About Overhead Cranes and Overhead Crane Manufacturers
Including: Bridge Cranes, Crane Manufacturers, Gantry
Cranes, Hoist Cranes & Jib
Cranes.
Overhead cranes are a type of industrial equipment which are essential for the construction, loading and unloading of large equipment. Also known as
hoist cranes, overhead cranes operate from an overhead steel beam or pair of beams bridged between two structural supports; a trolley runs along these beams carrying a hoist which is used to lift and reposition heavy loads. Several types of overhead cranes are made for a wide range of lifting and positioning applications and vary in load capacity up to nearly 1,000 tons.
Bridge cranes, or overhead traveling cranes are stretched across building structural beams and used as permanent fixtures in manufacturing or distribution facilities, operating from a set of overhead rails.
Gantry cranes are bridged between two movable supports, presumably on wheels, and are typically used outside in large industrial construction applications.
Jib cranes, unlike other classes of overhead cranes, are only supported on one side by a vertical support or wall fixture. A beam extends from the support or wall on a pivot, while the trolley carries the hoist along the overhead beam.
Most modern day structural feats have been accomplished with the help of large overhead gantry cranes. Bridges, monuments, cargo ships and sea vessels are built using overhead gantry cranes, and most industrial equipment manufacturing and large metalworking processes use built-in overhead traveling cranes to unload equipment and materials and to move them around the facility. Overhead bridge cranes present a safe, easy-to-use alternative to ground transportation in many situations, particularly when handling extremely heavy or awkwardly shaped objects. Small jib cranes can provide excellent relief from factory or assembly workers continually lifting and moving objects around a facility while taking up little or no valuable floor space. Cranes used for material and equipment handling within a facility are often referred to as workstation cranes.
Overhead
crane manufacturers build various configurations of hoist cranes. The stationary overhead traveling bridge crane builds trolleys for the bridge on existing structural supports within a facility; separate steel supports may also be used within a plant if it is too wide to bridge, although this takes up more space. Gantry cranes, aptly named "bridge cranes", span two structural steel supports. Gantries are sometimes supported on one side only and are usually counterbalanced on the side opposite the hoist; these are called half gantries, semi-gantries or cantilevered gantries. Jib cranes differ from semi-gantries or cantilevered gantries in that the overhead arm typically pans 180 degrees horizontally, as opposed to the half gantry's fixed arm. Jib cranes may have a portable one-sided support, or smaller workstation jib crane arms may be attached to the wall; these are often called wall cranes.
Regardless of a crane's configuration, overhead cranes share three basic elements of construction: each uses a bridge, a trolley and a hoist. The bridge is the overhanging arm which bears the weight of the lift; in bridge cranes and gantry cranes, the bridge spans two supports, while jib crane and cantilever crane bridges are suspended in air from one support. The trolley is the electrically or mechanically powered mechanism which moves the hoist and crane hook along the bridge. In extremely large industrial overhead cranes, trolleys contain compartments for crane operators in which multiple people may sit. The hoist is the fixture responsible for lowering and raising the crane attachment, hook, grapple, fork or auger. Wire rope or nylon cables connect the crane attachment to the crane's main electric, internal combustion or hydraulic lift located at its base or at the top of its support, using electric motors for smaller applications and internal combustion or hydraulic power for doing larger, heavier work.
Because cranes work with extremely heavy, dangerous loads, frequent inspections must be performed on overhead cranes for safety purposes. Every day the operating mechanisms must be checked for maladjustment, the pneumatic and hydraulic parts for leakage, the hooks for deformation or cracks and the hoist chains and end connections for wear, twist or distortion. The running rope and end connections should be checked on a monthly basis for wear, broken strands, etc. Periodically, the overhead cranes should be checked for deformed, cracked or corroded components, loose bolts or rivets, cracked or worn sheaves and drums, other worn, cracked or distorted parts (e.g. bearings, gears and rollers) and excessive wear on brake system parts, chain drive sprockets and chains. Other components to be inspected include electric or fossil-fuel motors, indicators and electrical components such as pushbuttons and limit switches. OSHA has published a set of guidelines for the safe operation of overhead cranes.
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Overhead Cranes and Overhead
Crane Manufacturers Image Provided by COH Inc. |
Overhead Cranes and Overhead
Crane Manufacturers Image Provided by Gorbel
Inc. |
Overhead Crane Types
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fall between completely manual and completely robotic systems and are
used in applications in which robotic systems are much too expensive
and complex to operate. Automated cranes are equipped with encoder-based
fixed belt position and drive assemblies, and operate through a preset
cycle or cycles.
- ,
the most common type of overhead crane, consist of girders, trucks,
end ties, a walkway and a drive mechanism, which carries the trolley
and travels in a direction parallel to the runway.
-
are a type of overhead crane in which the bridge for carrying the trolley
or trolleys is rigidly supported by two or more legs running on fixed
rails or a runway.
-
is a generic term for a crane that is capable of lowering and lifting
a load. Most cranes have hoists.
- are
designed with the bridge girder, commonly called the "boom,"
fixed at one end, allowing the opposite end to cantilever. The fixed
end generally is hinged to allow rotation, and the jib can be telescopic
-
have crane bridges to carry a heavy-lift hook trolley that is sometimes
equipped with an auxiliary host. Powerhouse cranes are able to be accurately,
reliably and safely operated due to their nearly infinitely variable
speed controls.
-
consist of a base bolted into a large concrete pad, and a mast (or tower)
that gives the tower crane its height. The mast is connected to the
base and the gear and motor-called a slewing unit-that allows
the crane to rotate. Tower cranes are used in construction of tall structures.
Overhead Crane Terms
- A rolled
structural steel member, typically used as a bridge girder for short span
or low capacity cranes.
- A type of short end
truck that is attached to the end of one girder or to a connecting member
if more than one truck is utilized per girder. Bogies are used when the
design of the runway necessitates more than four wheels on the crane.
- A mechanism mounted horizontally
on the trolley of an overhead crane. A load is lowered or hoisted by the
boom at a point other than directly under the hoist drum or trolley.
- An enclosed, rectangular
cross-section of girders, trucks or other members.
- The part of an overhead
crane that carries the trolley and travels parallel to the runway. Bridges
consist of girders, trucks, end ties, a walkway and a drive mechanism.
- An electrical
conductor, at times incorrectly referred to as a "trolley conductor,"
that provides power and control circuits to the trolley. Bridge conductors
are located along the bridge girders.
- The compartment from which
the operator controls the crane.
- The slight upward vertical
curve given to girders to partially compensate for deflection due to hook
load and weight of the crane.
- An assembly, also
called a "trolley," that supports a load and runs on a monorail
track or crane girders.
- The top or bottom
plate of a box girder.
- The loads on a structure
that remain in a fixed position relative to the structure.
- The walkway with
handrail and toe-boards, attached to the bridge or trolley for access
purposes.
- The principal horizontal
beams of the crane bridge, which support the trolley and are supported
by the end trucks.
- A mechanism used for
lifting and lowering a load.
- The lifting attachment
point suspended from the hoist machinery, typically single- or double-pronged.
Double-pronged hooks are known as "sister hooks."
- A sheave used
to equalize tension in opposite parts of a rope.
- The assembly of
hook, swivel, bearing, sheaves, pins and frame suspended by the hoisting
ropes.
- A load used in durability calculations
accounting for both maximum and minimum loads
- A grooved wheel or
pulley used with a rope or chain to change direction and point of application
of a pulling force.
- The unit carrying
the hoisting mechanism that travels on the bridge rails.
- The vertical plate
connecting the upper and lower flanges or cover plates of a girder.