Crane (machine)

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A crane is a type of machine generally equipped with a hoist rope, wire ropes or chains, and sheaves, that can be used both to lift and lower materials and to move them horizontally. It is mainly used for lifting heavy things and transporting them to other places. The device uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human.

History

The first cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, using human tread wheels, allowing the lifting of heavier weights. In the Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction—some were built into stone towers for extra strength and stability.

Types of Cranes

There are several types of cranes, each tailored to specific tasks and environments:

• Tower crane: Commonly used in the construction of tall buildings. It is fixed to the ground on a concrete slab and sometimes attached to the sides of structures.
• Mobile crane: A crane mounted on a truck carrier or a crawler-type carrier. It is designed to be easily transported to a site and used with different types of loads and conditions.
• Overhead crane: Also known as a bridge crane, it is typically used in factories for lifting heavy loads. It consists of parallel runways with a traveling bridge spanning the gap.
• Floating crane: Used mainly in bridge building and port construction, these cranes are mounted on pontoons.
• Gantry crane: Similar to an overhead crane but with the bridge supported on two or more legs running on fixed rails or other runway.

Components

The main components of a crane include:

• Boom: The long arm of the crane, which can be fixed or telescopic.
• Jib: A horizontal member supporting a moveable hoist, which is fixed to a wall or to a floor-mounted pillar.
• Counterweights: Weights that help balance the crane's load.
• Hoist: The mechanism that lifts and lowers the load.
• Rotex gear: Allows the crane to rotate.

Applications

Cranes are used in various industries, including:

• Construction: For building structures, lifting heavy materials, and assembling large equipment.
• Manufacturing: For moving heavy parts and machinery.
• Transportation: For loading and unloading cargo from ships, trains, and trucks.
• Mining: For lifting and moving heavy materials and equipment.

Safety

Operating cranes involves significant risks, and safety measures are critical. Operators must be trained and certified, and regular maintenance checks are essential to ensure the crane's integrity. Safety devices such as load moment indicators, anti-collision systems, and overload protection systems are commonly used.

Related Pages

• Construction equipment
• Heavy equipment
• Hoist (device)
• Pulley
• Winch

Categories

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