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Desiccant Compressed Air Dryers

Updated on February 29, 2012

Antique Air Compressors

photo by gavinkwhite on Flickr
photo by gavinkwhite on Flickr

Desiccant Air Dryers Protect Equpiment

If you have ever eaten that packet of silica gel beads that can be found in the toes of a new pair of Nikes or the bottom of a fresh bag of Jack Links beef jerky then you probably understand how desiccant compressed air dryers work. WARNING: That is not true and silica gel should certainly never be consumed or abused by humans or animals. But, there are a couple of great uses for the packets like dropping them into a toolbox to prevent corrosion or preventing underwater camera condensation. Desiccant compressed air dryers make use of the principle of hygroscopy in order to attract and hold water from the compressed air and provide cleaner output to air-powered tools and apparatuses.

It is all about the dew point. The process of compressing air raises the dew point of the air or gas that is being compressed and this often requires a dryer like desiccant compressed air dryers in order to lower the dew point back to a suitable level so that water vapor will not interfere with things down the line. For regenerative dryers (aka desiccant) that new dew point is generally rated from about -40 degrees Fahrenheit to -100 degrees Fahrenheit in higher-end models. The desiccant substance can often be in the form of beads which change color to indicate that they need to be regenerated. Different models can be regenerated through various means (even drying in the oven for 30 minutes at 350 degrees). Other desiccant compressed air dryers are known as twin tower dryers as they incorporate two canister towers which alternate use. While one dryer tower is being operated the other is being regenerated through one of a few regeneration methods. Desiccant compressed air dryers can use heatless types which utilize a portion of the dry air from the "in use" dryer tower to regenerate the idle tower. Heated regenerating air dryers are another approach which uses an external heating source to regenerate. Other purging methods such as a blower purge or heat of compression purge exist as well.

Often times, desiccant compressed air dryers can incorporate a staged system into the process. Often this is something like a 3 stage (or stage 5 or higher) system where the first stage is a filter that can trap water and contaminants down to a certain micron level. Stage 2 might be a coalescer that will remove oil and sub-micronic particles. Stage 3 could be the desiccant dryer portion. A quality 3 stage system will dry the air while minimally affecting the output air pressure (CFM cubic feet per minute) and have replaceable filter elements.

The use of desiccant compressed air dryers should be used to eliminate moisture for various reasons. Whether it is to prevent erosion of piping and other systems components, corrosion of valves, freezing in air lines or microbial contamination choosing the proper system is the key to system longevity. So whether you are using compressed air for smaller micro sandblasting applications or something as large scale as auto body spray painting take a look a air dryers.


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