Progress: Addressed, Not Adequately
DOT Relevance: 192.221 192.245
Welding of steel in pipelines is addressed under Subpart E of 49 CFR 192. Per the federal code, the scope of this section is as follows: This subpart prescribes minimum requirements for welding steel materials in pipelines. This subpart does not apply to welding that occurs during the manufacture of steel pipe or steel pipeline components.
Modifications to the CFR may be needed to account for welding of steel pipe to be used in hydrogen applications. It is important that all joining methods used are adequate to prevent leakage, permeation of hydrogen, pipe weld and HAZ embrittlement.
Over the years, organizations such as the SRNL, SNL, ORNL, and ASME have studied different aspects of welding of steel pipe for hydrogen use. The research categories studied include crack growth, procedures for welding, welding qualification, weld inspection, and appropriate weld hardness levels.
ASME has identified a knowledge gap in the study of welds for hydrogen pipe. ASME is concerned about the effect of pressure on sustained load cracking in welds and weld HAZs.
Current research regarding hydrogen pipe welds should be expanded to include a more in-depth analysis of the research areas mentioned above. Standards for hydrogen pipe welds should be established and incorporated by reference into the federal code. It is important that all joining methods used are adequate to prevent leakage, permeation of hydrogen, pipe weld and HAZ embrittlement. These standards should address procedures for welding, welding qualification, weld inspection, appropriate weld hardness levels, acceptable rates of crack growth (if any), and testing of welds. Without research data, all that the ASME B31.12 task group can do at the present is to add cautionary notes for welding for hydrogen service and require a maximum hardness limit that comes from NACE recommendations for sour service.