A bridge crane, also called overhead bridge crane, is a bridge-type crane with flexible bridge running on elevated tracks which are actually beams overhead. The bridge of a bridge crane runs forward and backward along tracks laying both sides while the trolley runs from side to side across the bridge. This rectangle work zone ensures the full use of space under the bridge to lift and move loads, with no equipment on the ground standing in its way.
 
Bridge cranes are widely used in indoor and outdoor warehouses, factories, harbors, storage places in the open air, etc. We can divide all the bridge cranes into three main categorizations. They are common bridge cranes, simplified beam bridge cranes and dedicated bridge cranes for metallurgy.
A common bridge crane consists of the crane trolley, the crane running configuration and the bridge metal configuration. While the crane trolley consists of the hoist, the trolley running configuration and the trolley frame.
 
The hoist has the motor, the brake, the reducer, the drum and the pulley block. Through the reducer the motor drive the drum rolling up, which makes the steel wire rope on it rolls up or down. And that is how the hoist lifts loads. The trolley frame supports and helps install frames of the hoist and the trolley running configuration. It is usually a welding configuration.
 
Drive modes of the crane running configuration could be divided into central drive and separated drive. Central drive means one motor drives driving wheels from both sides through the long transmission shaft. Separated drive means separated motors for driving wheels from both sides. Bridge cranes in middle and small size prefer “three-in-one” drive mode (brake, reducer and motor), while common bridge cranes with big lifting weight usually have universal coupling in the driving device for installation and adjustment convenience. Most of the time there are only four driving and driven wheels in the crane running configuration unless the lifting weight is so big that needs extra wheels to reduce the pressure of wheel. When there are more than four wheels.there must be a articulated equilibrium trolley frame device as well in order to average load from the crane onto each wheel.
 
The bridge metal configuration is a package of main beam and side beam, with tow main categorizations, single-girder versus double-girder cranes. A single-girder crane is composed of one main beam and one side beam on each end of the main beam. Similarly, a double-girder crane is composed of two main beams and side beams.
 
The main beam and the side beam are rigidly connected. Wheels on both ends of the side beam support the bridge running on the runway. There is also runway welded on the main beam, which allows the trolley to run across the bridge.