Welding Metallurgy and Process Development Research for the Gas Pipeline Industry

Abstract

The construction of gas transmission pipelines in Canada, as in other areas of the world, has placed heavy reliance on the use of traditional, manual SMAW techniques for field joining. Hydrogen-assisted cold cracking has been the most significant problem area with this process and, perhaps surprisingly, related research is still being conducted. The pursuit of greater productivity and reproducibility has led to wider use of mechanized GMAW; the limitations inherent in the original, short-circuiting process have led to both metallurgical investigations aimed at improving toughness and, more recently, process developments intended to bring metal transfer and metallurgical reactions under closer control. Current high levels of activity in the industry have also necessitated improvements in efficiency for small diameter pipelines and piping systems, and a number of developments, using both traditional and innovative welding processes, are in progress. Increasing application of a fitness-for-purpose approach to weld acceptance has led to a reassessment of NDE techniques, and to the development of mechanized ultrasonic testing techniques.