A pneumatic control valve uses compressed air as its power source and an air cylinder as the actuator. With the assistance of accessories such as valve positioners, converters, solenoid valves, lock-up valves, air reservoirs, and air filters, it drives the valve to achieve on-off or proportional regulation. It receives control signals from industrial automation control systems to regulate various process parameters of pipeline media, including flow rate, pressure, temperature, and liquid level.
The pneumatic control valve is characterized by simple control, fast response, and intrinsic safety-no additional explosion-proof measures are required.
1. Applications & Features
A. Applications
It features a right-angle rotary structure and can achieve proportional regulation when used with a valve positioner. The V-type valve core is most suitable for various regulation scenarios, with advantages including a large rated flow coefficient, wide turndown ratio, good sealing performance, sensitive regulation,compact size, and compatibility with both vertical and horizontal
installation. It is applicable for controlling media such as gas, steam, and liquid.
B. Core Feature
- Adopts a right-angle rotary structure, composed of a V-type valve body, pneumatic actuator, positioner, and other accessories.
- Has an inherent flow characteristic close to equal percentage.
- Equipped with a dual-bearing structure, featuring low starting torque, excellent sensitivity, and fast response.
- Possesses strong shearing capability.
C. Pneumatic Piston Actuator
It uses compressed air as the power source. The piston's movement drives the crank arm to rotate 90 degrees, enabling automatic valve opening and closing. Its components include: adjusting bolts, actuator housing, crank arm, cylinder block, cylinder shaft, piston, connecting rod, and cardan shaft.
D. Working Principle
- A pneumatic control valve consists of an actuator and a regulating mechanism.
- The actuator is the thrust component of the control valve. It generates corresponding thrust based on the pressure of the control signal to drive the regulating mechanism.
- The valve body is the regulating component of the pneumatic control valve. It is in direct contact with the regulated medium to adjust the fluid flow rate.
2. Summary of Features
- Simple control, fast response, and intrinsic safety.
- Powered by compressed air, it realizes on-off or proportional regulation with an air cylinder as the actuator.
- Receives control signals from industrial automation control systems to regulate process parameters of pipeline media.
3. Installation Principles
The installation position of the pneumatic control valve should be at a certain height from the ground, with sufficient space above and below to facilitate disassembly and maintenance. For valves equipped with a pneumatic valve positioner and handwheel, ensure easy operation, observation, and adjustment.
The control valve should be installed on a horizontal pipeline, keeping vertical alignment with the pipeline above and below. Generally, support should be provided under the valve to ensure stability. For special cases where the control valve needs to be installed horizontally on a vertical pipeline, support should also be added (except for small-diameter control valves). Avoid applying additional stress to the valve during installation.
The operating environment temperature for the control valve should be between -30°C and +60°C, with a relative humidity not exceeding 95%.
Straight pipe sections should be installed before and after the control valve, with a length of no less than 10 times the pipe diameter to prevent the short straight pipe section from affecting the flow characteristic.
If the diameter of the control valve differs from that of the process pipeline, a reducing pipe should be used for connection. For small-diameter control valves, threaded connection can be adopted. The medium flow direction arrow on the valve body must align with the actual fluid direction.
A bypass pipe should be installed to facilitate switching or manual operation, allowing maintenance of the control valve without shutting down the system.
Before installation, thoroughly remove foreign matter --such as dirt and welding slag from the pipeline.
4. Usage Precautions
- The valve should be stored in a dry indoor environment. Both ends of the flow path must be plugged, and stacking storage is not allowed.
- For control valves stored for a long period, regular inspections are required. Remove dirt and apply anti-rust oil to all moving parts and machined surfaces to prevent rusting.
Last but not least,the valve should be installed on a horizontal pipeline and must be mounted vertically with the valve stem facing upward and valve must be installed in accordance with the medium flow direction indicated by the arrow on the valve body.
