I inquired about obtaining air emission permits for oven drying. Aerospace components are coated in a spray paint booth and allowed to air dry tack free condition, usually about 30 minutes. Coated part then moved to the drying oven. Air District (SCAQMD) requires us to measure the emissions from the drying oven. You work with a good methodology for measuring the total emissions from the coating facilities, but does not identify how much of it comes from the oven.
So my question is how much VOC remaining in the coating at various intervals after the parts have been coated. Obviously most of the VOC came in the early drying period while the paint is still in the chamber. Everyone agrees on that, but no one has the empirical data for how many VOCs remain in the coating after a certain amount of time. Any help you could provide in the way of hard numbers or additional resources would be greatly appreciated.
If I were required to get data on the emissions at various stages of drying I would do the following:
- Perform a Method 24 analysis on the coating, but instead of curing the coating in a laboaratory oven, cure them in the actual production oven at the time and temperature that all the workpieces are cured. This test is very easy to perform. I have done it in painting operations numerous times. DO NOT USE MSDS DATA. ONLY USE THE ACTUAL MIXED COATING THAT IS BEING APPLIED IN OTHER WORDS, TAKE IT OUT OF THE PRESSURE POT AT THE TIME OF PAINTING. DO NOT MIX THE COATING YOURSELF IN A LAB. The SCAQMD loves statistical data; therefore conduct the test on a sufficient number of sample so that you can get a reasonably good mean and standard deviation.
- Apply the coating to several metal panels in exactly the same manner that the workpieces are coated. Insure that you use the same mixed paint, a sample of which was earlier taken from the pressure pot.
- Remove a few of the panels at each stage of the curing process and immediately transfer them to the oven. Determine the weight loss for each set of panels. Calculate your statistics.
- If you do this right, you will know how much VOC is given off in the oven.
- If for any reason you get erroneous results, you might need to hone your procedure some.
