Laboratory Fire Assay Electric Furnace Suitable for sample assay / cupellation assay Furnace door controlled by foot switch Essential for precious metal detection

The GWL-LBFS series 1000-degree fire assay electric furnace is presented as follows. It has a split design for the control system and the furnace chamber. The furnace lining is made of high-purity alumina via a vacuum forming process.

Applications of the fire assay electric furnace: Fire assay is a part of exploration geochemistry. Exploration geochemistry (EG) uses chemical principles for mineral exploration. Its purpose is to use chemical methods to assist in determining the geographical location of sedimentary deposits and the extension range of the discovered deposits. EG involves the analysis of the following samples: core samples, rocks, sediments, soil, glacial debris, or vegetation, etc.

Technical Parameters: GWL-LBFS Series 1400℃ High-Temperature Fire Assay Electric Furnace

As shown in the figure, the GWL-LBFS series electric furnace features a split design for the control system and furnace chamber. The furnace lining is made of vacuum-formed high-purity alumina lightweight material.

Applications of Fire Assay Electric Furnace

Fire assay is a method in exploration geochemistry that applies geochemical principles to mineral exploration. Its purpose is to help locate sedimentary ore deposits and determine the extension range of discovered deposits through chemical analysis. It is applicable to the analysis of samples such as core, rock, river sediment, soil, glacial debris, and vegetation.

Main Operating Steps

Sampling:Samples include minerals, refined products, and debris. Representative samples must be collected carefully. Since precious metals often exist in an irregularly dispersed state in minerals, a large amount of minerals is usually required to obtain a representative sample, which is then finely ground.
Sample Melting:Appropriate fluxes (e.g., crushed sodium carbonate, borax, silicate, lead monoxide) are added to the sample, followed by heating to melt the sample and fluxes. Lead monoxide is reduced to metallic lead, which sinks to the bottom of the container together with precious metals, forming a metal bead containing precious metals, a large amount of lead, and other metal impurities. The resulting slag from the reaction is discarded.
Cupellation Assay:The metal bead containing precious metals and lead is placed in a cupel made of unglazed porcelain, and the cupel is then heated in a specially designed GWDL electric furnace that provides a strong oxidizing atmosphere. At this stage, lead and other metal impurities in the bead are oxidized; the resulting lead oxide and other metal oxides form slag or penetrate into the pores of the cupel. Only gold and silver remain unoxidized in metallic form, separated from lead and other metal oxides. The cupel is removed from the GWDL furnace, cooled slowly, and the obtained bead is cleaned and dried—either used directly as a sample or hammered/rolled into a thin sheet.
Weighing:The total weight of gold and silver is determined by weighing the sample containing gold and silver.
Separation of Gold and Silver:The sample containing gold and silver is treated with hot dilute nitric acid to dissolve silver.
Weighing Again:The gold-only residue (after silver removal) is cleaned, dried, and weighed to determine the weight of gold.

Control and Performance

Control Panel:Equipped with an intelligent temperature regulator, control power switch, main heating on/off buttons, voltage/current meters, and a computer interface for real-time monitoring of the system status.
Electrical and Safety Features:Adopts reliable integrated circuits, ensuring a stable working environment and strong anti-interference capability. The outer shell temperature of the furnace body is ≤45℃ even at the maximum temperature, significantly improving the working environment.
Temperature ControlT;emperature Control Accuracy: ±1℃ (no overshoot):Constant Temperature Accuracy: ±1℃:Heating Rate: Fast heating, with a maximum rate of ≤45℃/min:Controlled by a microcomputer program, supporting programmable temperature curves and fully automatic heating/cooling. Temperature parameters and programs can be modified during operation, ensuring flexibility, convenience, and ease of use.
Furnace Lining:Made entirely of vacuum-formed high-purity alumina lightweight material, featuring high service temperature, low heat storage, resistance to rapid heating/cooling (no cracking or slag falling), and excellent thermal insulation (energy-saving effect is over 60% compared to traditional electric furnaces).
Structure:Reasonable design with inner and outer double-layer furnace sleeves and air-cooled heat dissipation, greatly shortening the test cycle.

Temperature	1400℃
Maximum Operating Temperature	1400℃
Long-term Operating Temperature	1350℃
Control Range	80 to 1400℃
Temperature Measuring Element	Platinum-rhodium S thermocouple, measuring range 0-1600℃
Installation Position of Heating Elements	Vertically installed on both sides of the inner wall of the furnace chamber
Temperature Control Precision	±1℃ (integrated circuit control, no overshoot phenomenon)
Furnace Temperature Uniformity	±1℃ (depending on the size of the furnace chamber; multi-point control can be adopted for large furnace chambers to achieve better temperature uniformity)
Heating Rate	Freely adjustable, with a range of 1℃/h (slowest) to 30℃/min (fastest)
Heating Elements	Silicon carbide rods (U-type equal-diameter). Silicon carbide rods are non-metallic high-temperature electric heating elements made of high-purity a-SiC as the main raw material. They feature fast heating, high thermal efficiency, long service life, no easy deformation at high temperatures, easy installation/operation/maintenance, and a maximum temperature of 1500℃.
Furnace Body	Processed by CNC machine tools, through polishing, grinding, pickling, phosphating, plastic powder spraying, and high-temperature baking. It adopts a two-color design with a novel and beautiful appearance, and has advantages such as oxidation resistance, acid and alkali resistance, corrosion resistance, high-temperature resistance, and easy cleaning.
Furnace Body Structure	Air-cooled double-layer structure. Effective air-cooled guide partitions enable overall cold air circulation in the furnace shell, which cools the conductive sheets of heating elements before being discharged, avoiding high-temperature oxidation of conductive sheets and ensuring a good working environment.
Furnace Door Opening Method	Electric-pneumatic top-opening, controlled by a foot switch to adjust the opening and closing height
Sampling Tongs	310S stainless steel
Furnace Loading Cart	310S stainless steel
Melting Mold	Cast iron
Refractory Materials	The furnace lining is made of vacuum-formed high-purity alumina lightweight materials. Easily collision and load-bearing positions (furnace mouth, furnace bottom) use lightweight hollow sphere alumina plates, featuring high operating temperature, low heat storage, resistance to rapid heating/cooling, no cracks, no slag dropping, and good insulation performance (energy-saving effect is over 80% compared with old-style electric furnaces).
Insulation Materials	Three-layer insulation: aluminosilicate fiberboard, alumina fiberboard, and alumina (polycrystalline) fiberboard. The energy-saving effect is over 80% compared with old-style electric furnaces.
Furnace Shell Temperature	≤45℃ during long-term continuous operation
Protection	Adopts integrated module control unit with accurate control precision, designed with dual-loop control and protection, featuring overshoot, undershoot, thermocouple break, phase loss, overvoltage, overcurrent, overtemperature, current feedback, and soft start protection.
Control Method	Uses closed-loop thyristor module trigger control (phase-shift trigger or zero-crossing trigger mode). Output voltage, current, or power is continuously adjustable with constant voltage, current, or power characteristics. The current loop is the inner loop and the voltage loop is the outer loop. When the load is suddenly applied or exceeds the current limit, the output current is limited within the rated range to protect heating elements from excessive current/voltage impact, ensuring safe and reliable control effect and precision.
Display Parameters	Real-time temperature, temperature segment number, segment time, remaining time, output power percentage, voltage, current, etc.
Temperature Curve Setting	Adopts intelligent temperature controller with multiple regulation modes (standard PID, artificial intelligence adjustment APID, MPT, etc.), featuring self-tuning and self-learning functions, no overshoot/undershoot, and 30-segment program control. It supports arbitrary slope heating/cooling control, with programmable commands (jump/cycle, run, pause, stop) and allows in-operation program modification. Equipped with AI adjustment algorithm with curve fitting function for smooth curve control.
Multiple Curve Input	30-segment program control (50 segments customizable): 30 (50) segments for one curve, 14 (28) segments each for two curves, 9 (15) segments each for three curves, 5 (9) segments each for five curves. Multiple curves can be input simultaneously and called arbitrarily.
Communication Interface	Equipped with RS485 interface with a communication distance of up to 1200 meters. It supports computer control for starting, pausing, stopping, setting/reading heating curves, and parameter adjustment. The computer display shows rich content (measured value, set value, output value, segment time, segment number, heating curve, power percentage curve). Heating curves can be stored in the computer, called arbitrarily, and modified. Historical curves and reports can be saved for a long time with selectable time intervals (1s-1h).
Random Accessories	2 heating elements, 2 sets of rod tools, 1 pair of crucible tongs, 1 pair of high-temperature gloves
Warranty Scope and Period	The electric furnace is covered by a 1-year free warranty; heating elements are not covered (free replacement for natural damage within three months)
Packing List	1 electric furnace, 2 heating elements, 2 sets of rod tools, 1 pair of high-temperature gloves, 1 instruction manual, 1 certificate of conformity, 1 acceptance report (factory inspection report), 1 sales delivery note
Shipping Information	1. Three-layer packaging: sponge paper wrapping → plastic film wrapping → wooden case.
	2. Free door-to-door delivery within domestic urban areas.
	3. We are responsible for any transportation damage.
	4. Logistics methods: domestic - truck; short distance - company-owned vehicles (packaged with wooden pallets + cartons); export - railway, ship, air.

Additional Equipment

Lift door：Pneumatic door opening, controlled by foot pedal, with hot surface facing away from the operator.
Touchscreen: Multilingual menu, multiple temperature rise process curve storage, historical curve storage, and data reports (7 inches).
Computer Control: Controls furnace start, pause, stop, stores historical curves, sets temperature rise curves, reads temperature rise curves, sets parameters, etc.
Siemens PLC Control: Real-time data reading with open ports for data communication with upstream and downstream equipment.
Manual or automatic gas supply system
Observation Window: Designed on the furnace door with high-temperature-resistant quartz glass.
Movable Casters: Two swivel casters and two fixed casters.
Rapid Cooling: Achieved with a frequency inverter and centrifugal fan for programmable cooling control.
Quick Discharge Rack: The material rack is made of high-temperature steel, with wear-resistant heavy-duty refractory bricks on the top, enabling rapid
transfer of materials from the furnace to an external platform in high-temperature environments.
Multi-Point Temperature Control: Independent temperature control on multiple sides for improved temperature uniformity.
High temperature furnace chamber with multi-sided heating for very good temperature uniformity.
Stirring Fan: Metal stirring fan, can be linked with PLC to automatically start at designated temperature segments.
Independent Control Cabinet: Separate control cabinet with an extended control cable length (up to 5 meters).
Heat Storage Furnace Bottom: The furnace bottom sinks 50mm with a hollow design, supported by multiple vertical columns, increasing Ceramic Load-Bearing Plate and ensuring uniform heat distribution at the bottom.
Exhaust Gas Treatment: Adds VOC exhaust gas treatment furnace with a capacity of 40m³/H or 80m³/H.
Corrosion-Resistant Furnace Lining: Furnace lining material resistant to acids, alkalis, and hydrofluoric acid corrosion.
Heating Element Protection: Prevents contamination from powder and corrosion from volatile substances and scratch.
Clean Furnace Lining: Furnace lining made of ceramics, high-temperature glass, and high-temperature metals to prevent dust and volatile substances.
Over-temperature limiter with adjustable cutout temperature as temperature limiter to protect the furnace and load
Customizable charging racks according to requirements, for loading the furnace in two levels.

Fire Assay Electric Furnace