Actuation & AutomationFull Glossary

Positioner

A device mounted on a control valve actuator that receives the controller signal (4–20 mA or HART) and precisely positions the valve to achieve the required Cv. Pneumatic positioners supply air to the actuator; digital (SMART) positioners add diagnostics (valve signature, friction measurement).

Frequently Asked Questions

What is a Positioner?

A device mounted on a control valve actuator that receives the controller signal (4–20 mA or HART) and precisely positions the valve to achieve the required Cv. Pneumatic positioners supply air to the actuator; digital (SMART) positioners add diagnostics (valve signature, friction measurement).

How is a Positioner sized for a valve?

Actuator sizing requires the valve's breakaway torque (BTO), running torque (RTO), and end-to-close torque (ETO) at the maximum differential pressure and operating temperature. The actuator output torque at minimum supply pressure must exceed the valve BTO by a safety factor (typically 1.25x minimum). For pneumatic actuators, the supply pressure range, fail-safe direction (spring return FC or FO), and speed requirements must also be specified.

When is a Positioner required versus manual operation?

Automation is required when: (1) the valve is in a remote or hazardous location, (2) rapid opening/closing is needed for emergency shutdown (ESD), (3) the valve must respond to a control signal (4–20 mA, HART, or fieldbus), (4) the operating torque is too high for manual operation, or (5) the valve is part of a Safety Instrumented System (SIS) requiring SIL certification. Contact Vajra Industrial Solutions for fully automated valve packages including actuator, limit switch, solenoid, and positioner.

Technical Support

Have a Technical Question?

Our valve engineers can help specify the right valve for your application. Full project documentation available: MTCs, test reports, dimensional inspection, and third-party inspection coordination.