Specific regulations for valve pressure testing

Pressure testing for general purpose valves: Standard: GB/T 13927. This standard is based on the international standard ISO 5208 \"Valves for industrial use – Pressure testing of valves\". 1. Terms: (1) Valve test pressure: The gauge pressure that should be applied inside the valve cavity during testing； (2) Shell test: A pressure test conducted on the entire valve housing, which is formed by combining the valve body, valve cover, and other components. The purpose is to test the tightness of the valve body and valve cover, as well as the pressure resistance of the entire housing, including the joint between the valve body and valve cover. (3) Sealing test: A test to evaluate the sealing performance of the moving parts and the sealing surfaces of the valve body. (4) Upper seal test: A test to evaluate the sealing performance of the seal between the valve stem and the valve cover. (5) Test duration: The length of time the test is conducted at the test pressure. 2. Test items, methods, and procedures: The items included in the pressure test are: (1) Shell test: The inlet and outlet of the valve are sealed, the packing gland is tightened to maintain the test pressure, and the moving parts are kept in a partially open position. Fill the cavity with the test medium and gradually increase the pressure to the test pressure (the check valve should be pressurized from the inlet side), then inspect the housing (including the stuffing box and the joints between the valve body and the valve cover). Shell test pressure: Duration of the shell test: (It should be no less than the value specified in the table.) (2) Upper seal test (This test is required for valves equipped with an upper seal mechanism). Seal the inlet and outlet of the valve, loosen the packing gland (if the valve has a device for checking the upper seal and it is possible to reliably assess the performance of the upper seal without loosening the packing gland, then there is no need to loosen it); the valve should be in its fully open position. Close the upper seal, fill the chamber with the test medium, and gradually increase the pressure to the specified test pressure, after which the performance of the upper seal is checked. (3) Sealing test: The method of applying pressure to major valves is as specified in the table; however, for valves for which a specified flow direction exists, pressure should be applied in that specified direction (except for check valves). During testing, the pressure should be increased gradually to the specified test pressure, after which the sealing performance of the sealing pair is checked. Pressure for the sealing and upper sealing tests: Duration of the sealing and upper sealing tests: (It should be no less than the value specified in the table.) 3. Evaluation criteria for valve testing (1) Shell test: During the shell test, there shall be no visible leaks at the pressure-bearing walls as well as at the joints between the valve body and the valve cover; the shell (including the stuffing box and the joints between the valve body and the valve cover) shall not suffer any structural damage. Unless otherwise specified, leakage at the packing is permitted at the shell test pressure, but no visible leakage should be present when the test pressure is reduced to the seal test pressure. (2) Upper seal test: No visible leakage during the duration of the test. (3) Sealing test: The maximum allowable leakage amount for the sealing test is specified in the table. The leakage amounts given in the table apply only to cases where emissions occur into the atmosphere. Grade A is suitable for non-metallic elastic-sealed valves, while grades B, C, and D are suitable for metal-sealed valves. Among them: Class B is suitable for relatively critical valves, while Class D is suitable for ordinary valves. The maximum allowable leakage amount (class) for each type of valve shall be in accordance with the provisions of relevant product standards. If the relevant standards do not specify otherwise, non-metallic elastic-sealed valves shall meet Class A requirements, while metal-sealed valves shall meet Class D requirements; if the customer requests Class B or Class C requirements, this shall be specified in the order contract. VI. Standards related to valves