Mandatory requirements for pressure vessels operating in wet H2S media

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For pressure vessels operating in wet H2S environments, it is mandatory that carbon steel and low-alloy steel sheets with a thickness of 12 mm or more (excluding the sheet layers of multi-layer pressure vessels) be used to manufacture the main pressure-bearing components of such vessels. In such cases, ultrasonic testing must be carried out on each sheet in accordance with NB/T 47013.3-2015, and the qualification grade required shall be no lower than Grade II. Cast steel shall not be used for compressed components. When the thickness of the steel plate used for the housing is ≥12 mm, ultrasonic testing shall be carried out on each sheet, with a grade of II considered acceptable. The H2S content in LPG spheres should be less than 20 ppm. Welded joints and base metals shall be subjected to sulfide stress corrosion cracking tests in accordance with Method A of GB/T 4157-2006. For more construction requirements in wet hydrogen sulfide stress corrosion environments, see HG/T 20581-2011, page 65, section 7.8.2.