Take it from a Mechanical Engineer: the right equipment makes all the difference in the quality of blasting and coating.
This is a topic that genuinely excites me, and I wanted to share some insights I’ve developed over years of trial and error, in case they can be useful to customers or our industry partners.
Let’s dive in.
Compressed air fuels a lot of what we do at Kaser – we rely on it to pressurize our blasting media, to power the powder coating guns, and to blow out parts after pretreatment. We need air, and we need a lot of it. That’s why we use multiple rotary screw air compressors sized for our different applications. Unlike reciprocating, piston-based compressors you might have in your garage, ours compresses air with a rotary screw.
Pressure is just half of the equation, however; we also do a lot to ensure that the quality of our air. Moisture and oil will inevitably mix in with the air during the compression process, and if we don’t filter that out, it will cause issues for us down the road.
If we try to blast a part with dirty air, for instance, we run the risk of impinging oil into the substrate, which we won’t necessarily see until after the part is cured and the oil has bubbled up through the powder coating. By then, it’s too late. If we blast with moist air, we immediately accelerate rusting. Blasted parts are very vulnerable to moisture, so much so that we avoid touching them with bare hands. Blowing moist air all over a vulnerable part is not ideal.
The same things hold true in the coating booth: oil vapors in the powder gun can gum up the powder and cause surface issues during curing. Moist air will cause the powder to clump, creating coating issues and endangering the gun itself.
I want to stress that oil and moisture won’t necessarily be immediately visible in the compressed air stream. Moist, dirty air doesn’t necessarily mean droplets – often, it’s a vapor that will come back to haunt you. That’s why it’s important to test air quality regularly, no matter how it looks to the naked eye.
So how do we avoid moisture?
It’s super important to find an air dryer that’s properly sized for your compressor. Take this into your own hands – manufacturers can tell you all about their products, but only you know what you need. For instance, manufacturers have no way of knowing how hot the Kaser powder coating shop gets. Heat from the oven directly affects the intake areas around the compressors; if that isn’t factored in, you can end up with the wrong size dryer. So take your environment into account.
And what about oil?
Filters, filters, filters. But be careful – a particulate filter won’t help with oil. Only a coalescing filter can do that, and they’re not all created equal. Coalescing filters are measured by physical size, as well as their porosity. For example, a .1 micron is a typical oil filter, known as a utility coalescer. This is usually the first filter you put in a line – it catches the bulk of the oil, but not all of it. If you blow air through a .1 micron filter and then across a white cloth, you might start to see a bit of an orange tinge, indicating there’s still some oil in the air. In this case you can add a fine coalescing filter, or a .01 micron filter. This will capture any oil that the utility filter missed.
Ideally, air will flow through this progression: from the compressor, through the utility filter, and into the air dryer. At this point, we like to store the air in a large tank, so that our compressor doesn’t have to work quite so hard. When it comes out of storage, the air goes through the fine coalescing filter, taking out what’s left of the oil vapors.
Needless to say, filtering moisture and oil vapors out of compressed air is no simple task. We’ve done research, gone through trial and error, and spent money. We tried a lot of things that didn’t work before finding a system that did. I welcome your feedback, and hope you’ll reach out with any questions you may have.