The continuous mining method eliminates the drilling and blasting procedures of conventional mining with a machine called a continuous miner, which both mines the coal and loads it onto conveyors or into shuttle cars in one continuous operation. Until recently, the Continuous Mining Machine Operator had to sit or lie in the machine's cab and operate the levers that cut or ripped out the coal from the coal bed and loaded it onto the conveyor or the shuttle car. However, the introduction of remote-controlled continuous mining machines now allows an operator to control the machine from a distance.
In longwall mining, which is similar to continuous mining, Longwall Machine Operators run large machines with rotating drums that automatically shear the ore and load it onto the conveyor. At the same time, hydraulic jacks continually reinforce the tunnel roof. As the coal is cut, these jacks hydraulically winch forward, supporting the roof as they progress along the tunnel. One advantage is that all the roadways behind the cutting are in worked-out areas in which no further mining is necessary.
The opposite of longwall mining is a process called shortwall mining, in which comparatively small areas of the coal face are worked separately. This process is commonly known also as room and pillar mining, and is frequently employed when the coal seam is four feet or under in thickness. The coal seams are mined by a machine manned by a Shortwall Coal Cutter Operator. It cuts a network of rooms into the coal seam. As the rooms are carved out, pillars composed of coal are left behind in each room to support the roof of the mine, often reinforced by timber beams.
A machine, known as a rock duster and operated by a Rock Dusting Machine Operator, sprays inert dust (dry or wet) on the roof, floor, and ribs in all working places and all the hauling tunnels to settle the coal dust. The machine has a flexible hose fed by a powerful blower, and typically employs powdered limestone to dilute the coal dust, thereby reducing explosion hazards and lessening the health hazard of breathing untreated coal dust.
In surface coal mining, earth usually has to be removed before the coal deposit can be tapped. This earthen layer is called the overburden. In many surface mines, the overburden is first drilled and blasted. Then, Dragline Operators (also called overburden stripping operators) scoop the earth away to expose the coal. Some of these dragline machines are the largest land machines on Earth. Next, Loading Machine Operators rip the exposed coal from the seam and dump it into trucks to be driven to the preparation plant where the coal is refined for use by utility companies and other industries.
According to the U.S. Department of Labor average wage and salary earnings in mining in general were significantly higher than the average for all industries in 2004. Average weekly earnings of nonsupervisory workers in coal mining in 2004 came to US Dollars 1,030. In May 2004, about 27.5 percent of workers in coal mining were members of the United Mine Workers of American (UMWA), receiving guaranteed paid holidays per contract and other benefits from the union's welfare and retirement funds.
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