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For pressure vessels containing moderately hazardous media, the following requirements are mandatory: 01 Cast iron shall not be used for the pressure-bearing components. 02 Cast steel shall not be used for pressure components. 03 For containers of highly permeable media with moderate hazard levels, their pipe flanges shall comply with the provisions of the HG/T 20592–HG/T20635 series of standards, and a necked butt-welded flange, a metal wound gasket with reinforcing rings, and high-strength studs of special grade shall be used in combination. 04 When it is necessary to enter the container for regular inspections, replacement, neutralization, disinfection, cleaning, and sampling for analysis must be carried out. The results of these analyses must meet the relevant standards and specifications, and the interval between sampling analyses should comply with the regulations set by the user entity. 05 A conduit should be installed at the outlet of the safety valve or rupture disc to direct the discharged medium to a safe location where it can be properly handled; toxic materials must not be released directly into the atmosphere. 06 To facilitate the cleaning and replacement of safety valves, a stop valve may be installed between the overpressure relief device and the pressure vessel only with the approval of the person in charge of safety management at the user facility, and provided that reliable preventive measures are put in place. The structure and diameter of the stop valve must not prevent the safe operation of the overpressure relief device. 07 To minimize the leakage of the medium outside through the safety valve, it can be used in series with a burst disc. 08 Packing-type heat exchangers shall not be used.