Precautions for using high-temperature vertical tube furnace

As a precision heat treatment equipment, the safety and experimental accuracy of high-temperature vertical tube furnaces highly depend on standardized operation. The following are the precautions that need to be strictly followed during use, covering four aspects: safety protection, operating procedures, equipment maintenance, and emergency response:

1. Security protection: dual protection of personnel and equipment
a. Personal protective equipment (PPE)
Basic protection: High temperature resistant gloves (such as aramid or aluminum foil materials), splash proof goggles, heat-resistant clothing, and anti slip shoes must be worn during operation to avoid direct contact with high-temperature components or splashes.
Gas operation protection: When handling flammable gases such as hydrogen and carbon monoxide, additional gas masks and gas detectors should be equipped to ensure good ventilation.
Case: A laboratory operated without wearing goggles, resulting in debris splashing into the eyes when the high-temperature furnace door was opened, causing corneal damage.
d. Equipment safety inspection
Electrical safety: Before each use, check whether the power cord is damaged, whether the grounding is reliable, and avoid leakage or short circuit.
Gas system: Check the fixation of gas cylinders, pipeline connections, and valve sealing. The hydrogen pipeline needs to be leak checked with soap water to ensure no leaks.
Mechanical safety: Confirm that the furnace door locking mechanism, lifting device (if any), and emergency stop button are functioning properly.
c. Environmental safety
Ventilation requirements: The equipment should be placed in a well ventilated laboratory, and an exhaust system should be installed in the hydrogen operation area to prevent gas accumulation.
Fire prevention measures: Flammable materials are prohibited from being placed within 1 meter around the furnace body. Fire extinguishers (dry powder or carbon dioxide type) and sandboxes should be equipped.
Warning signs: Post warning signs such as “high temperature danger” and “flammable gas” around the equipment.

2. Operation standard: precise control of experimental conditions
a. Heating and cooling control
Heating rate: Set according to the material characteristics, metal annealing is usually ≤ 10 ℃/min, and ceramic sintering can be appropriately accelerated, but thermal shock should be avoided.
Insulation stage: After reaching the target temperature, it is necessary to stabilize for 10-15 minutes before placing the sample to prevent temperature fluctuations.
Cooling control:
In furnace cooling: natural cooling after turning off heating, suitable for complete annealing and stress relief annealing.
Program cooling: Set the cooling curve through the controller (such as 5 ℃ per minute), suitable for precision material processing.
Forced cooling: Only applicable to models equipped with air/water cooling systems, please confirm that the equipment allows for rapid cooling.
d. Atmosphere control
Gas selection:
Inert protection: Nitrogen and argon are used to prevent oxidation (such as metal annealing).
Reducing atmosphere: Hydrogen gas is used to reduce the oxide layer (such as semiconductor doping).
Oxidative atmosphere: Air or oxygen is used to form an oxide layer (such as ceramic surface treatment).
Flow control: Precisely adjusted by a mass flow meter (MFC), with a typical flow range of 0.5-5L/min, to avoid sample movement caused by excessive airflow.
Vacuum operation: The maximum vacuum degree should be below 1 × 10 ⁻ ³ Pa, and after vacuuming, inert gas should be used to break the vacuum to prevent oxidation.
c. Sample placement
Bearing plate selection: Use aluminum oxide, graphite or silicon carbide materials to avoid reaction with the sample.
Uniformity of distribution: The samples should be dispersed and placed with a thickness difference of ≤ 2mm to prevent local overheating.
Special sample processing:
Powder sample: Use alumina crucible or fluidized bed device to prevent splashing.
Thin film sample: suspended in the center of the furnace tube to avoid contact with the furnace wall.

3. Equipment maintenance: Extend service life
a. Daily cleaning
Furnace tube cleaning: After each experiment, use a vacuum cleaner or soft brush to remove residue and avoid scratching with metal tools.
Bearing plate maintenance: Regularly check the surface flatness and replace it if it is severely worn.
Gas pipeline: Blow the pipeline with nitrogen every month to prevent blockage or cross contamination.
d. Regular calibration
Temperature calibration: Use standard thermocouples to calibrate the temperature control system every quarter, with an error of ≤± 2 ℃.
Gas flow calibration: Calibrate MFC annually to ensure flow accuracy.
Vacuum system: Check the oil level and sealing of the vacuum pump every six months, and replace aging components.
c. Component replacement
Heating element: The lifespan of silicon molybdenum rod is about 2000 hours, while graphite heating element is about 1000 hours and needs to be replaced regularly.
Thermocouple: K-type thermocouples have a lifespan of approximately 500 uses and need to be replaced based on wear and tear.
Sealing ring: The furnace door sealing ring is replaced every 2 years to prevent air leakage.

4. Emergency response: Quickly respond to unexpected situations
a. Temperature runaway
Phenomenon: The deviation between the displayed temperature and the actual temperature is greater than 5 ℃, or the continuous heating cannot be stopped.
Solution: Immediately press the emergency stop button, cut off the power, and notify the maintenance personnel.
b. Gas leakage
Phenomenon: The hydrogen detector alarms or a pungent odor is detected.
handle:
Close the main valve of the gas cylinder and the inlet valve of the furnace body.
Turn on the exhaust system and evacuate personnel to a safe area.
Use soapy water to check for leaks, repair them, and then retest for leaks.
c. The furnace door is stuck
Phenomenon: The furnace door cannot be opened or closed normally.
handle:
Stop heating and wait for the furnace temperature to drop below 100 ℃ before operating.
Check if the locking mechanism is stuck and avoid damage caused by forceful force.
Contact maintenance personnel to adjust the position of the furnace door.
d. Fire accidents
Phenomenon: Open flames appear inside or around the furnace.
handle:
Immediately cut off the power and gas supply.
Use dry powder fire extinguishers to extinguish initial fires, and do not use water.
When the fire cannot be controlled, evacuate and call 119.