Pressure Level (1.3)
Criticality: High
Progress: Addressed, Not Adequately
Score: 20
DOT Relevance: §192.51 – §192.65
Description of Key Area
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.”
Discussion of Criticality
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.
Discussion of Progress
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).
Recommendations
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.
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