Introduction: Many kinds of cranes are used for raising, shifting or laying load, equipment or other materials. They may vary in dimensions, viz, shape, weight, function, design, etc. We use cranes to help us do these activities with ease. In general, they are divided into two categories:
1) Overhead cranes
2) Boom cranes.
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Overhead cranes: These are sometimes called mobile overhead cranes or overhead travelling cranes. They are rated according to their load lifting ability and are mentioned as Ton capacity. These cranes are usually used inside building, workshops or areas where other types of crane cannot operate. These operate on elevated tracks and move throughout the area on a trolley with wheels to move along the rail.
These are used to lift loads and shift them to other destinations. These are controlled by levers/pendent that can be pushed or pulled. Some have their operating controls located in a cage that hangs below the bridge and travel along with it. These types of cranes are strong with high level of calibration, compact that is compliant to any need and available to varied series of applications.
The major parts of an overhead cranes are, track/rails, trolly with wheels, bridge with operating cage, trolly mounted block and hoist. The overhead crane allows load movement to travel in three directions, i.e. bridge travel, trolley block travel and hoist travel. These movements allow loading, unloading, transfer, repositioning of load, equipment or workpiece.
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On the type of components used, overhead cranes are divided as:
Single Girder Overhead Crane – The arrangement improves the use of minimum weight lifting and can be accommodated where there is space restriction.
Double Girder Overhead Crane – These are used for lifting heavy loads. It reduces the load on construction and provides superior firmness and easy handling.
Underslung Overhead Crane – These are useful when there are large distance and usual cranes not available due to outmoded runways.
Cantilever Overhead Cranes – These are used where there is difficulty to entree and when you need to serve several terminals without covering entire length or width of workshop. These are of added advantage where there is movement constraint on the ground.
Many overhead cranes have controls hanging from the bridge on a pendant. The pendant is a control box connected to the electrical system of the bridge. The controls have two buttons for each pair of actions, i.e. right or left, up or down, forward or backward. Care should be taken to have one function at a time as two pair function at a time can damage the control system.
Most of the overhead cranes are electric-powered and thus before using it, make sure you know it's operating, capacity, controls and other function as it is dangerous and life-threatening to operate it without proper working. Operating such equipment's requires certification, practice and knowledge of its safety techniques and procedures.
Applications of Overhead Cranes: The general uses of overhead cranes depend on the industries that they serve. Some of the common applications include:
Warehouse – It is used to move loads, equipment's or any other heavy items or products from docks to loading or unloading areas.
Storage – It helps to transport and organize bulky loads.
Transportation – It helps to load or unload trucks, trailers or railcars with cargos or products.
Assembly – It helps to move products through the assembly or production from the start to finish line.