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Gemlab Mini Muffle Furnace (Model M50-N-1700)

Gemlab's M50-N-1700 ("MINI MUFFLE") vertical muffle furnace is designed by Ted Themelis in response to the market demand for mini-size, desk-top, high temperature reliable furnace. Model M50-N-1700 is the smallest possible vertical muffle furnace can be engineered which rubies-sapphires can be easily loaded-unloaded into/from the heating chamber via mechanical elevator (electric elevator is optional).. The furnace is able to heat-treat about 1,500 carats of rubies-sapphires at temperatures between 1200oC to 1700oC under various heating configurations (modes). The furnace is equipped with a alumina 99.96% tube OD=50 mm, L=280 mm facilitating desirable atmosphere conditions selected by the operator (reducing, oxidizing, or vacuum) with or without using chemical additives. The furnace may be used without the muffle tube attachment to increase loading capacity.

Model M50-N-1700

Features & specifications

	Bench-top, only 400 (D) x 400 (W) x 980 (H) mm
	Net weight is only 55 kgs
	Max. operating temperature is 1700oC; best performance 1200oC-1700oC (air); 1200oC-1500oC (vacuum)
	Loading capacity: 850 carats of ruby-sapphire using a muffle, or 1100 carats without muffle
	Double steel shell design with dual cooling air fans
	Single gas purging apparatus (standard). Full atmosphere control arratauts (optional)
	Vacuum pump with valve and vacuum gauge (optional)
	Molybdenum desilicide 1800-grade elements
	Single program, auto tune, 51-step, artificial intelligent temperature programmer/controller with exceptional accuracy and easy operation
	SCR (Silicon Control Rectifier)
	Long life Platinum/Rhodium “B” type thermocouple
	Highest energy fiber-board 1900-grade insulation
	Analog voltmeter, ammeter, on-off switch, alarm-buzzer
	Electric elevator control (UP, DOWN) for slow/rapid loading-unloading
	Power: 1.5 KVA, plugs to any 220 Vac 10 A (1 phase)
	Very low power consumption, less than 900 watts needed to maintain operating temp. at 1700oC
	Safe and easy operation
	Long-lasting performance
	Delivery 6-8 weeks, FOB Bangkok
	One year warranty on all electric, electronic parts
	One year warranty on all electric, electronic parts
	Price US$8,550 FOB Bangkok., Thailand

Different modes of loading the crucible to heat-treat your gems (Model M50-N-1700)

Heating with Half Muffle Tube
The heating processes are performed using the ceramic half-muffle tube, COE (Close-One-End), OD=50 mm, L=280 mm fastened hermetcally and securely to the metal flange cover. In this mode, gases can be introduced in an open loop configuration providing controllable atmosphere conditions with positive pressure up tp 1800oC), or in vacuum up to 1500oC. The crucible is loaded in the chambers from the top or bottom using mechanical elevator (electric elevator is optional).

Heating without Muffle Tube
By removing the ceramic muffle tube attachment and inserting suitable ceramic plugs, the furnace is converted to a bottom or top-loaded furnace allowing to increase the loading capacity, up to 30% to be heated. The crucible is loaded in the chambers from the top or bottom using mechanical elevator (electric elevator is optional).

GLIMPSES & FEATURES

Model M50-N-1700 can reach 1700oC without the use of water cooling re-circulation to keep the muffle flanges below 90oC ; though this operation is workable for short soaking periods of time, normally water cooling is required for temperatures above 1300oC.

Control console of model M50-N-1700 shows PV (Process Value) and SV (Set Value) in complete agreement at 1700oC; Pilot light shows the furnace is in RUN mode, LED bar indicator of the temp. programmer- controller is about 65%, still 35% power available. Output voltage is 14 Vac and Current about 60 Amps, thus the power is about 840 Watts.

A unique feature of the M50-1700 furnace is the ability to load small quantities of ruby-sapphire in each of the 6 alumina (99.6% purity) dishes which are inserted into the crucible. If muffle is used, then one crucible OD=40mm is utilized where up to 6 small dishes (OD=30mm) may be fitted; each of these dishes hold about 60 carats of rubies-sapphires. Under this mode, stones from different localities, or stones with different features may be heated together on the same time, under the same heating parameters without been mixed or contaminated each other. Likewise, fluxed and unfluxed stones may be placed in different dishes. Loading these stones in this method is particularly useful in research heating projects where contamination must be avoided and precision is required.

STANDARD EQUIPMENT FOR MODEL M50-N-1700
	One set (3 ps) of 1800-grade MoSi2 heating elements. Maximum element temperature in air is 1810oC. Furnace temperature is 1700oC
	1 pc. long life B-type thermocouple and thermocouple extension assembly.
	Flangles for muffle: Two sets of water-cooling metal flanges (each set consists of a 3-part metal assembly, and 2 pcs of O-rings) for sealing hermetically the muffle ceramic tube at the top; one set seals the muffle tube at bottom, the other at the bottom.
	Technical ceramics (alumina 99.6% purity): Crucibles:- 1 pc. crucible: OD=40 mm, L=95mm, V=150 cc net; load is ~700 cts of ruby-sapphire) - 6 pcs dishes: OD=30 mm, H=16 mm, V= 7 cc net; load is ~50-60 cts of ruby-sapphire - 1 pc. alumina disk (OD=40 mm, d=3 mm) Tube for half-muffle: 1 pc tube Close One End, OD=50 mm, L=305 mm
	Refractories (alumina 99.6% purity: 1 pc. plug sealing the roof (of the floor) of the heating chamber, 1 pc. filler assembly
	Main temperature programmer-controller: Single program, auto tune, 51-segment artificial intelligence temp. programmer-controller
	Atmosphere control. Allows to purge one selected pre-mixed gas into the muffle via the flange assembly. The following includes: One 65 mm flow flow-tube, one pressure gauge, one on-off valve, fitting for gas input; It is mounted to the left side of the furnace frame.

OPTIONAL EQUIPMENT FOR MODEL M50-N-1700
	Vacuum package: 1 pc pump (3.6 m3/h, 5 Pa, 150 W), 1 pc vacuum gauge, fittings and vacuum hose. The vacuum assembly is used in conjunction with the half or full muffle tube.
	Water re-circulator unit: 1 set and related hoses fitted to the flange assembly which seals the ceramic muffle tube. The water reciculating unit is used on special heating processes where the soaking is performed for extended periods or time (weeks, months); up to 4 Gelab furnaces may utilize the same water recirculation unit. 220Vac, 5 A, sinle phase.
	Control buttons (UP, DOWN) are used to load or unload the crucible from the heating chambers at desirable speeds. Rapid removal of the crucible is desired feature to prevent re-re-crystallization of rutile when heating rubies, sapphires from soaking temperatures above 1650oC to 1250oC in about 20 minutes.
	Full atmosphere control. Includes the following: two 65 mm flow flow-tubes, two pressure gauges, two pcs on-off valves, two pcs one-way gas valves for purging directly into the muffle selected gas ( nitrogen, oxygen), or any mixture of nitrogen-oxygen, or selected mixture of forming gas (hydro-nitro) for fully controllable atmosphere conditions to max.1700oC. It can be used with half-muffle or with full-muffle tube.

Consumables and life expectancy of the parts

ELECTRICITY	Electricity consumption depends on many factors. On a typical heating process the furnace requires less than 900 Watts to maintain 1700oC furnace soaking temperature for several hours.
MUFFLE TUBE	A typical muffle tube lasts usually 12-15 runs if properly sealed at soaking furnace temperature about 1625oC in air; life expectancy is reduced proportionally as the furnace temperature is increased; 8-10 runs in vacuum at 1500oC for 2 hours
CRUCIBLE AND OTHER TECHNICAL CERAMICS	The life expectancy of technical ceramics (crucibles, disk, dish) depends on many factors (heating up rate, cooling down rate, soaking temperature, time are soaking temperature, type of fluxes and other additives is used. Technical ceramics usually last 10-12 runs at soaking 1700oC for several hours.
THERMOCOUPLE	B-type thermocouple assembly lasts over 200 runs at 1700oC furnace temperature.
HEATING ELEMENTS	The life expectancy of the heating elements depends on many factors which should be carefully considered. No guarantee is given by any heating element manufacturer around the world on the integrity of the heating elements. However, experience shows that more than 20 heating runs may be performed at 1700oC soaking time 10-70 hours/run before an element breaks or damaged. Generally, the estimated life expectancy for each element is about 1,500-1600 hours. If an element breaks is should be replaced without requiring to change all the other elements in the furnace.

Comparison features between all Gemlab models