The airtightness of pneumatic ball valves requires that the airtightness index of pneumatic ball valves shall be determined by the requirements for internal leakage and external leakage. The national standard stipulates that the airtightness of non-metallic sealed pneumatic ball valves shall comply with the requirements of GB/T13927 Pressure Test for General Purpose Valves.; No visible leakage during the test duration;; Aerospace industry standards stipulate pneumatic ball valves for ground gas pipeline systems.; Under the air pressure of 0.05MPa and 1.1 times of the nominal pressure, hold the pressure for 3min, and the internal leakage rate shall not be greater than 3 10-5Pa m3/s (no bubbles escape); Under the air pressure condition of 1.1 times of the nominal pressure, maintain the pressure for 3min, and the external leakage rate shall not be greater than 1 10-5 Pa m3/s (no bubbles escape).

1. Maintenance methods and standards. Maintenance method: (1) The valve shall be handed over according to the operating procedures, and the replacement shall be qualified. The maintenance personnel shall carry the gas filter tank, vinyl chloride olfactometer, and be supervised by the staff of the gas prevention station before dismantling and inspecting the valve. (2) Turn off the air source, remove the positioner and the air source pipe, disconnect the valve (3). Check the connection of the valve core and valve stem, and check whether the connecting pin can be removed. If not, use a special tool to remove it, or change the hole.