Progress: Addressed, Not Adequately
DOT Relevance: 192.51 192.65
While it is generally true that higher pressures increase the susceptibility of metals to hydrogen-assisted fracture, temperature effects are not as systematic. For example, some metals such as austenitic stainless steels exhibit a local maximum in hydrogen-assisted fracture susceptibility as a function of temperature.
Subpart B (Materials) of 49 CFR 192 prescribes the minimum requirements for the selection and qualification of pipe and components for use in pipelines. The code further states that, Materials for pipe and components must be able to maintain the structural integrity of the pipeline under temperature and other environmental conditions that may be anticipated.
Anticipated temperature operating ranges for hydrogen distribution piping may range between ‑40 and 150C (-40 and 302F). The temperature range should be consistent with 49 CFR 192.
ASME B31.12 will include information equivalent to ASME B31.3, ASME B31.8 and NFPA 54 for natural gas.
Work is underway at SNL examining hydrogen-assisted fracture which includes an assessment of temperature effects.
Research is needed to compile data regarding temperature transition ranges from hydrogen embrittlement to hydrogen attack (lower temperature data on embrittlement exists and most of the lower temperature alloys like 316 stainless are not really affected by embrittlement). Engineering data is needed in order for proper design decisions to be made. Conclusions from research should be incorporated where necessary into the federal code.