Experiences with Pneumatic Actuators
What readers are going to learn in this article?
Pneumatic (air operated) rotary actuators would be the favorite device used to open up and shut quarter-turn valves. A quarter-turn valve goes from fully open to fully close in 90° of spinning. Examples are butterfly, ball and plug valves.
To open the valve automatically from a remote signal that a mechanically controlled actuator is mounted in addition to the valve. The pneumatic actuator joins the valve stem to a piston within the actuator. A solenoid valve brings air to a single side of the piston or another along with the stem rotates.
The solenoid valve includes an electrical coil, a shuttle plunger along with a spring. The plunger covers openings within the solenoid body. When power is applied to the coil it will become magnetised and pulls the shuttle into position. When the electricity is switched off the spring pushes the shuttle back. The electric power is turned on and off by a sign in the procedure. When the solenoid works, compressed air flows through the open ports and onto a single facet of the actuator. The piston moves and the valve stem melts.
The actuator can contain a spring which pushes the piston back into position on release of the atmosphere pressure. Actuators that are shut by a spring are called fail-close actuators. If air pressure is dropped the valve will be closed by the spring and also stop the procedure flow through the tube. Double acting actuators want air to open and close the valve.
When selecting pneumatic actuators make certain that the actuator can produce a greater torque than that needed by the valve. Butterfly valves used as outlet valves on silos of powdered product might bind when the product causes the distance between the disc and chair to raise over the potential of the actuator. Air lines into the Freestyle as well as the actuator must be the identical diameter, as well as one diameter larger, than the vent link. This permits the air to quickly flow to the piston chamber for quick response. In addition, it provides the piston a surprising surge to assist break any seating torque.
Device quality air is best for long-lived dependable operation of air operated actuators. Specifically moisture has to be eliminated so it does not float in solenoids and actuators. Trapped moisture triggers corrosion in the actuator and solenoid bodies also will hydraulically lock the piston in part-stroke and block the valve out of turning.
Insure the pressure dew point of the compressed air will be below the coldest supply system temperature.