a mountain into the coal seam. Twin augers line up continuously inside the push-beams to bring coal from the cutter head to daylight, unaided by manual labor.
Highwall mining means drilling and blasting a 20 to 30 m 9 (or more) deep bench of overburden to expose a horizontal coal seam around a mountain. Earthmoving equipment then removes the overburden and carves the bench that gives mining equipment access to the coal seam. The process starts when the John Deere 724J Loader delivers a push-beam section to a table on the highwall miner. Next, lift arms on the miner grab the push-beam and set it into the miner's belly, behind the last beam. A worker locks it into place, and huge twin hydraulic rams push the continuous line of beams steadily into the coal seam as the cutter head mines deeper into the mountain.
Contour Highwall Mining's 724J loader sets the bar high for reliability and uptime, according to Dave Bundy, Contour's owner. In fact, by February 2007 the machine had chalked up 17 400 hrs with only a couple of minor issues since the company bought it in 2003.
"I'm depending on that loader to keep our operation moving. It's unheard of to have a loader last this long without touching the engine's top end," Mr. Bundy said. "It's like having a car that lasts 500 000 km."
Last year, the loader cost Contour just US$0,04/t of coal produced, not counting fuel. Repairs totaled one injector pump and one fan motor.
"The loader's operating cost is right where it should be," Dave Bundy said. "And now that it has many hours on it, the cost is probably lower than normal, because we've had virtually no breakdowns on it and next to no oil consumption between changes."
Both Dave Bundy and loader operator Greg Arthur like the way the 724J handles when carrying the big push-beam sections. "We've used competitive loaders, and this John Deere is a little heavier and handles the beams better," Mr. Bundy said.
"The loader is very stable when carrying the push-beam sections," Mr. Arthur added.
The 724J is still running on three of the four original tires, and have a lot of wear left. L5 tires have tread that is 2,5-times deeper than standard L3 tires and use a harder, more tear-resistant rubber compound. "The tires have worn like iron," Mr. Bundy said.
While the mining application is mostly a load-and-carry operation, the loader also cleans rocks from the push-beam auger sections after the miner extracts them from the mountain. Typically, each push under the mountain extends for 250 to 300 m before the mining machine pulls them back out again.
In response to an ever-increasing demand for coal, Dave Bundy added a second highwall mining machine in May. He also purchased a new 724J loader to support it.
"The John Deere loader has earned our respect," he said.
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