Single Girder Overhead Crane

LD overheard crane single girder travelling bridge overhead crane.

The configuration of a bridge crane is easy to visualize. It consists of two elevated runways that run in parallel along the travel length of the crane. These runways may be built into the support structure of your facility or, in the case of freestanding bridge cranes, may be supported by floor mounted columns.

Connecting or "bridging" the runways is a movable single or double girder beam. Each girder is supported by an end truck on each side that can propel the girder back and forth along the runway. (You might picture this as a pair of elevated railroad tracks with one or two parallel ties between them that can move along the length of the tracks). Each girder beam supports a trolley that can move from side to side along the girder. The trolley, in turn, supports a hoist and hook that can lift a load vertically.

The choice between a single or double girder system depends mostly on the span between the runways, the amount of weight to be lifted, and the lifting height required. If the span between the runways is more than about 65 feet, or the weight to be lifted is more than 15 tons, a double girder system is probably the best choice. The hook height (how high above the floor the hoist is required to lift) is also important because with a double girder system the hoist is located on top of the girders, allowing for a greater vertical range of movement.