What is pneumatic automation and--ultimately--how do pneumatic valves work? Well, our blog covers all types of information about valves, the valve industry, and the industries that valves serve. Sometimes these posts very technical, and other times less so. Today, I am going to talk about the less technical: I am going to focus on pneumatic (air) actuation.
Types of Pneumatic Actuators
The two most common valve types are: linear (move up and down), such as gate and globe valves; and rotary (quarter turn), like ball or butterfly valves. The quarter-turn valves usually move between the open and closed position by moving the stem 90 degrees. The majority of valves that are pneumatically actuated are rotary valves.
How Pneumatic Actuators Work
The primary principle behind quarter-turn actuation is a rack and pinion. In this design, a straight gear rack attached to a piston interfaces with a rounded pinion gear. As the compressed air drives the piston and rack linearly, it turns the pinion through a 90-degree rotation. That rotates the valve stem to open or close the valve. This mechanical linkage between the rack and pinion is what actuates, or moves, the valve between open and closed.
Sometimes there are springs on the opposite side of the shaft that will push the valve back to its original position. In the event of a loss of air pressure inside the actuator, the springs return the rack to its original position. These Spring Return pneumatic actuators” are very common when the valve needs to fail in a certain position. The most popular configuration for these types of valves and actuator packages is “Air to Open (ATO), Valves Fails Closed” on loss of air pressure.
The other type of actuator is a Double Acting actuator. This type of actuator requires air pressure on both sides of the piston to drive it back and forth. This air pressure in turn opens or closes the valve. Double-acting actuators are often referred to as 'air-to-open / air-to-close.' These valve and actuator packages will “fail in place” with loss of air pressure.
A popular accessory to be added to these actuated valve packages is limit switches. Limit switches give a confirmation electrical signal back to a PLC or DCS that a valve is in fact open or closed. Please check out our blog post “What is a limit switch?” to learn more.
Conclusion
The ValveMan Valve Store carries a wide array of quarter-turn valves- butterfly and ball valves. Make sure to check them out! And if you have any questions, valve experts are standing by to help.
