Overhead crane


Overhead crane
An overhead crane, featuring runways, bridge, and hoist in a traditional industrial environment.
Overhead crane at the Skanska precast concrete factory in Hjärup

An overhead crane, commonly called a bridge crane, is a type of crane found in industrial environments. An overhead crane consists of parallel runways with a traveling bridge spanning the gap. A hoist, the lifting component of a crane, travels along the bridge.

Unlike mobile or construction cranes, overhead cranes are typically used for either manufacturing or maintenance applications, where efficiency or downtime are critical factors.

Contents

Applications

The most common overhead crane use is in the steel industry. At every step of the manufacturing process, until it leaves a factory as a finished product, steel is handled by an overhead crane. Raw materials are poured into a furnace by crane, hot steel is stored for cooling by an overhead crane, the finished coils are lifted and loaded onto trucks and trains by overhead crane, and the fabricator or stamper uses an overhead crane to handle the steel in his factory. The automobile industry uses overhead cranes for handling of raw materials. Smaller workstation cranes handle lighter loads in a work-area, such as CNC mill or saw.

Almost all paper mills use bridge cranes for regular maintenance requiring removal of heavy press rolls and other equipment. The bridge cranes are used in the initial construction of paper machines because they facilitate installation of the heavy cast iron paper drying drums and other massive equipment, some weighing as much as 70 tons.

In many instances the cost of a bridge crane can be largely offset with savings from not renting mobile cranes in the construction of a facility that uses a lot of heavy process equipment.

Configurations

While sharing major components, overhead cranes are manufactured in a number of configurations based on applications.

Rotary overhead crane

This type of overhead crane has one end of the bridge mounted on a fixed pivot and the other end carried on an annular track; the bridge traverses the circular area beneath. This offers improvement over a jib crane by making possible a longer reach and eliminating lateral strains on the building walls.[1]

History

Demag Cranes & Components Corp. was one of the first companies in the world to mass-produce the first steam-powered crane.[2] Since that time Alliance Machine, now defunct, holds an AISE citation for one of the earliest cranes in the USA market. This crane was in service until approximately 1980, and is now in a museum in Birmingham, Alabama. Over the years important innovations, such as the Weston load brake (which is now rare) and the wire rope hoist (which is still popular), have come and gone. The original hoist contained components mated together in what is now called the built-up style hoist. These built up hoists are used for heavy-duty applications such as steel coil handling and for users desiring long life and better durability. They also provide for easier maintenance. Now many hoists are package hoists, built as one unit in a single housing, generally designed for ten-year life, but the life calculation is based on an industry standard when calculating actual life. See the Hoists Manufacturers Institute site[3] for true life calculation witch is based on load and hours used. In today's modern world for the North American market there are a few governing bodies for the industry. The Overhead Alliance is a group that represents Crane Manufacturers Association of America (CMAA), Hoist Manufacturers Institute (HMI), and Monorail Manufacturers Association (MMA). These product counsels of the Material Handling Industry of America have joined forces to create promotional materials to raise the awareness of the benefits to overhead lifting. The members of this group are marketing representatives of the member companies.

Early manufacture

  • 1830: First Crane company in Germany Ludwig Stuckenholz company now Demag Cranes & Components GmbH.[2]

Gallery

See also

References

  1. ^ Towne, Henry (1883). A treatise on cranes. Stamford, CT: Yale and Towne. p. 129. OCLC 938144. "Rotary Bridge Crane...provided with a circular overhead track carrying the outer end of the jib, or rotary bridge. It...avoids the severe lateral strains upon the building and thus dispenses with heavy walls." 
  2. ^ a b c d Kurrer, Karl-Eugen (2008). The history of the theory of structures: from arch analysis to computational mechanics. Berlin: Ernst & Sohn. pp. 411–415. ISBN 3-433-01838-3. 
  3. ^ http://www.mhia.org/industrygroups/hmi/technicalpapers
  4. ^ Towne (1883: 124)
  5. ^ "Improved overhead steam traveling crane". Scientific American (New York) XXXI (794). 21 March 1891. 

External links


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