Powder Clinic: Why Not to Convert Liquid Paint Booth to Powder

Q. I have a liquid paint booth I use to coat my parts and I am getting more requests for powder coating on my products. I am wondering if I can spray both liquid and powder in my present booth. If not, can I convert the paint booth to make it suitable for powder coating?

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A. I would not recommend that you try to spray both powder and liquid paint in the same booth. The overspray from liquid paint includes liquid paint solids and vapors. The overspray in powder is a dry particulate. They require different types of filtration. A paint arrestor filter used for liquid will either allow powder to pass through or quickly load up with powder and restrict the booth airflow. 

A liquid paint booth can be converted to powder by changing the filtration to a two-stage layer with a suitable blanket first layer and a dry material pocket filter for a second layer. If your volume is relatively low this can be effective. There are a couple of issues to consider. The blanket will not last very long because the powder will accumulate and begin to block airflow. This will require more frequent filter change than what you are used to with the liquid paint. 

Also, while it is necessary to ventilate a liquid paint to the outside atmosphere, a powder operation can discharge the booth air through a high-efficiency particulate arresting (HEPA) filter back into the plant. This is a significant advantage for powder because the booth does not need any make-up air. You will not have that advantage if you convert your liquid paint booth for powder. A better option would be to purchase a powder booth that needs less maintenance and does not need air make-up (AMU). That will save you a lot in maintenance and operating costs.

Originally published in the October 2016 issue.