Rotary

Rotary positioners are used on quarter-turn pneumatic actuators for precise angular control of butterfly valves, ball valves, and plug valves. The positioner compares the control signal with the actual shaft position and modulates pneumatic output pressure to the actuator so the valve follows the setpoint despite changes in differential pressure, seat friction, hysteresis, or operating torque.

The category includes ARI STEVI-POS P20 and OMC R99E, R99P, YT3300R, and YT3400R. The STEVI-POS P20 is a digital electro-pneumatic smart positioner with 4-20 mA input, optional 4-20 mA feedback, non-contact Hall sensor, instrument air supply 1.4-7 bar, G1/4 connection, IP66 enclosure protection, and rotary travel range of 25°-100°. It supports dead band adjustment and tight shut-off, with full actuator venting at defined signal thresholds.

OMC R99E and R99P are applied to rotary actuators in single-acting or double-acting configurations. The R99E is an electro-pneumatic positioner, while the R99P is a pneumatic positioner that can also be supplied with position transmitter and limit switches. ATEX versions are available and should be assessed where the installation is located in hazardous gas or dust zones.

OMC YT3300R and YT3400R are smart positioners for double-acting rotary actuators. The YT3300R is specified as intrinsically safe with ATEX marking II 2 G D Ex ia IIC T5-T6, while the YT3400R is specified as flameproof with II 2 G D Ex d IIC T5-T6.

Selection should verify rotation angle, actuator type, instrument air pressure, control signal, air consumption, fail action, ATEX requirement, linearity, hysteresis, and access for calibration. Maintenance checks typically include air filtration, nozzle condition, linkage wear, mechanical stops, leakage at pneumatic connections, and deviation between setpoint and actual valve position.