Precautions for using gas filled tube furnaces

When using a gas filled tube furnace, strict control should be exercised from four aspects: safe operation, gas management, equipment maintenance, and environmental control to ensure experimental safety, accurate data, and equipment lifespan. The following are specific precautions:

1. Safety operation standards
personal protection
Protective equipment: High temperature gloves (temperature resistance ≥ 200 ℃), protective goggles (splash proof), and lab coats (corrosion-resistant) must be worn during operation.
Gas protection: When handling toxic or flammable gases (such as H ₂, CO), it is necessary to operate in a fume hood and be equipped with a gas alarm (such as an H ₂ detector, threshold ≤ 1% volume fraction).
operating procedure
Start sequence: First, pass gas (flow rate ≥ 50mL/min) to exhaust the air inside the furnace, and then raise the temperature; When shutting down, first cool down to below 100 ℃ before stopping the gas.
Pressure control: The pressure inside the furnace must not exceed the design value to avoid seal failure.
Emergency stop: In case of gas leakage, temperature loss or abnormal noise, immediately press the emergency stop button to cut off the power and gas supply.
Fire and explosion prevention
Prohibited area: Flammable materials (such as alcohol and organic solvents) are not allowed to be stored within 1 meter around the furnace body.
Static elimination: Before operation, touch the grounded metal to release static electricity and avoid sparks igniting gas.
Fire extinguishing equipment: equipped with dry powder fire extinguishers (suitable for flammable gases) and carbon dioxide fire extinguishers (suitable for electrical fires).

2. Key points of gas management
Gas selection and purity
Inert gas: High purity nitrogen or argon gas is commonly used as a protective gas to prevent oxidation.
Reaction gas: Select according to experimental requirements (such as H ₂ for reduction reaction, CO ₂ for carbonization), but confirm compatibility with furnace tube material (such as quartz furnace tube not resistant to HF gas).
Impurity control: Gas pipelines need to be equipped with filters to remove impurities such as oil stains and particles.
Gas supply system
Pressure reducing valve: Choose a pressure reducing valve that matches the gas type (such as stainless steel pressure reducing valve for H ₂ and polytetrafluoroethylene diaphragm pressure reducing valve for corrosive gases).
Flow control: Use a mass flow meter (MFC) to accurately control the flow rate and avoid experimental failure caused by flow fluctuations.
Pipeline layout: Gas pipelines should be short and straight, reducing bends and joints to minimize the risk of leakage; Hydrogen pipelines need to be grounded and anti-static.
Gas leakage treatment
Testing method: Apply soapy water to the connection or use a portable gas detector.
Emergency measures: In case of leakage, immediately turn off the gas source, open windows for ventilation, and prohibit starting electrical equipment; If the leakage is severe, evacuate quickly and call the police.

3. Equipment maintenance and inspection
routine inspection
Seals: Before each use, check whether the O-ring and gasket are aging (such as hardening or cracking), and whether the flange bolts are loose.
Furnace tube: Observe whether there are cracks, deformations, or abnormal colors in the furnace tube (such as quartz tubes turning blue due to overheating).
Temperature control system: Verify that the deviation between the temperature sensor (such as thermocouple) reading and the actual temperature is ≤± 5 ℃.
regular maintenance
Cleaning the furnace: After every 10 uses, wipe the inner wall of the furnace with a dust-free cloth dipped in alcohol to remove any residue (such as carbon deposits).
Replace seals: Replace O-rings every 6 months in high-temperature environments and every 3 months in corrosive gas environments.
Calibration equipment: Every year, professional institutions are commissioned to calibrate temperature controllers and gas flow meters to ensure accuracy.
Fault handling
Abnormal temperature: If the temperature rises slowly or exceeds the limit, check whether the heating element (such as silicon carbon rod, silicon molybdenum rod) is broken or has poor contact.
Unstable gas flow: Clean or replace the mass flow meter sensor and check if the pipeline is blocked.
Sealing failure: Reinstall the seal or replace it with a higher temperature/pressure resistant model (such as a metal bellows seal).

4. Environmental and operational condition control
Environmental Requirements
Temperature: The ambient temperature around the device should be controlled between 5-40 ℃ to avoid extreme temperatures affecting the performance of electronic components.
Humidity: Relative humidity ≤ 80%, to prevent condensation water from corroding electrical components.
Ventilation: The laboratory needs to install an exhaust system (with a ventilation rate of ≥ 6 times/hour) to promptly discharge exhaust gases.
Operating condition limitations
Heating rate: The heating rate of the quartz furnace tube should be ≤ 10 ℃/min to avoid thermal stress causing rupture.
Maximum temperature: shall not exceed the allowable temperature of the furnace tube material (such as quartz tube ≤ 1100 ℃, alumina tube ≤ 1600 ℃).
Cooling method: natural cooling or forced air cooling. It is forbidden to directly cool the furnace tube with water to prevent explosion.
Sample processing
Sample size: The sample diameter should be less than 80% of the inner diameter of the furnace tube to ensure gas circulation.
Sample placement: Use an alumina crucible or quartz boat to carry the sample, avoiding direct contact with the furnace tube and causing contamination.
Preprocessing: Volatile or flammable samples need to be dried in advance to prevent gas shock at high temperatures.

5. Recording and Training
Usage Record
Record the parameters of each experiment (temperature, time, gas flow rate), abnormal phenomena, and treatment measures for easy traceability of problems.
Save equipment maintenance records (such as seal replacement time, calibration date), and develop preventive maintenance plans.
personnel training
Operators need to undergo professional training to become familiar with equipment structure, safety operating procedures, and emergency response processes.
Regularly organize safety drills (such as gas leak simulations) to improve emergency response capabilities.