Compressed air dryers are rated using a few parameters, including temperature, maximum pressure, differential pressure and flow.  Flow is the rating you'll first look at when shopping.  Flow tells you how much air you can push through the dryer.  Here in the U.S., flow is stated in terms of cubic feet per minute (CFM).

Simply put, a flow rating defines how how big or small the dryer is.

For reasons we won't get into here, the flow rating on a dryer's name plate almost always assumes an operating pressure of 100 PSI.  Dig into the dryer's operating manual and you'll see that the flo

w rating changes depending on the pressure.

In other words, the flow rating is not fixed.  It changes.  It depends on the pressure.

Take for example the single tower deliquescent dryers from Van Air Systems.   The chart below shows different flow ratings for the dryers (in CFM) at different operating pressures.  Note that the flow rates under the 100 PSI column is the "advertised" rating.

Why does this matter?  Well, if you operate your air system at a pressure other than 100 PSI you might need a bigger (or smaller) dryer than what's shown on the nameplate.

Buy a dryer that's too big and you've wasted money.  Buy a dryer that's too small and you risk having wet air.

What other questions do you have?  I enjoy helping folks so call me at 303-444-2869 or email me at tyler@moistureboss.com. 

The D12 is rated for 100 CFM @ 100 PSI

AND 121 at 120 PSI.