Arc Machines' orbital pipe welding equipment was the answer for Haugesund Mekaniske Versted, one of Norway's leading construction yards, in a recent riser construction project. The risers, which consist of a 3-in. pipe running parallel to a 7-in. pipe, are used in the maintenance of oil wells. The materials specified for the risers presented a difficult technological challenge. Structural steels, the API 5L X70 (modified) chosen for the piping and the AISI 4130 specified for the couplings, were selected on the basis of the strength required. These materials required very precise control of the welding thermal cycle in order to retain their favorable mechanical properties after welding. Results? Weld quality was high with a failure rate of only 1.5% on the AISI 4130. The maximum allowable shrinkage was 0.5 mm in a 15-m line, which was easily accomplished. Haugesund Mekaniske Versted made a total of 574 welds on the riser project, including 287 on the 3-in. pipe and 287 on the 7-in. pipe with AMI's Model 15 and Model 81 weld heads.
Reprinted from The Welding Journal
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