Overhead crane

An overhead crane, commonly called a bridge crane, is a type of crane found in industrial environments. An overhead crane consists of two parallel rails seated on longitudinal I-beams attached to opposite steel columns by means of brackets. The traveling bridge spans 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 two fixed rails at ground level, the crane is called a gantry crane (USA, ASME B30 series) or a goliath crane (UK, BS 466). Another variant is the semi-goliath crane, where one fixed rail is at ground level, and the other fixed rail is overhead, commonly used along the exterior of an existing building.

An overhead crane, featuring runways, bridge, and hoist in a traditional industrial environment.

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

Single Girder Overhead Crane

Also known as Top Running Single Girder (TRSG). This is the most widely used configuration. The bridge consists of a single beam, making it well suited to lighter duty applications, typically up to about 15 tonnes.

Double Girder Overhead Crane

Also known as Top Running Double Girder (TRDG). Built with two bridge beams, this configuration handles much heavier loads, up to roughly 400 tonnes, and accommodates spans exceeding 100 feet. It also offers greater available lifting height, since the hoist travels on top of the beams with the hook positioned between them rather than below.

Suspended Overhead Crane

Also known as Under Running Single Girder (URSG). The runway rails are fixed directly to the building's roof structure rather than to floor mounted columns. Removing the dedicated support columns frees up floor space, though it reduces the maximum lifting capacity. A double girder version can be engineered for specific requirements.

Wall Mounted Overhead Crane

Mounted to the building's wall or columns rather than spanning the full width of the bay. It serves a defined work zone and can operate independently beneath an existing overhead crane, which allows two lifting operations to run in the same bay at the same time.

History

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.^[1] 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^[2] for true life calculation, which 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 of 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.^[3]
1840: Mass production of overhead cranes starts in Germany.
1854: Sampson Moore & Co in Liverpool, England patents a new winch mechanism that allowed the lifting of heavier weights (such as naval guns) by an electric motor.^[4]
1861: The first steam powered overhead crane is 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.^[3]
1887: The Ludwig Stuckenholz company introduces electrical components to overhead cranes, determining industry design.
1910: The first mass-produced electric motor hoist starts in Germany.

Functions and possible movements

Overhead cranes are installed at height and travel on rails fixed to runway beams made of steel or concrete, and even wood. The main axes of movement are called:

1.Hoisting: vertical axis; raising or lowering of the load through a movement of the hoist; 2.Cross travel: transverse axis; generated by a movement of the trolley; 3.Long travel: axis of the runway tracks (the greatest distance), corresponding to an overall movement of the bridge;

On more specialized cranes, additional movements such as rotation or tilting can be found. The lifting height refers to the vertical distance measured between the floor and the lifting hook when it reaches its highest position. This measurement is essential to ensure that the equipment can perform the intended operations.

The width of an overhead crane is referred to as the span. From a structural standpoint, the span corresponds to the distance measured between the centerlines of the two runway rails. This dimension is a fundamental parameter for sizing the main girders, selecting the end trucks, and configuring the overhead crane as a whole.

Traditionally, overhead cranes are equipped with two-speed motors for each of the three axes of movement. However, the integration of variable frequency drives (VFDs) is becoming increasingly common in the industry. These systems make it possible to achieve a wider speed range, improve the precision of movements, and reduce mechanical wear, particularly on the brakes, since they limit the stresses associated with abrupt stops and starts.

The duty classes of an overhead crane help determine its level of mechanical stress, its frequency of operation, and the proportion of loads handled. The ISO 4301-1 standard defines eight classes, from M1 (light, occasional service) to M8 (very intensive, continuous service). In Europe, the FEM classification uses groups such as 1Am to 4m, based on the load spectrum and the total number of cycles anticipated. In North America, the CMAA 70 and 74 standards classify equipment from Class A (very light service) to Class F (continuous heavy service). These classification systems are used to select an overhead crane that meets the requirements for use, durability, and maintenance.

Operation

The machine is operated by remote control or pendant control. Some units have an operator cab, but they can also be operated from the ground using a remote control.

Operating an overhead crane usually requires comprehensive training that includes both theoretical concepts and hands-on exercises. It is important to note that the regulatory requirements surrounding this training vary from one country and jurisdiction to another.

In a semi-automated system, the operator can launch preprogrammed sequences, such as repetitive movements between two points, precise positioning, or standardized lifting cycles. The overhead crane then carries out these tasks automatically, but the operator remains responsible for monitoring the environment, making real-time decisions, and taking back control when necessary. Fully automated overhead cranes, on the other hand, do not require an operator to be in the immediate vicinity. Their operation is supervised and controlled from a centralized control room, which may be located a considerable distance away, depending on the layout of the plant or industrial site. In this type of installation, a video monitoring system combining industrial cameras and monitors ensures full visibility of operations, allowing human intervention only when required. It is important to emphasize that automated zones are protected by advanced safety systems that prevent any human presence while the overhead crane is in automatic mode, in order to eliminate any risk of collision or crushing.

Configurations:

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

EOT (Electric Overhead Traveling) Crane

EOT cranes are a common type of overhead crane. They are found in many factories and warehouses. These cranes are electrically operated by a control pendant, radio/IR remote pendant, or from an operator cabin attached to the crane.

A woman operating a 20-ton^[which?] EOT crane, 1914
An EOT overhead crane is used to move and build this submersible, the Ictineu 3, in a warehouse of Sant Feliu de Llobregat, Spain.
A VFD crane currently performing a load test
An overhead crane using a lifting beam for a customized application

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.^[5]

Polar crane

This type of overhead crane has both ends of the bridge mounted on an annular track. The bridge runs to entire diameter of the track, as opposed to just the radius for a rotary crane. Polar cranes are commonly used in containment buildings at nuclear power stations, fitting their circular, steam pressure containing design.^[6]

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 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^[which?].

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 processing equipment.

Gallery

Examples of overhead cranes
Example of steam powered overhead crane from 1875, produced by Stuckenholz AG, Wetter, Germany. Design developed by Rudolf Bredt from an original installation at Crewe railway works^[3]
Rotary overhead crane installed in a foundry, c. 1880^[7]
Steam-powered overhead crane from c. 1890. Three separate, two-cylinder engines provided transverse, longitudinal, and hoisting motion; a feature of the design was the ability to raise or lower the load while in transit.^[8]
One of two overhead cranes hoisting a space shuttle payload in the Space Station Processing Facility