Air and water don't mix when it comes to compressed air systems.

A build-up of water, either liquid or gas, can wreak havoc on air compressor systems including the equipment they power.

The list of potential problems are endless, but includes corrosion in piping and equipment, freezing of air lines (outdoor), pneumatic instrument and tool failure, fouling of processes and products, and more.

*Note: Before using a desiccant dryer, you'll need an oil-coalescing filter placed before it in the air system in order for it to work correctly.

What Does Desiccant Mean?

Meaning: A hygroscopic substance used as a drying agent.

Application: In compressed air systems, air passes through a container filled with the water-absorbing (hygroscopic) media such as: activated carbon, silica gel, activated alumina, or other desiccant material. As water vapor clings to the desiccant, the material becomes saturated and will need to be replaced with new material.

Not Afraid of Cold

Desiccant dryers make wonderful air dryers for any season because they don't rely on a reduced dew point like refrigerated dryers do. They can actually filter moisture in temperatures as cold as -100 degrees Fahrenheit.

Best Desiccant Dryer Types

There are a couple different types of desiccant used in these dryers. You may be best suited with one over the other depending on your application.

Activated Carbon

A very effective and resilient material used is activated carbon. This is a very porous material with enormous surface area capable of holding onto any impurity that touches it.

Activated carbon is more resilient than silica gel, and so it can be regenerated and reused rather than continuously replaced.

With two towers containing activated carbon, a desiccant dryer can actually regenerate one tower while using the other to adsorb incoming moisture. This creates a continuous cycle that makes the dryer very reliable.

The desiccant most commonly used is silica gel. Silica is what comes in the little paper pouches found in packaging, but in this case, there's a lot more of it.

As the incoming air is passed through the silica gel, the moisture sticks to the surface of the many small pores contained in it. This process is called adsorption.

When the silica has become fully saturated, it generally changes color, indicating that it needs to be replaced.

Author： Joshua A.