Basic drying room components
We are installing two new spray booths with air make-up. We are spraying a Becker Acroma catalyzed lacquer. We have a drying room 12' wide x 22' long that is completely sealed off from the rest of the plant. Feeding into this room from one end is a propane furnace mounted outside that can blow in 2500 cfm of heated outside air. Parts inside are stacked on drying racks.
How can we set up air movement inside the room to achieve the best possible drying environment? Would an exhaust fan at one end and the air intake at the opposite end do the trick or do I need something more elaborate?
The system doesn't have to be elaborate, but you need those three things. You can create more problems by heating the parts in this room and keeping it closed up. When a finish cures, it emits fumes from the solvents in the coating. Once heated and trapped, you will have a pocket of fumes in your dry room, preventing the curing process and actually doing more harm than good.
Put a few closed housing fans in the room to create some air movement. Then put an exhaust fan in. It doesn't have to be a real big fan--a squirrel cage fan would do fine blowing the fumes outside. You also may want to look at a supplier who can advise you on these things. A good tech rep should be able to answer questions like these and keep you out of trouble.
You missed one:
4) UV curing,
either short or medium wavelength. This can be used with either conventional solvent finishes, standard water borne or UV cure waters.
From contributor J:
Sure you're not talking about infra-red? UV curable and infra-red are two totally different animals. Infra-red will dry any solvent or water system. UV works with photo initiators and UV light. Besides, the questioner is curing a catalyzed lacquer, and it sounds like he almost has his dry room ready except a few minor changes. I don't think he is ready for the expense of either UV or infra-red lights to cure the finish.
The system that contributor J has outlined will work very well. You will want to make sure, however, that you don't have too much air velocity over the freshly sprayed pieces to prevent bubbling and kicking up dirt, etc. Just out of curiosity, which Becker Acroma product are you using? What area is your shop in?
From the original questioner:
I am using Becker's Fiesta line, which seems to work very well for us. The pieces we are finishing will have sufficient time to flash off before they are put in the drying room. We are located in Cape Breton, Nova Scotia. That's on the east coast of Canada.
You need to maintain a constant airflow through the drying room to get rid of the fumes. Also, you should keep an eye on the temperature in the room--if you get it too hot, you can actually slow the drying time. Talk to a rep about the proper temperature. I don't think that you would want it any more than 70 degrees at 55% humidity.
Heat and ventilation will speed the curing process of Becker's Fiesta. Warm air should be introduced close to the floor, and exhausted or made-up close to the ceiling. Thinning Fiesta to 10% (even 15%) will speed it up, too. Which catalyst are you using? I find that 2750 is extremely fast. 494 grinds it to a halt. If you want to speed up the process between first and second coats, use Intro or Facett LV to seal, then re-coat with Fiesta.
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