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Specially Modified Welders Cope With Underground Emissions Standards.

Underground mining is one of the most grueling applications imaginable for engine-powered equipment. Not only must vehicles and machinery withstand the rugged environment, they must also do it while meeting strict Mine Safety & Health Administration (MSHA) engine emissions standards.

Among the many types of diesel equipment typically used in mines are engine driven welders, which are used for a variety of repair and cutting applications. Late last year, the Canyon Fuel LLC Dugout Canyon Mine near Wellington, Utah, needed to augment its existing welding fleet. Working through Praxair Distribution Inc., Canyon mine Maintenance Manager Kirt Tatton selected two Miller Electric Big Blue 402 welding generators specially modified to operate in the underground environment.

Tatton needed to upgrade his aging Miller machines to comply with 30 CFR (Code of Federal Regulations) Part 7. This new regulation, effective May 1, set standards for exhaust emissions, ventilation requirements and protection against explosion, fire and other safety and health hazards related to the use of diesel-powered welding equipment in underground coal mines. Over and above the new regulations, Tatton wanted a machine that afforded the maximum level of safety for his employees.

"I contacted several welding supply companies," said Tatton. "I asked them to approach me with welding machines that as a base had MSHA-approved engines on them and Praxair came through with the Big Blue."

Praxair Distribution, a subsidiary of Praxair Inc., is the largest industrial gases company in North and South America, providing shielding gases, welding equipment and applications support to the metal fabrication and other industries. "When Kirt called us in the fall of 1999, only the Big Blue 402 met MSHA requirements because of its Deutz F4L1011 air/oil-cooled engine option," said Dan Hamilton, a Praxair sales representative based in Price, Utah. "Deutz has obtained MSHA approval for this engine, as well as approval for the smaller F3L1011 engine available on the new Big Blue 302."

The engines meet mine safety standards because they emit low levels of carbon monoxide and various oxides of nitrogen 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. The engine alone, however, does not make a welding machine fully MSHA compliant. The unit still requires fire safety equipment, and that's where Praxair added significant value.

Starting with a Big Blue 402 welder mounted on Miller's heavy-duty, off-road trailer, Hamilton coordinated three subcontractors to make the necessary modifications. First, a fire suppression system was put in place. This involved installing canisters containing a chemical fire suppressant and emergency stops on each side of the machine.

"When the operator hits one of those dead stops, it kills the engine, and the canisters immediately discharge a dry chemical dust that completely covers the interior of the machine in order to help contain flames," said Hamilton. "I know the flame retardant was well dispensed because we spent two days cleaning that yellow dust off the machine after we tested the system."

Next, all electrical components (e.g., battery switches, fuel line switches) were encased in a wire loom for total insulation. Finally, the shape of the exhaust pipe was modified. Though not required by MSHA, Tatton had Praxair add full rollover protection structures (ROPS) to shield the welder and trailer wheels from impact damage.

"While a smooth, steady welding arc is important, safety is my priority," stated Tatton. "Durability and ruggedness come in right behind safety. Unlike surface mining, we're maneuvering the machine in a very confined environment. We need to negotiate a tunnel 6-1/2 ft. to 8 ft. high by 20 ft. wide and travel on underground roadways that are not paved or even well-graded.

"The welding unit is traveling 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."

Penetrating about three miles into the earth, work in the longwall Dugout Canyon Mine often moves into remote areas without power. However, the diesel support equipment and electric face equipment still require maintenance. 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 all-day welding service.

"Underground work in remote areas need illumination," added Tatton. "In those instances, we'll use the Big Blue's auxiliary power to run a string of 100 W bulbs, as well as run grinders and drills."

Since purchasing two modified Big Blue 402 welders in December, Tatton said that "our experience with the Miller machines in the mine has been good. Welding performance is important, and our results are good. The reliability's been there, too." He said that the mine has an expected operating life of 15 years and he anticipated that his new welders machines would last for the duration. "My old Miller diesel welders had good longevity in this type of use," he noted, "but the new MSHA regulations dictated that they be replaced with equipment that complied."

The Big Blue 402 welder delivers 20 to 600 amps of welding output, has stick, d.c. TIG and wire welding capabilities, gouges with 3/8 in. carbons and comes standard with 4 kW of auxiliary power, with an option for an additional 20 kW. Compared to previous models, it features a frame that is more robust, yet 15 percent smaller and 10 percent lighter. It's also much quieter than the previous design, Hamilton said. "In confined areas like an underground coal mine, operators really appreciate less noise."
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Title Annotation:Big Blue 402 from Praxair Distribution
Comment:Specially Modified Welders Cope With Underground Emissions Standards.(Big Blue 402 from Praxair Distribution)
Publication:Diesel Progress North American Edition
Article Type:Brief Article
Geographic Code:1USA
Date:Sep 1, 2000
Words:955
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