Oil free refrigerated compressed air dryers are designed to remove water vapor from compressed air. When air is compressed, the temperature and atmospheric contaminants (in this case, water) increase. Compressed air has a 100 percent relative humidity rate. As the air cools, the water condenses and runs off into the machinery—similar to how your car might “leak” water after running the air conditioner for an extended length of time.

Using an oil free refrigerated compressed air dryer helps reduce this humidity and prevent water from leaking, which in turn protects your machinery from rust and corrosion. Here is an overview of the basic types of oil free refrigerated compressed air dryers, and what they’re used for in Wisconsin:

Refrigerated air dryers: This is the most common type of compressed air dryer. They use two heat exchangers to cool the air down to about 38 degrees Fahrenheit, then remove the condensed water in a controlled fashion—that is, safely away from any parts subject to rust or corrosion. One of the benefits of this type is that the two heat exchangers make it possible to use a smaller air compressor. Refrigerated air dryers come in cycling and non-cycling varieties. While they have a limited dew point, they’re affordable, with relatively low operation and maintenance costs. Refrigerated air dryers tend to be popular for most industrial applications.

Desiccant air dryers: This type of air dryer adsorbs the moisture (this is different than “absorb”) by using a desiccant. The water vapor adheres to the desiccant, which can then be removed by either applying heat, dry air or both. Models that use heat naturally include heaters. If you need a very low dew point for your compressed air, this type of compressed air dryer is a good choice. The heatless type can be used in mobile locations, and they offer a moderate operating cost.

Membrane dryers: Membrane compressed air dryers use a dehumidification membrane to remove moisture from the compressed air. Air is blown over a special membrane that attracts moisture. As the water vapor passes through the membrane to get to the membrane dryer’s low pressure side, a dry cover gas blows through, absorbs the water and is sent out through the output valve. This type of dryer doesn’t require electricity to operate, and can do so 24/7—all you have to do is change the prefilter cartridge twice per year. Although they put out a fairly limited amount of compressed air, they’re quiet and easy to use and maintain. Laboratories, medical facilities and specialized manufacturing facilities tend to use membrane dryers more than any other type.