Comparison of ASME B31.12 Versus B31.3 for Hydrogen-Containing Piping in Refinery Services

For more than fifty years the oil refining industry has been using American Society of Mechanical Engineers (ASME) B31.3 “Process Piping” for the design of piping systems in hydrogen-containing services. In 2008, ASME B31.12 “Hydrogen Piping and Pipelines” was released, which caused uncertainty within the refining industry about which Code to apply in these services. The foreword of B31.12 states that it “applies to design, construction, operation, and maintenance requirements for piping, pipelines, and distribution systems in hydrogen service. Typical applications are power generation, process plants, refining, transportation, distribution, and automotive filling stations.” Typical refinery services containing hydrogen include a gamut of applications. Some operate at high pressures and/or temperatures; some also contain water, hydrogen sulfide (H₂S) and/or other corrosives and others are pure hydrogen at mild conditions. This paper describes the various services along with a summary of associated material degradation or cracking mechanisms and the measures used to prevent piping failures. This is followed by a discussion about whether the more rigorous requirements of B31.12 provide safeguards for these potential degradation mechanisms. A comparison of the two Codes in design, materials, fabrication and non-destructive examination (NDE) requirements is provided along with qualitative estimates of the cost differences. This comparison should help new design and construction projects choose which Code to apply. The paper also has suggestions for clarifying the scope of B31.12.