The invisible "air" determines the visible "paint." Oil and water in compressed air are the hidden culprits behind fish eyes and particles.
In a nutshell: Clean air source = three-stage filtration + refrigeration dryer + oil-water separation; if the air is not clean, even the best paint is useless.
I. Why the gas needs to be purified
The spray gun atomizes the coating by compressed air; if the air contains oil, water, dust, they will directly mix into the paint film: oil causes fish eyes and craters, water causes blushing/bubbles, and dust causes particles.
Figure: Three-stage filtration + refrigerated dryer + oil-water separation to ensure clean air source.
II. Purification Chain
Aftercooler: Cool down and separate water.
Air receiver tank/automatic drain: Settle and discharge condensate water.
Refrigerated air dryer: Further lowers the dew point.
Three-stage filter: Gradually filters water, oil, and particles.
End-of-line oil-water separator: The last line of defense before the spray gun.
Figure: Oil and water carried in the air source directly cause paint defects such as fish eyes and particles.
Maintenance: Drain regularly and replace filter elements; if fish eyes keep reappearing, first check the status of the oil-water separator and filter element, rather than blaming the paint.
Summary
Oil, water, and dust in compressed air directly cause fish eyes, blushing, and particles. Purification relies on after-cooling, air receiver drainage, refrigerated dryer, three-stage filtration, and end-of-line oil-water separator. Drain regularly and replace filter elements; if fish eyes recur, inspect the air source first.
Frequently Asked Questions (FAQ)
Why is a clean air source required for spray painting?
Spray guns use compressed air to atomize coating. Oil in the air causes fish eyes and craters, water causes blushing and bubbles, and dust causes particles, so the air source must be purified.
What is three-stage filtration?
It refers to installing filters step by step along the air path to respectively remove moisture, oil, and fine particles, combined with a refrigerated dryer and drain of the air receiver, to ensure the air reaching the spray gun is clean.
Where is the oil-water separator installed?
Usually installed at the very end before the spray gun air inlet, serving as the final safeguard against oil and water, used together with upstream refrigeration drying and three-stage filtration.
Are recurring fish eyes a problem with the paint?
Probably not. For recurring fish eyes, first check whether the air source oil-water separator and filter element have failed and whether drainage is timely; the source is the air, not the paint.
Is a refrigerated dryer necessary?
It is quite necessary in high-humidity or continuous operation scenarios, as it lowers the dew point of compressed air, reduces condensate, and cuts the risk of blushing and bubbles at the source.
Kexin New Materials · Automotive Coating Technology Library | This article is technical Q&A content, for reference in selection and construction
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