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For pressure vessels filled with wet hydrogen sulfide medium, the following requirements are mandatory: 01 When carbon steel and low-alloy steel plates with a thickness of 12 mm or more (excluding the plates of multi-layer pressure vessels) are used to manufacture the main pressure-bearing components of such vessels, ultrasonic testing must be carried out on each plate in accordance with NB/T 47013.3-2015, and the acceptance grade must be at least level II. 02 Cast steel shall not be used for pressure components. 03 When the thickness of the steel plate used for the shell is ≥12 mm, ultrasonic testing shall be conducted on each sheet, with a grade of II considered acceptable. 04 The H2S content in the LPG tank should be less than 20 ppm. 05 Welded joints and base metals shall be subjected to the sulfide stress corrosion cracking test in accordance with Method A of GB/T 4157-2006. Pressure vessels containing media that are not allowed to leak in trace amounts must meet the following requirements: 01 After passing the pressure resistance test, a leakage test must be conducted; the type of leakage test, the pressure levels, and the technical requirements are specified by the designer in the design documents. 02 During regular inspections, a leak test shall be conducted in accordance with the requirements of the design drawings. 03 To minimize the leakage of the medium outside through the safety valve, it can be used in series with a burst disc. 04 Filler box type heat exchangers shall not be used.