Inside a compressor air filter

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What is inside a compressor air filter? What do the components do?

This is page two of information about the compressor air filter. Here is page one if you wish to start there.

After you have removed the compressor air filter bowl guard, you can remove the polycarbonate bowl. In the image below, the polycarbonate inner bowl of the air filter has been removed.

Compressed air filter carbonate bowl
Compressed air filter carbonate bowl showing the O ring seal on the right, and the bowl drain on the left.

Typically this polycarbonate bowl inserts into the compressor air filter head easily. It is is held in place, until the exterior bowl guard is installed that is, by friction. That friction is created between the O ring seal (seen on the right end of the polycarbonate bowl in the image above)  and the inside surface of filter-head housing.

What is inside a compressor air filter?

Now let’s have a look at what’s inside the bowl of the compressor air filter.

Inside a compressor air filter
Inside a compressor air filter

In the image just above we have removed the metal bowl guard and the polycarbonate inner bowl. We have numbered the various components that we found inside. Your compressor air filter, if it is not the same brand, will look differently but should still have the same inner components as our example above.

Item1 – filter cap or head

Item 1 in the image above is the filter cap. The filter cap will have two ports, one for the incoming air, and the other for path of the compressed air out of the filter after that air has been treated.

When installng a compressed air filter note the direction of the arrow on the cap. It shows the path of the compressed air through the filter, and must be installed in the correct orientation. The air filter only works properly when air is flowing in the right direction through it. Here is an image of the top of this air filter cap. Note the directional arrows. They point towards the outlet of the treated air from the filter and on downstream to the various air using applications.

Compressor air filter cap
The direction of the arrow shows the flow of the air through the filter from the source towards the downstream applications.

Item 2 – Directional Control Vanes

The actual color and shape of this component will change based on the brand of air filter you have. Yet every compressor air filter will have something like this inside it.

The purpose of this part of the compressed air filter is to direct the incoming air stream into a twisting, circular motion inside the bowl of the compressor air filter. Why do that?

Inner baffle of compressor air filter
Inner vanes of compressor air filter. Note that the vanes are angled to force the incoming air into a tight spiral inside the air filter bowl.

Compressed air travels very quickly from high pressure to low. As this torrent of air is forced into the compressor air filter, the baffle directs that stream of air into a vortex inside the bowl. The air is forced to twirl which, very effectively, spins any free water in the air stream outwards agains the side of the filter bowl. That free water then drips down into the bottom of the bowl and out of the compressed air stream which is heading for your air tools.

Item 3 – the filter element

After spinning down into the filter bowl, the compressed air makes an abrupt turn – which removes more free water – up into and through the filter element.

More on the air filter element and other filter parts can be found right here.

By Ashley Pearce

As a passionate manufacturing and mechanical engineer, I've had my fair share of run ins with air compressors and compressed air systems. With over a decade of experience in the industry, I have both a fresh perspective and time-served hands and mind to help you with your compressor problems (along with our able community!)

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