An overhead crane, also called a bridge crane, is a type of crane used in industrial environments. An overhead crane consists of parallel runways with a traveling bridge spanning the gap. A hoist, the lifting component of a crane, travels along the bridge.
Cranes are industrial machines that are mainly used for materials movements in construction sites, production halls, assembly lines, storage areas, power stations and similar places.
Their design features vary widely according to their major operational specifications such as type of motion of the crane structure, weight and type of the load, location of the crane, geometric features, operating regimes and environmental conditions.
There are various types of overhead cranes with many being highly specialized, but the great majority of installations fall into one of three categories: a) Top running single girder bridge cranes, b) Top running double girder bridge cranes and c) Under-running single girder bridge cranes.
Overhead Traveling Cranes come in various types:
1) Single girder cranes – The crane consists of a single bridge girder supported on two end trucks. It has a trolley hoist mechanism that runs on the bottom flange of the bridge girder.
2) Double Girder Bridge Cranes – The crane consists of two bridge girders supported on two end trucks. The trolley runs on rails on the top of the bridge girders.
3) Gantry Cranes – These cranes are essentially the same as the regular overhead cranes except that the bridge for carrying the trolley or trolleys is rigidly supported on two or more legs running on fixed rails or other runway. These “legs” eliminate the supporting runway and column system and connect to end trucks which run on a rail either embedded in, or laid on top of, the floor.
4) Monorail – For some applications such as production assembly line or service line, only a trolley hoist is required. The hoisting mechanism is similar to a single girder crane with a difference that the crane doesn’t have a movable bridge and the hoisting trolley runs on a fixed girder. Monorail beams are usually I-beams (tapered beam flanges).