MAMMOET WORLD Issue 13 | 201470

MOVIN’

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Jack-Up System JS2400Skid track.

Hydraulic skid shoe.

2 x ‘full’ cans, exact height of a container.

Jack frame.

4 hydraulic operated locking pins.

Insert (‘half’can), height: 480 mm.

Bolt connections.

Typical jacking column (‘full’ can), height: 960 mm.

Power pack unit (PPU).

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ON UP

TWENTY-EIGHT JACK-UPS, AND COUNTING

This method involves lifting thetopside onto a support frame,subsequently on a barge andthen moving it offshore to thejacket for installation. Roel Wesel,a Project Manager who oversawa number of jack-ups, explains:“Jack-ups are constantly increasing in height. One of theleading factors is safety at sea: ifa platform is going to be operat-ing in rough seas, the higher up itis out of the water, the safer it is.The deck must always be abovethe expected maximum height ofthe waves. So you start with therequired operating height of theplatform, and then work back-wards: the higher you want theplatform to be above the water,the taller the jacket has to be.That in turn determines theheight of the support frame,which gives you the height of thejack-up.

Jack-up technology makes it possible to build the topside onthe ground and saves crew fromhaving to work at heights – whichis a safer way of working andmore efficient too. Only once thedeck is finished, it is elevated tothe required height.

Consequently, while the float-over technique gained popularity,we stayed ahead by continuously

Since then, various developmentshave been pushing the boundariesof Mammoet’s jack-up technology.Production platforms are gettinglarger, due to a combination ofreasons, such as remote locationsand increased difficulties of extrac-tion that require larger and moresophisticated installations.

Also, oil companies are looking foreconomies of scale. “Doing anykind of assembly offshore isexpensive and complex”, explainsErik Kroes, Manager of Opera-tions, Special Devices. “So themore assembly you can do onland, the better for your bottomline. Our jack-up technology helpsmake this possible.”

Necessity driving inventionThe necessity for elevating top-sides is directly linked to the float-over method (see illustration onpage 72). With topsides continu-ally increasing in size and weight,the float-over has become morepopular.

It all started ten years ago, whenMammoet devised a newapproach to elevate a topside.“Our customer was building threedecks in a row and came to uswith a request for a system to elevate them, with some clearlydefined requirements”, explainsJohn Vermeeren, Director ofGlobal Operations. “The decksneeded to remain as light as possible, which meant there wasno room for reinforcements andwe could only use small assemblycranes during construction.Budget was strict; building thedecks at height, on top of the sup-port frames, would have beenexpensive, subject to safety risksand would have taken a long time.Crew would have had to climb upand down constantly and thedeck would have needed rein-forcements. We invented a solu-tion that allowed our client to buildthe three topsides on theground – one after the other – andelevate them only after they hadbeen finished: the jack-up.”

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Last July, Mammoet jacked up its 28th topside. Since the

first jack-up, in Baku, Azerbaijan, in 2004, Mammoet has

been pushing the envelope in terms of both the tonnage

and height of the objects it elevates.

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improving our technique. Westarted with a jack-up using eighttowers simultaneously, and weare now up to 22. As long asmodules keep growing, we keepinnovating our systems.“

Jack-up technology:the basicsThe basic idea of jacking is touse hydraulic pressure to raisethe object in small incre-ments – 480 millimeters – in whatis known as a stroke: the distance between the retractedand extended positions of a jack.After a stroke, you secure thisgain in height with a section ofthick steel tubing known as anintermediate half-can, then jack itup another 480 mm and place aone-meter ‘full’ can, and so on(see illustration).

That is for one tower. The morepush-up towers you have, themore you can lift in this way. Threeyears ago, in Ulsan, South Korea,Mammoet used 15 towers to pushthe North Rankin B topside weighing over 23,000 tons to aheight of over 26 meters.Mammoet got into the GuinnessBook of Records, twice, with thatone lift – once for height, and oncefor weight.

Erik Kroes explains further: “Thejack-up introduces its forces intothe pressure points at the bottomof the module – which are thesame whether it’s sitting on theground, or on the support frame,or on the jacket out at sea. If youwanted to use a gantry with astrand jack, for instance, then youwould need support steel, or

some kind of sub-structure, andthat would be quite costly. Thejack-up system, by contrast, is rel-atively small. It can be assemblednext to the deck and then skiddedunderneath. Then we connect tothe deck, and we start jacking itup. The fact that we need no rein-forcements is of vital importance.”

Hydraulics and electronics“The key to success is to beinvolved at an early stage”, saysJohn Vermeeren. “The main thingis the weight you’re lifting, butthen there are factors that have tofigure into your calculations, suchas wind speeds.” That matteredfor the North Rankin B jack-up inUlsan: Mammoet’s standard sys-tem is designed to withstandwinds of up to 25 meters a second, but the jack-up date was

MAMMOET WORLD Issue 13 | 201472

As long as

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systems.

       

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Skidding jack-up sys-tem under the topside.

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Jack-up: jackingtopside up (A)..

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After topside has beenjacked up to thedesired height (A) thesupport frame is skid-ded underneath (B).

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Load-out: skidding topside on support frameonto barge. Barge is counterbalanced withpumps to stay level with the quay.

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… and its place in a float-over operation

Jack-Up stroke by stroke…

Hydraulic system pushes the jack frame(A) and jack column up a stroke(480 mm) and a ‘half’ can (B) is inserted.

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4 hydraulic operated locking pins (C)are released.

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The jack frame (A) is lowered and thelocking pins (C) are reinserted.

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close to the end of the typhoonseason, so the customer askedthat the capacity be raised to30 meters a second.

And even with the enormousscale of these decks, precisiondown to the nearest millimeter iskey. Roel: “If you have 10 towers,and one or more is higher thanthe others, then they are attract-ing more weight, just like thelonger legs on a wobbly table. Sothe teams use sensors to keepthem at the same height.

Everything is integrated with specialized software. Indeed, with-out the coordinating software, youhave no system. Roel: “The steelstructure works only because it ismoved by hydraulics. But thehydraulics work only because of

       

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Float-over: sailing barge with topside onsupport frame to offshore location andpositioning barge between the jacket legs (C).Mating topside with the jacket by submergingbarge (D).

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Topside installed. Sailing barge with supportframe away.

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Jack-Up System JS9600Mammoet is currently developing anew system, based on the provencomponents and techniques of ourpresent system. The new system willhave a maximum capacity of 9,600tons for each unit. It can be set upwith different units, which means themaximum capacity can be significantlyincreased. See also page 75.

Hydraulic system pushes the jackframe (A) and jack column up anotherstroke (480 mm) and the ‘half’ can (B)is replaced by a ‘full’ can (D).

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4 hydraulic operated locking pins (C)are released.

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The jack frame (A) is lowered and thelocking pins (C) are reinserted. Readyfor the next stroke (beginning at 1).

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the electronics. The electronicstell the valves to open or close.So our software requirements are precisely specified.”

Ever onward“We started with 12 meters in2004”, says John, “and by thetime of the twenty-fifth jack-up,we had already reached 25meters – and we’re still counting.Erik adds: “In theory there is nolimit in terms of the heights andweights the system can manage.In practice, further developmentand up scaling of the system willbe defined by our customers’needs.”

Roel: “We’ve just done jack-upnumber 28, in Russia, and we’repleased with how it went off. Sonow, it is ‘On to number 29.” n