topless tower crane,luffing tower crane,topkit tower crane

A wide range of industries, especially manufacturing, mining and construction require heavy loads to be lifted or lowered in various processes. Machineries like hoist and cranes have greatly refused the human efforts and also brought down the process timing, thereby increasing the output.

A crane is a machine used for lifting materials. It has a winder (also called a wire rope drum), wire ropes or chains and sheaves to lift and lower loads and to move them horizontally. It has one or more simple machines to produce the mechanical power for moving the loads, which otherwise is beyond a human''s physical capability. Cranes are commonly used in the transport industry for loading and unloading freight. It is widely used in the construction industry, especially while building tall buildings, and also in the manufacturing industry for assembling of heavy equipment.

The earliest cranes were used for construction activities in Ancient Greece. They were mostly powered by labourers or men or other animals. Later, as their application increased, they evolved into larger cranes to lift heavier weights. With the growth in the shipping industry, harbour cranes were introduced for loading and unloading material and even building of huge ships. Wood being the commonly used material back then, most of the earliest cranes were made from wood. Later after industrial revolution, cast iron and steel cranes came into existence.

The invention of steam engines added to the power of these cranes. The earliest steam crane being introduced in the 18th or 19th century and were used till the late 20th century. With increase in the scope of their usage, today''s cranes are powered by internal combustion engines or electric motors and hydraulic systems and operate with advanced computerised systems. Some industries though still use manual cranes power supply is a concern.

Cranes exist in an enormous variety of forms ¡ª each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. For a while, mini-cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Larger floating cranes are generally used to build oil rigs and salvage sunken ships.

There are three major considerations in the design of cranes. First, the crane must be able to lift the weight of the load; second, the crane must not topple; third, the crane must not rupture.

Cranes illustrate the use of one or more simple machines to create mechanical advantage.

Cranes, like all machines, obey the principle of conservation of energy. This means that the energy delivered to the load cannot exceed the energy put into the machine. Cranes can also get in chain reactions; the rupture of one crane may in turn take out nearby cranes. Cranes need to be watched carefully.

Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of the dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered.

For stationary pedestal or kingpost mounted cranes, the moment created by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the crane will fail.

There are many types of cranes depending on their use. They include mobile crane, truck-mounted crane, sidelift crane, rough terrain crane, all terrain crane, crawler crane, aerial crane, fixed carne, tower crane, hammerhead crane, overhead crane, deeck crane, jib crane, bulk-handling crans et al.