We had a question on the ASK page of this website that went as follows: Can someone explain the differences between using an air compressor after cooler with filters versus using an after cooler and dryer with filters?

Aftercooler Versus Filter

You will know if you’ve had a chance to experience it with your compressor, or read the pages about it on this site, air compressors always generate warm to hot, moisture laden, compressed air.

If this hot, wet, compressed air is passed through an after cooler, the aftercooler causes the air temperature of the compressed air to lower. A typical after cooler is shown in the image.

after cooler

As a result of the cooling of the compressed air by the after cooler, the compressed air can carry less moisture and water condenses out of it, and the air stream becomes dryer.

Downstream from the after cooler a general purpose compressed air filter will strip much of the free water (actual liquid water) from the air stream, furthering the work the after cooler has done.

At this point, and depending on how dry the compressed air has to be for your use (remember, the drier the compressed air has to be the higher the cost is to make it so) sometimes the compressed air is run through a air dryer.

Dryers work better with cooler compressed air, so it makes sense then, if your compressor is working hard and pumping really hot air into the mains, that this air gets passed through an after cooler before it gets to the dryer.

Consider your compressed air moistness shown on a line from wettest to driest. At the wettest end you will have the air as it exits the compressor pump, and the driest end is the application that is using the air.

In order to get the compressed air dry enough for your air-using equpment, you will install equipment that dries compressed air between your application and the wet compressed air source which is the compressor.

Between the compressor and your air-use application, you will commonly see – and again, depending on how dry the air has to be for your use – after cooler(s), general purpose filters, refrigerant or desiccant air driers, more general purpose filters, point of use air dryers, another air filter and so on.

You will need to keep treating your compressed air with additional air-drying equipment until it reaches your point of use as dry as it needs to be for you.

That’s why some plants have tons of “air-treatment” equipment, and others have less.

Hope this helps.


New comment? New question? Please add it here along with photos to help others help you with your compressor and equipment problem!