Pneumatic coaxial valve structure

May 20,2025

I. Basic Definition:

Pneumatic Coaxial Valve is a valve driven by compressed air, utilizing coaxially arranged valve core and valve seat to achieve fluid switching or regulation. Its core feature is the coaxial movement of the valve core and stem, resulting in a compact structure and sensitive response, suitable for precision control scenarios (such as semiconductors, medical devices, and automated equipment).

II. Core Structural Components:

The typical structure of a pneumatic coaxial valve mainly includes the following components:

Component Name	Function Description
Valve Body	Serves as the main body of the valve, providing a fluid passage. Materials are often stainless steel, engineering plastics (such as POM, PVDF), or aluminum alloy, requiring corrosion and pressure resistance.
Valve Core	The core actuator, connected coaxially with the valve stem, seals or opens the valve seat hole by moving up and down. Valve core materials are often ceramic, stainless steel, or rubber (for sealing).
Valve Seat	Located inside the valve body, it works with the valve core to form a sealing surface. High precision is required, and the surface is often hardened (such as nickel plating, polishing).
Pneumatic Actuator	Includes a cylinder, piston, and spring, etc., which drives the piston to move the valve stem and valve core through compressed air. Single-acting cylinders (spring return) or double-acting cylinders (bi-directional pneumatic) are optional.
Sealing Ring	Used for sealing between the valve core and valve body, valve stem and cylinder, and other moving parts. Materials are often fluororubber (FKM), silicone rubber (VMQ), and need to adapt to the fluid medium and temperature.
Inlet / Outlet	Connects to the air source, controlling the inflation and deflation of the cylinder to achieve valve opening or closing. Some valves integrate solenoid valves or pneumatic control modules.
Sensor / Feedback Device	(Optional) Installation of position sensors (such as proximity switches) to provide real-time feedback on the valve opening and closing status for automated system monitoring.

III. Working Principle:

Opening Process:
- Compressed air enters the upper chamber of the cylinder from the inlet, pushing the piston downward, causing the valve core to separate from the valve seat, and the fluid passage opens.
- Double-acting cylinders require continuous air supply to maintain opening; single-acting cylinders rely on air pressure to overcome spring force to open.
Closing Process:
- Cut off the air source or exhaust. In a single-acting cylinder, the spring pushes the piston to reset, and the valve core presses against the valve seat to achieve sealing; in a double-acting cylinder, the piston is reset by reverse air supply.

IV. Structural Features and Advantages:

Coaxial Design:
- The valve core and stem move coaxially, the force is even, and the sealing precision is high (leakage is as low as 10⁻⁹ Pa・m³/s level), suitable for high-purity gases, liquids, or micro-flow control.
Fast Response:
- Pneumatic drive is fast (response time ≤50ms), suitable for high-frequency switching scenarios (such as gas control in semiconductor wafer transfer).
Low Torque / Low Wear:
- Linear motion without rotational friction, low wear, long life (up to millions of cycles), and low maintenance cost.
Corrosion-Resistant Design:
- Components in contact with fluids can be made of corrosion-resistant materials (such as PVDF, Hastelloy), suitable for harsh media such as strong acids and strong alkalis.

V. Typical Application Scenarios:

Semiconductor industry: Precise control of high-purity gases (such as N₂, O₂, NF₃), gas path switches in lithography machines and deposition equipment.
Medical equipment: Drug liquid transfer, sterile fluid control in bioreactors, requiring low residue and easy cleaning.
Automated production lines: Pneumatic actuators in food packaging and electronic assembly, cooperating with PLC to achieve precise motion control.
Laboratory instruments: Micro-flow fluid switching valves in gas chromatography (GC) and high-performance liquid chromatography (HPLC).

VI. Comparison with Other Valves:

Type	Drive Method	Sealing Method	Response Speed	Applicable Scenarios
Pneumatic Coaxial Valve	Compressed Air	Coaxial Plane Seal	Fast (≤50ms)	Precision control, high-purity media
Solenoid Valve	Electromagnetic Coil	Iron Core Attraction Seal	Relatively Fast (≤100ms)	Small and medium flow, general industrial scenarios
Ball Valve	Manual / Pneumatic	Ball Rotation Seal	Medium	Large flow, high-pressure pipelines
Butterfly Valve	Manual / Electric	Valve rotary seal	Relatively slow	Large-diameter ventilation or liquid pipelines

VII. Key Selection Parameters:

Nominal Diameter (DN): Fluid passage diameter, typically ranging from φ1mm to φ50mm.
Operating Pressure: Pneumatic pressure range (e.g., 0.4~0.8MPa), fluid medium pressure (e.g., ≤1.0MPa).
Medium Characteristics: Gas/liquid, temperature (-20℃~150℃), corrosiveness, particle content, etc.
Control Method: Single-acting (spring return) or double-acting pneumatic, whether feedback signal is required.
Connection Method: Compression fitting, flange, quick-connect, etc., needs to match the pipeline interface standard.

For specific model design drawings or 3D models, more detailed structural sectional view descriptions can be provided.