Giant dragline excavators from the 1960s

Today’s dragline excavator sizes are much smaller than they were more than 40 years ago. Larger draglines like the Bucyrus model 4250W and Marion 7900 made the 1960s the era of super draglines. The mining industry has valued the extremely low disposal cost benefit of these machines over their high capital cost.

Little information is available to the public about Utah International’s Marion 7900. The largest of the former Utah Construction and Mining Company dragline excavator sizes had a boom length of 275 feet (83.8 meters) and a bucket capacity of 40 cubic yards (30.6 cubic meters). He was digging 7,000 tons of coal a day. The large dragline unit was disassembled for a major inspection in 2005. Repairs and upgrades in Morocco have returned the machine to smooth operation with smaller dragline excavators.

CEMEX’s operation outside of Pittsburgh, Pennsylvania, purchased a 2,000-ton walking-type dragline. The Marion 7820-M, nicknamed ‘Brutus’, discovered the limestone needed to make cement. She has a boom length of 305 feet and a working radius of 289 feet. The bucket can carry 45 cubic yards of materials and can dig up to 170 feet. The 4,000,000 pound weight was somewhat common for dragline excavator sizes of the time. It was originally manufactured for Pyramid Coal Company’s Rockport Surface Mine in Rockport, Kentucky, in the 1980s.

Another large unit is the 4250 W dragline unit from Central Ohio Coal Company (a division of American Electric Power). He was popularly known as the ‘Big Muskie’. It took three years for mining equipment manufacturer Bucyrus International, Incorporated to build the machine that made other sizes of dragline excavators seem less powerful. The 27 million pound (12 million kilogram or 12,000 ton or 13,000 metric ton) earthmoving machine operated in Muskingum County, Ohio from 1969 to 1991. The only dragline of its size ever built extends at 487 feet, 6 inches (149 m.) with boom lowered. Its width of 151 feet 6 inches (46 m) necessitates an eight-lane highway to circulate; while its height of 222 feet 6 inches (68 m.) will be more than enough to look down from the roof of a 22-story building. The machine was later scrapped in 1999 after demand for high-sulfur Ohio coal plummeted in 1991. The 220-cubic-yard (165-cubic-meter) bucket weighing 230 tons is preserved as a monument to miners from southeastern Ohio.

Today, construction and mining equipment manufacturers have considered the risks of building large excavators. The new models, although much smaller in size, can be used for both civil engineering projects and infrastructure construction and open-pit mining operations, such as moving tailings over coal and oil sand extraction.

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