Power shovel

A Power shovel (also stripping shovel or Front Shovel or Electric Mining Shovel) is a bucket equipped machine, usually electrically powered, used for digging and loading earth or fragmented rock, and mineral extraction.

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 boom or crane which supports a handle with a digger at the end. The machinery is mounted on a base platform with tracks or wheels. The bucket is also known as the dipper. Modern bucket capacities range from 8 m3 to nearly 80 m3.

Use



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.

From http://en.wikipedia.org/