I. Classification of Muffle Furnaces
Muffle furnaces are classified according to their heating elements, operating temperature, controller, and insulation materials as follows:
1. By heating element: electric wire muffle furnace, silicon carbide rod muffle furnace, silicon molybdenum rod muffle furnace;
2. By operating temperature: generally divided into: box-type muffle furnaces below 1000°C, 1100°C~1300°C muffle furnaces (silicon carbide rod muffle furnaces), and silicon molybdenum rod muffle furnaces for temperatures above 1600°C;
3. By controller: PID control muffle furnace (SCR digital display temperature controller), program control muffle furnace (computer time-temperature program controller);
4. By insulation material: ordinary refractory brick muffle furnace and ceramic fiber muffle furnace.
II. Maintenance
1. When using the muffle furnace for the first time or after a long period of disuse, it must be preheated. The preheating time should be four hours at 200°C to 600°C. During use, the furnace temperature must not exceed the rated temperature to avoid burning out the heating elements. It is forbidden to pour various liquids and easily soluble metals into the furnace. The muffle furnace is best operated at a temperature 50°C below the maximum temperature, as this will extend the life of the heating elements.
2. The muffle furnace and controller must be operated in a place where the relative humidity does not exceed 85%, and there is no conductive dust, explosive gases, or corrosive gases. When heating metal materials containing grease, a large amount of volatile gas will affect and corrode the surface of the heating elements, causing damage and shortening their lifespan. Therefore, precautions should be taken to prevent this during heating, such as using sealed containers or providing appropriate ventilation.
3. The muffle furnace controller should be used within an ambient temperature range of 0-40°C. 4. According to technical requirements, regularly check that all connections of the electric furnace and controller are properly connected. The thermocouples connected to the controller may cause interference, resulting in phenomena such as fluctuating readings on the controller display and increased measurement errors. This phenomenon becomes more pronounced at higher furnace temperatures. Therefore, it is essential to properly ground the metal protective tube (housing) of the thermocouple. If necessary, use a three-wire output thermocouple. In short, all effective measures should be taken to reduce interference.
5. Do not suddenly pull out the thermocouple at high temperatures to prevent the outer casing from cracking.
6. Keep the furnace chamber clean at all times and promptly remove oxides and other substances from the furnace.
7. During use, when melting samples with alkaline substances or calcining precipitates, the operating conditions should be strictly controlled. It is best to lay a layer of refractory plate at the bottom of the furnace to prevent corrosion of the furnace chamber.
III. Safe Use
1. Do not exceed the maximum temperature of this resistance furnace during use.
2. Always disconnect the power supply when loading or unloading samples to prevent electric shock.
3. The furnace door should be opened for as short a time as possible when loading or unloading samples to extend the service life of the electric furnace.
4. Do not pour any liquid into the furnace chamber.
5. Do not put samples contaminated with water or oil into the furnace chamber; do not use clamps contaminated with water or oil to load or unload samples.
6. Wear gloves when loading or unloading samples to prevent burns.
7. Samples should be placed neatly in the middle of the furnace chamber; do not place them haphazardly.
8. Do not touch the electric furnace or surrounding samples indiscriminately.
9. After use, the power and water supply should be turned off.
10. Do not operate the resistance furnace without permission from the management personnel, and strictly follow the equipment's operating procedures.