Pneumatic stop valve is an automatic control valve powered by compressed air, mainly used for accurate cutoff, distribution or switching of pipeline medium flow. Its core features are as follows:
1. Basic definition and function
Functional characteristics
The pneumatic actuator drives the valve disc to make linear lifting and lowering movements to achieve rapid cutoff or flow regulation of fluid (liquid, gas or steam). It is suitable for full open/full closed working conditions and has the advantages of rapid opening and closing and reliable sealing.
Control method
Receive external control signals (such as PLC instructions or pressure sensor feedback), switch the air circuit by the solenoid valve, drive the actuator to move, and support remote automation operation.
2. Core structure and components
Actuator
Pneumatic diaphragm type: Use air pressure to push the diaphragm to produce displacement, suitable for low pressure and small thrust scenarios.
Pneumatic piston type: Adopts floating piston structure, large output thrust, suitable for high pressure or large diameter valves (such as DN300 and above).
Single-acting cylinder: Built-in reset spring, automatically restores the initial position when pressure is lost (such as emergency shutdown scenario).
Double-acting cylinder: Relying on bidirectional air pressure drive, it requires an external air source to switch the direction, with stronger thrust but no automatic reset function.
Valve body and sealing system
Valve flap design: Most of them are plug-cone structures, and the sealing surface adopts flat or conical hard seal (such as surfacing Stellite alloy), and the forced sealing mechanism ensures zero leakage under high pressure conditions.
Valve stem guide: Usually a guide sleeve is provided to reduce friction and extend service life.
3. Working principle
Air source drive
After compressed air enters the actuator cavity, it pushes the piston or film to generate mechanical force, driving the valve stem to move vertically, so that the valve flap contacts or separates from the valve seat.
Control process
By adjusting the air intake direction (positive or negative) and the air pressure, the valve opening is accurately controlled to achieve complete medium cutoff or flow rate graded regulation.
4. Materials and performance parameters
Body material: optional WCB carbon steel, 304/316L stainless steel, chrome-molybdenum steel, etc., with a temperature range of -29℃ to 550℃, and a pressure level covering PN1.6~16.0MPa.
Sealing level: in line with API 598 standard, leakage rate is less than 10^-6 mL/s, suitable for high-cleanliness or hazardous media environments (such as LNG, acid and alkali solutions).
5. Typical application scenarios
Energy industry: boiler steam pipeline cut-off, emergency shutdown of gas transmission and distribution system.
Chemical production: reactor medium switching, corrosive fluid control.
Environmental protection engineering: sewage treatment system flow regulation, flue gas desulfurization device isolation.
Summary: Pneumatic stop valve integrates pneumatic drive and forced sealing technology, has both efficient responsiveness and high reliability, and is a key fluid control equipment in industrial automation systems.
