Valves for Compressed Air Systems

Valves have many applications in compressed air systems. They are located throughout the process, from operating as a safety net with safety relief valves to the outlet valve in your compression chamber. To better understand them we need to know how they are categorized.

There are two main categories when determining the type of valve:

• Location
  • Either Inlet or Outlet
• Function
  • The valves’ primary functions are unloading, throttle, shutting off, draining, and relieving pressure.

By combining location and function, you get your type of valve. 

Types and Models of Valves 

Your compressed air system contains many different types of valves. Each valve, based on its location, has a specific function. 

Inlet Valve

The inlet valve is a crucial component of air compression, which is the key to getting air into the compression chamber. The valve opens and closes based on the pressure difference between the atmosphere and the compression chamber. 

Shockingly, these valves are located on the air intake of your compressors.

Outlet Valve

Outlet valves, working in tandem with the inlet valve, release compressed air from the chamber. During the discharge stroke, this valve opens to allow the compressed air to flow to the next point in production.

As you would expect, this valve is located on the discharge side of the compressor. 

Unloader Valve

These valves remove excess pressure from the compression chamber during unloaded/idle periods. By releasing the excess pressure, unloader valves avoid pressure buildup in the system and save you money on energy costs.

Your compressor’s design will dictate exactly where this valve sits. For reciprocating compressors, it can be found on the cylinder head. Rotary screws, on the other hand, typically have it in the discharge line.

These valves open when the pressure has reached a predetermined differential. Once the differential reaches this point, the valve opens and clears the excess pressure.

Control Valve 

Control valves are responsible for maintaining the flow rate and pressure of compressed air leaving the compressor. They ensure that your output matches your point-of-use requirements. 

These valves are traditionally found between the compressor and the air receiver tank, typically on the tank’s inlet or discharge line. This allows those operating the valves to adjust as they see fit to maintain airflow and pressure.

For more advanced systems, control valves can be integrated into a control panel to allow remote control of the valves. Convenient management makes optimal performance more manageable. 

Check Valve

Check valves are your one-way valves, they are also referred to as non-return valves. They allow the air to move in only one direction, which is crucial for preventing backflow to the compressor. Backflow can cause pressure fluctuations and damage the compressor.

The location and quantity of check valves can vary depending on your system. Depending on how complex your system is and the requirements of your air, these valves can be found anywhere backflow is detrimental.

Three main spots these valves can be found are:

• Compressor head/ Discharge Port
• The Tank Inlet
• Downstream for proper flow

Shutoff Valve

For applications and scenarios that require a complete stop of air flow, shut off valves are the answer. These valves are primarily useful for maintenance, repairs, isolating systems, and emergencies. 

These valves are primarily located at:

• Compressor inlet
• Compressor outlet
• Distribution lines
• Tank inlet and outlets

The most common shut-off valves are ball valves due to their simplicity and reliability in these situations

Drain Valve

Simply put, these are the valves located on the bottom of your compressed air tank or air compressor that is responsible for discharging built-up condensate.

These valves can be found at the bottom of your tank or at any point where condensation might collect. The precise location may need to be found in the manual, but this area is a good rule of thumb for drain valve placement.

Pressure Relief Valve

If you are concerned about the safety of your compressed air operation, which you should be, you need pressure relief valves. These valves are vital to protect your system and equipment from overpressure situations. They prevent equipment failure, leaks, and safety hazards by discharging excess pressure before it becomes problematic.

Wherever pressure regulation and protection are required are good locations for pressure relief valves, such as the air tank or discharge line.

Additional Valve Factors 

You need to consider a few other factors when deciding on the type of valve you need. 

• Material
  • The material of your valve can vary by application. Stainless steel and brass are the most common materials but cast iron and various alloys are also available.
• Load/Unload Cycle
  • Your valves should be able to handle the load/unload cycle of your compressor without enduring excessive wear or worsened performance. 
• Air Contamination 
  • Compressed air is dirty, with oil, moisture, and particulates floating about. Your valves need to be able to handle this contamination without being blocked or affecting performance. Specific models have filters, strainers, and built-in separators to combat this problem.
• Noise Levels
  • Air compressors can be noisy during peak operating hours. To reduce overall noise levels, consider a valve with features like a muffler, silencer, or a casing made with dampening materials.
• System integrations
  • Depending on how integrated your system is with communication protocols, electrical connections, or automation, certain valves can tie in better than others. If applicable, it can make your process even more seamless.

Consider all of your options when you are selecting a valve, you don’t want to end up with the wrong one in place.