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Continuous Miner

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Mining Equipment

A continuous miner is a mining machine that produces a constant flow of ore from the working face of the mine. The machine continuously extracts as it is loading coal with a cutting steel drum and conveyor system. Continuous miners are typically used in room and pillar mining operations. The continuous miner is different from conventional or cyclical mining methods, which halt the extraction process in order for ore-loading to proceed.[1]

Continuous miners, which began to take off in the mining industry in the 1940s, make up of 45 percent of the underground coalmine production. Today, continuous miners are being developed as driverless machines controlled via remote control.

Contents

[edit] History

[edit] Early Miners

The continuous miner has been available in some form since the late 1800s. The first machine to resemble a continuous miner was known as the English Channel Machine. The pneumatically driven machine could travel 1.5 miles (2.4 km), mining 70 m (21 m) per day. Developed in 1870 to work on the English Channel, the machine ceased operation when political turmoil brought the project to a quick halt.[2]

The continuous miner did not appear again until 1912 when the Hoadley-Knight Machine was produced to reduce the size of coal to that of a nut. This machine was electrically driven by a rotor and consisted of a hydraulic swing and a set of water sprays. In addition to the Hoadley-Knight, several machines appeared in this decade: the Jeffrey MM32 in 1911, a machine capable of cutting and loading coal; the Jeffrey MM34 in 1913, known as the Jeffrey Entry Driver; and the McKinlay Entry Driver, a British boring machine produced in 1918.[3]

These machines were moderately received in the mining industry. Mckinlay Entry Drivers were used in the New Orient Mine in 1926 and developed a positive reputation for the amount of work they could efficiently complete. This machine went on to become the standard prototype for the Marietta Miner, a mining machine produced and manufactured by Marietta Manufacturing Co., based in Point Pleasant, West Virginia.[4]

The early twenties saw the development of a new type of miner constructed by Colonel O’Toole. The miner had a capacity that could complete 154-tons of work in under 10 hours. The machine evolved to feature a pneumatic conveyor belt for the coal but such a development only reduced the power of the machine.

[edit] Modern Miners

The first ripper-type continuous miner appeared in the early 1900s but did not prove to be immediately successful. The first machine to see success was built by an American, Harold Silver, in 1943 and was used for work in the Consolidated Coal & Coke Co. mine. The machine attracted the interest of Joy Manufacturing Co. three years later and Joy purchased the patents for the machine, developing two prototypes deriving from the original. They became known as the JCM models and were used for mining projects beginning in 1948.

Joy Manufacturing Co. laid its claim to fame in its early years in the mining industry with several continuous miners. By the 1950s, a series of continuous miners had been produced and manufactured. The company's 3JCM model was so successful it stayed in production for the next 18 years with 212 being built in total. Although successful, it was only gradually accepted as an efficient miner.

This miner was beneficial in that it could adapt to different mining conditions. It had many drawbacks, however, including its complex structure, which made it difficult to clean, and its slow mining rate, which was attributed to the small area provided for face cutting.

Continuous miners were also developed as a borer type machine. The borer type continuous miner was first produced in the form of the Colmol model in 1948. The Colmol was able to provide low-boring intensity of 400 tons per day with a 48-inch (122-cm) seam capacity. Jeffrey Mining Co. quickly scooped up the patents for this machine. When Jeffery took over the prototypes and used them to construct its own models, it featured machines with horsepower as high as 150 to 190. Not to be outdone, Marietta, Goodman and Joy all produced larger machines with more work capacity.

Marietta was acquired by Clarkson Manufacturing Co., which overtook their miners before being acquired itself by National Mine Service in 1957. Larger borers began to be produced after the acquisition, namely the Marietta 675, consisting of 375 horsepower and able to cut seven feet, six inches (2 m, 15 cm) high by 13 feet (4 m) wide. The prototype was increased to 450 horsepower. The weight was increased to 57 tons and the machine became a prime potash miner at 250 tons, this time capable of cutting eight feet (2.4 m) high and 25 feet (7.6 m) wide. The rotor was operated by a 400 horsepower motor, proving to be a tough contender for other manufacturers to beat.

Goodman was up to the task when it developed the Type 500 in 1954. This miner could cut seven feet (2.1 m) high and 13.5 feet (4 m) wide. Its rotors were each driven by a 400-pound (181.4-g) motor; the machine's total weight was 73,000 pounds (33,112 kg).

Joy also attempted to develop a larger miner when it produced the 2BT and the 2BT6, which consisted of 510 horsepower and weighed 52 tons.

Although manufacturers were interested in producing larger borer type miners, their use declined rapidly in the 1970s because of problems that arose with their face ventilation and lack of flexibility for different mining conditions.

Another type of miner was the auger head miner, a device with dual augers, first built in 1955. Produced by A.G. Wilcox, it was built primarily for low-seam applications. As expected, Jeffrey Manufacturing began producing a similar machine after its introduction in the 1950s. The 100-L, built in 1960, consisted of a chassis with a height of 20.5 inches (50 cm). Although Jeffrey ceased production of the auger head, Wilcox (now a subsidiary of Fairchild Inc.) continued to produce them.

Oscillating head ripper miners also made an appearance in the 1950s. Invented by E.M. Arentzen, president of Lee Norse Co., the Roadmaster was a machine featuring rotating cutter wheels that turned horizontally while engaged in a downward direction. The initial machine was mounted on rubber tires and evolved to crawler tracks by 1951. These machines gradually grew in size and became more complex over time. Joy countered this with its 8CM and 9 CM miners, complete with hydraulic oscillation and triple bit rings. These miners were most successful in the 1960s, with the other types of miners experiencing steady declines.

The drum head type continuous miner was introduced in 1967 by Jeffrey Manufacturing Co. The first version was known as the Heli Miner, with a 14-foot (4.2-m) wide, non-oscillating cutter head. Joy, National Mine Service, and Lee Norse also produced this type of miner. The most successful in the early 1970s were Lee Norse’s Norse 10 and Norse 11 models.[5]

[edit] Today’s Remote-controlled and Robotic Miners

Today’s miner can extract at least 38 tons of coal per minute, depending on the thickness of the seam, although manufacturers are constantly beating the record.[6]

Modern day continuous miners are remote-controlled and customized for different mining conditions. The number of robotic miners operated via computer controls is increasing, eliminating the need for an operator in this sometimes dangerous task.[7]

The remote-controlled continuous miner is likely to continue paving the path of the future, with the Mining Safety and Health Administration employing resources to ensure the efficient operation of this type of machine. With remote-controlled machines gaining widespread popularity, as evidenced by the 699 units that were in operation in the U.S. in 2004 alone, more safety and health concerns involving their use have been brought to the attention of the industry.

[edit] Features/How it Works

Continuous miners consist of a large rotating drum comprising steel and tungsten carbide teeth, a material with enough strength to scrape coal from the seam or face of the mine. Used in room and pillar mining operations, the mine is often divided into a series of rooms, usually 20 to 30 feet (6.1 to 9.1 m) in length. The continuous miner rotates the oscillating steel drum to cut a way designated sections of the coal bed. When the coal is extracted, a conveyor system is utilized to transport and load the coal from the seam.[8]

One of the pioneering elements about the continuous miner is the speed and efficiency with which it operates. The typical continuous miner is capable of producing five tons of coal in a minute; more than a miner from the 1920s would be able to produce in a single day.

Continuous miners can be customized for any mining conditions: mounted on rubber tires or crawler tracks; and different sizes of drums and conveyor systems, depending on what is needed. Modern miners even include a self-diagnostics system.

The modern remote-controlled continuous miners feature ever-changing technology as the machine evolves. New technologies includes a proximity detection device that detects the proximity of the miner, developed to cut down on the hazards and fatalities that have occurred in the machine’s history. A red zone and visual indicator available by remote control is another feature that is improving the new miners. The indicator enables the operator to select a safe position from which to operate.[9]

[edit] Types

  • Auger head continuous miner
  • Borer-type continuous miner
  • Drum head type continuous miner
  • Oscillating head ripper miner
  • Remote-controlled or robotic miner
  • Ripper-type continuous miner

[edit] Common Manufacturers

[edit] References

  1. Folklore in SWPA Bituminous Coal Mining. Members. 2008-09-24.
  2. Technology. Illawarra Coal. 2008-09-24.
  3. Technology. Illawara Coal. 2008-09-24.
  4. Technology. Illawara Coal. 2008-09-24.
  5. Technology. Illawara Coal. 2008-09-24.
  6. Continuous Mining. Coal Leader. 2008-09-24.
  7. Underground Continuous Miners. Coal Education. 2008-09-24.
  8. Underground Continuous Miners. Coal Education. 2008-09-24.
  9. Improving Continuous Miner Safety. Coal News. 2008-09-24.