How to choose a compressed air filter

Why is filtration so important for compressors? Choosing a good compressed air filter system can have a positive impact on the entire system. Let’s see why in this article and how to choose a compressed air filter. 

Filters are elements that are used in a wide variety of situations, such as when making coffee or a good herbal tea. In each of these cases, if we did not use filters, we would find ourselves drinking solutions full of unwanted grains and residues. Well, compression systems work in exactly the same way; they need a filter to prevent the air from being contaminated. Compressed air is already made up of various particles and, especially in oil-lubricated screw compressors, it retains harmful vapors. 

READ ALSO: Removing harmful substances from compressed air

These greatly reduce the quality of the compressed air, to the point of making it harmful to end users. The answer to all this is the filter, which is why choosing the right compressed air filter is a fundamental crossroads in the application of compression systems. 

How to choose compressed air filters: are they all the same? 

No, compressed air filters are not all the same. This is because the choice of filter depends on the type of application and process that uses compressed air. Knowing these two variables is very important in order to avoid making the wrong choice: each process or application requires its own degree of filtration. Let’s look at some practical examples: 

I use compressed air for tires, which compressed air filter should I use? 

In this case, normal dry particulate filters can be used, or filters that ensure filtration down to 1 or 0.01 microns. What if I also need to remove oil vapors? In this case, we will choose activated carbon filters. 

What are the contaminants in compressed air?

Compressed air can be contaminated by three elements in particular: dust, aerosols, and vapors. 

Dust is simply solid material residues from the ambient air: dust, pollen, dust from pipe corrosion. 

Aerosols, on the other hand, are droplets of liquid, such as oil from lubricated compressors.

Oil vapors: as above, for those who use lubricated compressors, these elements are commonplace and must be eliminated. 

Why? Because in all these cases, air quality is reduced and can be harmful to people and end products. 

Air filters to eliminate dust residues 

To eliminate dust, the ideal filters are those for dry particulates, which work in three ways: 

• inertial impact: solid particles are trapped in the fiber support
• interception: smaller particles are allowed to pass through, while larger ones are blocked and captured
• diffusion: smaller particles moving on the surface are intercepted by the filter and extracted from the compressed air flow

Air filters to remove aerosol residues and vapors

In this case, two different types of filters are used: coalescing filters and adsorption filters. 

Coalescing filters: ideal for dust and aerosols, less so for vapors. These filters bring together small drops of liquid to form larger ones. As the drops grow, they fall from the filter into a moisture separator, generating drier and cleaner air

Adsorption: this is a chemical process used to remove vapors. In particular, bonds are formed between vapors and a support (called an absorbent). Activated carbon is the preferred material due to its high capacity to attract oil vapors.