Pneumatic Actuator Operated
The most commonly applied actuator is the pneumatically driven actuator, because the power source – compressed air – is relatively cheap as compared to a human resource or electric or hydraulic power sources. From a maintenance point of view, pneumatic actuators are more easily service and calibrated than other types of actuator. Pneumatic actuators can generate substantial thrust to handle a majority of applications, including high-pressure and high-pressure-drop situations. Pneumatic actuators also bleed compressed air to atmosphere, which is environmentally safe, when compared to hydraulics. The main disadvantage of pneumatic actuators is that some response and stiffness are lost because of the compressibility of gases. Pneumatic actuators are available in two main forms; piston actuator and diaphragm actuator. They are available in single acting and double acting features. Smart positioner are available.
Key features
- Quick disconnect – permits removal of the actuator without depressurizing the valve. This greatly reduces downtime and lost production.
- Rising stem – provides visual indication of valve position.
- External safety relief device – protects the actuator for over pressurization.
- Compact design – permits easy maintenance in restricted areas.
- Manual override – top mounted and side-mounted hand wheel.
- Electro-pneumatic positioners with communication protocols – analog, HART and Foundation Fieldbus with diagnosis feature for configuration.
- Fail conditions on the loss of signal failure and supply air/gas failure – fail close, fail open and fail last.
- Pneumatic actuator operation from wellhead/production gas.
- Instruments used with pneumatic actuated chokes are certified for all Harzadous Area locations around the globe.