Intelligent Compressed Air: Refrigerant Dryers

When we talk with customers about their EXAIR Products, we also discuss the quality of their compressed air. Many of our products have no moving parts and are considered maintenance-free when supplied with clean, moisture free compressed air. One of the most critical aspects of a compressed air distribution system is the dryer.

No matter where you are in the world, the atmospheric air will contain water vapor. Even in the driest place in the world, McMurdo Dry Valley in Antarctica, there is some moisture in the air. As this air cools to the saturation point, also known as dew point, the vapor will condense into liquid water. The amount of this moisture will vary depending on both the ambient temperature and the relative humidity. According to the Compressed Air Challenge, a general rule of thumb is that the amount of moisture air can hold at a saturated condition will double for every increase of 20°F. In regions or periods of warmer temperatures, this poses an even greater problem. Some problems that can be associated with moisture-laden compressed air include:

  • Increased wear of moving parts due to removal of lubrication
  • Formation of rust in piping and equipment
  • Can affect the color, adherence, and finish of paint that is applied using compressed air
  • Jeopardizes processes that are dependent upon pneumatic controls. A malfunction due to rust, scale, or clogged orifices can damage product or cause costly shutdowns
  • In colder temperatures, the moisture can freeze in the control lines

In order to remove moisture from the air after compression, a dryer must be installed at the outlet of the compressor. It is recommended to dry the compressed air to a dew point at least 18°F below the lowest ambient temperature to which the distribution system or end use is exposed. A dew point of 35-38°F is often sufficient and can be achieved by a refrigerated dryer (Best Practices for Compressed Air Systems). This makes the refrigerant dryer the most commonly used type in the industry.

A refrigerant dryer works by cooling the warm air that comes out of the compressor to 35-40°F. As the temperature decreases, moisture condenses and is removed from the compressed air supply. It’s then reheated to around ambient air temperatures (this helps to prevent condensation on the outside of distribution piping) and sent out to the distribution system.

With your air clean and dry at the point of use, you’re making sure you get the most out of EXAIR’s Intelligent Compressed Air Products without adhering to pesky maintenance procedures.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

Compressor image courtesy of Tampere Hacklab via Flickr Creative Commons License

Refrigerant Dryers for Compressed Air

A refrigerant air dryer is is used with compressed air for removing moisture from the compressed air system . Compressed air always contains water because your are taking in outside air which contains moisture. It is vital to have a compressed air dryer system in place to protect your equipment and tooling from damage. How does a refrigerant dryer work and why select this type of dryer system?

Refrigerant air dryers are commonly used as they are easy to operate, economical and low maintenance. Once installed it is likely that you may never have to think about it again. The system works by cooling the air to around 37 degrees Fahrenheit. At this point all the water vapor condenses into water. The water can then be removed by a simple water trap. Once the liquid water has been removed the air gets reheated to room temperature. Since most of the water has been condensed and removed the reheated air will be significantly dryer than from before.

Fundamental Schematic of a Refrigerant-Type Dryer

The cooling process of refrigerated dryers is the same process used in refrigerators and freezers. The liquid refrigerant is evaporated in a separate circuit and used to cool down the compressed air. As the air cools the refrigerant gets warmer. The refrigerant moves into a compressor and gets re-cooled in a condenser, this process is a continuous cycle as more air is introduced into the compressor.

Here a few items to consider when making your purchase:

Maximum pressure: The dryers max pressure should be the same or higher than your compressor.

Inlet Temperature: If you exceed maximum inlet temperature you are at risk of damaging parts of your equipment. Some refrigerated dryers have an after cooler making sure your compressed air stays within acceptable temperature ranges.

Maximum Flow: Make sure your dryer has the capacity needed to there are no drops in air pressure.

Maximum Room Temperature: If you are placing your refrigerated dryer into a room with a hot environment there is a change that it could overheat, Make sure that your max operating temperature for the dryer is able to accommodate the max temperatures in the room where it will be operating.

EXAIR wants you to be successful in every aspect of your compressed air system. If you have a need for any of EXAIRS Intelligent Compressed Air Systems please give any of our Application Engineers a call or contact us through our TecHelp.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com
Twitter: Twitter: @EXAIR_EK