FNSeries

Atmosphere Box Furnace With Certifiable Uniformity Of +/-5°F From 300°F (150°C) To 2200°F (1200°C)


Type Large Box
Power Source Electric
Loading Front
Uniformity AMS Class 2 (± 10ºF / 6ºC)
Atmosphere Inert
Lining Ceramic Fiber

Applications

Description

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.


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Markets

Standard Model Sizes

Our most popular model sizes are listed below. Discuss a custom solution that fits your exact needs by contacting our sales team today.
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LOCKED BY MODEL
Model
#
Working Dimensions
W
H
D
Outside Dimensions
W
H
D
Std Power
(kW)
Max Load
(Lbs)
Ship Weight
(Lbs)
FN222
24
24
24
72
100
65
40 400 5500
FN223
24
24
36
72
100
77
55 600 6000
FN324
36
24
48
84
100
89
90 1200 7500
FN326
36
24
72
84
100
113
125 1800 9000
FN434
48
36
48
96
112
89
120 1600 9000
FN436
48
36
72
96
112
113
150 2400 10000
FN545
60
48
60
108
124
101
155 2500 10000
FN546
60
48
72
108
124
113
180 3000 11000
FN555
60
60
60
108
136
101
160 2500 11000
FN646
72
48
72
120
124
113
225 3600 13000
FN666
72
72
72
120
148
113
240 3600 15000

Additional Features

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.
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 3200 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 1200 digital high limit control with manual reset, back up contactors and separate thermocouple is standard. Single point power connection. Meets National Electrical Code.
SIX OR MORE ZONES OF CONTROL
The element circuits are broken into six sor more separate 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 separate 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.
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.
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.
START UP SERVICE FOR ATMOSPHERE PANEL
L&L will check out and leak test the atmosphere system, inspect the customer’s assembly of the furnace, check tightness of elements, start up equipment, tune controller, adjust SCR, instruct customer’s personnel in how to do this, train operator in the use of the control systems, review the furnace manual, test for proper operation of all components and systems and start, watch and run the bakeout cycle. This typically takes 2 to 3 days. See link for details
WARRANTY
The furnace is warranted for one year except for elements and thermocouples which are warranted for six months. See warranty sheet Q12W.
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.
CIRCULATING FANS
One or more fans circulate the furnace atmosphere and promote uniformity. Water cooled fans are used for 2000F and 2200F models.
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 86 safety standards. Mixing panels for inert gas with hydrogen or natural gas are available.
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.
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.
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.

Additional Options

ATMOSPHERE PANEL FOR NITROGEN/HYDROGEN
This creates forming gas which is slightly reactive and is better at preventing oxidation than plain inert gas. The MPH flow control panel for inert gas/hydrogen mixing is included. See the MPH Series Bulletin.
ATMOSPHERE PANEL FOR NITROGEN/NATURAL GAS
This is ideal for neutral hardening applications. The MPN flow control panel for inert gas/natural gas (or propane) mixing is included. See the MPN Series Bulletin.
CALIBRATION AND CERTIFICATION
The recorder and all controls of the furnace will be checked against a standard potentiometer that has been recalibrated and recertified to NIST (National Institute of Standards and Technology) standards within the last 6 months.
CAST ALLOY HEARTH TRAY
Cast alloy grids. Grade depends on temperature, quench severity and loading service factors.
CAST ALLOY ROLLER RAIL HEARTH
Cast alloy roller hearths and cast trays with roller wheels mounted in bottom rails are commonly used for loading of heavy loads. External roller assemblies, either fixed or movable on casters, which match the roller trays are also made.
CONTROL, RECORDER AND ELECTRICAL OPTIONS
CONTROL, RECORDER AND ELECTRICAL OPTIONS
COUNTERBALANCED VERTICAL DOORS
Manual hand crank, pneumatic or electric operation. For dual chamber furnaces available only for the top chamber.
FAN WATER COOLING SYSTEM
This is used typically when a water cooled fan or fans are employed. A manual ball valve shut off, flowmeter and regulating valve, and low flow switch are included plus hook ups for the inlet and outlet. The adjustable low flow switch alarm turns off element power and sounds an audible alarm.
FLAME CURTAIN
Automatically controlled flame curtain to reduce oxygen inrush. Requires 1 PSI natural gas pressure. (Can be specified for propane also.) Includes natural gas fed pilot light with its own regulator to prevent pressure feedback from flame curtain. Gas turns off automatically if pilot goes off. Includes electronic ignition which is activated from control panel. The flame curtain is activated when the door opens. Uses compressed air.
HEAT SHIELD
A perforated heat shield is attached to the outside of the furnace back, sides and door. This maintains a low external case temperature below 120F (50C).
HORIZONTAL DOOR
The door is a double pivoted horizontal door with thrust bearings for ease of operation. The double pivoting allows the hot face to be kept from the operator. There are four large manual turndown clamps for tight sealing. There are two overlapping gaskets for gas tightness. This door is typically used only because of overhead space limitations.
IN HOUSE RUN OFF TESTING
The furnace will be completely tested in L&L factory up to maximum temperature. A nine point uniformity survey will run at several selected temperatures. Customer will be invited to witness the test. Prior to the final test the furnace will be cured and the controls tuned. Customer may witness test.
INERT GAS PANEL
The furnace case is tightly sealed for use with a protective inert atmosphere. Argon, nitrogen and gases enriched with up to 4% combustible gas (such as hydrogen or propane) can be used. No safety systems are required. A threaded alloy fitting introduces the gas into the furnace chamber. The element connection chamber is typically purged. The door seal is augmented with a woven ceramic fiber gasket. A properly sized flowmeter/regulator is included with the atmosphere system. A rule of thumb on atmosphere usage is to figure six to ten times the furnace volume times the number of hours the work will be in the furnace.
LOADER
A heavy duty loader will pick up the hearth tray by pivoting slightly in the back by means of a hydraulic cylinder actuated by a hand pump located on the loader. The loader can have two swivel wheels and two fixed wheels. Optionally, the wheel can be mounted on either inverted "V" tracks or railroad tracks embedded in the floor. All distances are engineered for precise and trouble free operation. The loader is typically designed to pick up the maximum rated load of the furnace. The loaders can be fitted with motorized drives.
ON SITE START UP AND TRAINING
L&L will check out and leak test the atmosphere system, inspect the customer’s assembly of the furnace, check tightness of elements, start up equipment, tune controller, adjust SCR, instruct customer’s personnel in how to do this, train operator in the use of the control systems, review the furnace manual, test for proper operation of all components and systems and start, watch and run the bakeout cycle. This typically takes 2 to 3 days.
ON-SITE UNIFORMITY SURVEY
L&L will do a nine point uniformity survey on the furnace at several levels of temperature stabilization. L&L will provide the recorder, survey thermocouples and survey cage plus all labor. Case temperature can be recorded.
VARIOUS ELEMENT ALLOYS
The standard elements used are Nickel Chrome 80-20. These are good for furnaces rated to 2100F (1150C). On 2200F (1200C) furnace Iron-Aluminum-chrome alloy elements are used. On furnaces with a carbon rich atmosphere Kanthal APM alloy elements are used.

Downloads

Brochure For FN
Aerospace Brochure