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Sunday, August 12, 2012

Cranes


Cranes are used to move materials over variable paths within a restricted area. The major types of cranes are:
  1. Jib crane
  2. Bridge crane
  3. Gantry crane
  4. Stacker crane

General characteristics of cranes:
  • Used to move loads over variable (horizontal and vertical) paths within a restricted area
  • Used when there is insufficient (or intermittent) flow volume such that the use of a conveyor cannot be justified
  • Provide more flexibility in movement than conveyors
  • Provide less flexibility in movement than industrial trucks
  • Loads handled are more varied with respect to their shape and weight than those handled by a conveyor
  • Most cranes utilize hoists for vertical movement, although manipulators can be used if precise positioning of the load is required
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1. Jib Crane

Operates like an arm in a work area, where it can function as a manipulator for positioning tasks
A hoist is attached to the arm for lifting
Arm mounted on the wall or attached to a floor mounted support
Arm can rotate 360°
The hoist can move along the arm
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2. Bridge Crane

Bridge mounted on tracks that are located on opposite walls of the facility
Enables three-dimensional handling
Top riding (heavier loads) or underhung (more versatile) versions of the crane
Underhung crane can transfer loads and interface with other MHS (e.g., monorail systems)
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3. Gantry Crane


Single leg, double leg, and mobile types of gantry cranes
Similar to a bridge crane except that it is floor supported at one or both ends instead of overhead (wall) supported
Used to span a smaller portion of the work area as compared to a bridge crane
The supports can be fixed in position or they can travel on runways
Can be used outdoors when "floor" supported at both ends
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4. Stacker Crane

Similar to a bridge crane except that, instead of a hoist, it uses a mast with forks or a platform to handle unit loads
Considered "fork trucks on a rail"
Used for storing and retrieving unit loads in storage racks, especially in high-rise applications in which the racks are more than 50 feet high
Can be controlled remotely or by an operator in a cab on the mast
Can be rack supported
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