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Pit Furnaces

BULLETIN
PH-770

2000°F
HEAVY DUTY
ELECTRIC AND GAS
HEAT TREATING
PIT FURNACES


 

Grieve standard 2000°F Pit Furnaces are used for a variety of heat treating applications including those requiring inert atmospheres where overhead handling equipment is used. Full opening door exposes entire work space for easy loading. Precision microprocessor based temperature controls and energy-saving insulation maximize the cost efficiency and performance of these rugged units. Nine standard models from 3 to 45 cubic feet built for long, hard, continuous use. Ideal for severe service applications - load capacities to 1200 lbs.

STANDARD FEATURES Back to Top
UL LISTED CONTROL PANEL

Standard Box Furnaces from Grieve meet the requirements of National Fire Protection Association Standard 86, Industrial Risk Insurers, Factory Mutual and OSHA standards. For some applications, such as those involving special atmospheres or hazardous locations, the above organizations require additional safety devices.

Controls
—Digital, microprocessor based, thermocouple actuated, indicating temperature
   controller
—Modulating burner on gas furnaces
—Motor control push buttons and on-off heat switch
—LED pilot lights


Safety Equipment — Electric Furnace
—Adjustable, thermocouple actuated, manual reset excess temperature interlock
—Separate heating element control contactors
Door interlock switch turns off power to heating elements when door is opened;
   restores power when door is closed


Safety
Equipment — Gas Furnace
—Adjustable, thermocouple actuated, manual reset excess temperature interlock
—Electronic flame safeguard protection
—Combustion air blower with air flow safety switch
—Purge timer
—High and low gas pressure switches
—Two pilot safety shutoff valves with leak test stations
—Two main safety shutoff valves with leak test stations (Industrial Risks Insurers vent
   valve only provided on specific request)
—Valve position indicator on main safety shutoff valves
—Over 400,000 BTU/HR safety shutoff valve interlocked with purge timer


Construction
—3/16" steel plate reinforced furnace shell
—1/2" thick steel top plate
—Brushed stainless steel control panel face
—Powered rear hinged door
—Energy-saving lightweight ceramic fiber insulation reduces operating costs
—Insulating refractory floor to support heavy loads
—Excellent temperature uniformity throughout work space
—Fast heat-up and cool-down
—1 year limited warranty


All equipment fully assembled and individually factory tested

 

   
SPECIFICATIONS Back to Top
NOT FOR USE WITH FLAMMABLE SOLVENTS, VAPORS OR GASES
Model
Work Space
Outside
Dimensions*
(WxDxH)
Height
Door
Open
Door
Type
Hearth
Rating
Lbs‡
Heat Input
Operating Characteristics†
Approx
Shipping
Weight
Dimensions
(WxDxH)
Volume
Cu Ft
KW
BTU/HR
Control
Accuracy
Furnace
Uniformity
Rise Time
230V 460V
PT-181818 18" x 18" x 18" 3.4 59" x 54" x 54" 69"   Electric 250 15 165,000 ± 0.3% ±25°F 75 min 65 min 1550 lbs
PT-181824 18" x 18" x 24" 4.5 59" x 54" x 60" 75"   Electric 300 18 200,000 ± 0.3% ±25°F 75 min 55 min 1650 lbs
PT-242424 24" x 24" x 24" 8.0 65" x 60" x 60" 81"   Electric 430 26 285,000 ± 0.3% ±25°F 60 min 45 min 2050 lbs
PT-242430 24" x 24" x 30" 10 65" x 60" x 66" 87"   Electric 500 30 330,000 ± 0.3% ±25°F 60 min 45 min 2200 lbs
PT-303030 30" x 30" x 30" 16 71" x 66" x 67" 93"   Electric 600 36 400,000 ± 0.3% ±25°F 60 min 45 min 2700 lbs
PT-303036 30" x 30" x 36" 19 71" x 66" x 73" 99"   Electric 700 39 425,000 ± 0.3% ±25°F 65 min 45 min 2900 lbs
PT-363636 36" x 36" x 36" 27 77" x 72" x 74" 106"   Air 900 52 575,000 ± 0.3% ±30°F 50 min 40 min 3500 lbs
PT-363648 36" x 36" x 48" 36 77" x 72" x 86" 118"   Air 1050 62 675,000 ± 0.3% ±30°F 50 min 40 min 3950 lbs
PT-363660 36" x 36" x 60" 45 77" x 72" x 98" 130"   Air 1200 72 800,000 ± 0.3% ±30°F 50 min 40 min 4400 lbs
*All Models—Control panel overhang 9" right side.
 Gas Models—Outside depth increases by 10".
                      Combustion blower overhang 36" rear.
†Accuracy as percent of controller span. Uniformity at 100°F below maximum temperature. Rise Time in minutes to 100°F below maximum temperature. Tests run with empty furnace. Performance will vary with load and application. See Bulletin TC-920 for additional details.
‡Uniformly distributed.
STANDARD EQUIPMENT   Back to Top
All Models
— 208 volts, 3-phase, 60 Hz
— 230 volts, 3-phase, 60 Hz
— 460 volts, 3-phase, 60 Hz
— Other electrical characteristics available


Wall insulation, 9" thick, consisting of:
— 5" of 2300°F, 8 lbs/cf of ceramic fiber blanket
— 4" of 1900°F, 4 lbs/cf of ceramic fiber blanket

Floor insulation, 6" thick, consisting of:
— 4" of 2300°F insulating castable
— 2" of 1900°F, 18-1/2 lbs/cf block insulation

Furnace shell is made of 3/16" thick steel plate reinforced with structural steel. Powered door supported at rear by heavy duty shaft and pillow block bearings. Open door exposes entire work space for easy loading. Floating door construction provides an excellent heat seal by pressing soft insulation against the 1/2" thick steel top plate. Exterior painted with Trilite Green enamel.

Each features completely wired, side access UL listed control panel assembled on the furnace enclosing terminals for incoming power, temperature controllers, push buttons and pilot lights.

Electric Models
Safety devices as listed on the top of this bulletin. Heating element contactors electrically interlocked with door to shut off power to heaters as door opens and restore power when closed. High temperature alloy wire heating elements supported in vacuum cast ceramic fiber. Heating elements located at four side walls.

Gas Models
— 1,000 BTU natural gas at 2 psig pressure;
    1" NPT inlet up to 800,000 BTU/HR;
    1-1/4" NPT 850,000 to 1,000,000 BTU/HR;
— Other gas characteristics available

Safety devices as listed on the top of this bulletin. Automatic pre-ignition purge period and push button electric ignition contributes to ease of operation. Modulating gas burners fire from opposing sides to circulate heated air through the work space. Gas burners protected with electronic flame safety relay. Door interlock switch drives main burners to low fire when door is opened and restores control when door is closed.

ELECTRIC DOOR
Door pivots upward above furnace, clearing top opening for easy loading. In the closed position, full door weight seats door firmly against furnace top plate. Structural steel pivot arms supported on furnace top plate by rugged pillow blocks connected to a heavy duty electromechanical actuator. The door is controlled by a switch at the furnace control panel.


AIR DOOR
Door pivots upward above furnace, clearing top opening for easy loading. In the closed position, full door weight seats door firmly against furnace top plate. Structural steel pivot arms supported on furnace top plate by rugged pillow blocks are connected to a large diameter air cylinder. The door is controlled by a manual air valve with supply filter, lubricator and regulator.
.


 
ADDITIONAL EQUIPMENT AVAILABLE Back to Top

See Bulletin TC-960 for modifications and other optional equipment.

Programmable Temperature Controller, microprocessor based, digital indicating, thermocouple actuated, in lieu of standard controller
Option PTC3


Recording Thermometer, thermocouple actuated, 24-hour, 10" diameter circular chart, used in conjunction with standard controller, includes floor stand to house recorder. Floor stand cannot be used for storage
Option RT



Digital Timing Temperature Controller, microprocessor based, digital indicating, incorperates 99 hour 59 minute timer. Starts timing when temperature reaches set point and shuts down oven at end of set time
Option DTS3


Digital Shut Down Timer, with continuous "hold" feature
Option SDT


Digital Batch Timer, for uniformly timing batch operations. Continuous alarm with door interlock; alarm at end of preset time period until door is opened or timer reset
Option BT


Inert Atmosphere Construction, electric only, includes continuously welded shell, inert atmosphere gas inlet and outlet, sealed terminal boxes, recirculating blower shaft seal, high temperature door gasket, optional forced cooling systems are available at additional cost
Option IAC

Inert Atmosphere Inlet Piping, with indicating flow control and manual gas valve. Specify atmosphere
Option IAIP


High Temperature Construction, 2200°F maximum operation temperature, 9" thick insulation
Option HTC

 
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