Transport Equipment - Cranes

Cranes are used to move materials over variable paths within a restricted area. The cranes mentioned are the major types of cranes currently used in the industry.

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

1. Jib Crane

Information:

• 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

2. Bridge Crane

Information:

• 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)

3. Gantry Crane

Information:

• 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

4. Stacker Crane

Information:

• 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