QDH236

QDH Series Dual Chamber Over/Under Heat Treating Furnaces 2350°F / 1875°F (1285°C / 1025°C)

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LOCKED BY SERIES
Type Dual Chamber
Power Source Electric
Loading Front
Uniformity AMS Class 4 (± 20ºF / 10ºC)
Atmosphere Air
Lining Brick

Applications

LOCKED BY SERIES

Description

The QDH Series Dual Chamber Heat Treating furnaces feature a 2350°F (1285°C) high heat chamber for hardening and a 1875°F (1025°C) recirculating chamber for preheating and/or tempering. The over/under configuration saves floor space. The tempering/preheat furnace is mounted on top with the high heat hardening furnace mounted below. Agitated and heated quench tanks are optional. The furnaces achieve high precision by featuring highly accurate controls, solid state contactors for fast cycle times, two zone control (top and bottom) on the hardening furnace, and very even spacing of elements. The preheat/tempering chamber features a powerful fan and recirculation muffle for high uniformity.


Processes


Markets

Specifications

Dimension
W
H
D
Inside
20
12
32
Working
21
15
32
External
63
96
73
Hearth
25
-
37
Hard Chamb Inside
25
21
37
Hard Chamb Work
21
15
32
Temp Chamb Muffle
20
12
32
Work Cubic Feet 5.83
* All dimensions in inches unless otherwise specified.
Power
Standard Pwr 21
High Power 27
Hard Chamb Pwr 27
Temp Chamb Pwr 21
* All power values in KW unless otherwise specified.
Weight
Ship Weight 3500
Max Load 300
* All weights in Lbs unless otherwise specified.


Additional Features

DOUBLE PIVOTED PLUG DOORS
Both doors are double pivoted horizontal doors with 1/2” refractory plugs for a superb heat lock around the door seal. The double pivoting allows the door to be opened so that the hot face stays away from the operator.
HARDENING FURNACE FEATURES CERAMIC HEARTH
The standard hearth for the hardening furnace is a 3/4” thick ceramic plate elevated on ceramic standoffs 1/2” above the bottom.
DIGITAL PID CONTROL AND HIGH LIMIT SYSTEM
The standard controls are Honeywell UDC 2500 digital PID 3 mode tuning controls. All fuses, transformers, contactors, and controls are housed in a NEMA 1 panel. Quiet, long life solid state power contactors are standard. The thermocouples on the hardening furnace are Type R while the tempering oven has Type K. Thermocouple break protection is included. Limit switches shut off power when doors are opened or the backs are removed. Control voltage is transformed to 120 volts. A NEMA 13 lighted On/Off switch is included. The control circuit and each power branch circuit are fully fused. A Honeywell UDC 1200 digital high limit back up control with manual reset, back up contactors and separate thermocouple is standard for both chambers. Customer must connect fused power supply to single point on panel.
TWO ZONES AND EVEN ELEMENT PLACEMENT
The elements of both furnaces are divided into top and bottom zones. The control output is routed through two input switches which allow adjustment of the total time on to each zone. There are thermocouples mounted in the top and bottom with a selector switch to read the temperature differential. The elements are evenly spaced on the door, back, sides and bottom for even heating. The elements are supported in proprietary high temperature ceramic element holders. These provide perfect support for the coiled element as well as excellent radiating characteristics. The smooth surface prevents premature failure of the element as it expands and contracts. Elements are iron-aluminum-chrome alloy although nickel-chrome elements are optional.
HIGH UNIFORMITY
The hardening furnace is uniform to within +/-20F(+/-10C) above 1500F (815C). The tempering oven is uniform to within +/-10F (+/-5C) above 300F (150C).
TESTING AND INSTRUCTIONS
The furnace is power tested to insure proper watt ratings. The controls are fully calibrated and the control system completely tested. A complete instruction manual includes easy start up instructions, theory of operation, maintenance instructions, parts list, general dimension drawing, general assembly and subassembly drawings where required, and a detailed trouble shooting guide. A ladder logic diagram and panel layout are prepared on CAD for easy readability.
WARRANTY
The furnace is warranted for one year except for elements and thermocouples which are warranted for six months. See warranty sheet Q12W.
FAN AND RECIRCULATION MUFFLE
The tempering/preheat furnace features a vertically mounted four bladed alloy fan. It is belt driven with a 3/4 H.P. motor. A heat dissipator protects the bearings. The removable recirculation muffle is constructed of 330 alloy. The muffle protects the work from direct radiation of the elements and creates a recirculation pattern for the air.
EFFICIENT MULTILAYERED INSULATION
Both chambers are insulated with 4-1/2” of low K factor refractory firebrick as the primary insulation. This is 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 so lid hearth support. This yields an excellent combination of strength, insulating quality and fast heat up and cool down time. All refractory is coated with a special facing that prolongs firebrick life and helps prevent spalling and dusting. The refractory sections are available completely shaped for easy replacement without cementing. All sections fit together with engineered heat locks which improve the insulating integrity of the furnace.
INTEGRATED CASE
Both chambers are mounted in one integrated 10 gauge steel case with structural stiffeners and lifting rings. The entire case is primed with 800F silicone paint and finished in machine enamel

Additional Options

AGITATED AND HEATED QUENCH TANKS
AGITATED HEATED QUENCH TANKS
ALLOY HEARTHS
Lower temperature furnaces are available with fabricated alloy hearths. These have welded sides (normally 1" high) and reinforced bottoms. 304, 330 and Inconel 601 series stainless steels are commonly used.
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.
HIGH K.W.
See specifications for amount.
HIGH K.W. FOR HARDENING CHAMBER
Available on hardening furnace only. Increases K.W. from 8.0 to 12.0 by adding another element plate on the bottom. This reduces the available working space by 2 inches.
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.
JIC CONTROL OPTION
This includes a NEMA 12 control cabinet, all oil tight switches and a panel mounted fused disconnect switch. Zone switches if included are percentage timers.
MISCELLANEOUS OPTIONS
MISC OPTIONS
SILICON CARBIDE HEARTHS
These are standard on higher temperature furnaces like the GLF and GF. They are available as an option on XLE furnaces. The optional hearths often feature molded sides. The silicon carbide hearths are normally 1-1/2" thick and are fixed in place with cemented firebrick. Silicon carbide features high strength at high temperatures, a non warping flat surface, and excellent heat transfer (which is important if there are elements under the hearth).
SINGLE ZONE SCR POWER CONTROLLER
A zero fired SCR power control with two-leg control is used instead of contactors. This is constructed with transient voltage protection, sub-cycle fuse protection, extra large heat sinks, and positive zero firing. Gain and bias adjustments are included for tuning.

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Brochure For QDH