Derrick
A derrick is a
Derricks are especially useful for high-rise rigging, jobs that cover a long period of time, or jobs when the impact to street or pedestrian traffic is a concern.
The term derrick is also applied to the framework supporting a drilling apparatus in an
Types
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A-frame derrick
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Basket derrick
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Breast derrick
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Chicago boom derrick
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Gin pole derrick
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Guy derrick
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Guy derrick with nonrotatable mast
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Stiffleg derrick
There are various types of derrick based on how the tower or mast is set up and the use of boom:[2]
A-frame
An A-frame derrick is one in which the boom is hinged from a cross member between the bottom ends of two upright members spread apart at the lower ends and joined at the top; the boom point secured to the junction of the side members, and the side members are braced or guyed from this junction point.[2][4]
Basket
A basket derrick is a derrick without a boom that is supported by a rope-and-pole system that forms a basket. The basket is constructed from a group of poles to form a polygon. There are crossbars between the pole members to strengthen their support. The supporting ropes are tied to the top of the basket poles on one end and joined together on the other end at a lower elevation than the top of the basket poles to form the base for the derrick tower. The derrick tower can be a mast or a post with the bottom hinged at the base where all ropes meet. The top of the tower is secured with multiple reeved guys to position the top of the tower to the desired location by varying the length of the upper guy lines. The load is lifted using a pulley system connected to the top of the tower.[2]
Breast
A breast derrick is a derrick without a boom and with a mast constructed from two upright members. The upright members are more spread at their bottom ends than their top ends. There are crossbars to join the two members from the bottom to the top to form a mast.[2][4]
Chicago boom
A Chicago boom derrick is a derrick with a boom which is attached to an external structure. The external upright member of the structure serves as the mast, and the boom is stepped in a fixed socket clamped to the upright. The boom is connected to at least three pulley systems to control the position of the boom. For example, a pulley system is connected to the top of the boom and the higher area of the external structure and two pulley systems near the top of the boom connected on either side of the boom to the external structure. The position of the top of the boom can be controlled by manipulating these pulley systems. The load is lifted from a separate pulley system that is connected to the top of the boom.[2][4]
Gin pole
A gin pole derrick (also known as standing derrick or pole derrick) is a derrick without a boom and with single tower or mast supported by four guy wires (two side guys, a fore guy and a rear guy). Its guys are so arranged from its top as to permit leaning the mast in any direction. The base of the tower is hinged and the top of the tower is connected to a pulley system for load lifting. As this is a simple derrick system, it is recommended for use by some agencies as an improvised rescue derrick in an emergency situation where no suitable rescue derrick or crane is available.[1][2]
Guy
A guy derrick (also known as boom derrick) is a fixed guyed mast derrick that can be rotated and connected to a boom. The mast is in upright position with the base that can make the mast rotate, but not lean in any direction. The top of the mast is connected to many guy wires which are anchored to the ground to support the load. At the base, the mast is also connect to the bottom end of the boom. The boom extends outward and upward to the desired position. The top of the boom is a pulley system that is connected to the top of the mast to control how far the boom is to be from the mast. When the mast is rotated, the connected boom is swung from to the side. The control of the lifting location is done by the manipulation of the top pulley system and the rotation of the mast at the base. The load is lifted by another pulley system connected to the top of the boom.[2] In a medium load lifting, another construction method can be used. In this case, the mast is fixed without being rotated, but the boom can be swung around the mast. This can be done by connecting the bottom of the boom with two boards on the opposite sides around the surface of the boom to form a fork. The fork and the bottom part of the boom are lashed to secure them together. Another lashing between the fork area and the mast at a higher position supports the weight of the boom. The fork is put around the mast such that the bottom of the boom rests on the mast without being permanently fixed to it. The fork prevents the boom from coming off the mast while it swings up to 180 degrees.[7]
Shearleg
A shearleg derrick is similar to a breast derrick with the exception that, instead of fixed guy wires that secure the top of the mast, it is secured by multiple reeved guys to permit handling loads at various radii by means of load tackle pulley system suspended from the mast top.[2] In a simpler construction, a shearleg derrick can be assembled from two posts to form A-frame shear legs without any crossbar. The bottom of the legs are set in two holes on the ground, spreading them apart. There is a rope to tie the two legs together near the bottom to prevent them from spreading apart further. On the top side, the two legs are connected together by a lashing but with a small spacer block placed between the legs. A sling, which may be made from ropes, is placed around the area that two legs meet to be used to put a tackle pulley system for lifting the load. There are two guy wires, front and rear, to support the shear legs. The rear guy may be reeved to allow adjustment of the angle of the shear legs.[7]
Stiffleg
A stiffleg derrick, also known as a Scotch derrick, is a derrick with a boom similar to that of a guy derrick, but instead of using guy wires to secure the top of the mast, it uses two or more stiff members, called stifflegs, which are capable of resisting either tensile or compressive forces. Sills may also be used to connect between the bottom ends of the stifflegs and the base of the mast.[2] There may be a counterweight to place on the sills behind the stifflegs in heavy load lifting.[7] A stiffleg derrick on a vessel is called a floating stiffleg derrick.[4]
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Stiffleg derrick performing high rise rigging on a rooftop[8]
Oil derrick
Another kind of derrick is used on oil wells and other drilled holes. Both the structure itself and the complex set of machines associated with it are referred to as a derrick. A derrick is also used on some offshore oil and gas rigs.
Patent systems
This section includes a improve this section by introducing more precise citations. (July 2014) ) |
Hallen
The
Velle
The Velle derrick is similar to the Hallen but without the use of outriggers. On top of the boom is a T-shaped yoke. As in the Hallen, the guys serve for topping and lowering the boom, but they are fastened on the yoke with four short, steel-wire hanger ropes. The ends of the topping and lowering ends of the halyard are secured to half-barrels on one winch. In this way the boom moves at the same speed as the winch veers the topping end of the halyard and hauls the lowering end of the halyard, and vice versa. The slewing ends are also wound on to another half-barrel. There is a third winch to hoist to cargo on the yoke. Runners decrease swing and rotation of the cargo. A joystick duplex controller steers the Velle derrick.
Stülcken
The patent Stülcken derrick is used for heavy cargo. It stems from the German shipyard
See also
References
- ^ ISBN 1921152028. Archived from the original(PDF) on 21 March 2014. Retrieved 5 July 2014.
- ^ a b c d e f g h i j "Regulations (Standards - 29 CFR) - 1910.181: Derricks". Occupational Safety and Health Administration. Retrieved 5 July 2014.
- ^ "Derricks". Budco Enterprises, Inc. Retrieved 2016-06-10.
- ^ a b c d e "Subchapter 7. General Industry Safety Orders; Group 13. Cranes and Other Hoisting Equipment; Article 91. Definitions". Department of Industrial Relations, State of California. Retrieved 5 July 2014.
- ^ Freudenrich, Craig; Strickland, Jonathan (12 April 2001). "How Oil Drilling Works". HowStuffWorks. Retrieved 5 July 2014.
- ISBN 978-0425260791. Retrieved 5 July 2014.
- ^ a b c Field Manual 5-125 - Rigging Techniques, Procedures, and Applications (PDF). The United States Army. 3 October 1995. Archived from the original (PDF) on 13 August 2012. Retrieved 6 July 2014.
- ^ "Derricks". Budco Enterprises, Inc. Retrieved 2016-06-10.
Further reading
- Ministry of Defence (Navy) (1995). Admiralty Manual of Seamanship. The Stationery Office. pp. 3–194. ISBN 0-11-772696-6.
External links
- Media related to Derricks at Wikimedia Commons