Valve positioners compare a control signal to a valve actuator’s position and move the actuator accordingly. They are used with both linear valves and rotary valves. Valve positioners are used when the 0.2 to 1 bar pressure in the diaphragm chamber is not able to cope with friction and high differential pressures.
The positioner is fitted to the yoke of the actuator and is linked to the spindle of the actuator by a feedback arm in order to monitor valve position. When a control signal differs from the valve actuator’s position, the valve positioner sends the necessary power to move the actuator until the correct position is reached. This uses a high air supply.
Intrinsically safe (IS) valve positioners do not produce sparks or other thermal effects that would ignite a specified gas mixture. Devices that are made from stainless steel are used in corrosive or high temperature environments. The valve positioner should also come with a valve position indicator that suits the intended application.
Valve positioners differ in terms of applications, features, and approvals. Some products are designed for automotive, aerospace, marine, medical, or military applications. Other products are suitable for food processing or pharmaceutical applications. General-purpose devices are commonly available.