Books on Heat Treatment of Ruby-Sapphire
by Ted Themelis


Technical

Comparison features between MB50, M50 and M76 1700 GEMLAB furnaces
Description and Features
MB50-1700
M50-1700

M76-1700
Applications Heat treating ruby sapphire and other gems at temperatures between 1200oC to 1700oC Heat treating ruby sapphire and other gems at temperatures between 1200 to 1700oC Heat treating ruby sapphire and other gems at temperatures between 1200 to 1700oC
Furnace type
Box-type with vertical tube attachment, bench type
Vertical tube, top/bottom loading type, bench type
Vertical tube, top/bottom loading semi-floor type
Operating conditions Air, oxygen, oxygen-nitrogen, forming gas-nitrogen, vacuum Air, oxygen, oxygen-nitrogen, forming gas-nitrogen, vacuum Air, oxygen, oxygen-nitrogen, forming gas-nitrogen, vacuum
Max. operating temperature in air, oxygen, oxygen-nitrogen, forming gas-nitrogen
1700oC
1700oC
1700oC
Max. operating temperature in vacuum (full -muffle)
1525oC
1525oC
1525oC
Max. operating temperature in vacuum (half-muffle)
1500oC
1500oC
15700oC
Loading capacity
No muffle: 2 crucibles. Each crcucible OD=60 mm H = 95 mm, 250 cc
With muffle: 1 crucible OD = 40 mm, H=95 mm 180 cc
No muffle: 1 crucible OD = 50 mm, H=95 mm, 180 cc
With muffle: 1 crucible OD = 40 mm, H=95 mm 180cc
No muffle: 1 crucible OD=70mm, H=95mm 330 cc
With muffle: 1 crucible OD=50mm, H=95 mm)180cc
Overall dimensions
325 D) x 320 (W) x 670 (H) mm
330 (D) x 330 (W) x 675 (H) mm
800 (D) x 880 (W) x 1100 (H) mm
Net weight (installed)
38 Kgs
40 Kgs
108 Kgs
Construction (shell)
Double steel with single cooling fan
Double steel with dual cooling fans
Double steel with dual cooling fans
Heating chamber
rectangular, box-type
octagon-shape
Octagon shape
Heating elements
1800-grade MoSi2
1800-grade MoSi2
1800-grade MoSi2
Insulation
1900-grade hot-face
1900-grade throughout
1900-grade hot-face
Muffle tube
Alumina 99.6% Close one end (OD=50, H=305mm
Alumina 99.6% Close one end (OD=50, H=305mm; Alumina 99.6% Open Both ends (OD=50, H=610mm
Alumina 99.6% Close one end (OD=76, H=305mm; Alumina 99.6% Open Both ends (OD=76, H=610mm
Muffle flange covers
One set (3-part aluminum water-cooled outlets, double O-ring for OD=50mm muffle
Two sets (each set is a 3-part aluminum water-cooled outlets, double O-ring for OD=50mm muffle
Two sets (each set is a 3-part aluminum water-cooled outlets, double O-ring for OD=76mm muffle
Crucible loading modes
No muffle: Up to 2 crucibles (each 250 cc) may be placed in the heating chambers
With half-muffle: top loading
With half-muffle: bottom or top loading
With full-muffle: bottom or top loading
With half-muffle: bottom or top loading
With full-muffle: bottom or top loading
Loading mode
manual
Electric elevator with Up-Down, Stop buttons
Electric elevator with Up-Down, Stop buttons
Main temperature programmer-controller
51-segment artificial intelligence temp.program-control
51-segment artificial intelligence temp.program-contro
51-segment artificial intelligence temp.program-contro
Atmosphere control Standard item: Single gas purging is provided with flowmeter, pressure gas gauge, and ON-OFF gas valve, outlet cable
Optional item: Dual gas mixing system: Dual 65 mm flowmeters, dual one-way valves, dual gas pressure regulators, dual pressure gauges, dual valve on-off valves, outlet cables
 Standard item: Dual gas mixing system: Dual 150 mm flowmeters, dual one-way valves, dual gas pressure regulators, dual pressure gauges, dual valve on-off valves, inlet-outlet cables
Water cooling re circulator system. It is required for -muffle heating processes over 1500oC. Includes built-in pump, motor 220Vac-3 A, 2.4 gallon tank hoses, ready to be installed into the muffle flange. Optional item Optional item Standard item
Vacuum system includes: vacuum pump (3.6 m3/h, 5 Pa, 150 W), gauge, fittings and hose. Optional item Optional item Standard item
Temperature Limit controller
Not available
Not available
Single temperature set point alarm
Temperature sensor
B-type thermocouple (1 set)
B-type thermocouple (1 set)
B-type thermocouple ( 2 sets)
Power management
SCR (Silicon Control Rectifier) Controller and Trigger
SCR (Silicon Control Rectifier) - Controller and Trigger
SCR (Silicon Control Rectifier) - Controller and Trigger
Instrumentation
Main breaker, analog ammeter, analog voltmeter, digital voltmeter, on-off temp.controller switch, run pilot light, alarm-buzzer,, stop button
Main breaker, analog ammeter, analog voltmeter, on-off temp.controller switch, run pilot light, alarm-buzzer, stop button
Main breaker, analog ammeter, analog voltmeter, digital voltmeter, digital ammeter, on-off temp.controller switch, run pilot light, alarm-buzzer, start, stop button
Rated Power
1 KVA
1 KVA
2,2 KVA
Power Consumption

About 700 watts needed to maintain operating temperature at 1700oC
About 700 watts needed to maintain operating temperature at 1700oC
 about 18750 watts needed to maintain operating temperature at 1700oC
Main power
208-230 Vac, 10 A, 1-phase
208-230 Vac, 10 A, 1-phase
208-230 Vac, 20 A, 1-phase

Maintenance - Consumables
Heating elements:
 Eventually, the long-life heating elements must be replaced. The failed element can be replaced in less than 15 minutes without using special tools.
Thermocouples: The long-lasting B and 20/40 type thermocouples have life expectancy of 3,000-4,000 hours, and it is instantly replaced.
Thermocouple extension: Life expectancy may be up to 10,000 hours depending on the environment.
Technical ceramics (alumina muffle tube, crucible, dish, disks): Depending on the mode of operation, atmosphere environments, operating temperature, heat-up and cooling rate and other parameters, the technical ceramics used in the heating processes may last between 10-25 heating processes or longer. The alumina tube can be replaced in less than 20 minutes..
Average power consumption: At maximum operating furnace temperature 1700oC, steady state power consumption is about 85% of the total power (2,200 W). The furnace consumes only 1870 Watts @1700oC (very economical to operate). In Bangkok, the average cost of electric consumption is about US$5/day

Facility requirements
Electric:     208-230 Vac, 50 Hz, 1-phase fuse to 20 A (model M76, fuse for M50 and MB50 is 10 A.
Water:   A water-cooler is used to cool the O-rings of the flanges installed at the end of the alumina tube of the muffle attachment when the furnace operates over 1500oC. The water-cooler re circulates 2.5 gallons per minute at 50 psi and it is required for furnace temperature over 1500oC.
Space: Recommended floor (Model M76) or bench area (model MB50, M50) 150 cm x 150 cm max. in well-ventilated room (preferably open-space)

Installation

The furnace fully assembled and shipped without the heating elements installed. The following preparatory tasks are needed before the furnace is ready for operation:
1. Installation of the heating elements, a process that will take less than 10 minutes.
2. Plug the mains power cable to suitable electric outlet
3. Plug thermocouple(s) to corresponding thermocouple jacks;
3. Fill up with distilled water the water cooler and install the hoses to the flange(s)
4. Install copper lining to the exhaust gas port. Gas will be vented directly to the open air.
TERMS OF USE
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