FAST HEAT UP & COOL DOWN
An empty furnace will heat up to 2000F (1093C) in approximately 1-1/2 hours.
The high K.W. (superpower) option will trim this to 1 hour. Cool down to 500F (260C) is
approximately 5 hours. Optional 300 or 600 CFM venturi will speed cooling.
The furnace is uniform to within +/-20F (+/-10C) above 1400F (760C) within
the Uniform Working Dimension (see specification chart). Optional fan systems are
available for tighter uniformity of up to +/-5F.Tighter uniformity is also achieved by
reducing the working dimensions and with multi-zoning.
TEMPERATURES TO 2350F
With optional nickel-chrome elements the maximum temperature is 2100F(1134C.)
Some options such as fans and other alloy components may also limit the temperature.
|PRESHAPED BRICK SECTIONS SAVE ON HEAT LOSS AND MAINTENANCE COSTS
The refractory is cemented in sections on a very flat table. These sections
are then precision cut and routed. All sections fit together with engineered heat locks
which improve the insulating integrity of the furnace even after many years of service.
Brick sections can easily be installed by in-house maintenance personnel saving on
expensive specialized bricklayer labor.
EFFICIENT MULTILAYERED INSULATION
The furnace is insulated with 4-1/2 of low K factor refractory
firebrick backed up by 2 of very low K factor mineral wool board on all surfaces
except the bottom which has 2 of hard calcium silicate back up for solid hearth
support. This yields an excellent combination of strength, insulating quality, and fast
heat up and cool down times. The roof of all models which are 24 wide or above is
made from 2600F ceramic fiber modules to prevent roof failure.
LOW WATT DENSITY ELEMENTS FOR LONG LIFE
The standard elements are coiled from high grade iron-aluminum-chrome alloy
(Kanthal A-1 or the equivalent). Nickel-chrome (80-20), Chromel AA, and other alloys are
available for special atmospheres and applications. A watt density normally below 10 watts
per square inch maximizes element life. (Watt density is the ratio of watts to square
inches of radiating surface area.)
EVEN ELEMENT PLACEMENT
Each element is separately and evenly spaced on the bottom, sides, door and
back. This is the finest method of distributing radiant heat energy at high temperatures.
|CERAMIC ELEMENT HOLDERS
The elements are supported in proprietary high temperature ceramic element
holders. These provide perfect support for the coiled element and excellent radiating
characteristics. The smooth surface of the holder prevents premature failure of the
element as it expands and contracts. These holders, coupled with a unique all ceramic
element terminal, make element replacement easy. Being recessed into the wall of the
furnace these elements are not as susceptible to mechanical damage as some other types of
element support systems.
HEAVY DUTY CASE WITH INTEGRATED STAND
The furnace case is constructed of 10 gauge steel with external bracing
angles welded to the entire case and base assembly. Leveling bolts, anchoring holes and
lifting rings are included. The main seams are continuously welded for an attractive
appearance. The entire case is primed inside and out with a high temperature (800F)
silicone based paint. The final coat is a heat resistant light gray-green enamel. Custom
colors are available. Sealed cases for controlled atmosphere use are optional.
|DOUBLE PIVOTED PLUG DOOR
The standard door is a double pivoted horizontal plug door. The double
pivoting allows the door to open like a parallelogram which keeps the hot face from the
operator. There are two heavy duty clamps for tight sealing. Because of the completely
horizontal motion of the door as it is sealing there is no wear on the seal face. The door
has a 3/4 refractory plug which protrudes into the furnace chamber and provides a
highly effective heat lock. There is a 3-1/2 refractory to refractory seal around
the perimeter of the door. Counterbalanced vertical doors with hand crank, pneumatic or
electric actuator are options. Vertical doors lift away from the furnace seal before
lifting up. They also include a heat locking plug.
|CERAMIC ELEMENT TERMINALS
Unique L&L designed all ceramic element terminal blocks allow the element
ends to be clamped without twisting the whole end around a terminal bolt, making it easy
to remove an element. The connection wires can be easily removed without disturbing the
element termination (which allows you to easily isolate an element for a resistance
check.) The terminal block features superb electrical isolation characteristics.
A WIDE VARIETY OF HEARTHS
The standard hearth is one or more 3/4 thick ceramic plates elevated on
ceramic blocks 1-1/2 above the bottom elements. This air space improves uniformity.
Silicon carbide plates, alloy plates, roller hearths, baskets, racks, loaders, castable
piers, air cooling tables and many other loading options are available.
SIDE MOUNTED CONTROL PANEL WITH HINGED DOOR HOLDS ALL COMPONENTS
All temperature controls, relays, contactors, power controls, switches,
transformers and fuses are located in a side mounted NEMA 1 control panel with a gasketed
hinged door. J.I.C. wire coding is used throughout. An oil tight NEMA 13 lighted on/off
push -button switch turns the furnace on. Controls are mounted at eye level for easy
visibility. A NEMA 12 panel with fused disconnect switch is optional. A cooling fan is
included with SCR power controls.
DIGITAL HONEYWELL UDC 2000 PID TEMPERATURE CONTROL
A Honeywell UDC 2000 microprocessor based digital single set point control is
standard. Two full vacuum fluorescent displays include English language programming
information for easy set up. This is one of the easiest digital controls to operate.
Accuracy is .25% of scale. All PID tuning constants (proportioning band, reset, rate) plus
maximum temperature, scale range, thermocouple type and many other parameters are
programmable. Ramp/Soak programming is optional. Many other controls are optionally
DIGITAL HIGH LIMIT CONTROL
A Honeywell UDC 2000 digital high limit control, complete with back up
contactors and separate thermocouple, shuts off furnace if temperature or power control
fail. The digital control allows a maximum temperature to be programmed into the control.
MERCURY CONTACTORS FEATURE FAST CYCLE TIME FOR ACCURATE CONTROL
Other benefits are long contactor life and quiet operation. SCR power
controls are optional.
TWO ZONE CONTROL FOR CLOSE GRADIENTS
The elements are divided into top and bottom zones. The control output is
routed through two input switches to allow adjustment of the total time on to each zone.
There are thermocouples mounted top and bottom with a selector switch to read the
differential. Special designs with up to six zones or more can be used to promote even
greater temperature uniformity.
TYPE K THERMOCOUPLES WITH SHIELDED EXTENSION WIRE
Type K open thermocouples are standard. All thermocouple lead wire is
shielded from electrical noise and grounded to a common ground. Lead wires are carefully
run to avoid interference from power wiring. Inconel sheathed Type K are a commonly
supplied option. Type R and Type S platinum thermocouples are also optional.
MANY SAFETY FEATURES
Thermocouple break protection is included. Limit switches shut off power to
furnace if the door is opened or the power panel back is removed. Control voltage is
transformed to 120 volts. The control and branch power circuits are fully fused.
BUILT IN RELIABILITY
The furnace is warranted for one year except for the elements and
thermocouples (six months.) The control system is burnt in and calibrated at actual
operating temperatures in a test furnace and a recording of this test is provided. As a
result of having made a large number of these furnaces, the engineering thought and detail
devoted to this series is extensive. L&L has paid great attention to small details,
interchangeable parts, serviceability, reliability, adjustments, documentation and
instructions . The design has continuously evolved over 40 years.
EXTENSIVE INSTRUCTIONS AND DOCUMENTATION
Along with the informative J.I.C. wiring diagram, which includes a sequence
of operations and a ladder diagram (for easy troubleshooting), there is an extensively
detailed instruction book with a general dimension and assembly drawing, start up,
installation, operation, maintenance and troubleshooting information.
Although these furnaces are designed for easy in-house start up and
maintenance, worldwide factory service and start up assistance is available.
- CONTROL, RECORDER AND ELECTRICAL OPTIONS
- VERTICAL DOORS: Counterbalanced with hand crank, electric gear
drive or pneumatic operator.
- SCR POWER CONTROLS: Single and multi-zone with biasing.
- NEMA 12 CONTROL PANEL: With fused disconnect switch.
- SPECIAL HEARTHS: Silicon Carbide and alloy, baskets, racks,
roller hearths, special loading devices.
- VIEWING PORTS
- VENTS AND VENTURIS: Manual or pneumatic dampers, 300 and 600 CFM
venturis for fast cooling.
- FANS: Various fans for temperatures up to 2200oF for high
uniformity and atmosphere distribution.
- ATMOSPHERE CONTROL: Case is sealed for inert or combustible
atmospheres. One option is nitrogen spiked with propane for high decarburization
resistance. Alloy retorts for low dew point operation. Atmosphere control systems with
safety systems to meet NFPA 86C.