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美國Posi-flate蝶閥工作原理？
閱讀：1101 發(fā)布時(shí)間：2016-8-15Model 7000
Pneumatic Positioner
Accurate Valve Positioning
The Posi-flate Model 7000 Pneumatic Positioner provides accurate valve positioning with advanced features. A current-to-pressure transducer for 4-20 mA signal inputs proportionally positions the disc.
Applications
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
- 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
The Posi-flate Model 7000 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. |  |
Posi-flate Butterfly Valve |