Saturday, December 15, 2007
(I) Types of Conveyors
There are several types of conveyors that are commonly used. They are mainly:
(1) Roller Conveyor
There are two types of roller conveyors. It may be powered (or live) or nonpowered (or gravity).
Materials must have a rigid riding surface
Minimum of three rollers must support smallest loads at all times
Tapered rollers on curves used to maintain load orientation
(a) Gravity Roller Conveyor
Alternative to wheel conveyor
For heavy-duty applications
Slope for gravity movement depends on load weight
For accumulating loads
(b) Live (powered) roller conveyor
Belt or chain driven
Force-sensitive transmission can be used to disengage rollers for accumulation
For accumulating loads and merging/sorting operations
Provides limited incline movement capabilities
(2) Chain Conveyor
Uses one or more endless chains on which loads are carried directly
Parallel chain configuration used to transport pallets
Vertical chain conveyor used for continuous high-frequency vertical transfers (cf. vertical conveyor used for low-frequency intermittent transfers)
(3) Flat Belt Conveyor
For transporting light- and medium-weight loads between operations, departments, levels, and buildings
When an incline or decline is required
Provides considerable control over the orientation and placement of the load.
No smooth accumulation, merging, and sorting on the belt
The belt is roller or slider bed supported; the slider bed is used for small and irregularly shaped items
(4) Vertical Lift Conveyor
Carrier used to raise or lower a load to different levels of a facility (e.g., different floors and/or mezzanines)
Differs from a freight elevator in that it is not designed or certified to carry people
Can be manually or automatically loaded and/or controlled and can interface with horizontal conveyors
Personality, I think that this type of Vertical lift Conveyors are good for warehouses that have different levels of floors and is quick and convenient in carrying heavy goods.
(II) Cranes
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
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
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
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
Storage Equipment
Storage equipment used for holding or buffering materials over a period of time.
(1)Drive-Through Rack
Loads are supported by rails attached to the upright beams
Lift trucks are driven between the upright beams/
Requires similar-width loads
Open at both ends, allowing access from bith ends (FIFO)
(2) Drive-In Rack
Same as drive-through rack, except closed at one end, allowing entry from only one end (LIFO)(3) Cantilever Rack
Loads are supported by cantilever "arms"
Used to store long loads (e.g., bar stock, pipes, lumber)
Similar to pallet racks, except the front upright beams and the front supporting beams are eliminated
(4)Sliding Rack
Only one mobile aisle is used to access several rows of racks
Location of the aisle is changed by sliding the rows of racks along guide rails in the floor
Typically found in library stacks
(5)Mezzanine 
Inexpensive means of providing additional storage or office space
Makes use of clear space over activities not requiring much headroom (e.g., restrooms, block storage, etc.)
At least 14 ft. of clear space is needed for a mezzanine
posted at 9:35 PM