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.
If the bridge is rigidly supported on two or more legs running on a fixed rail at ground
level, the crane is called a gantry crane or a goliath crane.
Unlike mobile or construction cranes, overhead cranes are typically used for either manufacturing
or maintenance applications, where efficiency or downtime are critical factors.
Applications Overhead cranes are commonly used in the refinement
of steel and other metals such as copper and aluminium.
At every step of the manufacturing process, until it leaves a factory as a finished product,
metal is handled by an overhead crane.
Raw materials are poured into a furnace by crane, hot metal is then rolled to specific
thickness and tempered or annealed, and then stored by an overhead crane for cooling, 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 to handle raw materials.
Smaller workstation cranes, such as jib cranes or gantry cranes, handle lighter loads in
a work area, such as CNC mill or saw.
Almost all paper mills use bridge cranes for regular maintenance needing removal of heavy
press rolls and other equipment.
The bridge cranes are used in the initial construction of paper machines because they
make it easier to install 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.
EOT Crane This is most common type of overhead crane,
found in most factories.
As obvious from name, these cranes are electrically operated by a control pendant, radio/IR remote
pendant or from an operator cabin attached with the crane itself.
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.
History Demag Cranes & Components Corp. was one of
the first companies in the world to mass-produce the first steam-powered crane.
In 1876 Sampson Moore in England designed and supplied the first ever electric overhead
crane, which was used to hoist guns at the Royal Arsenal in Woolwich, London.
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 and the wire rope
hoist, 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 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,
Hoist Manufacturers Institute, and Monorail Manufacturers Association.
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.
1840: Mass production of overhead cranes starts in Germany
1854: Sampson Moore & Co in Liverpool England patented a new winch mechanism that allowed
the lifting of heavier weights by an electric motor.
1861: First steam powered overhead crane, installed by John Ramsbottom at the Crewe
Railway workshops. Power was transmitted to the crane from a pulley driven by a stationary
engine through an endless cotton rope.
1887: Ludwig Stuckenholz company introduces electrical components to overhead cranes determining
industry design.
1910: The first Mass production Electric motor hoist started being produced in Germany.
Gallery
See also Container crane
Crane Gantry crane
References
Standards ASME B30.2: "Overhead and Gantry Cranes"
ASME B30.17: "Overhead and Gantry Cranes" ASME B30.11: "Monorails and Underhung Cranes"
BS 466: "Specification for Power driven overhead travelling cranes, semi-goliath and goliath
cranes for general use" ISO 4301-5: "Cranes; classification; part
5: overhead travelling and portal bridge cranes" ISO 8686-5: "Cranes; design principles for
loads and load combinations; part 5: overhead travelling and portal bridge cranes"
Indian Standard - 807 Indian Standard - 3177
Indian Standard -4137 External links
OSHA Regs for overhead cranes