Collection: Air Dryers

A compressor pulling 100 degree F air at high humidity drops roughly 20 gallons of water per 100 CFM over an eight hour shift. All of it ends up in your piping, your tools and your paint unless something takes it out first.

A refrigerated dryer chills the air to about 38 degrees F and holds the pressure dew point at the same number. That covers any system where the pipe stays above 38 degrees, which is most indoor shops. It is cheaper to buy, cheaper to run, and the only real maintenance is a condensate drain that actually works.

A desiccant dryer gets you to minus 40 degrees F, and you need it when the pipe runs outdoors where it freezes, when the air feeds powder coating, paint, pharmaceutical or food packaging equipment, or when a control spec calls for it. The price is purge air: a heatless desiccant dryer burns 15 to 20 percent of its rated flow to regenerate, so a 200 SCFM unit quietly takes 30 to 40 SCFM back off your compressor. Heated and blower purge designs cut that down and add a heater to maintain.

Where sizing goes wrong

Dryer capacities are published at 100 degrees F inlet, 100 degrees F ambient and 100 PSIG. Feed one 120 degree air, or run the line at 80 PSIG, and real capacity falls 20 to 40 percent. Correct for your actual conditions before you pick a model. Above 104 degrees F inlet a standard refrigerated dryer is simply out of range, so add an aftercooler or go high temperature.

Our articles on pressure dew point and dryer types work through the math. If your process calls for ISO Class 3 air or better, stop reading about refrigerated units. They top out at Class 4.