Welding and Quality Control for the Consolidation of the LHC Superconducting Magnets and Circuits

The first LHC long shutdown was driven by the need to consolidate the 13 kA splices between the superconducting magnets to safely attain its center of mass design energy of 14 TeV. Access to the splices requires the opening of welded sleeves by machining. After consolidation, the sleeves are re-welded using a TIG orbital welding. The welding process has been modified from the original “as-new” installation in order to better adapt to the “as repaired” situation. The intervention has been thoroughly prepared through qualifications, organisation of teams, their training and follow-up. Quality control is based on the qualification of equipment, process and operators; the recording of production parameters; regular process audits and production witness samples; visual inspection through an official certifying body. The paper also describes welding and quality control of special intervention cases, with issues of difficult access requiring innovative solutions. This work concerns over 10 000 welds and a team of 40 engineers and technicians over a period of 18 months. The experience and lessons learnt will be applicable to similar large complex projects.