What is the best compressed air dryer?  That’s not an easy question to answer.  It depends on the answers to a variety of more fundamental questions.  How is the compressed air being used?  What ambient temperature ranges will the compressed air piping be exposed to?  Are there footprint, electrical, or other constraints at the installation site?

There is no single air dryer that’s best for every application.  The best compressed air dryer for a home user will be much different than for, say, a scientist in a high tech research laboratory.

To begin answering this question – what’s the best compressed air dryer? – let me first ask yet another one.  What dew point do you need?

Let’s cover some basic terms and definitions.  A compressed air dryer removes water vapor from the air line.  Water vapor is a gas.  A dryer is not intended to remove liquid water.  (Liquids must be separated and filtered out upstream of a dryer using liquid separators and coalescing filters.)  A dryer, by removing water vapor from the air line, lowers the dew point.  Dew point is the temperature where condensation begins to form in compressed air.  By removing water vapor and lowering dew point with a dryer you prevent new condensation from forming downstream in system piping and points of use.  Generally speaking, the more you want to drop the dew point, the more you’ll need to spend.   The lower you drive the compressed air dew point, the more costly the dryer becomes, in terms of both capital and operating costs.   Another way of putting it is that one should dry compressed air only to the extent required by the application.

The ISO standard 8573.1 defines various compressed air quality classes.  This standard is helpful for quickly identifying various levels of compressed air purity, but it will not help you answer this most important question, What dew point do I need?  If you’re an industrial user of compressed air you will need to further examine your air system and processes to evaluate your dew point requirements.

Let’s take a quick look at the various types of compressed air dryers.

Deliquescent dryers – a specialty of Van Air Systems – deliver a dew point 20 to 65F below the inlet compressed air temperature.  These dryers are used for applications where the unique features of a “deli” are of primary value – portability, simplicity, durability are the defining traits of the deli dryer.  For example, a deli dryer is the best compressed air dryer for portable abrasive blasting applications.  It’s also the best dryer for a point-of-use installation to protect paint booths or blast cabinets in an air system that has no primary dryer.  Here's a video we did not long ago.

Refrigerated air dryers are the most pervasive type.  A refrigerated dryer typically yields a dew point between 35 and 50 Fahrenheit.  These dryers are suited for general manufacturing environments and air systems that have neither low dew point process requirements nor air lines exposed to sub-freezing ambient temperatures.  Atlas Copco, Ingersoll Rand, SPX, and Parker are the biggest makers of these dryers in North America, although there are many other domestic and foreign manufacturers.  A large manufacturing facility that primarily uses compressed air for operating pneumatic tools and air cylinders, where no air lines are exposed to low ambient temperatures, would likely use a refrigerated air dryer.

Regenerative desiccant dryers deliver -40⁰ dew point compressed air.  This purity level is commonly referred to as “instrument quality.”  Regenerative desiccant dryers are relatively costly to purchase and operate.  They are used in cases where compressed air is used with sensitive instruments and processes or to prevent condensation from forming in air lines that are exposed to low ambient temperatures.  Regenerative dryers are commonly used in power plants, high tech manufacturing, food and beverage facilities, and the oil & gas industry.

Bottom line.  Every application is unique.  If you’re simply using air to blow dust off the floor then you probably don’t even need a dryer.  But if you’re using compressed air in a process that involves, for example, contact with a food product then evaluating your dryer requirement will be of great importance.  So what is the best compressed air dryer?  The honest yet unsatisfying answer will always be, It depends.

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