Compressed air powers most of what we do at Kaser. There could be no blasting, no blowing off, and no spraying powder – or paint – without it.
Because it’s both invisible and baked into all of our processes, it’d be easy to take air for granted. If it’s been a while since you’ve thought about air quality, take note: it may be responsible for more problems than you realize.
The problems you’ll encounter depend largely on what air compression system you’re using. Let’s look at the big two.
Rotary Screw Compressors
Rotary screw compressors are common for jobs requiring high CFM (cubic feet of air moved per minute). A large screw compresses the air. While this method is efficient, it also exposes the air to oil, which must be filtered out (“separated”) before the air is used on the part. Failure to do so impinges microscopic oil onto the substrate, causing problems down the road.
Good filtration is the key to success. Ideally, air coming out of the compressor will travel through a coalescing filter before passing through the dryer and entering the holding tank. At Kaser, we like to have an additional filter for air coming out of the holding tank – this may seem like overkill, but we’ve learned to be cautious. Our goal is to catch any lingering moisture or contamination that might be floating around the holding tank, a precaution that has served us well over the years.
Popular for lower-volume finishing processes, reciprocating compressors consist of a piston cylinder mounted directly on top of a tank. Compressed (and often very hot) air travels directly from piston to tank, where it is stored until it’s ready for use.
Unlike their rotary screw counterparts, reciprocating compressors tend to put out clean, oil-free air. That’s great. However, where there is extremely hot air that is cooling, there will be moisture. Expect the air coming out of the tank to be damp, and dry it accordingly. Filtration is slightly less of a concern on reciprocating compressors. A particulate filter may do the trick; for added protection, consider using a low-grade coalescing filter. And, most importantly, invest in a dryer. Air should travel from piston, to tank, through filter, to dryer – it’s the only way to eliminate moisture before spraying it all over your part.
I’ll blog another day about the dangers of poorly-filtered air. In the meantime, I’ll leave you with this: no matter what system you’re using, know its CFM, and shop for parts accordingly. Make sure that your dryer and all filters meet your CFM needs, taking any environmental concerns (i.e., dust, climate, and humidity) into account.
This topic is near and dear to my heart, and I’ve gone through several years of trial and error to learn what I know. There’s a lot more I could say, particularly about rotary screw compressors – if you have questions about setting up your air supply, please put them in the comments. I would be thrilled to address them in detail on the podcast.