Ž.Oškutis

While it may seem that overhead cranes are relatively new devices and more complex than the typical truck-mounted or crawler cranes you probably see around construction sites all the time, in fact, overhead cranes are significantly more simple machines than any other type of crane and have been around for quite a while, longer in fact than the other types of cranes most people are more familiar with.

Most people will live their entire lives without ever seeing an overhead crane, but that doesn’t mean they aren’t extremely important machines that affect each of our lives. Any manufacturing operation that requires the transport of heavy equipment or materials around a factory floor will likely make use of some type of overhead crane. Without these fairly simple machines, companies would have to use the traditional cranes that are more familiar to everyone.

The problem with the traditional truck mounted cranes are that they take up an enormous amount of floor space; in other words, they have a huge footprint. And in a factory setting, where floor space is at a premium both for cost and safety reasons, overhead cranes provide an excellent lifting capability without almost none of the footprint of a traditional crane.

Some major overhead crane types, as well as equipment options that are associated with overhead cranes are as follows:

• Bridge Crane - this is simply another name for an overhead crane…all overhead cranes are, in fact, bridge cranes
• Runway system – many overhead cranes are mounted on a series of girders that span a large area, which allows them to move all around the factory floor
• Jib Crane – although a jib crane is, technically, a type of overhead crane, it’s actually floor-mounted with the use of a “jib arm” rather than being a hoist mounted on a steel girder
• Single girder overhead crane – these use a single steel girder that the hoist is mounted on and are generally capable of lifting loads of up to 15 tons
• Double girder overhead crane – these use two steel girders and the hoist is mounted between the two girders. These are generally capable of lifting up to 20 tons
• Chain hoists – this is a hoist type that uses a chain to lift the load. The hoist consists of a mounting system, a motor (or winch), and a chain that actually connects to the load
• Wire rope hoist – this is just like a chain hoist, except instead of using a chain to connect to the load, it uses a steel cable (the wire rope) that connects to the load

In addition to the saving of square footage on the factory floor, an overhead crane is also quite a simple machine. You can see from the image below that an overhead crane is really nothing more than a hoist (which actually does the lifting) mounted on a steel girder with a wired remote control that controls the vertical and lateral movement of the crane. This simplicity is one of the benefits of an overhead crane in that simple machines with fewer moving parts are less likely to break down or need repairs.

Single Girder Overhead Crane with Wire Rope Hoist

In addition to the above image, here’s a video that illustrates the functionality of an overhead crane and hoist. Skip the first few seconds to get to the nitty gritty: