The GHH SERIES Ultra High Temperature Front Loading Box Furnaces feature a unique lightweight ultra high temperature ceramic fiber insulation system for fast heat up and low BTU input requirements. The GHH series achieves 3100°F (1700°C) under continuous operation. The insulation system, which is the most fragile and difficult aspect of this type of furnace, is uncompromised in quality and detail. It is guaranteed for one full year, unlike much of the competition where you can expect insulation failure fairly quickly.
The horizontally opening door features a deep plug type seal with triple heat locks. Two pivots, one on the left and one in the center of the door, insure very tight sealing. A vestibule around the door opening further reduces heat loss and helps protect the elements.
ALUMINA HEARTH SUPPORTED FROM COLD FACE
The hearth is a series of flat alumina plates supported by a series of insulating alumina posts which transfer the weight of the hearth all the way to the bottom of the cold face of the bottom insulation.
PID DIGITAL CONTROL , HIGH LIMIT CONTROL AND SCR POWER CONTROL
The standard control used is a Honeywell UDC 2500 digital PID 3 mode tuning control. All fuses, transformers, contactors, and controls are located in a NEMA 1 panel. A matched transformer and phase angle fired SCR controls power to the elements. This insures even, precise control and long element life. The thermocouples are Type B. The control voltage is 120 volts. A NEMA 13 lighted On/Off switch and NEMA 13 door power cut off switch are included. A Honeywell UDC 1200 digital high limit back up control with manual reset, back up contactors and separate thermocouple is standard. Customer must connect fused power supply to single point on panel.
TEMPERATURE UNIFORMITY OF +/-10C ( +/-20F)
Uniformity of +/-10C (+/-20F) is normal above 1200C (2200F) within 2/3 of the working dimensions.
TESTING AND INSTRUCTIONS
The furnace is tested to insure circuit integrity. 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 and panel layout are prepared on CAD for easy readability.
The furnace is warranted for one year except for elements and thermocouples which are warranted for six months. See warranty sheet Q12W.
FAST HEAT UP:
Heats up to 2100 Deg F in less than one hour at 240 volts, less than 2-1/2 hours at 208 volts.
MULTILAYERED, EFFICIENT, HIGH ALUMINA CERAMIC FIBER INSULATION
The furnace is insulated with multi-layered high alumina and alumina-silicate ceramic fiber board. The hot face is prefired high alumina board by Zircar, Rath or other highly reputable insulation manufacturer. The insulation is segmented and supported by a series of splines, alumina rods and sapphire clips. This is the most critical part of the furnace design in terms of longevity. Triple heat locks are designed into the system for extra protection at high temperatures. A vestibule protects the molybdenum disilicide elements, and prevents excessive heat loss when the front door is opened. No asbestos is used.
MOLYBDENUM DISILICIDE ELEMENTS
The elements are molybdenum disilicide 3300C grade U-shaped elements. These will withstand (3275F) 1800C in air. All electrical connections are at the top, and the elements are suspended from the roof. The electrical resistivity of these elements remains constant over time with little aging. This allows replacement of one element without changing all elements, a distinct advantage over silicon carbide elements. Low watt density is designed into the elements for maximum element life. All aluminum element connection hardware is used to prevent galvanic corrosion.
DOUBLE WALL CASE CONSTRUCTION
The insulation module has its own rigid refractory board exterior. This insulation module is inserted into a ventilated steel casing leaving an air space between the exterior case and the insulation module. This allows for cooling of the insulation, important in long insulation life, and helps maintain a cool external case temperature. Larger furnaces feature integral cooling fans to insure good cold face strength of the insulation. The two smallest sizes are bench mounted while all others are floor mounted. The case is primed with 800F silicone paint and finished in machine enamel.
CONTROL, RECORDER AND ELECTRICAL OPTIONS
CONTROL, RECORDER AND ELECTRICAL OPTIONS
INERT ATMOSPHERE CONTROL FOR FURNACES WITH MOLYBDENUM DISILICIDE ELEMENTS
The GHH furnaces can be fitted for use with inert or combustible atmospheres. This is accomplished by having a secondary atmosphere casing that contains the insulation module. This casing has its own gasketed door. Inlet of the atmosphere is through the element connection chamber to maintain cool element connections. A completely piped flowmeter and regulator with ball valve, pressure gauge and pressure relief valve is included. Complete safety systems for use with combustible atmospheres are available . Maximum furnace use temperature is limited to 1600C (2910F) in nitrogen, argon or helium, to 1300C (2370F) in dry hydrogen, 1400C (2550F) in moist hydrogen (15C/60F dew point), 1350C (2460F) in endogas, and 1600C (2910F) in exogas.
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.