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The term gantry carries a literal meaning of bridge-like overhead structure with a platform supporting equipment such as a crane, etc. Normally, I don’t make the distinction in terminology between a bridge crane and a gantry crane because to me a bridge crane is a subset of the larger gantry classification. However, in this article I will make the distinction because in my experience at least in my geographical area people jump to the bridge beam crane prematurely without out at least considering the pros and cons.
Bridge beams and gantry cranes or both used primarily in industrial applications. Both types are very common in manufacturing facilities and material handling locations such as ship yards where they are used to handle bulk material or shipping crates. Light duty applications are common for gantry cranes and they can often be found in mechanics shops.
There are three basic types:
1. Bridge Beam Crane:
This is a very common shop crane in North America. It is characterized by a trolley supported by one or more bridge beams which travel up and down a pair of runway beams. The unique characteristic of a bridge beam is that the runway beams are high in the air supported be either columns in a standalone system or built into the structure of the building. At the ends of the bridge beam, there is an end truck that guides the crane down the length of the runway beams.
2. Gantry Crane:
A gantry crane shares many of the same components as a bridge beam. They usually consist of one or more bridge beams carrying a trolly spanning over where the load will be lifted. The major difference is that there is one set of vertical supports at each end of the bridge for support and the end trucks run at ground level. The end truck system used for carrying the structure down the length of the runway can vary depending on application and duty. On light weight systems, it is common for the end trucks be made of four casters and have the unit pushed around by hand. On heavier duty applications, the crane will run down a track and be powered similar to a bridge beam.
3. Hybrid Systems:
In some specific applications it is common to combine a bridge beam and gantry crane so that one end of the beam is supported in the air and the other end runs along the ground. In my experience, the most common application is for a crane that runs down the length of a building outside where the one side is supported high on the building and the side furthest from any existing structure is a gantry style. These cranes combine the best of both systems and can be very efficient in specific applications.
Why I think Gantry Cranes Deserve More Thought?
Now that we have a basic description of the types of systems – why choose one over the other?
Pros to both gantry and bridge beam cranes:
- Great capacity potential because they are supported at both ends
- Control over load in 3 dimensions X,Y and height.
- Maximum hook height over the entire area.
- Very efficient coverage area
- Variety of options – powered, mechanical, electronic control.
The main differentiation between the two is that a gantry crane will be significantly cheaper to build. A bridge beam crane requires substantially more structure to support the load which will increase the overall cost in of the crane. Bridge beam cranes require columns down the full length of the crane to support the two run way beams where as a gantry crane only requires on set of upright structures and no run way beams. A gantry crane’s ability to use the floor as a supporting structure will cut thousands of lbs worth of steel and labor from a typical installation.
Use of the dead space:
A gantry crane obviously has no columns but has a track running on the ground down the length of the runway. This requires people to section off this part of the shop and pretty much dedicate it for only the crane. In a bridge beam system, everything is in the air so the space below the crane can be used for walkways, doors or storage. You won’t have crane coverage in this area but at least it’s not dead space. So a bridge beam crane will net you better use of space for an identical area of coverage.
Safety and Maintenance:
Both systems need annual maintenance and inspections completed by qualified personal. A bridge beam will have more components off the ground making inspection more difficult. With a gantry crane, all of the working parts are on the ground and easily accessible. On that same note, because the gantry has tracks that are on the ground they will be more susceptible to damage. Gantry cranes also pose an increase safety risk since there are electrical and pinch points at ground level.
Ability to Transfer Loads:
One aspect of gantry cranes that I think is grossly underutilized is the fact that you can cantilever a load past the vertical upright and get it outside of the crane coverage area. This is really common in shipyards where there is a cantilevered section of a gantry crane on one side to pick shipping containers off of ships and move them between the uprights for storage. There is another cantilever out the other side to load trucks. This is only possible in a gantry style system since bridge beams have fixed runway beams blocking this operation. I see potential for this kind of operation in a hybrid system over a steel yard where the cantilevered section is used to unload steel from a truck that parks parallel to the length of the crane. The material can be sorted and stored under the main body of the crane. The other application that I can think of is transferring a load from one shop bay to the other across the crane boundaries. To do this with a bridge beam you have to put the load down and move it across the dead space by some other means but with a gantry crane you could just use a cantilevered section to move the load across.
The last application where I feel a gantry crane would really shine is in the case where the system is just a temporary installation in a building. If you were to rent a shop rather than investing in the money for a bridge crane that would never come out of the building, you could build a gantry system that could with relative ease be moved to a different shop at a different date.
Select the Correct Crane for the Job
Thanks for taking the time to read this. Like I mentioned before I am not really partial to one crane over the other I just want people to understand a few of the less mentioned benefits of one style over the other so that the correct type of crane can be selected for the application.