Q: In South Africa, it is very difficult and very expensive to get piped gas into my plant. We are starting up a powder coating section for architectural extrusions.
I would like to get some input as to whether I should select my ovens to be gas/diesel or infrared. Is there a SWOT analysis that has been done to determine the best options?
A: This is a very common problem in the African continent. We ran into a similar problem in Nairobi. The coating operation there could either pay for gas lines to be laid to their plant (cost prohibitive and would take an indeterminate amount of time for installation) or install a large gas storage tank and buy a year’s worth of gas (also cost prohibitive). They elected to use electric resistance heating for their finishing line. I felt this was the lowest-cost option for capital expenditure, though the operating costs are quite high.
For your situation, I recommend a combination of infrared (IR) and electric resistance heat. The infrared will have to be electric, as opposed to gas-fired or gas-catalytic infrared for the reasons you’ve mentioned. I think it will be best to use a medium- to long-wavelength infrared system, as it provides better heat-up consistency and is less sensitive to coating color differences as compared to short wavelength types.
It is important to orient the elements so they do not cause “striping” from localized focal points of IR energy. IR energy is relatively “line-of-sight” and will preferentially heat up the surfaces it “sees” (lots of quotation marks today). Because of this localized delivery of heat, it is wise to follow the infrared zones with convection heat (in your case, resistance electric). Convection heat will even out the overall temperature of your parts and is “color-blind” as opposed to infrared. This way, you can be assured of thorough, even cure across your parts.
I would avoid diesel-fueled ovens. They are rather inexpensive to purchase and operate, but the combustion is not as clean as that of natural gas and can cause inconsistencies in color. If your target market was less critical than architectural, you could contemplate using a diesel-fueled oven, but I don’t think this is an option for you.