API RP 934 pdf download.Materials and Fabrication Requirements for 2- 1 / 4 CR-1MO & 3CR-1MO Steel Heavy Wall Pressure Vessels For High Temp., High Pressure Hydrogen Service 1 Introduction This recommended practice applies to new heavy wall pressure vessels in petroleum refining, petrochemical and chemical facilities in which hydrogen or hydrogen-containing fluids are processed at elevated temperature and pressure....