This standard specifies the classification, requirements, test methods, inspection rules, marking and packaging of flanged stainless steel stop-check valves with flange connection dimensions and sealing surfaces in accordance with GB/T 569 and GB/T 2501. This standard is applicable to the design, manufacture and acceptance of stop and check valves for piping systems of liquefied gas carriers, bulk chemical tankers and ships with a nominal pressure not higher than 6.4MPa and a design temperature not lower than -165°C. The cut-off check valves in the piping systems of corrosive media on other ships can be adopted as a reference.