Precautions for operating high-temperature gas vacuum tube furnace

When operating a high-temperature gas vacuum tube furnace, it is important to pay attention to the following precautions to ensure experimental safety and stable equipment operation:

1. Equipment inspection and preparation
environment check
Ensure good ventilation in the laboratory and keep it away from flammable and explosive materials, fire sources, and water sources.
Check whether the equipment and accessory components (such as vacuum pumps, cooling systems, and air pipelines) are intact, tightly connected, and leak free.
personal protection
Wear lab coats, heat-resistant gloves, protective goggles, and gas masks (if toxic gases are involved) to prevent burns or gas poisoning.
Cooling system startup
Prioritize opening the cooling water circulation system to ensure that the furnace temperature is within a safe range before proceeding with subsequent operations.

2. Vacuum and gas operation specifications
Vacuum pump usage
Before starting the vacuum pump, confirm that the pump oil level is above the marked line and there is no emulsification phenomenon.
When vacuuming, observe the indication of the vacuum gauge to ensure that the vacuum degree inside the furnace meets the experimental requirements.
Regularly replace the vacuum pump oil to avoid blockage or deterioration of the oil circuit.
Gas introduction and replacement
Before inflation: first evacuate the vacuum inside the air pipe to prevent damage to the sealing ring caused by air pressure impact.
Combustible gases such as hydrogen:
Before use, use soapy water to check for leaks. After confirming that there are no leaks, collect gas through a test tube for a detonation test.
During ventilation, the flow meter adjusts the bubble velocity to 2 bubbles per second, and then heats up after 10 minutes of ventilation.
Oxygen cylinder: Strictly prohibit oil stains, ensure that the gas pipeline and equipment are free of oil stains, and avoid explosions under high pressure.
Acetylene gas: The use of copper gas pipelines is prohibited to prevent the generation of explosive acetylene copper.
Air pressure monitoring
During the heating process, if inert gas is used, the pressure should be stable below 0.02 MPa; If overpressure occurs, immediately open the outlet valve to release air.
When cooling down, if hydrogen gas is used, it is necessary to monitor the gas outlet of the conical flask to prevent backflow; If backflow occurs, immediately adjust the flow meter to increase the intake volume.

3. Temperature control and operation
Design of temperature rise and fall curve
Heating rate:
Quartz tube: ≤ 10 ℃/min (≤ 5 ℃/min below 500 ℃, ≤ 10 ℃/min between 500-800 ℃, ≤ 5 ℃/min between 800-1000 ℃).
Corundum tube: ≤ 5 ℃/min.
Cooling rate: ≤ 15 ℃/minute, naturally cool to below 300 ℃ before turning off the circulating water to prevent flange deformation caused by thermal expansion and contraction.
Maximum temperature limit: quartz tube ≤ 1100 ℃, corundum tube ≤ 1200 ℃, avoid exceeding the rated temperature of the equipment.
Insulation and thermal stress control
Do not open the furnace door when the temperature exceeds 1000 ℃ to prevent the quartz tube from exploding.
Avoid insulation at 300-900 ℃ to prevent cracking of furnace tubes due to thermal stress concentration.
The sample placement should be aligned with the constant temperature zone in the middle of the furnace chamber (such as aligning the ink cartridge with the marking point) to ensure temperature uniformity.
Program settings and monitoring
Set the temperature time program through the panel, and set the last step time to -121 to end the program.
Observe the ammeter and voltmeter in real-time during operation. If the working current continues to exceed 150A, immediately turn off the power and check the parameter settings.
The operator shall not leave the site and shall immediately close the power supply in case of tripping.

4. Safe operation and emergency response
Prohibited acts
Do not pour liquids or easily soluble metals into the furnace to prevent corrosion of heating elements.
Do not pull out the thermocouple at high temperatures to avoid jacket rupture.
Do not touch high-temperature furnace tubes with low-temperature objects to prevent explosion.
emergency response
Vacuum pump smoking: Immediately cut off the power, check if the oil circuit is blocked, and replace the deteriorated pump oil.
Gas leakage alarm: trigger ESO emergency shutdown system, evacuate personnel and ventilate for 30 minutes.
Reverse suction causes quartz tube explosion: emergency stop, wear heat-resistant face mask and insulated gloves to open the furnace door.

5. Daily maintenance and cleaning
Furnace body cleaning
Regularly clean the oxide in the furnace, keep it clean, and avoid impurities affecting the experimental results.
Clean up residual materials in a timely manner after using the quartz tube, store it in a fixed position, and avoid collision.
Component replacement
Regularly inspect vulnerable parts such as gaskets, furnace plugs, and gas pipelines, and replace aging or damaged components in a timely manner.
After use, the crucible needs to be acid washed and ultrasonically cleaned to avoid residual impurities contaminating subsequent experiments.
Gas cylinder management
Hydrogen argon and oxygen cylinders should be placed separately to avoid the risk of mixing and explosion.
After calcination, close the main valve of the gas cylinder and reset the pressure gauge value to zero.