Ambient Temperature Temperbead welding employs the GTAW machine process, and avoids both the elevated temperature preheat and post-soak heating operations associated with conventional temperbead welding. ASME Code Case N-638-4 governs ambient temperature temperbead welding activities. N-638-4 currently limits the depth of an ambient temperature temperbead weld repair to 50% of the base material thickness. This restriction precludes use of the GTAW ambient temperature temperbead process for buttering of through wall repairs and replacements. This paper describes the ongoing ASME activity to revise N-638-4 to permit through-wall temperbead repairs. The methodology, Code text, applicable restrictions, and technical bases for this Code Case revision will be addressed.

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