Cranes

Cranes are used to move materials over variable paths within a restricted area.

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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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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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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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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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