The FN Series Electric Box Furnaces feature extremely uniform temperature gradients over a wide temperature range, and atmosphere tight construction. Two uniformity ranges are offered:+/-10°F (+/-5°C) and +/-5°F (+/-3°C). Several important features are combined to achieve uniformity within the defined work zone. These features are uniform distribution of elements, fan circulation of furnace atmosphere, all ceramic fiber insulation, six zones of element control, SCR power control, generous extra area inside the furnace for air circulation and to keep direct radiation of elements at a minimum, and a very tight gasketed and interlocked door seal. Atmospheres may be air, inert or combustible. The uniformity specification is guaranteed from 300°F (150°C) to the maximum temperature of the furnace. The maximum temperature rating depends on the type of fan used, type of elements, and grade of insulation. Three temperature ranges are offered: 1800°F (980°C), 2000°F (1095°C), and 2200°F (1200°C). These furnaces are ideal for aviation work or any critical heat treating that requires certifiable uniformity. The design details are carefully thought out for convenience of use, service and flexibility. See just how good the uniformity of the FN Series furnace: Look at a PDF of an actual uniformity test.

HEAVY DUTY ATMOSPHERE TIGHT CASE
The case is 3/16" steel with a reinforced 3/8” base plate. Case is welded gas tight. Element connection boxes are fully gasketed. Entire case is primed with 800F silicone paint and finished in machine enamel.

EVENLY DISTRIBUTED ALLOY ELEMENTS
Coiled alloy elements are evenly distributed along the sides, back and door creating an even wall of radiation. Alloy used depends on application and temperature.

SUPER HIGH TEMPERATURE UNIFORMITY
No other series of furnaces made can maintain the strict uniformity specifications of the FN Series. Depending on options it can range form +/-10 F to +/-5F. or better. See this example of an actual nine point uniformity survey done on an FN333.

SIX OR MORE ZONES OF CONTROL
The element circuits are broken into six sor more eparate zones. One power control is used for +/-10F furnaces, although there is space in the panel to add six SCRs in the future for closer uniformity. +/-5F models are controlled with six sor more eparate SCR power controls with digital biasing for easy and repeatable adjustment of gradients. A multi-channel control can be used to put each of these zones on an independent loop of control.

CERAMIC FIBER INSULATION FEATURES FAST HEAT UP AND COOL DOWN
The entire furnace is insulated with 8” of ceramic fiber and mineral wool back up. 2600F (1425C) fiber is used for the 2200F rated furnaces and 2300F (1260C) fiber is used on all others. Standard K.W. will heat the maximum load to 1800F (980C) in 2 hours. High K.W. will do the same job in approximately 1-1/4 hours. Cool down from 1800F to 500F (260C) takes about 18 hours with an empty furnace. No asbestos is used.

CIRCULATING FANS
One or more fans circulate the furnace atmosphere and promote uniformity. Water cooled fans are used for 2000F and 2200F models.

ELECTRIC VERTICAL DOOR WITH FOUR POWERFUL PNEUMATIC CLAMPS
The standard door is a counterbalanced vertical door driven by an electric brake motor with a torque limit safety. When the door is in the full down position, four powerful pneumatic clamps pull the door closed tightly against the two independent seals and into the heat interlock. The main gasket is a wide pad of ceramic fiber which is compressed by the pneumatic clamps. This is augmented by a tadpole gasket which surrounds the outside of the door. A precision interlock between a fiber plug protruding from the door and a matching notch in the furnace case seal helps the atmosphere seal and greatly helps the heat seal. Atmosphere and heat leakage is minimal with this system.

ATMOSPHERE CONTROL
The FN furnaces are designed for controlled atmosphere use. Flow controls for inert or combustible atmosphere are available. Combustible atmosphere systems meet NFPA 86C safety standards. Mixing panels for inert gas with hydrogen or natural gas are available.

SURVEY PORT, SAMPLE PORT, PRESSURE GAUGE
There is a 1" NPT port for uniformity surveys. In addition, a separate port with a valve allows easy sampling of the atmosphere. A 0”- 1” W.C. pressure gauge reads furnace pressure.

VARIOUS HEARTHS AND LOADING SYSTEMS
A convenient loading system is shown in this brochure. It features an alloy serpentine hearth tray which is loaded into the furnace with a hydraulically operated lifting cart (also shown.) Other hearths are simple castable piers for forklift loading and roller hearths. Hearth height is 42".

DIGITAL PID CONTROL WITH SCR POWER CONTROL
The standard control is a Honeywell UDC 3300 digital PID 3 mode tuning control. All fuses, transformers, SCRS, contactors, and controls are located in a NEMA 12 floor standing panel with a panel mounted fused disconnect switch. Thermocouples are inconel sheathed Type K. The control voltage is 120 volts. A Honeywell UDC 2000 digital high limit control with manual reset, back up contactors and separate thermocouple is standard. Single point power connection. Meets National Electrical Code.

TESTING AND INSTRUCTIONS
The furnace is tested to insure proper watt ratings. Complete in house testing including full load test, uniformity test and certification to NIST standard is available. A complete instruction manual includes easy start up instructions, theory of operation, maintenance instructions, parts list, and a detailed trouble shooting guide. A ladder logic diagram, panel layout, interconnection diagram, atmosphere and pneumatic schematics, general dimension drawings, assembly and subassembly drawings are provided.

WARRANTY
The furnace is warranted for one year except for elements and thermocouples (warranted for 6 months.)

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Download PDF Brochure of FN Series Box Furnaces
(Large Precision Atmosphere Box Furnaces)

Download PDF of actual data from a 9 point uniformity survey of an FN333

Download PDF Brochure of XLE Box Furnaces

Download PDF Brochure of FB Series Box Furnaces
(Large Fiber Lined Box Furnaces)