Positioners

Positioners are used on pneumatically actuated control valves to match the command signal to the actual stem or shaft position. They are applied on linear globe-type valves and quarter-turn rotary valves where the process requires modulating control of flow, pressure, temperature, or level rather than simple on/off duty.

This category includes linear and rotary positioners such as ARI STEVI-POS P20, OMC RP01, RE01, PTL7L, RE20L, R99P, R99E, YT3300/3400 L-R, and YTC series YT-2300, YT-2400, YT-2500/2550, YT-2600, YT-2700, YT-3300/3350, and YT-3400/3450. Available versions cover pneumatic and electro-pneumatic control, single-acting and double-acting actuators, and smart positioners with auto-calibration, PID control, alarm functions, and HART communication for integration with PLC or DCS architectures.

The ARI STEVI-POS P20 operates with a 4-20 mA input signal and optional 4-20 mA feedback. It uses a non-contact Hall sensor, supports automatic adaptation to valve stroke or rotary angle, and requires an instrument air supply of 1.4 to 7 bar. Air connection is G1/4, enclosure protection is IP66, and ambient temperature range is -20 to +80 °C. It covers linear strokes from 10 to 120 mm or rotary travel from 25° to 100°, with adjustable dead band and tight shut-off function by complete actuator venting.

OMC RP01 and R99P are pneumatic positioners for linear or rotary actuators with 3-15 psi signal range. Electro-pneumatic and smart versions are used where the control system provides analog output signals and position feedback or diagnostics are required. ATEX-certified versions are available for hazardous gas or dust areas, depending on model and approval scope.

Selection should consider actuator type, stroke length or rotation angle, instrument air pressure, control signal, fail action, air consumption, hysteresis, linearity, enclosure rating, ATEX requirement, and vibration conditions. Maintenance should include inspection of air filters, nozzles, pneumatic tubing, feedback linkage, zero/span calibration, and deviation between setpoint and actual position.