Wendelstein 7-X, the largest fusion experiment in the world of the stellarator type, is at present under construction in Greifswald at the Max Planck Institute for Plasma Physics and is to be completed by 2014. In development work shared with the Karlsruhe Research Centre (Forschungszentrum Karlsruhe), BUTTING produced an optimum solution in relation to the casing pipes and protective pipes for the superconducting electricity supply to the fusion plant. It is the aim of fusion research to produce energy from the fusing of atoms – a similar process to the one which takes place on the sun. Wendelstein 7-X is intended to test the main components of a possible future fusion reactor, which will work on the basis of a stellarator. However, the plant itself is not a fusion reactor. Instead, its task is to examine the suitability of this type of power plant or reactor. The Karlsruhe Research Centre contacted BUTTING in the summer of 2007 – initially with a query about standard pipes, which were to be used as casing and protective pipes. However, it soon became clear that these standard pipes would not meet the tight tolerance requirements. After intensive dialogue with the customer, BUTTING offered an alternative technical complete solution: the strict tolerance requirements were implemented partly by the use of precision half-shells, which reach the desired (final) tolerances only after welding. The half-shells in size 126 x 3 x 1077mm were manufactured with a permeability of µr ≤ 1.01, which should not be exceeded throughout the entire production process. Thereafter, shrinking of the pipe-ends took place. In addition to the half-shells, BUTTING also continued to manufacture pipes in sizes 180 x 3 x 550mm, 180 x 3 x 1127mm and 277 x 3 x 564mm. The total pre-materials provided, made from material 1.4429, came from a smelter specially manufactured for that project. The pipes are used as connecting components for the cooling element. The pipe-ends were shrunk, and then the wall thickness of the pipes was manufactured in the course of mechanical completion, to the most precise diameter tolerances and wall thicknesses. Furthermore, the surfaces were processed vacuum-usable, then glass bead blasted and electro-polished. At the end of June 2008 BUTTING delivered the half-shells and pipes to its customer.
