7.2.3 Gas Tungsten Arc Welding (GTAW)
7.2.3.1 All GTAW equipment shall be equipped with arc starting (e.g. high frequency) and crater eliminating devices.
7.2.3.2 Welding without the addition of filler metal (autogenous welding) shall be subject to Owner review and approval. Where this is proposed for 300 series stainless materials and Ni-base alloys, Contractor shall ensure that suitable heats of steel are identified and welding procedures developed to avoid weld metal penetration problems associated with “cast-to-cast” variations.
7.2.3.3 GTAW shall be used in the following circumstances:
• The root pass of single-sided welds without backing in lines subject to pre-commission cleaning
• The root pass of single-sided welds without backing in gaseous oxygen service