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During the operation of a control valve, air leakage can cause the actual valve position to deviate from the set position, which leads to repeated charging of the servo amplifier. As a result, the valve cannot remain at the set position and vibrates. So, how should air leakage in the actuator be detected and addressed? Next, let’s take a look together. 1. Air leakage locations: (1) In pneumatic diaphragm actuators, the diaphragm may be damaged, the push rod and spring tray can become loose, and the O-rings may be damaged; there can also be air leakage at the seal between the push rod of the reaction actuator and the lower diaphragm cover, usually due to wear of the V-shaped seals. Air leakage can occur at the seal of the upper diaphragm cover in top-mounted handwheel mechanisms as well. (2) Air leakage in the piston seal ring of the linear stroke cylinder actuator (including those used in fork-type angular stroke actuators), air leakage in the seal of the piston cylinder head, air leakage in the seal assembly of the limit screw, and air leakage in the seal between the output shaft and the cylinder head. (3) In the angular travel actuator with a double-rack structure, there is air leakage at the sealing ring on the back side of the piston, as well as air leakage at the sealing rings between the cylinder head and the cylinder block. There is also air leakage at the upper and lower support sealing rings that connect the output shaft to the cylinder block, and air leakage occurs at the limit screws on the cylinder head. (4) External attachments: Leaks in the output pipeline connections of various positioners, as well as leaks in pneumatic speed controllers or actuators, quick-release valves, one-way speed regulators, and hold-down valves. 2. Leak treatment: Different methods are employed depending on the type of leak. (1) If there are no strict time limits on the opening and closing of the valve, pneumatic accessories and process connections should be minimized, such as eliminating auxiliary components like quick-release valves, pneumatically controlled speed regulators, one-way speed controllers, reducers, and elbows. (2) Perform regular cleaning and lubrication to keep the push rods and valve stems clean and free from rust, ensure that the chromium plating does not flake off, and maintain adequate lubrication; this helps to prevent wear and leakage of the seals. (3) During inspections, leak checks are conducted on areas such as the exhaust ports of pneumatic diaphragm actuators (with the exhaust port for direct-acting types located on the lower diaphragm cover and that for reverse-acting types on the upper diaphragm cover) as well as the exhaust ports of single-acting piston cylinders; any leaks detected are repaired promptly. The above are the methods for dealing with air leakage in the actuator of control valves. Air leakage can cause the control valve to vibrate, affecting its proper operation; it is essential to check for such issues regularly during use. That’s all for this issue; feel free to follow us.