Moisture is always present in the air. When air is compressed in a compressed air system and cooled above its dew point, it condenses into liquid water. Compressed air systems rely on dry air to operate properly, and the system will malfunction if the air is humid. More specifically, the air must be free of any liquid moisture, and the relative humidity should be kept below 50% to prevent corrosion.

Moisture in compressed air is causing significant damage:(1) It can block control air circuits, prevent instruments from reading or starting correctly, and lead to general instrument failure.(2) It may cause water hammer events, which can damage equipment and pipelines.(3) It may result in product deterioration and compromise product integrity.(4) Processes can be directly affected when water is introduced into the air stream.

Removing moisture to prevent corrosion is also critical for both the equipment that uses compressed air and the air system itself. Particulates generated by rust and scale can contaminate pipelines and damage components of the air system. In the worst-case scenario, corrosion can render pipelines inoperable, cause leaks, and cut off the supply of air to required processes.

Most manufacturers use compressed air dryers as one of the dehumidification methods. Air leaving the compressor is heated and saturated with 100% water vapor. As the air cools, liquid water begins to condense. While filters and separators can remove liquid droplets from the system, they cannot eliminate water vapor. To remove water vapor, a dryer must be used.

How to Remove Moisture from Compressed Air?

Cooling and Separation The hot compressed air is cooled, causing a large amount of water to condense. Once condensed, the water can be separated from the air. This is typically accomplished using an after cooler or heat exch anger.

Membrane Drying This method separates water vapor through a process of selective permeation of the gaseous components in the air. When filtered wet compressed air enters the membrane module, water vapor permeates the membrane coating and accumulates on the fibers, leaving dry air to pass through.

Adsorption Drying This is a physical process where water vapor adheres to porous adsorbent materials (such as silica gel, molecular sieve or activated alumina). The adsorbent materials are solid and have a high affinity for water vapor, trapping it from the compressed air stream.