Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 229 of 331

on the face of a burner. Catalytic gas heaters operate at temperatures below 950°F, which puts them into the third category of infrared heater products, al- though they offer the same efficiencies and processing times as many of the medium-wavelength heaters. Long-Wavelength/Low-Intensity Heaters This final group includes heaters that emit energy at wavelengths of 4.0 µm and long with energy densities below 15 W/in2 . Operating temperatures can be reached of up to 850°F with a mean life expectancy of 15,000 to 20,000 hours. Construction types of the electric emitters include metal-faced panel heaters, fiberglass emitting surfaces, or ceramic cylinders mounted in concave reflec- tors. Radiant-wall systems fall into this category. The gas heaters that comprise this category are catalytic infrared heaters that chemically catalyze the gas on the surface instead of burning the gas to produce infrared energy. Generally, these types create a combination of convection and low-intensity in- frared radiation suited for coatings that must have longer bake times owing to surface or coating characteristics and where the user wants a system that is more efficient than a standard convective oven. This group tends to be less expensive in initial cost than the two other groups, but it is unable to provide the same efficiencies in energy consumption and sav- ings in floor space possible with the medium-and short-wavelength systems. Metal-faced panel heaters are constructed in strips with the heating element within and commonly provide lower available energy outputs than some of the other types. Ceramic heaters are available in building-block sizes and require re- flectors to direct their energy to the product. SUMMARY Infrared radiation can be used in curing and drying processes to provide precise control of color, gloss, texture, and surface finish. The consistency of infrared ra- diation to enable organic coatings to perform well in the environments in which the product will be used is the function of the controllability of the radiant out- put and temperature of the emitter, as well the proper design of the system. When it is possible to match the peak output emission of the emitter to the peak absorption of the coating, high efficiency is the result. The temperature of the infrared heater can be controlled within one degree of the determined op- erating set-point. This means that day in and day out, infrared radiation can be used to accurately and precisely heat, dry, and cure modern organic coatings. Prepared as a joint effort by the sales engineering department of Casso-Solar Corp. 228

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