Lucifer Furnaces shipped a Series 4000 recirculating heat-treating oven to a machine-parts manufacturer for stress relieving. The oven has a stainless steel liner forming the interior 12-inch x 18-inch x 24-inch chamber. The liner baffles the workload from the fan and heating elements to create a horizontal airflow of uniform heat throughout the chamber. Heating elements of coiled low-watt-density wire are held in easy-to-replace element holders located on the side walls. Precision heating is obtained with a Honeywell digital time-proportioning controller along with a digital over-temperature safety system and soak timer.

The oven is lined with multilayered lightweight firebrick and mineral-wool block insulation to maximize heat retention, and the unit is sealed with a horizontal swing door with an adjustable latch for a firm seal. This freestanding floor oven is built with heavy sheet-metal-shell construction and structural reinforcements.