Valve positioners are devices used to precisely control the position of a control valve's actuator in response to a control signal. They are commonly used in industrial processes where accurate and reliable control of flow, pressure, temperature, or level is required. The function of valve positioners is to improve the performance and efficiency of control valves by ensuring that they respond accurately to control signals and maintain the desired setpoint under varying process conditions. Here are some key functions and applications of valve positioners:

1. Accurate Valve Positioning:

   • Valve positioners ensure that control valves are accurately positioned according to the desired setpoint or control signal received from the process controller.
   • They compensate for variations in actuator response, friction, hysteresis, and other factors that may affect the valve's position, allowing for precise control of process variables.

2. Enhanced Control Loop Performance:

   • By providing precise positioning of the control valve, positioners improve the performance and stability of the control loop.
   • They help reduce overshoot, hunting, and oscillations in the control system, resulting in smoother operation and tighter control of process variables.

3. Increased Process Efficiency:

   • Valve positioners help optimize process efficiency by maintaining the desired operating conditions within tighter tolerances.
   • They ensure that control valves respond quickly and accurately to changes in process conditions, minimizing deviations from setpoints and improving process control.

4. Compensation for Actuator Characteristics:

   • Valve positioners compensate for nonlinearities, deadband, and other characteristics inherent in pneumatic, electric, or hydraulic actuators.
   • They translate the control signal into precise actuator movements, regardless of the actuator type or operating conditions.

5. Remote Monitoring and Diagnostics:

   • Some advanced valve positioners include diagnostic features that allow for remote monitoring of valve performance and condition.
   • They provide valuable information on valve position, actuator health, and process conditions, enabling predictive maintenance and troubleshooting to prevent downtime and optimize performance.

6. Safety and Reliability:

   • Valve positioners contribute to the safety and reliability of industrial processes by ensuring that control valves operate within specified limits and respond appropriately to abnormal conditions.
   • They help prevent valve stalling, sticking, or failure due to improper positioning or control signal errors.

Valve positioners find widespread use in various industries, including oil and gas, chemical processing, power generation, water and wastewater treatment, pharmaceuticals, and food and beverage production. They are employed wherever precise control of process variables is critical to achieving desired product quality, efficiency, and safety standards.