Valve Sealing Performance

The sealing performance of Lined Valve mainly includes two aspects, namely internal leakage and external leakage. Internal leakage refers to the degree of sealing between the valve seat and the closing part to the medium. There are two standards for assessing internal leakage in my country. One is the national standard GB/T13927-1992 "General Valve Pressure Test" (applicable to general industrial valves) issued by the State Bureau of Technical Supervision in December 1992 and implemented on June 1, 1993. This standard is formulated with reference to the international standard ISO5208-1982 "Industrial Valves Pressure Test of Valves". The other is JB/T9092-1999 "Testing and Inspection of Valves" (applicable to valves for the petroleum industry) issued by the former Ministry of Machinery Industry. This standard is formulated with reference to API598-1986 "Inspection and Testing of Valves". External leakage refers to leakage at the valve stem packing, leakage at the Chinese-French gasket, and leakage caused by casting defects in the valve body. External leakage is not allowed at all.