TYPES OF ELECTRIC OVERHEAD CRANES
There are various types of overhead cranes with many being highly specialized, but the great majority of installations fall into one of four categories:
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 runways. These “legs” eliminate the supporting runway and column system and 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. This type of crane is designed using I-beams like those found in ceiling structures of many factories. The trolleys run along the flat surface on the bottom horizontal bars of the beam. The hoisting mechanism is similar to a single girder crane with the difference that the crane doesn’t have a movable bridge and the hoisting trolley runs on a fixed girder.