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Safe welding underground.

Kirt Tatton, maintenance manager for Canyon Fuel's Dugout Canyon mine in Utah, US, recently needed to upgrade welding equipment to meet new Mine Safety Health Administration (MSHA) regulations covering diesel engine-driven welding machines. The new 30 CFR Part 7 sets standards for exhaust emissions, ventilation requirements and protection against explosion, fire and other safety and health hazards related to underground coal mines. So, he purchased a Miller Electric Big Blue 402 welding generator.

At the time Mr Tatton started his search, only the Big Blue 402 met MSHA requirements because of its Deutz F4L 1011 air/oil cooled engine option. Deutz has MSHA approval for this engine and the smaller F3L 1011 engine available on the new Big Blue 302. These engines meet mine safety standards because they emit low levels of CO and [NO.sub.x], and they have a ventilation rate that dilutes the gaseous exhaust emissions with large volumes of air when the engine operates at full rated output.

However, the Deutz engine did not satisfy all the requirements. The local Miller Electric supplier, Praxair Distribution, started with a Big Blue 402 mounted on Miller's heavy-duty, off-road trailer. Three subcontractors were then brought in to make the necessary modifications. First, a fire suppression system was installed. This required canisters containing a chemical fire suppressant and emergency stops on each side of the machine. If the operator has to hit one of the dead stops, it kills the engine and the canisters immediately discharge a dry chemical dust that completely covers the interior of the machine to help contain flames.

Next, all electrical components (for example, battery switches and fuel line switches) were encased in a wire loom that totally insulates them. Lastly the shape of the exhaust pipe was modified. Though not required by MSHA, the mine also chose to have full roll-over protection structures added to shield the welding machine and trailer wheels from impact damage. The machine needs to negotiate drifts 2-2.4 m high by 6 m wide and be hauled on roadways that are not paved or even well graded. As Mr Tatton says, "the welding unit is travelling over some pretty rough terrain and getting pushed into tight locations. It has to be rugged by design. Components can't vibrate, jiggle or break off, and the welding performance must be superior without compromising safety."

At least one of the three daily shifts needs to weld or air carbon arc gouge, such as when replacing a bit holder on the cutter drum of a continuous miner, The maintenance crew also fabricates new transfer points for the conveyors carrying the coal, which can demand welding all day. Big Blue's auxiliary power is often used to power a string of 100 W bulbs, as well as grinders and drills.

Dugout Canyon purchased two modified Big Blue 402s in December 1999. They deliver 20-600 A of welding output and have Stick, DC TIG and wire welding capabilities, as well as gouging really well. Compared to previous models, it features a frame that is more robust yet 15% smaller and 10% lighter. It is also much quieter, which is greatly appreciated by the underground workforce.

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Publication:Mining Magazine
Article Type:Brief Article
Geographic Code:1USA
Date:Nov 1, 2000
Words:527
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