Clean compressed air can mean a lot of different things to different people.
What is clean compressed air?
It all depends what you use it for. If you work in a bakery and use compressed air somewhere in your bread-making machine, ‘clean air' probably means something completely different than to someone who uses compressed air on a construction site.
For more information about general air quality and whether you need it or not, visit our compressed air quality page.
There are a lot of different things that contaminate your compressed air system, like water, dust and oil. The dust usually comes from the air that is sucked in by the compressor.
The water also comes from the surrounding air. Oil usually comes from the compressor itself.
Here's a list of the main things that contaminate your compressed air system.
Remove them and you have ‘clean compressed air':
Water in the air
The number one problem I often see in compressed air systems is water in the system... lots of water.
Where is all this water coming from? It comes from the air that is sucked in by the compressor!
When the air is compressed, it cannot hold all that water anymore, so a lot of water will condensate and get trapped in your compressed air system.
Dewpoint / pressure dewpoint and relative humidity
So what is exactly the dewpoint of your compressed air?
The dew point is the temperature at which water vapor in the air will condensate. We see it around us every day (if you live in a cold climate ;) … when it gets colder at night and you get to your car in the morning, it will be covered in a thin layer of dew.
It's water vapor that was once in there air. But because it was cold at night, the air couldn't hold all that water anymore and some of it condensed into liquid water: dew.
More information on water and how to get rid of it on our compressed air dryer page.
Oil in air
Oil in air is another common problem and often a result of bad maintenance. Often, it's not even noticed or cared for, as many people don't care about a little oil in their compressed air, as it lubricates their air tools.
But, if there is a rise in the amount of oil in your system (today more oil than last month), there is something wrong. Something is changing.
Depending on the type of compressor you have, there could be something breaking down (like the oil separator in a screw compressor).
How to get rid of the oil? Install a compressed air oil filter. It will filter out most oil from the compressed air to get clean compressed air.
My advice: a little oil in the air is often not a problem, but keep an eye on the amount of oil. Also, if you need oil for lubrication of your air tools (grinders, cutters, etc) or other equipment, you should install a compressed air oiler, or an air line lubricator. It's a small device that you fill with oil and that you install near the machine that needs lubrication.
The lubricator will add a few drips of oil to the air every minute or hour (depends on what you want) to lubricate the equipment.
Oil free compressed air
On the other hand, there are a lot of people that require oil free compressed air.
When you work in the food business, chemical plants or electronics manufacturing for example, oil-free and clean compressed air is often a must-have.
There are basically to ways to get oil free air:
- Make sure oil will never enter the compressed air in the first place.
- Filter out all the oil from the air before it leaves the compressor room, or before it enters the machine that requires oil-free air.
The first option is the safest one and produces the cleanest air. Not surprisingly, it's also the costliest one, as it requires an oil-free compressor. Oil-free compressor are always more expensive than oil-lubricated compressors and the maintenance costs will often be higher.
The second option is a good alternative: install a cheaper oil-lubricated compressor and filter the air when it leaves the compressor. There are special oil filters that will filter out most oil from the air.
Next on the list: dust.
Dust will simply get sucked in by the compressor and travel with the air though the compressor into your compressed air system.
So my first advice would be to install proper, quality air inlet filters on the suction side of your compressor.
Not only does it prevent dust in your compressed air. It will also save your compressor. Dust will wear down screw elements (screw-type compressor), wear down cylinders (reciprocating compressor), it will clog up oil separators, oil filters and compressed air filters.
So the best thing you can do: make sure dust can't get into your compressor in the first place!
The next thing you can do: install dust filters in the compressed air line. There are basically two places you can install dust filters: a big one near the compressor, or small ones near the air consumers (machines, tools, etc).
Smells and micro organisms
There are other contaminants like smells and micro organisms that can be removed with special filters, often activated-carbon filters.