Monday 22 October 2012

Derrick cranes


Derrick cranes consist of a mast, a boom, a bullwheel on which it rotates about a vertical axis, and supporting members (also known as guys). These cranes are very widely used in construction projects, industrial and multistoreyed building construction,  plant errection, loading and unloading of cargoes at ports, in ship building etc. When used with grabs it can handle loose materials like sand, ballast, coal etc.

Derrick cranes


You can see in the image the most of the derrick cranes are supported by a number of guys. The boom can revolve through 360 degree and can pass below these guys. A bullwheel is attanched to the mast and rotates it. These are operated by either a diesel engine or by an electric motor.

As mentioned above, mast is generally supported by guy ropes but when this is replaced by structure it becomes stiffleg derrick. In this case the mast is supported at its upper end by two braced stiffleg, therefore the boom rotates through angle of 270 degree to 290 degree.

The derrick cranes are sometimes mounted on rail wagons for quick transportation and for working near rail lines, and are known as whirler cranes. These cranes are available upto capacities of 40 tonnes with 25 meters boom length and 15 meter work radius.

The derrick cranes can be used as tower cranes for the purpose of errection of high industrial and residential builidings of height 100 meter or above. The derrick cranes are also designed to work as port tower cranes (for use in ports for container and general cargo handling), as shipyard cranes (for use in ship building and ship repairing works with longer capacities and larger working radii).

No comments:

Post a Comment