Power shovel

Principle of rope-shovel operation.[1]

A power shovel (also stripping shovel or front shovel or electric mining shovel or Electric Rope Shovel [2]) is a bucket-equipped machine, usually electrically powered, used for digging and loading earth or fragmented rock and for mineral extraction.[3] Power Shovels are a type of rope/cable excavator, where the digging arm is controlled and powered by winches and steel ropes, rather than hydraulics like in the more common hydraulic excavators.

P&H 4100 XPB cable loading shovel.


Design

Shovels normally consist of a revolving deck with a power plant, driving and controlling mechanisms, usually a counterweight, and a front attachment, such as a crane ("boom") which supports a handle ("dipper" or "dipper stick") with a digger ("bucket") at the end. "Dipper" is also sometimes used to refer to the handle and digger combined. The machinery is mounted on a base platform with tracks or wheels.[4] Modern bucket capacities range from 8 m3 to nearly 80 m3.

Use

Shovel digging overburden.

Power shovels are used principally for excavation and removal of overburden in open-cut mining operations, though it may include loading of minerals, such as coal. They are the modern equivalent of steam shovels, and operate in a similar fashion.

Operation

The shovel operates using several main motions:

  • hoist - pulling the bucket up through the bank (i.e. the bank of material being dug)
  • crowd - moving the dipper handle out or in to control the depth of cut and when positioning to dump
  • swing - rotating the shovel between digging and dumping
  • propel - moving the shovel unit to different locations or dig positions

A shovel's work cycle, or digging cycle, consists of four phases:

  • digging
  • swinging
  • dumping
  • returning

The digging phase consists of crowding the dipper into the bank, hoisting the dipper to fill it, then retracting the full dipper from the bank. The swinging phase occurs once the dipper is clear of the bank both vertically and horizontally. The operator controls the dipper through a planned swing path and dump height until it is suitably positioned over the haul unit (e.g. truck). Dumping involves opening the dipper door to dump the load, while maintaining the correct dump height. Returning is when the dipper swings back to the bank, and involves lowering the dipper into the tuck position to close the dipper door.

Giant Stripping Shovels

Big Brutus.

In the 1950s with the demand for coal at a peak high and more coal companies turning to the cheaper method of strip mining, excavator manufacturers started offering a new super class of power shovels, commonly called giant stripping shovels. Most were built between the 1950s and the 1970s. The world's first giant stripping shovel for the coal fields was the Marion 5760. Unofficially known to its crew and eastern Ohio residents alike as The Mountaineer,[5] it was erected in 1955/56 near Cadiz, Ohio off of Interstate I-70. Larger models followed the successful 5760, culminating in the mid 60s with the gigantic 15,000 ton Marion 6360, nicknamed The Captain.

Notable Examples

Ranking Bucket Capacity
(m3/yd3)		 Operating weight
(tons)[6]		 Type Name Service Scrapped
50/652,750Marion 5760The Mountaineer19561988
138/18015,000Marion 6360The Captain19651992
107/1409,350Bucyrus Erie 3850BRiver King19641993
99/1306,850Bucyrus Erie 1950BGEM of Egypt19671991
96/1259,338Marion 5960Big Digger19691989
88/1156,950Bucyrus Erie 3850BThe Big Hog19621985 (Accident)
80/1057,200Bucyrus Erie 1950BThe Silver Spade19652007
69/905,220Bucyrus-Erie 1850-BBig Brutus1962Preserved as a
National Landmark

See also

Further reading

Extreme Mining Machines - Stripping shovels and walking draglines, by Keith Haddock, pub by MBI, ISBN 0-7603-0918-3

References

  1. ↑ Simionescu, P.A. (2014). Computer Aided Graphing and Simulation Tools for AutoCAD users (1st ed.). Boca Raton, FL: CRC Press. ISBN 978-1-4822-5290-3.
  2. ↑
  3. ↑ US Department of the Treasury, IRS: Appendix I - Glossary of Mining Terms
  4. ↑ Encyclopædia Britannica, Power Shovel
  5. ↑ "16 Tone Mobile Shovel Take 90 Ton Bite of Earth" Popular Mechanics, April 1956, p. 95.
  6. ↑ Extreme Mining Machines, by Keith Haddock, pub by MBI, ISBN 0-7603-0918-3
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