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Orbital Welding Beats Competition
Orbital GTAW for tube and pipe contribute to record-breaking performance at the Angra II Nuclear Power Plant in Brazil. |
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New construction of nuclear power plants has been a rare event in recent years and the opportunities to explore the advantages of orbital welding in the welding of nuclear instrumentation tubing as well as larger diameter piping have been limited. The construction of the Siemens-KWU design PWR Angra II in Brazil between 1996 and 1999 has provided such an opportunity. When Angra I was built in the mid-1970s, all of the welds were done manually. Since all of the manual welding procedures and pipe end-preparation procedures for manual welding had been previously qualified, there was some resistance on the part of FURNAS, the owner at the time, and Siemens who oversaw the project, to permit the use of orbital welding.
However, the Brazilian consortium of subcontracting companies for building nuclear power plants known as UNAMON had had some previous experience with orbital welding and were interested in using the newer technology. They identified the pipe sizes on which orbital welding would be most effective and qualified the orbital welding procedures to meet the stringent DIN standards. While the Angra II project had a total of 200,000 welds of which only 3,865 were done with orbital welding technology, both the quality and productivity of orbital welding was shown to be superior to manual welding both in the pipe shop and in the field. These results were thoroughly and systematically documented. The Angra II project has clearly demonstrated the potential of orbital welding for reducing the reject rate and improving the productivity of code-quality nuclear tube and pipe welds and thus lowering the overall cost of construction.
Barbara K. Henon, Ph.D., and Eng. Angel Brond, Arc Machines, Inc. and Eng. Hélcio Bravo Mosciaro, UNAMON Consórcio de Montagem Nuclear
Reprinted from Welding Design & Fabrication, September, 2002
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