The precursor to the modern crane was born in 6th century BC Greece. At this time, the Archaic Greeks replaced ramps and cranes in construction with the winch and pulley hoist. Later, they invented the compound pulley.
After this, the Romans worked on improving the winch and pulley hoist until they created the treadmill crane. It was the main crane for 1000-plus years, until the fall of the Roman Empire. In the Middle Ages, though, the treadmill crane was rediscovered and put to use once again.
During the Industrial Revolution, engineers began creating cranes that we might recognize as such today. This started with William Armstrong, who in 1838, created the first hydraulic water-powered crane. Also, around this time, German manufacturers began mass producing overhead cranes.
Between the late 1800s and the early 1900s, scientists and engineers had come up with many new ways of externally powering machines, including overhead cranes. These included: electric motors, internal combustion engines and steam engines. The first steam powered overhead crane, for example, was installed in 1860. A mechanical engineer named John Ramsbottom installed it at the workshop of a British railway engineering facility called Crewe Railway. In 1876, inventor Sampson Moore produced the first electric overhead crane. (Mass production of these began around 1910.) The Royal Arsenal in Woolwich, London used his crane to hoist guns. They used this crane for a little over 100 years. In 1980, it was retired and moved to a museum in Birmingham, Alabama. The tower crane debuted in 1908.
During the mid-20th century, we saw the development of more versatile cranes. For instance, the first mobile cranes were developed in Germany after World War II by a team of engineers led by Hans Liebherr. Today, great companies like Gorbel Crane are making overhead cranes that are stronger and more adaptable than ever.
How They Work
No matter the overhead crane type, they basically function using a series of pulleys and cables. These pulleys and cables do their hoisting, lifting, lowering, carrying and positioning from either a single or a pair of overhead steel beams, or girders, to which they are attached. From these girders they also gain structural support.
Different overhead cranes work using different additional power lending mechanisms attached. Examples include: counterweights, hydraulic cylinders, chain hoists, levers and pivoting extended arms.
As noted earlier, overhead cranes are quite diverse. They are available in a number of configurational varieties, including overhead stacker cranes, overhead jib cranes, overhead gantry cranes, and overhead bridge cranes.
Stacker cranes move vertically or horizontally on tracks so that they can reach and move items. They are used frequently as forklift alternatives in warehouse areas that are not appropriate for human access and with CNC operated warehouse systems.
Jib cranes are smaller, workstation-appropriate cranes, suitable for work on military vehicles and in industrial plants. Their movable hoist is supported on one side by a vertical support, called a jib or boom, or a wall fixture. From this support, a beam reaches out on a pivot as the trolley moves the hoist. Notice that jib cranes are not the same thing as semi-gantries, which have a fixed arm while jib crane arms can move horizontally at 180 degrees.
Gantry cranes are built atop gantries, which consist of two movable support structures used to straddle a workspace or object. Sometimes, a crane is only supported by one of these and a counterbalance. If this is the case, the crane is renamed a semi-gantry, half gantry, or cantilever gantry crane. Crane gantry subtypes include: ship-to-shore gantry cranes, full gantry cranes, portable gantry cranes, rubber tyre gantry cranes, and workstation gantry cranes, which work with smaller items in more compact environments.
Most often, gantry cranes are for large applications, such as bridge construction, monument construction, ship cargo loading and unloading, metalworking, and ship and vehicle movement.
Bridge cranes, sometimes called track cranes, are quite similar to gantry cranes, in that they both use structural support beams and a trolley to straddle their workload. The main difference between the bridge crane and the gantry crane is the fact that, while the structure of gantry cranes is usually completely mobile, bridge cranes have fixed structures, with only a movable hoist.
They operate with the help of a set of overhead rails. Instead of being used for construction, bridge cranes are mostly utilized for manufacturing or maintenance applications at one facility. Bridge cranes are popular for the ergonomic, organized workspace they allow, and for being safe and easy to handle.
Tower cranes are cranes designed for demolition and construction applications. They feature: a tall mast, a bolted down base and a slewing unit used for rotation.
Mobile cranes are any portable crane. Mobile cranes are usually mounted on a land vehicle, ship or airplane for transportation.
Rubber tyre gantry cranes are mobile gantry cranes used to stack or ground containers.
Overhead shop cranes are overhead cranes used in auto shops. With it, workers in shops can access and work on the underside of vehicles.
Similar to overhead cranes are lifting mechanisms called electric wire rope hoists.
Electric wire rope hoists are used to lift and lower extremely heavy loads. Overhead electric hoists are mounted directly to the ceiling or to a single girder. They are driven by an electric motor and use wire rope, or wire strands surrounding a rubber core, to do the hoisting.
Typical crane components include: a bridge, a hoist, a crane attachment, a trolley.
The bridge is an overhanging arm from which cranes gain the majority of their lifting power. The hoist is a raising and lowering component; it connects on one end to the bridge and on the other end to the crane attachment. The attachment may be any number of tools, but generally it is a hook, a fork, an auger, or a grapple. It is connected to the hoist via wire rope or nylon cables. Finally, the trolley is an electrically or mechanically powered mechanism that moves the hoist along the bridge. Sometimes, the trolley also has attachments, like the boom. Booms are attached to the trolley horizontally, where they assist in hoisting and lowering.
Overhead cranes offer their users a slew of benefits. These include: efficiency, safety, versatility, relative ease of use, low labor costs and low maintenance costs.
Overhead cranes have few moving parts, yet they can move materials and products far heavier than their more complicated counterparts (forklifts, lifting excavators, etc.). Not only that, but they can do their work using a lower amount of energy and less fuel.
Because overhead cranes are generally controlled using wireless controls, operators are much safer during operation than they once were. To load and unload the cranes, they do not even need to be in close proximity, just at a safe distance within view.
Overhead cranes are versatile in a few different senses of the word. First, if the bridge is equipped with a few extra tools, users can use one crane to perform many separate tasks. Second, overhead cranes can be modified in-shop to take on new or changing applications. Third, they are appropriate for both indoor and outdoor use. Fourth and finally, many lifting applications are laid out in such a way that cranes can adapt to them quite easily.
Ease of Use
Relative to other lifting equipment, overhead cranes are easy to operate. For one, overhead cranes do not require manual lifting; the bridge and attachments do most of the work. For two, while training for comparable lifting equipment can take weeks, training for overhead crane use usually only takes a matter of days.
Another advantage of overhead cranes is the fact that it generates much lower labor costs than other equipment like it. This is because one operator can handle the overhead crane loads, and they do not need to worry about driving around.
Finally, because overhead cranes have so few moving parts, they are easier to maintain and they break down less often. This spells lower maintenance costs for you.
Design and Customization
When designing an overhead crane, crane manufacturers consider application specifics like: work space dimensions, load weight, frequency of use, length of application (long term or short term), standard requirements, mobility requirements, etc.
Based on these applications, manufacturers can decide details like: crane dimensions, whether to go with single girder crane or double girder crane design, crane type, crane lifting capacity, etc.
Every overhead crane is customizable. As a general rule, crane manufacturers may produce overhead cranes with custom dimensions and with special features or attachments that meet the needs of individual applications. For example, to meet height requirements of winch hardware, they may produce the bridge crane with either using single girder or double girder design. Bridge cranes with these girder designs are known as single girder bridge cranes and double girder bridge cranes, respectively.
Safety and Compliance Standards
To ensure the long working life and correct and safe functioning of any overhead crane, operators must attend to its maintenance with frequent inspections. To help maintain standardized and adequate crane working conditions, OSHA has published a set of guidelines, to which operators may refer.
However, in short, the maintenance requirements of overhead cranes are as follow: On a monthly basis, operators must check running ropes and end connections for problems like fraying, broken strands, and wear. Daily maintenance includes: checking hoist chains and end connections for twisting, distortion or wearing, checking hooks for cracks or deformations, checking hydraulic and pneumatic components for leaks, and checking operating mechanisms for maladjustments.
Also, it is important to periodically inspect overhead cranes for corrosion, deformation or cracking, to check drums and sheaves for cracking or wearing, and to keep an eye out for issues like loose bolts or rivets, sprocket and chain wear, problematic brake part and system wear, and general part distortion. Often, it helps to have a crane kit on hand with which you can quickly replace any of these system elements. Furthermore, it is essential that review of the state of electric and fossil fuel motors, indicators, and electrical components, including limit switches and pushbuttons, not be neglected.
Things to Consider
If you’re considering purchase an overhead crane, we can’t stress this enough—it’s very important that you work with an experienced and reliable overhead crane manufacturer. If you don’t, you could end up with, at best, a poorly matched crane or, at worst, a terrible accident with staff.
Find a manufacturer you can trust by checking out those we’ve sandwiched in between these information sections. We’ve provided for you the complete profiles of several crane companies we trust. Before you check them out, we recommend you put together a list of your specifications, so that you can compare and contrast as you go. Don’t forget to write down you budget, your delivery timeline and your standard requirements. When you’ve completed your list, take some time browse our list. Pick out three or four companies that appear to potentially best match your needs and reach out to each of them. You can either send a request for a quote or call them for a direct conversation. We prefer the latter approach, because it allows you to better gauge a crane supplier’s customer service attitude. Once you’ve spoken with each of them, compare what each can offer, and choose the one you think is right for you. Good luck!