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A strand jack (also known as strandjack) is a
Strand jacks can be used horizontally for pulling objects and structures, and are widely used in the oil and gas industry for skidded loadouts. Oil rigs of 38,000 t have been moved in this way from the place of construction on to a Strand Jack Lifting
/ref>
Strand jack
is used for heavy lifting and skidding operations are owned and operated by a large number of construction and heavy lifting companies around the world. They are currently manufactured by a small number of companies based in Europe.
A strand jack (also known as strandjack) is a jack
Jack may refer to:
Places
* Jack, Alabama, US, an unincorporated community
* Jack, Missouri, US, an unincorporated community
* Jack County, Texas, a county in Texas, USA
People and fictional characters
* Jack (given name), a male given name, ...
used to lift very heavy (e.g. thousands of tons or more with multiple jacks) loads for construction and engineering purposes. Strandjacking was invented by VSL Australia's Patrick Kilkeary & Bruce Ramsay in 1969 for concrete post tensioning systems, and is now widely used for heavy lifting, to erect bridges, offshore structures, refineries, power stations, major buildings and other structures where the use of conventional cranes is either impractical or too expensive.
Use
Strand jacks can be used horizontally for pulling objects and structures, and are widely used in the oil and gas industry for skidded loadouts. Oil rigs of 38,000 t have been moved in this way from the place of construction on to a barge
Barge nowadays generally refers to a flat-bottomed inland waterway vessel which does not have its own means of mechanical propulsion. The first modern barges were pulled by tugs, but nowadays most are pushed by pusher boats, or other vessels ...
.
Since multiple jacks can be operated simultaneously by hydraulic controllers, they can be used in tandem to lift very large loads of thousands of tons. Tandem use of even two cranes is a very difficult operation. /ref>
How it works
A strand jack is a hollowhydraulic
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
cylinder with a set of steel cables (the "strands") passing through the open centre, each one passing through two clamps - one mounted to either end of the cylinder.
The jack operates in the manner of a caterpillar
Caterpillars ( ) are the larval stage of members of the order Lepidoptera (the insect order comprising butterflies and moths).
As with most common names, the application of the word is arbitrary, since the larvae of sawflies (suborder Sym ...
's walk: climbing (or descending) along the strands by releasing the clamp at one end, expanding the cylinder, clamping there, releasing the trailing end, contracting, and clamping the trailing end before starting over again. The real significance of this device lies in the facility for precision control.
The expansion and contraction can be done at any speed, and paused at any location. Although a lone jack may lift only 1700 tons or so, there exist computer control systems that can operate 120 jacks simultaneously, offering fingertip feel
A finger is a limb of the body and a type of digit, an organ of manipulation and sensation found in the hands of most of the Tetrapods, so also with humans and other primates. Most land vertebrates have five fingers ( Pentadactyly). Chambers ...
movement control over extremely massive objects.
In construction
Strand jacking is a construction process whereby large pre-fabricated building sections are carefully lifted and precisely placed. The alternative would be to do all assembly ''in situ'', even if expensive, technically risky, or dangerous.Strand jack
is used for heavy lifting and skidding operations are owned and operated by a large number of construction and heavy lifting companies around the world. They are currently manufactured by a small number of companies based in Europe.
Notable uses
*Kursk submarine disaster
The nuclear-powered Project 949A ''Antey'' (''Oscar II'' class) submarine '' APL Kursk'' (Russian: ) sank in an accident on 12 August 2000 in the Barents Sea, during the first major Russian naval exercise in more than 10 years, and all 118 pe ...
Uses outside of construction
* Costa Concordia disaster
On 13 January 2012, the eight-year-old Costa Cruises vessel ''Costa Concordia'' was on the last leg of a cruise around the Mediterranean Sea when she deviated from her planned route at Isola del Giglio, Tuscany, sailed closer to the island, an ...
, in the ship salvage phase.
References
{{Reflist Construction equipment Machines