Precautions for using bell type lifting high-temperature muffle furnace

As the core equipment for high-temperature experiments and industrial processing, the bell type lifting high-temperature muffle furnace involves multiple risks such as high temperature, vacuum, and electrical safety in its operation. To ensure stable operation of the equipment, extend its service life, and ensure personnel safety, the following usage precautions must be strictly followed:

1. Preparation before operation: comprehensive inspection and parameter calibration
Equipment appearance and structural inspection
Check whether the sealing ring of the furnace body is intact, without cracks or aging phenomena (especially pay attention to the sealing strip on the contact surface between the bell jar and the furnace bottom).
Confirm that the heating element (such as silicon molybdenum rod, graphite rod) is not broken or loose, and there is no risk of short circuit in the resistance wire.
Check if the lifting mechanism (such as hydraulic cylinder, guide rail) is well lubricated and there is no jamming or abnormal noise during the lifting process.
Vacuum system verification
After connecting the vacuum pump, close the furnace door and start vacuuming, and observe whether the vacuum degree can reach the target value within the specified time.
Check if there is any air leakage at the vacuum pipeline interface (apply soapy water to the interface and observe if any bubbles are generated).
Confirm that the calibration of vacuum gauges (such as thermocouple gauges and ionization gauges) is effective to avoid distortion of vacuum readings.
Temperature control system calibration
Use a standard thermometer (such as a platinum rhodium platinum thermocouple) to calibrate the temperature inside the furnace, ensuring that the displayed value of the temperature controller has a small deviation from the actual value.
Check if the temperature control function of the multi-stage program is normal, to avoid material overheating or undercooking caused by incorrect execution of the temperature curve.
Safety device testing
Simulate over temperature alarm: manually set the over temperature threshold (such as 50 ℃ higher than the target temperature), observe whether the equipment automatically cuts off the heating power and triggers the sound and light alarm.
Test emergency stop button: After pressing the emergency stop button, confirm that all actions such as heating, lifting, vacuum pump, etc. stop immediately.
Check the sensitivity of gas leak detectors (such as hydrogen detectors) to avoid explosions caused by the accumulation of combustible gases.

2. Standardized operation: precise control of process parameters
Key points of temperature control
Heating rate: Set a reasonable heating curve based on the material characteristics. For example, when annealing titanium alloys, the heating rate should be ≤ 5 ℃/min to avoid cracking caused by thermal stress; When sintering ceramics, the heating rate can be accelerated, but it is necessary to keep the temperature at critical points (such as 600 ℃, 1200 ℃) for 30 minutes to eliminate internal stress.
Temperature uniformity: Regularly check the temperature distribution inside the furnace. If the temperature difference is greater than ± 5 ℃, adjust the heating element power or optimize the insulation layer structure.
Long term use temperature: The long-term use temperature of silicon molybdenum rod heating elements should be ≤ 1700 ℃. Overtemperature use will accelerate volatilization and shorten the service life.
Vacuum operation specifications
Pre vacuuming: Before introducing reaction gases (such as nitrogen and argon), it is necessary to evacuate to below 10 ⁻ Pa to avoid gas mixing and explosion (such as hydrogen and oxygen mixing).
Vacuum degree selection: Choose the appropriate vacuum degree according to the process requirements. For example, metal annealing typically requires 10 ⁻ ³ Pa.
Vacuum pump maintenance: Regularly replace the vacuum pump oil (such as replacing the mechanical pump oil every 3 months) to avoid oil contamination that may cause a decrease in vacuum degree.
Gas inlet and pressure control
Gas flow rate: When introducing protective gas (such as argon), the flow rate should be stable to avoid damage to the heating element caused by the impact of the gas flow.
Pressure monitoring: If pressure treatment is required (such as hot pressing sintering), the pressure should gradually increase to the target value and the pressure sensor reading should be monitored in real time to prevent overpressure damage to the furnace body.
Gas purity: Use high-purity gas to avoid impurities contaminating the material surface.
Sample placement and fixation
Sample size: The sample height should be 10-20 mm lower than the effective height of the furnace to avoid collision with heating elements during the lifting process.
Sample fixation: Use alumina crucible or graphite tray to fix the sample to prevent tipping or volatilization pollution of the furnace at high temperatures.
Sample spacing: When multiple samples are processed simultaneously, the spacing should be ≥ 20 mm to ensure uniformity of airflow and temperature.

3. Post operation maintenance: cleaning and performance restoration
Furnace cleaning
High temperature residues: After the furnace cools to<200 ℃, use a soft bristled brush to remove residues such as oxide scale and carbides, to avoid scratching the inner wall of the furnace with hard objects (such as corundum coating).
Vacuum gauge cleaning: Regularly wipe the thermocouple gauge or ionization gauge probe with anhydrous ethanol to prevent dust or oil from affecting measurement accuracy.
Gas pipeline cleaning: Blow the pipeline with high-purity nitrogen for 10 minutes to remove residual reaction gases.
Heating element maintenance
Silicon molybdenum rod inspection: Observe whether the surface of the silicon molybdenum rod is blackened or cracked. If the resistance value changes too much, it should be replaced in a timely manner.
Resistance wire replacement: When replacing the resistance wire, it is necessary to ensure that it is insulated from the furnace to avoid short circuits and fire hazards.
Graphite element oxidation prevention: If graphite heating elements are used, they should be stored in an inert atmosphere to avoid contact with air oxidation.
Sealing system maintenance
Sealing ring replacement: Replace the fluororubber or silicone rubber sealing ring (temperature resistance ≤ 300 ℃) every 50 uses or when air leakage is found. The metal sealing ring needs to be polished regularly.
Furnace door lubrication: Apply high-temperature grease (such as molybdenum disulfide grease) to the hinge of the furnace door to ensure smooth opening and closing.
Cleaning of observation window: Wipe the quartz observation window with anhydrous ethanol to avoid the influence of volatile matter adhesion under high temperature on observation.
Electrical system inspection
Grounding resistance: Use a grounding resistance tester to check the grounding resistance of the equipment to prevent electric leakage and injury.
Line aging: Regularly check whether the power cord and heating element connection wire are damaged. If the insulation layer cracks, it should be replaced immediately.
Temperature controller calibration: Send the temperature controller for inspection every year to ensure that the temperature control accuracy meets the standards.

4. Security protection: dual protection of personnel and equipment
Personal protective equipment
Operators are required to wear heat-resistant gloves (such as aramid fiber gloves), protective face shields, and dust masks to avoid burns from high temperatures or inhaling harmful gases.
When introducing toxic gases (such as chlorine), it is necessary to operate in a fume hood and equip it with a gas purification device.
Fire and explosion prevention measures
Flammable materials are prohibited from being stacked within 1 meter around the furnace body, and dry powder fire extinguishers or carbon dioxide fire extinguishers should be equipped.
If handling combustible materials (such as lithium metal), it is necessary to operate under an inert atmosphere and install explosion-proof valves.
Emergency Response Plan
Overtemperature accident: Immediately press the emergency stop button, cut off the heating power supply, and check the cause of the temperature control system malfunction after the furnace cools down.
Vacuum leakage: Turn off the vacuum pump, introduce nitrogen gas to atmospheric pressure, check the sealing ring or pipeline interface and repair it.
Electrical malfunction: Disconnect the main power supply, use a multimeter to detect short circuits or open circuit points in the circuit, and have it repaired by a professional electrician.