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Accurate Valve Positioning
The Posi-flate® Pneumatic Positioner provides accurate valve positioning with advanced features. A current-to-pressure transducer for 4-20 mA signal inputs proportionally positions the disc.
Unit of Measure

Brands

 N/A Posi-flate®

Full Scale Repeatability

 N/A 0.5 %

Full Scale Hysteresis and Deadband

 N/A 0.8 %

Full Scale Linearity

 N/A 0.7 %

Standard Air Capacity at 60 Pound Per Square Inch (psi)

 N/A 9.6 scfm

High Standard Air Capacity at 60 Pound Per Square Inch (psi)

 N/A 18 scfm

Position Sensitivity of Span

 N/A 0.2 %

Air Consumption at 87 Pound Per Square Inch (psi) (6 Bar Gauge Pressure (barg))

 N/A 0.31 scfm

Temperature Range

 N/A -4 to 185 ºF-20 to 85 ºC

Input Signal

 N/A 3 to 15 psig0.2 to 1 barg

Maximum Supply Pressure

 N/A 150 psig10 barg

Weight

 N/A 0.9 kg2 lb

Housing/Cover

 N/A Epoxy Coated Aluminum

Shaft

 N/A Stainless Steel

Diaphragm Cover

 N/A Epoxy Coated Aluminum

Diaphragm

 N/A Nitrile Rubber

Balance Arm

 N/A Stainless Steel

Feedback Spring

 N/A Stainless Steel

Lower Arm Assembly

 N/A Die Cast Aluminum

Rod

 N/A Stainless Steel

Spring

 N/A Stainless Steel

Twist Stop

 N/A Stainless Steel

Cam Follower Bearing

 N/A Hardened Steel

Spool Valve

 N/A Gold-Plated Steel

Cam Locknut

 N/A Zinc-Plated Steel

Ball Bearing

 N/A Stainless Steel

Cam

 N/A Stainless Steel

Indicator

 N/A Polycarbonate

Feedback and Cam Springs

 N/A Stainless Steel

Shaft Snap Rings

 N/A Stainless Steel

Posts and E-Clips

 N/A Stainless Steel

Applications

 N/A A high flow spool valve, plus an adjustable gain system, make the pneumatic positioner well suited for use with all pneumatic rotary actuator types including rack-and-pinion, heavy-duty and others. The positioner housing is constructed of durable epoxy coated, die cast aluminum for protection against the toughest applications in all process industries.

Features

 N/A
  • Non-interactive span adjustment Reduces calibration time.
  • Corrosion-resistant materials All exposed parts are constructed of heavy-duty anodized aluminum or stainless steel.
  • Captive cover screws Permits calibration without potential for losing screws.
  • Visual dome indicator Provides fully adjustable, high-contrast, full-angle viewing of valve position.

Principles of Operation

 N/A The Posi-flate® positioner causes rotation of a valve actuator in proportion to an input signal. The spool shifts and a differential pressure is created across the actuator, causing rotation. Rotation is fed back through the positioner shaft and cam. Cam rotation causes rotation of both follower arm and feedback arm about their respective pivot pins. Rotation of feedback arm changes compression in the feedback spring which forces the balance beam and spool back to their neutral positions. This shuts off the flow of air to the actuator.

Zero adjustment is made by varying spring compression via a screw in the feedback arm. Span adjustment is made by moving the point of contact between the follower arm and feedback arm via a carriage assembly featuring rack-and-pinion adjustment. Since both arms are parallel at zero, span adjustment does not affect zero setting.

When used on a Posi-flate® butterfly valve as shown, the positioner is enhanced with the addition of controls which automatically inflate and deflate the seat. Once the disc is in the fully closed position, the seat is automatically inflated. When the positioner is energized to open, the seat deflates and the disc opens.