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Working principle of pneumatic coaxial valve

Jul 29,2024

Pneumatic coaxial valves, as advanced fluid control devices, are widely used in modern industry. Their unique working principle and superior performance enable them to excel in various complex working environments. This article will detail the working principle of pneumatic coaxial valves to better understand their advantages in practical applications.

I. Basic Structure of Pneumatic Coaxial Valves

Pneumatic coaxial valves adopt an integrated design of valve body and actuator, i.e., the actuator and fluid pipeline axis coincide. This design not only makes the valve structure compact but also greatly improves the valve's sealing and response speed. The valve seat, control tube, and valve drive are located on a common reference axis, with the circular valve drive arranged around the control tube and valve seat, forming an extremely compact and efficient structure.

II. Working Principle of Pneumatic Coaxial Valves

The working principle of pneumatic coaxial valves mainly relies on the force of compressed air, achieving valve opening and closing by controlling the reciprocating motion of the piston. The specific process can be divided into the following stages:

1. Closing the Valve

When it is necessary to close the valve, compressed air enters the pneumatic coaxial valve's actuator through the air inlet (usually marked as P port), pushing the piston toward the valve seat. Simultaneously, the exhaust port (usually marked as R port) on the other side vents gas, ensuring the piston moves smoothly. As the piston gradually approaches, it ultimately presses against the valve seat seal, achieving tight valve closure. In this process, if the spring is in the return NC (normally closed) state, the valve remains closed even without a control signal.

2. Transition Stage

In the transition stage from closing to opening or opening to closing, the piston moves axially to change the valve's on/off state. This process is very rapid, usually lasting less than a second. In return NC execution, closing is caused by the spring (without a control signal); in return NO (normally open) execution, opening is caused by the spring. This design allows the valve to automatically maintain an open or closed state according to the preset spring state without a control signal.

3. Opening the Valve

When it is necessary to open the valve, compressed air again enters the actuator through the air inlet, but this time it pushes the piston away from the valve seat. Simultaneously, the exhaust port vents gas to balance the pressure in the system. As the piston moves away, a larger gap forms between it and the valve seat seal, allowing fluid to flow smoothly through the valve. In this process, if the spring is in the return NO state, the valve remains open even without a control signal.

III. Advantages of Pneumatic Coaxial Valves
Rapid Response: Due to its pressure-balanced design and very short valve stem stroke, the pneumatic coaxial valve has a fast and repeatable switching speed.
High Sealing: The coaxial valve has a unique valve seat design with excellent sealing, maintaining stable sealing performance even under high pressure.
Maintenance-Free: With only one moving part (piston rod) and no packing seals between the valve stem and actuator, or additional drive actuators, the coaxial valve requires virtually no additional maintenance.
Wide Applicability: Coaxial valves are suitable for various media, including gaseous, vacuum, liquid, gel-like, particulate, highly polluting, and corrosive media. Their compact structure and efficient performance also allow for wide application in various industrial environments.

In summary, pneumatic coaxial valves play a significant role in modern industry due to their unique working principle and superior performance. With continuous technological advancements and expanding application areas, pneumatic coaxial valves are expected to play an even more important role in the future.