5 Factors to Consider When Choosing...

Pneumatic Control Valves

When it comes to selecting the right type of pneumatic 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:

Media
Method of Valve Actuation
Spring-Return Valve or Detented Actuation Valve?
Pneumatic Valve Configuration
Flow Capacity (Valve Size)

Media

The first and most obvious question is—what gas (or liquid) will be controlled by this pneumatic control 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 pneumatic control valve. The four most common methods of valve actuation 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)
Remote air operated (from an output signal of another valve).

Spring-Return Valve or Detented Actuation Valve?

This is the return method the pneumatic 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.

Pneumatic Control Valve Configuration

Most pneumatic 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: These 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: These 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 pneumatic control 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.