Feasibility of the Short-Circuit Gas Metal Arc Welding Process for In-Service Repair of Thin-Wall Pipelines

Abstract In-service welding is widely employed for pipeline repair due to its operational and economic advantages, notably the avoidance of shutdown-related losses while maintaining uninterrupted fluid transport. However, its application in pipelines with reduced remaining wall thickness presents critical challenges, including the risks of hydrogen-induced cracking (HIC) and burn-through from the welding arc. This study evaluated the feasibility of direct-deposition repair using Gas Metal Arc Welding (GMAW) in short-circuit transfer mode on in-service API 5L Grade B PSL2 pipelines, aiming to ensure safe welding conditions. An experimental test bench was developed, and six longitudinal weld beads were deposited on water-filled pipes while varying wall thickness and travel speed. GMAW short-circuit transfer was assessed as an alternative to traditional Shielded Metal Arc Welding (SMAW) due to its lower heat input, reduced diffusible hydrogen levels, and improved reproducibility in field operations. Burn-through susceptibility was examined using both experimental and thermal analysis models, which approved all welding conditions. No HIC or lack-of-fusion defects were observed in any weld. The results demonstrate that pipelines with wall thicknesses ranging from 3.2 to 5.3 mm can be safely repaired under in-service conditions using direct GMAW short-circuit deposition, and all welds met the integrity criteria of API 1104 Appendix B, confirming the process as a technically viable and safe alternative for operational repairs.