Thermcraft Inc. received an order for a large gas-fired car-bottom furnace from a U.S.-based manufacturer of CNC machining centers. The furnace will be used for stress relieving machining-center frames and has an internal chamber size of 8 feet high x 13 feet wide x 34 feet deep. The overall footprint of 13 feet high x 17 feet wide x 72 feet deep includes the space required for unloading the car bottom. Heat is provided by 16 direct-fired burners, eight down each side of the furnace, for a total of 8 million BTUs. The motorized car bottom will have a firebrick hearth capable of supporting a maximum load of 50,000 pounds. Lightweight ceramic-fiber insulation will line the walls and roof of the unit, which has a maximum operating temperature of 1500°F (816°C) and a normal operating temperature of 1125°F (607°C). A two-zone control system will be used to maintain the desired temperature, and an independent over-temperature controller will ensure that the furnace does not self-destruct in the event of a malfunction.