A crane is a mechanical instrument required for heavy duty work. It is used when large, heavy objects are required to be moved from one place to another. It finds its applications mostly at construction sites but can also be used for other purposes such as junkyards, scrap yards, factories and other such areas. Cranes consist of three major parts – hoist, wire and sheaves.
Overhead cranes can be of many types according to their need and usage. Given below are various types of cranes:
Bridge cranes are installed on metal beams that run along the ceiling of the room of the factory or warehouse. It needs two strong beams on the sides, a trolley which travels with it and carries the load as well as a hoist, which is needed to lifting and lowering the objects. These types of cranes can be again of two types.
- Top running bridge cranes: These cranes run on the top of the beams. This requires quite some space above the beams for the easy movement of the crane. The installation must be planned as the rooms require higher ceilings. These cranes are stronger and can lift very heavy objects. They can be single single girder (which can lift lighter weights, up to 20 tons) or double girders (which can lift weights up to 100 tons).
- Bottom running bridge cranes: These cranes run at the bottom of the beam. They reduce the available room height. They can even be installed in an already built factory. However, they can not carry very heavy loads and can carry only up to 15 tons.
These are simpler types of cranes as compared to the bridge cranes. Unlike the latter, they operate on a single rail mounted on the ceiling. They operate by means of a forklift. They can be run from either a distance or by a car that moves behind the forklift.
The forklift can be used for lifting objects such as boxes, cartons and other similar objects. These cranes can be used in a small unit as well.
These cranes are very compact and efficient for smaller work places with limited space. One end is fixed on something stationary, such as a wall. Hinges are provided so that the crane can swivel within the room. The distance covered is quite small at about 20 feet. They carry lighter loads.
These cranes are the advanced modification of the bridge cranes. The tracks that they run on are mounted on the floor. Due to this, they can carry heavy loads as much as 350 tons. They have deep water access as well. They are mainly used for loading and unloading cargo and hence found at ports and docks.
Like the rest, these cranes are also mounted on horizontal beams. They remain at an angle of 90 degrees to the floor when they are stationary. But they can go up and down as and when required. They can be used to lift loads in a circular motion.