Pneumatic control valves use compressed gas as a power source and cylinders as actuators. When the control system sends a signal, the air pressure processed by accessories such as valve positioners and converters acts on the diaphragm or piston of the actuator, generating thrust; This thrust will drive the valve stem to move, which in turn drives the valve core to change the opening of the valve. It receives control signals from industrial automation control systems, which can be analog or digital, and accurately adjusts the degree of valve opening based on the magnitude of the signal. For example, when adjusting the flow rate of the pipeline medium, if it is necessary to increase the flow rate, increase the input signal to open the valve; Vice versa. This process achieves proportional adjustment of process parameters such as flow rate, pressure, temperature, liquid level, etc.

Precautions for using pneumatic control valves:

1. Function identification: Distinguish between "Air Open" (RA) and "Air Closed" (DA) based on the nameplate identification to avoid system failures caused by misjudgment. Different modes of operation correspond to different fault safety positions, which need to be matched with the process requirements.

2. Manual operation specifications: Use the handwheel only when there is no air source, and be sure to reset the handwheel to the specified position after completion. Excessive force may damage the manual mechanism and affect the stroke accuracy during automatic control.

3. Cleaning and maintenance requirements: Clean the inside of the valve chamber before the test to prevent impurities from remaining and causing loose closure or stuck guide components. After debugging, use compressed air/nitrogen to blow away internal moisture, avoid corrosion, and ensure a dry state.

4. Signal quality control: Regularly check the stability of the signal output by the control system. Unstable signals may cause abnormal valve action (such as oscillation). Suggest configuring filtering devices to improve anti-interference ability.

5. Travel scale monitoring: Using the 0 (fully open) - S (fully closed) travel indicator mark on the valve body, real-time monitoring of the deviation between the actual opening and the commanded value, and timely detection of looseness or jamming problems in the mechanical transmission system.

6. Leakage detection: After the strength test, focus on testing the sealing performance, especially paying attention to the leakage situation at the contact surface between the valve core and the valve seat. Excessive leakage not only reduces efficiency, but may also pose safety hazards.

7. Environmental adaptability management: Avoid long-term exposure to high, low, or corrosive environments, and install protective covers if necessary; For working conditions containing particulate media, it should be considered to add filters to extend their service life.

8. Regular inspection system: Establish a periodic maintenance plan, including lubricating moving parts, replacing vulnerable parts (such as seals), verifying locator accuracy, etc., to ensure long-term stable operation.