Crane

April 25, 2013 by  


tufailA crane is a tower or derrick equipped with cables and pulleys that can be used both to lift and lower materials and to shift them horizontally.

Cranes are commonly employed in the construction industry and in manufacturing heavy equipment.

Construction cranes are usually temporary structures, either fixed to the ground or mounted on a purpose-built vehicle.

Cranes may either be controlled from an operator in a cab that travels with the crane, by a pushbutton pendant control station, or by infrared or radio control.

Where a cab operator is employed, workers on the ground will communicate with the operator through a system of standardised hand-signals or, in larger installations, radio systems; an experienced crew can position loads with great precision using only these signals.

Industrial cranes raise, shift, and lower loads with a projected, swinging arm or a hoisting apparatus supported on an overhead track. There are many different types of products. Bench or cart-mounted cranes are designed for small workspaces and one-hand operation. Jib cranes mount on walls or floors and consist of a horizontal beam (jib) upon which a shuttle or hoist is mounted. Floor or foundation-mounted jib cranes have higher load ratings than wall-mounted cranes. A cantilevered jib crane can incorporate full or partial rotation. Gantry cranes have a horizontal beam and end supports or legs. Machines range in size from small, workstation cranes to very large, heavy-duty construction cranes. Overhead cranes or bridge cranes attach a horizontal load-carrying beam to wall columns (overhung) or the underside of the ceiling (underhung). Boom cranes use a structure, pole or boom to support a suspended cable for load attachment. Tower cranes use a cantilever boom, but are designed for very heavy-duty operations. Mobile cranes and truck-mounted can be moved or driven to different locations. Ship cranes and deck cranes are designed for shipboard mounting and the loading or ships, freighters, and other maritime vessels. Stacker cranes are similar to bridge cranes; however, instead of a hoist, these industrial cranes use a mast with forks or a platform to handle unit loads.

Industrial cranes differ in terms of product specifications, features, and applications. Performance specifications to consider include load capacity, vertical available lifting height, and horizontal available span. In terms of features, products such as tower, davit and jib cranes have a titling boom. Machines with a cantilevered boom or a jib that can be rotated with our without a load are also available. Industrial cranes with wheels are designed for load transport and positioning. Typically, these machines are equipped with a brake or stabilizing outriggers. Industrial cranes that provide motorized motion move loads with a motor instead of manual pulling. With some applications, an industrial pendant is used to enable an operator to actuate lift or trolley travel. There are many different sizes of industrial cranes. Small site-based cranes are used for designed for on-site applications. Immense tower cranes and deck cranes are designed to move cargo containers, steel and concrete; large tools such as acetylene torches and electrical generators; as well as a wide variety of other building materials

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