X100 Welding Technology: Past, Present and Future

A significant amount of research has been conducted within the last decade on the development of X100 line pipe and associated welding technology; including, several field demonstration projects of limited size and scope. Although considerable advances in steelmaking and pipeline construction have occurred, innovations in welding process technology generally lag pipeline industry needs. Clearly, the number of historically viable welding options declines as pipe strength increases. Weld strength becomes more sensitive to cooling rate variation, cold cracking sensitivity increases, and overall weldability tends to decline. Also, achieving the balance between weld strength, toughness, and ductility necessary for pipeline performance requires more highly controlled welding practice, procedures, precision in weld bevel design, and pass sequence. Successful fabrication and field pipelay welding requires greater control of essential welding variables in order to satisfy increasingly stringent weld property requirements. Accordingly, there are few proven welding process options for X100 and detailed knowledge resides within a small number of oil/gas and contractor companies. Recognizing that industry wide implementation of X100 requires the range of manual, semi-automatic and automatic (mechanized) welding processes needed for double jointing, mainline, tie-in and repair, US Department of Transportation Pipeline and Hazardous Materials Safety Administration (DOT-PHMSA) and Pipeline Research Council International (PRCI) have co-funded a consolidated program to begin addressing the issues (Project PR-354-074506). This paper summarizes the program findings that address the current state of the art regarding welding technology applied to X100 pipeline construction. The main issues addressed are: • synopsis of experience, • current status and pending developments in welding processes and consumables, • assessment of first and second level contractor capability, and • key knowledge and experience gaps.