Progress: Addressed, Not Adequately
DOT Relevance: 192.51 192.65
Most hydrogen pipelines in operation today operate at pressures less than 6.9 MPa (1000 psi) with low cycling. A pipeline system built to serve a much larger market for hydrogen might operate at increased loads and pressure cycles. Most discussions related to pipeline transport of hydrogen incorporate operating pressures up to 20.7 MPa (3000 psi).
Subpart B (Materials) of 40 CFR 192 prescribes the minimum requirements for the selection and qualification of pipe and components for use in pipelines.
Current materials knowledge is sufficient for pressures up to 15.2 MPa (2200 psi) with 290 MPa (42 ksi) and 359 MPa (52 ksi) steels being used at 30% to 40% SMYS. With these steels in this pressure range, no embrittlement failures have been seen. Higher pressures may be required for more widespread hydrogen pipeline deployment. A maximum allowable operating pressure needs to be determined as well as a SMYS percentage.
Sandia National Labs has spent a significant amount of time addressing these topics. Since the 1970s, Sandia has conducted high pressure hydrogen materials testing.
ASME B31.12 will include information equivalent to ASME B31.3, ASME B31.8 and NFPA 54 for natural gas. The anticipated operating range for hydrogen distribution piping is from full vacuum to 20.7 MPa (3000 psi).
For higher line pressures and/or or higher strength steels, the current knowledge base is insufficient. Research already underway related to embrittlement must be useable by engineers to write standards for which regulators can write clear rules.