Tech Notes

Compressed Air Moisture Content

Another major element in assuring a successful compressed air rental program lies in addressing the moisture content of the compressed air.  

Most manufacturing plants today already use compressed air aftercoolers and air dryers to remove liquid water and/or water vapor from their compressed air systems. This same care and concern should be extended to the rental air system, to insure consistent high quality compressed air being delivered to critical manufacturing systems.

With most permanently installed compressors in use today, aftercoolers are an integral part of the design.

The two most common air dryer designs are the refrigerated air dryer and the twin tower desiccant air dryer. As the name suggests, refrigerated dryers use a refrigeration system to physically reduce the temperature of the air, condensing water vapor, which is then separated and removed from the compressed air system. There are several control variations used, such as direct expansion, thermal mass, etc. Refrigerated dryers usually achieve a Pressure Dew Point (PDP) of 35 to 39 F.

Twin tower desiccant dryers use an entirely different principle of operation desiccant materials (usually Activated Alumina) to adsorb water vapor directly out of the compressed air. Once the desiccant bed has adsorbed sufficient water vapor, the two towers switch, and while the second tower is actively drying the compressed air stream, the first tower is being "regenerated," meaning the vapor is dried out of the desiccant material. The towers then switch again, and this process is repeated over and over. Desiccant dryers can reduce moisture to a much lower level than refrigerated dryers, typically producing a PDP of -40 F to -100 F.

How does one handle compressed air moisture in a rental scenario? In one of two ways the rental compressors can be connected to the plant air system UPSTREAM of the permanently installed cooling/drying equipment, or aftercoolers and either refrigerated or desiccant air dryers can be rented along with the compressors, to supply dry air directly to the system. 




AirNow Industrial Compression Services
8150 North Central Expressway, Suite 1525
Dallas, Texas 75206
Phone: 1-972-861-1200