L&L Special Furnace Co. Inc. manufactured and supplied a high-uniformity, pit-style furnace used for annealing to a manufacturer of aerospace fasteners. The annealing process occurs when the parts are evenly heated to 1400°F (760°C) and held for a predetermined amount of time. Temperature uniformity is critical to this process, and both ambient and load temperature must maintain ±10°F throughout the cycle. The fastener parts are placed in baskets and loaded by an overhead crane into the furnace. There are guide bars to ensure that the load is centered and cannot damage the furnace liner. The program or recipe is entered into the program control, and the cycle is started. At the completion of the cycle, the parts are removed and are ready for inspection and shipment.
The furnace was manufactured in accordance with the ASM 2750E pyrometry specifications. All thermocouple reference ports along with TUS survey ports and recording devices are included. A 5-HP, air-cooled turbo convection fan aids in temperature uniformity. The furnace includes Eurotherm controls and a recorder with SCR power controls. There is an audible/visual stack light and element branch indicator located on top of the control panel. The branch indicator is a visual indicator to tell that all the elements in the furnace are working correctly.