API RP 934 pdf download Materials and Fabrication of 1 1 / 4 Cr- 1 / 2 Mo Steel Heavy Wall Pressure Vessels for High-pressure Hydrogen Service Operating at or Below 825 °F (441 °C) 1 Scope This recommended practice presents materials and fabrication requirements for new 1 1/4Cr-1/2Mo steel heavy wallpressure vessels and heat exchangers for high-temperature, high-pressure hydrogen...