When it comes to selecting the right type of pneumatic directional control valve for any application, you have many options at your disposal. Each comes with its own specific function, so it is helpful to understand differences and pick the type best-suited for your requirements.
To help you arrive at the valve “type” that’s right for your pneumatic application, this post will highlight five basic requirements to consider.
The first and most obvious question is—what gas (or liquid) will be controlled by this valve, and at what input pressure? Compressed Air? Water? Negative Pressure? Gas? Before checking for any additional factors, ensure that the valve is compatible with the media and pressure passing through.
Method of Valve Actuation
There are a variety of methods available to open or close a valve. The four most common are Solenoid operated (via electrical current), Manually operated (by skilled labor and via a lever, pushbutton, foot peddle, etc.), Mechanically operated (via tooling or work pieces in contact with a cam, ball or plunger), or Remote Air operated (from an output signal of another valve).
Spring-Return or Detented Actuation
This is the return method the valve will take “back” to its original, un-actuated state. Typically, this is either a mechanical spring, or a separate form of the same actuation method described above. Manufacturers call these methods “spring return” and “detented” valve types. Said another way, are you looking for a “momentary contact, momentary output” or “momentary contact, maintained output”? Decide whether you want your valve to return to its initial position or stay in its last position after actuation.
Most pneumatic directional control valves are 2-way, 3-Way or 4-Way and, as a rule of thumb, it is a count of their active media ports.
2-Way valves have one INLET and one OUTLET port and, upon actuation, allow media to pass through (known as a 2-way Normally Closed), or to stop flow (2-way Normally Open)
3-Way valves add a third port to allow for venting (EXHAUST port) of pressure at the OUTLET port, when the INLET port is blocked. 3-Way valves are offered Normally Closed or Normally Open, as well.
4-Way valves add a second OUTLET and corresponding second EXHAUST port to the 3-Way function, and are most commonly used for control of double acting pneumatic cylinders and actuators. Upon 4-Way Valve actuation, INLET pressure switches from one OUTLET port to the other.
Note: As an option, 4-way valves can be configured with 3 positions, where the center position is forms a “neutral” position choice of three options (either all OUTLET ports exhausted, pressurized, or checked).
Flow Capacity (Valve Size)
Flow capacity is a fifth factor to address in valve selection. An undersized valve will slow down fill time or cause other forms of inefficiency in the system while an oversized valve can be classified as a form of waste in the system. It’s important to estimate a maximum flow capacity for your application and select the valve size with enough capacity. All valve suppliers provide a flow capacity, and have easy reference material to assist you, but essentially your valve will need to fill a specific downstream volume within your acceptable period of time.
Tip: Most manufacturers state a “Cv” value, which is a universally accepted flow capacity index, known as “flow coefficient”. It forms an easy way for you to compare similar sized valves.
Once you’ve used these five factors to identify the valve type you need, then weigh specific performance and integration attributes of matching brands and models available from valve manufacturers. Still a bit overwhelmed? Don’t worry! We’ve made it easy to browse our online catalog and narrow your results until you have found the exact products needed for your specific application. You can even search within results for the exact terms you’re looking for.
If you’d like more help choosing the right valve, or have questions about any of our products, please contact us at 1-800-477-8707.
4-Way Detented Toggle Valve for 100psi Compressed Air; Flow of 22 SCFM.
3-Way Normally Closed, Spring Return, Solenoid Valve for 25"Hg Vacuum; Flow of 0.14 Cv.
2-Way Normally Closed, Spring Return, Air Piloted Valve for 30psi Water; Flow Capacity of 8 GPM minimum.