SILVER SPADE RETIRES
One of America's largest earthmoving machines ceases production
September 01, 2006
|
On April 10 this year, the Silver Spade — one of America's largest earthmoving machines — shuddered to a halt, bringing to an end the era of giant stripping shovels. For almost a century, these giants of the strip-mining world helped to uncover rich coal seams lying relatively close to the surface and provide coal for the nation's electricity-generating facilities. Stripping shovels worked in the same way as regular cable shovels, but unlike their smaller counterparts, they did not load trucks to carry material away. Their huge proportions allowed them to cast the excavated material into worked-out pits, clear of the working area.
Today most of the coal within the range of even the largest stripping shovel is worked out, and other types of equipment are now employed to mine the deeper coal. Strip miners prefer walking draglines which are more flexible in operation and can uncover deeper coal, or they prefer smaller shovels in combination with truck fleets as dictated by the geology of the vast coal seams in the western States now providing the lion's share of the nation's coal needs.
The Silver Spade, or Bucyrus-Erie 1950-B to use its model designation, was not the largest shovel built but was probably the most famous as the last of its type operating. With an estimated weight of 7,200 tons, she operated with a 105-cubic-yard dipper on a 200-foot-long boom, measured 59 feet wide at ground level, and reached a height of 191 feet to boom tip.
The behemoth shovel was served by a 7,200-volt trailing cable weighing 20 pounds per foot. On board, AC main driving motors totaling 9,000 horsepower drove DC generators for the shovel's main motions — hoist (8 motors), swing (4 motors) and crowd (2 motors). The massive weight of the machine was supported on eight crawler track assemblies, each with its own DC motor.
The 1950-B was built by Bucyrus International and started work in November 1965. Purchased by the Hanna Coal Co., a division of Consolidation Coal (Consol), for coal stripping in the Georgetown area of Ohio, she was named to commemorate the 25th anniversary of Hanna Coal.
The Silver Spade's final production day was April 3, 2006. After that, she proceeded to climb out of the final pit and head for a designated resting place. But before she arrived, a breakdown occurred on April 10 leaving the shovel dead in her tracks and marking the end of an era. She had served her owners well during her active life, moving a total of 607,226,370 cubic yards of overburden. The Spade's final fate is unknown at the time of writing, but a local preservation group wants to see the shovel preserved as a tourist attraction.
The Spade and other giant stripping shovels built in the 1960s helped to lower production costs and boost an ailing coal industry. Now, with modern earthmoving equipment, that trend continues with coal currently providing over half the electric power generated in America today.
Read more about stripping shovels and walking draglines in Keith Haddock's book "Extreme Mining Machines" available in most bookstores. For more information about the Silver Spade's preservation group, call Claren Blackburn at 740-937-2460. Also, consider a membership in the Historical Construction Equipment Association, http://www.hcea.net/.
Kommentaare ei ole:
Postita kommentaar