Overhead Cranes

About Overhead Cranes and Overhead Crane Manufacturers Including: Bridge Cranes, Gantry Cranes, Hoist Cranes & Jib Cranes.

Overhead cranes are a standard fixture in many industrial, manufacturing and assembly environments. The products made by overhead crane manufacturers consist of a variety of components, which include hoists, hooks and ropes. They are devices that raise and lower a desired load and move it along a horizontal plane. This plane of movement is determined by the type of overhead cranes used. The end of the load-bearing arm is attached to wall columns, referred to as “overhung,” or to the underside of the ceiling, also called “underhung,” Most overhead crane systems are controlled via an operator remotely or via a fixed housing control. Many of the more complex systems are fully automated, acting as part of a larger assembly system.
 
Gantry, semi-gantry, cantilever gantry, storage bridge and wall cranes are among the types of the products made by overhead crane manufacturers. Gantry cranes are very similar to overhead cranes with the exception of the bridge for the trolleys. Two or more legs support it as the crane runs on fixed rails or another runway. One end of the bridge of a semi-gantry crane is supported by one or more legs, with the other end attached to a truck running on an elevated rail or runway. Cantilever gantry cranes are either gantry or semi-gantry cranes on which the bridge girders or trusses extend beyond the crane runway on one or both sides. Storage bridge cranes are a type of gantry crane in which the bridge girders or trusses are rigidly or non-rigidly supported on one or more legs and may have one or more fixed or hinged cantilever ends. These long-span overhead cranes are typically used for bulk storage applications. Wall cranes are a traveling type of crane which has a jib, with or without a trolley. These overhead cranes are supported from a side wall or lined columns of a building to which the runway is attached.
 
Overhead crane manufacturers supply machinery to many different industries. The automotive industry utilizes overhead cranes extensively in their production facilities. Overhead cranes are also commonly used in the construction of very tall structures. Conventional material handling methods cannot be used for the oversized loads that must be shifted in those industries. Moving heavy loads, like engines, requires the use of heavy-duty overhead cranes. Relocating cargo containers and other heavy non-assembly materials, such as blocks of concrete, is another common use for overhead cranes. Other machinery, like hydraulic lifts, is also used for the raising and lowering of loads, sometimes in tandem with overhead cranes.
 
Frequent inspections must be performed on overhead cranes for safety purposes. Every day the operating mechanisms should 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, limit switches or contactors that may be corroded. OSHA has published a set of guidelines for the safe operation of overhead cranes.

Overhead Cranes and Overhead Crane Manufacturers Image Provided by COH Inc.	Overhead Cranes and Overhead Crane Manufacturers Image Provided by Gorbel Inc.

Types of Overhead Cranes

• Automated cranes 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.
  
• Bridge cranes, 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.
  
• Gantry cranes 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.
  
• Hoist cranes is a generic term for a crane that is capable of lowering and lifting a load. Most cranes have hoists.
  
• Jib cranes 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
  
• Powerhouse cranes 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.
  
• Tower cranes 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.

Common Terms Related to Overhead Cranes

Beam – A rolled structural steel member, typically used as a bridge girder for short span or low capacity cranes.
 
Bogie – 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.
 
Boom – 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.
 
Box Section – An enclosed, rectangular cross-section of girders, trucks or other members.
 
Bridge – 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.
 
Bridge Conductors – 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.
 
Cab – The compartment from which the operator controls the crane.
 
Camber – The slight upward vertical curve given to girders to partially compensate for deflection due to hook load and weight of the crane.
 
Carrier – An assembly, also called a “trolley,” that supports a load and runs on a monorail track or crane girders.
 
Cover Plate – The top or bottom plate of a box girder.
 
Dead Load – The loads on a structure that remain in a fixed position relative to the structure.
 
Footwalk – The walkway with handrail and toe-boards, attached to the bridge or trolley for access purposes.
 
Girder – The principal horizontal beams of the crane bridge, which support the trolley and are supported by the end trucks.
 
Hoist – A mechanism used for lifting and lowering a load.
 
Hook – The lifting attachment point suspended from the hoist machinery, typically single- or double-pronged. Double-pronged hooks are known as "sister hooks."
 
Idler Sheave – A sheave used to equalize tension in opposite parts of a rope.
 
Load Block – The assembly of hook, swivel, bearing, sheaves, pins and frame suspended by the hoisting ropes.
 
MEL (Mean Effective Load) – A load used in durability calculations accounting for both maximum and minimum loads
 
Sheave – A grooved wheel or pulley used with a rope or chain to change direction and point of application of a pulling force.
 
Trolley – The unit carrying the hoisting mechanism that travels on the bridge rails.
 
Web Plate – The vertical plate connecting the upper and lower flanges or cover plates of a girder.