Causes of air leakage in electrical valve positioners and solutions

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Recently, we have received feedback from customers stating that the electrical valve positioners suddenly started leaking air while in use, which affected their functionality. When a general electrical valve positioner causes air leakage from the valve, it refers to air leakage from the pneumatic actuator and its accessories. Next, the editor will introduce to you the common situations that exist. 　　Reasons for air leakage in electrical valve positioners and solutions: 1. Air leakage from the solenoid valve on the cylinder is caused either by damaged sealing rings at the location where the solenoid valve is installed on the cylinder, or by air leakage directly from the solenoid valve itself. It is necessary to perform the venting operation several times at the lower part of the solenoid valve; sometimes it may also be necessary to replace the solenoid valve, or to realign the seal ring between the solenoid valve and the cylinder before reinstalling the solenoid valve. 　　2. Cylinder leakage may be caused by the drilling of the mounting holes in the cylinder being too deep, resulting in a connection between the outside of the cylinder and its internal bore. The cylinder needs to be replaced or the unit discarded. 　　3. The three-piece assembly is leaking. Check the triple-piece seal and replace the triple-piece assembly. 　　4. Scratches on the inner wall of the cylinder: Since some cylinders have not undergone hard anodizing, repeated switching operations cause wear on the inner wall of the cylinder, which in turn leads to damage of the piston O-rings and results in air leakage inside the cylinder. We can solve this by using a Shenyi actuator or by replacing the cylinder. 　　5. Air leakage from the cylinder’s exhaust port may be caused by cross-flow of air inside the cylinder, which also leads to leakage at the exhaust port ； It could also be due to the air nozzle hole being drilled too deep, penetrating straight through the air cylinder, which causes a leak in the air path between cylinder B and cylinder A. We can apply for it to be scrapped, or replace it with a new cylinder. 　　6. Air leakage occurs at the upper and lower parts of the cylinder shaft, which is due to insufficient precision in the machining of the upper and lower shaft holes; repeated opening and closing causes wear of the sealing ring, resulting in air leakage ； It is also possible that the fit between the cylinder and the shaft is too tight, causing the sealing ring to wear out easily. Therefore, we need to replace the upper and lower shaft seals and improve the surface finish of the holes. 　　Above, we have explained the reasons for cylinder air leakage in electrical valve positioners as well as the solutions to address it. However, in practice we need to act according to the actual circumstances, taking into account the surrounding environment and the condition of the cylinders in order to find a solution.