Introducing Auxiliary Components of Pneumatic Control Valves

Pneumatic control valves, which operate using compressed air, are actuation components known for their quick opening and closing speeds. They are widely used in applications requiring rapid two-position shut-off operations. Additionally, they are suitable for scenarios that necessitate precise flow regulation. Due to their reliance on air supply, pneumatic control valves exhibit excellent practicality in flammable and explosive environments, making them ideal for monitoring and controlling various gases, liquids, oils, and corrosive media.
 

Versatile Control Methods and Flexible Configuration

Pneumatic control valves come with a wide variety of accessories, enabling different control methods through various configurations. Users can flexibly choose appropriate configuration items based on specific operational needs, making pneumatic control valves indispensable in the industrial sector.

1. Basic Control Functions

Pneumatic control valves can achieve both on-off control and modulation control. With simple on-off control, the valve can quickly cut off or open the fluid passage; with modulation control, it can precisely control the flow to maintain system stability.

2. Wide Range of Applications

Due to their reliability and versatility, pneumatic control valves are extensively used in industries such as chemical, petroleum, natural gas, power generation, food processing, and water treatment. In these fields, pneumatic control valves enhance automation levels and ensure operational safety and stability.
 

Pneumatic FRL and Their Functions

The pneumatic air preparation unit is one of the most common auxiliary accessories in pneumatic control valves, offering multiple functions such as filtration, pressure regulation, and oil mist removal. The pressure regulator, a critical component, provides the standard power air pressure required by the pneumatic control valve, typically ranging from 0.4 to 0.7 MPa. Different types of pneumatic control valves require pressure regulators to ensure proper operation. Specific configurations include:

• Pneumatic FR&L: Consists of a filter and a pressure regulator, which filter and regulate compressed instrument air. The filter removes impurities and moisture from the air, while the pressure regulator adjusts the air pressure to the required level.
• Pneumatic FRL: Includes a filter, pressure regulator, and oil mist lubricator. In addition to filtration and pressure regulation, it lubricates the compressed air, preventing wear and tear on internal valve components and extending the system's lifespan.

 

Key Auxiliary Components

Pneumatic control valves are complemented by several key auxiliary components that enhance their functionality and ensure efficient operation. These components include pneumatic solenoid valves, valve limit switches, valve positioners, pilot valves, valve position transmitters, and pneumatic dampers.

1. Pneumatic Solenoid Valve

Also known as a directional control valve, the pneumatic solenoid valve is an essential component of pneumatic control valves. It controls the opening and closing states of the pneumatic control valve through excitation/de-excitation, making it suitable for two-position switch function valves. The solenoid valve operates by using a voltage signal to control the on-off state of the air supply, enabling the valve to open and close. It is known for its quick response, precise control, and long service life, fitting various automated control systems.

2. Valve Limit Switch

The valve limit switch, also called a travel switch or feedback switch, is an on-site instrument used to detect the valve's status. It converts the valve's open or closed position into a switch signal output, which can be received by a programmable controller, collected by a computer, or used to confirm subsequent program execution. This device can also serve as interlock protection and remote alarm indication for critical valves in automatic systems. The reliability and precision of the valve limit switch are crucial for ensuring the safe operation of the system.

3. Valve Positioner

The valve positioner is a vital component of pneumatic control valves, capable of accurately controlling the valve's opening degree. It compares the valve stem displacement signal with the controller's output signal and adjusts the output signal to the actuator when there is a discrepancy, ensuring a one-to-one correspondence between the valve stem displacement and the controller's output signal. The use of valve positioners not only enhances control accuracy but also effectively reduces valve response time, improving the system's overall performance.
 

Configuration for Safety and Rapid Operation

In scenarios requiring safety condition control, solenoid valves are configured to ensure the valve is in a safe position in case of an emergency. For large-capacity cylinder valves, pilot valves are needed to improve the valve's actuation speed. The pilot valve, which switches high-flow air circuits using a small amount of control air signal, achieves rapid inflation and deflation of the cylinder valve. The specific type of pilot valve should be selected based on the application requirements.

1. Function of Pilot Valves

Pilot valves significantly enhance the actuation speed of large-capacity cylinder valves, allowing them to complete opening and closing operations in a short time. This improves the system's efficiency and response speed. Various types of pilot valves are available to meet different control requirements.

2. Valve Position Transmitter and Pneumatic Dampers

To precisely monitor the control valve's position, a valve position transmitter is essential. It provides feedback on the valve's position at any point. For processes requiring specific operation speeds, pneumatic dampers are used. They regulate airflow to achieve desired valve operation speeds, such as normal opening with slow closing or slow opening with normal closing. The application of pneumatic dampers effectively controls the valve’s operating speed, preventing impacts and wear due to rapid movements, thus extending the valve's service life.

In summary, pneumatic control valves and their various auxiliary devices play a crucial role in industrial control systems. Their versatile configurations and flexible control methods meet the diverse demands of different working environments. By selecting and configuring these components appropriately, the automation level, operational safety, and stability of the system can be significantly enhanced.