Control valve accessories are additional components or devices that are often installed alongside control valves to enhance their performance, functionality, and reliability in industrial process control systems. These accessories may provide additional functionality, improve valve operation, or facilitate maintenance and monitoring. Here are some common control valve accessories:

1. Positioners:

   • Positioners are devices that attach to the actuator of a control valve to precisely position the valve plug or disc based on an input signal from the control system. They ensure accurate control of valve position and enhance the responsiveness of the valve.

2. Position Transmitters:

   • Position transmitters, also known as valve position indicators, provide feedback on the actual position of the valve to the control system. They detect the movement of the valve plug or disc and transmit this information electronically, allowing the control system to monitor and verify valve position.

3. Limit Switches:

   • Limit switches are used to detect the extreme positions (fully open or fully closed) of the valve and provide electrical feedback to the control system. They are often used for safety interlocking, indicating valve status, and initiating alarm signals.

4. Solenoid Valves:

   • Solenoid valves are used to control the flow of air or other fluids to actuate the valve. They are typically installed in pneumatic control systems to provide on/off control of the actuator based on signals from the control system.

5. Air Filter Regulators:

   • Air filter regulators are installed in pneumatic control systems to regulate and filter the air supply to the control valve actuator. They ensure consistent air pressure and prevent contaminants from entering the pneumatic system, thereby improving valve performance and reliability.

6. Position Feedback Devices:

   • Position feedback devices, such as potentiometers or encoders, provide continuous feedback on the position of the valve throughout its entire stroke. They are often used in applications requiring precise control or monitoring of valve position.

7. Volume Boosters:

   • Volume boosters are used to increase the speed and responsiveness of pneumatic control valves by amplifying the air supply to the actuator. They improve the dynamic response of the valve and reduce the effects of hysteresis and deadband.

8. Position Indicators:

   • Position indicators are visual indicators or displays that provide a visual indication of the valve position. They allow operators to monitor the status of the valve visually and verify that it is operating correctly.

9. Locking Devices:

   • Locking devices are used to secure the valve in a specific position to prevent unauthorized or accidental adjustment. They are often used in critical applications where maintaining a specific valve position is essential for safety or process control.

10. Handwheels or Manual Overrides:

    • Handwheels or manual overrides allow operators to manually control the valve position in the event of a control system failure or during maintenance activities. They provide a backup method for operating the valve manually when necessary.

These are just a few examples of control valve accessories commonly used in industrial process control systems. The selection of accessories depends on factors such as the type of control valve, application requirements, and system design considerations.