Compressed air dryers 

They are special types of filter systems that are specifically designed to remove the water that is inherent in compressed air. The process of compressing air raises its temperature and concentrates atmospheric contaminants, primarily water vapor. Consequently, the compressed air is generally at an elevated temperature and 100% relative humidity. As the compressed air cools, water vapor condenses into the tank(s), pipes, hoses and tools that are downstream from the compressor. Water vapor is removed from compressed air to prevent condensation from occurring and to prevent moisture from interfering in sensitive industrial processes.

Excessive liquid and condensing water in the air stream can be extremely damaging to equipment, tools and processes that rely on compressed air. The water can cause corrosion in the tank(s) and piping, wash out lubricating oils from pneumatic tools, emulsify with the grease used in cylinders, clump blasting media and fog painted surfaces. Therefore, it is desirable to remove condensing moisture from the air stream to prevent damage to equipment, air tools and processes. The function of removing this unwanted water is the purview of the compressed air dryer.

There are various types of compressed air dryers. These dryers generally fall into two different categories: primary, which includes coalescing, refrigerated, and deliquescent; and secondary, which includes desiccant, absorption, and membrane. Their performance characteristics are typically defined by flow rate in Standard Cubic Feet per Minute (SCFM) and dew pointexpressed as a temperature, (sometimes referred to as Pressure Dew Point.)


Refrigerated compressed air dryers use a small refrigerator to cool down the compressed air to about 3 degrees Celsius. At this low temperature, condensate will form which is removed by a condensate trap. When all the water is removed, the air is re-heated to room-temperature. Your air is now dry and will not form any water as long as it stays above 3 degrees Celsius.


Desiccant air dryers use desiccant to remove the water from the compressed air. Basically, the water will ‘stick’ to the surface of the desiccant, resulting in dryer air. Every once in a while, the desiccant is re-generated. This is done automatically by the dryer. It blows dry, hot air through the desiccant to remove the water. The desiccant is now ready to do its job again. Desiccant compressed air dryers can reach much lower dew-points, up to -70 degrees Celsius.