Page 37: of Offshore Engineer Magazine (Mar/Apr 2014)

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EPIC

Left: The deck nodes and deck supports in situ, illustration.

Right: Stress analysis on a leg node.

Below: A truss node pattern in construction.

Images: Vulcan SFM.

and measuring 4.6 x 4.6 x 4.6m,” Deck nodes and deck leg supports created from two cone-shaped castings,

The 140-tonne deck leg supports, fabri- with the lower piece coming complete

Mockford says. “But that was then also cated from two cast cone sections, are with a 5.9m-diameter ? ange ring (the broken when we also won the contract the uppermost component of the hull’s ? ange is usually cast, with the rest of the to supply the deck nodes (at 120-tonne union with the topside. They will be node rolled plate). each).” been driven by project requirements–the In total, Vulcan SFM is providing 36 spaced 27m apart, from center line to To design the nodes, Vulcan uses criti- 1300m water depth, harsh environment, castings for the Aasta Hansteen spar, center line, on top of the hull. The most cal load data gathered from the client. and need for condensate storage. from relatively small pull-tube castings, highly-loaded deck leg support has been The data is ran through stress-strain

In turn, the scale has driven further to the ultra-large truss and deck nodes, designed for a maximum vertical, fac- analysis, which allows Vulcan to create a ? rsts. Supplier Vulcan SFM, a subsidiary which it has designed. tored design load of 19,300-tonne. high-quality casting by controlling how of Shef? eld Forgemasters International, The 120-tonne deck nodes, which will the steel ? ows through the mold, and

The spar believes the four cast deck connection have shaped stubs, onto which the hori- how it will cool and solidify.

The Aasta Hansteen spar is formed nodes it is providing to connect the deck zontal I-beams will be welded, and con- Once cast, the separate deck leg sup- from two main segments, a truss spar to the hull will be the largest cast nodal nection points for the tubular columns, port pieces will transported through the hull, and 23200-tonne topside. The joints manufactured to date. Vulcan will form an integral part of the topsides’ port of Goole, England, and probably topside will rest on the top of the hull believes it will also be the ? rst time cast super-structure. Once completed, the Antwerp, Belgium, to Korea, where they via four deck leg supports, and four nodes have been used within a spar truss topside will be transported from Hyundai will be welded together and integrated deck nodes. hull. Heavy Industries’ yard in South Korea onto the hull. To give an idea of scale,

The largest offshore cast nodes previ- The hull section will comprise of a to Norway, and the deck nodes will be the ? ange rings for previous spars cast by ously supplied by Vulcan were two truss connected to the hard tank at the mated with the deck leg supports on the Vulcan have weighed about 7-tonne. On 110-tonne trunnion nodes, used for lift- top and the soft tank at the bottom. The hull in a Norwegian fjord. Aasta Hansteen, the equivalent section ing Statoil’s 9000-tonne Valemon jacket main leg and brace tubulars will be con- After initially designing fabricated (ring ? ange only) would weigh nearly into place in the Norwegian sector of the nected by eight truss nodes of varying deck leg supports with cast ring ? anges, 50-tonne.

North Sea, in 2012 (OE: August 2012). sizes, which also connect to the heave discussions with supplier Vulcan SFM

Ultra-large truss nodes

They measured 4.6x4.4x3.7m. plates. Four nodes connect the legs to led contracted hull-designer Technip to “That record was soon broken by the the hard tank. Rigid steel catenary riser opt for a fully-cast ? ange and cone. The ultra-large truss nodes are more com- truss nodes (also known as leg nodes pipes will run through the truss hull Due to manufacturing and logisti- plex to cast. These weigh 70-117-tonne, or heave plate nodes) in the hull for section down to the sea bed, more than cal constraints, including road bridge depending on where they are in the spar

Aasta Hansteen, weighing 117-tonne 1300m below the platform. heights, each deck leg support will be truss hull. The largest would occupy a oedigital.com March 2014 | OE 39 000_0314_Epic2_Vulcan.indd 39 2/21/14 1:54 PM