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What to consider when choosing a valve positioner
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Which valve positioner is right for your control valve? This depends on the valve and actuator design, how the valve will be controlled and your control requirements.
Here, we guide you through the key factors to consider and provide an overview of different types of valve positioners and their functions.
1. Start with the valve and actuator
A valve positioner ensures that the valve moves to the position requested by the control system. The positioner must be suitable for the valve's movement, whether linear or rotary, and for a single- or double-acting actuator. Stroke length, rotation angle and available air supply pressure are also important.
2. What control signal will be used?
Valve positioners are available for different types of control signals, including pneumatic signals of 3–15 psi (0.2–1 bar), electrical signals such as 4–20 mA, or communication via fieldbus. Digital models may also offer configuration and diagnostic functions through the control system. The choice depends on the plant's control system and the functions required.
3. What are your control requirements?
For accurate process control, the valve needs to reach the required position quickly and reliably. The positioner must be able to handle the actuator size and valve movement without unnecessary oscillation or delays. Air capacity and control functions affect how well the valve and positioner work together.
4. Do you need diagnostics and monitoring?
Digital valve positioners can provide information about valve movement, operating conditions and potential deviations. Depending on the model, self-diagnostics and valve testing functions can help identify problems and support maintenance planning.
5. Consider installation and process conditions
Mounting, air supply and electrical connections must be compatible with the valve assembly and installation. Ambient temperature, vibration, enclosure requirements and explosion protection may also influence the choice. Correct mounting and calibration are important to ensure that the positioner operates as intended.
6. Which type of valve positioner is right for your application?
A brief overview of different designs and functions.
Electropneumatic valve positioners
Convert an electrical control signal into pneumatic control of the actuator. Used for control valves where the control system sends a signal such as 4–20 mA.
Digital valve positioners
Use electronic control and may offer automatic calibration, diagnostics and digital communication. Suitable for applications requiring more advanced valve control and monitoring.
Valve positioners with advanced diagnostics
Allow valve performance to be monitored and changes to be detected over time. Depending on the model, valve testing and monitoring functions can support preventive maintenance.
The most suitable solution depends on the valve assembly, control system and requirements for control and monitoring.