You can probably picture a bridge crane in your head—it consists of two overhead runways built into the building’s support structure, connected by a single or double beam configuration, called a “bridge.” The bridge is supported on either end by an end truck, which rides on wheels along a runway or beam—allowing it to move up and down the bay.
A bridge crane can be configured in a single girder or double girder design. In simple terms, a bridge girder, or beam, is the support structure that allows the trolley and hoist to move from side-to-side along the bridge. The trolley is used to precisely position the hoist prior to raising or lowering a load.
The bridge consists of one girder beam supported on each side by an end truck. The trolley and hoist are most commonly underhung—meaning they run on the bottom flange of the bridge. They also tend to be less expensive due to:
However, in the instance that a crane needs to handle more than 15 tons, or the span is more than 65 feet, a double girder configuration may be the better option.
There are two girder beams that make up the bridge, and they are supported by an end truck on each side. The trolley and hoist run on a rail installed on top of the bridge girders.
Double girder cranes are recommended for heavier-duty applications where the crane has to handle more than 15 tons, or the span is more than 65 feet.
Double girder cranes are the best option when the crane needs to be customized with things like walkways, cabs, magnet cable reels, or other specialized equipment. And on a top running design, they can provide more lifting height since the hoist isn’t hanging underneath the beam.
These cranes have no limiting capacity—meaning they can be built to go from small capacities to very large capacities. They include a rail installed on top of each runway, and the bridge wheels move on the rail instead of the bottom flange of the runway beam. These cranes are supported by the building structure or runway support columns, or sister columns, and are ideal for moving extremely heavy loads.
Often called “underhung,” because the crane wheels are supported by the bottom flange of the crane runway beams acting as the crane rail. These types of cranes can allow you to maximize your facility’s floor space for production and storage of material because they are supported from the ceiling trusses or the roof structure. Or, they can be designed to utilize an existing support structure (if adequate), or run on a newly-engineered support structure.
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