What Causes Air Leaks in Air Actuated Valves?
Leave a message
Air Actuated Valves are widely used in the field of industrial automation control due to their advantages such as fast response speed, high control accuracy, and easy operation. However, in long-term operation, air actuated valves often suffer from air leakage problems. Air leakage not only reduces system efficiency, but may also cause safety hazards. This article will systematically analyze the root causes of air leakage in air actuated valves from the perspectives of structure, materials, use environment and maintenance.
The seal of the air actuated valve is a key component to achieve air tightness. Common materials include rubber, fluororubber, polytetrafluoroethylene, etc. Although these materials have certain elasticity and corrosion resistance, they will gradually age, crack or deform when they are opened and closed frequently and exposed to high temperatures or corrosive media for a long time. Once the seal fails, gas can leak through the gap. Especially at the valve stem seal and the seal between the cylinder and the piston, the sealing surface is more likely to be damaged due to wear or insufficient lubrication, causing air leakage in the air actuated valve.
Valve body material defects or processing errors
The valve body of air actuated valves is generally made of metal, such as stainless steel, aluminum alloy or carbon steel. These materials may develop trachoma, pores or micro-cracks during the casting, welding or machining process. These tiny defects may not be easily noticeable in the early stages, but under the long-term action of high-pressure gas, the micropores will gradually expand and form gas leakage channels. In addition, poor processing accuracy, such as the matching gap between the valve body and the sealing ring exceeding the tolerance, will also cause sealing failure. Therefore, selecting qualified manufacturers and strictly controlling the processing technology are important prerequisites for ensuring the air tightness of pneumatic valves.
Air actuated valves are often connected to the air source pipeline through pipe joints. If the connection is not tightened in place, or substandard sealing tapes or gaskets are used, air leakage points will form at the interface. In addition, if the force applied during the pipeline installation process is uneven or the threaded connection is not tightened according to the specified torque, it may also cause the threads to loosen and the sealing surface to be damaged. In particular, some users do not conduct a leak test after replacing accessories or repairing, often ignoring the potential leakage risks caused by improper installation. Therefore, after each installation and maintenance is completed, be sure to conduct a sealing test to ensure that there is no air leakage at each connection part.
The core component of the air actuated valve, the actuator, is composed of a piston and a cylinder. The compressed air drives the piston to move to achieve the valve switching action. During long-term operation, the relative movement between the piston and the cylinder wall will cause wear, especially when lubrication is insufficient or the compressed air contains a large amount of impurities. As the tightness between the piston edge and the cylinder wall decreases, gas begins to leak in the gap, which eventually manifests as gas escaping outside the valve body. This type of internal leakage is difficult to detect through external visual inspection and requires diagnosis by pressure maintenance testing or acoustic testing. Therefore, strengthening air filtration and keeping the air source clean are effective means to delay piston wear and reduce the risk of leakage.
Improper operation and maintenance accelerate leakage
In the daily use of pneumatic actuating valves, the standardization of operators and the soundness of the maintenance system are also directly related to the sealing performance of the valve.
For example, some operators frequently use the manual forced switch function during valve operation, and even perform forced operations when the control signal is not disconnected. This behavior will cause abnormal stress on the piston inside the actuator. In the long run, the sealing ring will easily shift or locally compress and deform, resulting in a decrease in sealing performance. In addition, in order to save costs, some users do not carry out periodic lubrication of the valve stem, piston and sealing ring as required before servicing the equipment after abnormality or damage. The lack of lubricating grease will increase the friction between metal parts and directly shorten the service life of the seal.
Therefore, it is recommended that the factory be equipped with regular air tightness testing equipment (such as pressure drop testing, liquid injection method or ultrasonic detector), and set up a "inspection record + review" mechanism to conduct periodic testing of key parts such as valve stem seals, joint threads, and cylinder sealing surfaces.
