Infrared lamps, used in an oven for about 18 years, required replacement about twice a year. Furthermore, breakage of lamps caused a cleaning and salvage problem.
Six years previous to the writing of this report, infrared lamps were removed and replaced with Chromalox electric radiant heaters for paint baking, and Chromalox electric strip heaters were installed in the temperature holding zone which follows the Radiant Heater section.
Fifteen Chromalox Type RAD-4183 Electric Radiant Heaters, 1800 watts each, are installed at the top of the oven and are angled about 45° across the conveyor. This, the baking zone, is controlled by two Chromalox Input Controllers which permit control of the heaters' input anywhere from 4 to 100°/0 of capacity in each of two zones. One Controller is used with the first six radiant heaters, the other with the next nine.
Twenty Chromalox Electric Strip Heaters, 1500 watts each, are used in the holding zone. Control here is an indicating thermostat which permits close control of the holding zone. A recirculating fan is used to obtain uniform air temperatures.
Operating temperatures are approximately 375 ° F. in the baking zone, and about 325°F. in the holding zone.
- Lower operating temperatures may be used than is the case with lamps. This is because of the intermittent cycling effect of the Input Controller by which any input from 4 to 100% of heater capacity may be used. Finishing cost per unit of production was reduced.
- Radiation can be precisely controlled to suit types of work, conveyor speed, finishes, and humidity conditions.
- Operating life of elements is longer. Little heater element replacement has been made in the six years the Chromalox Electric Radiant heaters have been used. When lamps were used, replacements were made "at least twice a year".