Daily maintenance of gas filled tube furnace

The daily maintenance of gas filled tube furnaces should revolve around four core areas: safety inspection, component maintenance, environmental control, and operational standards. The following are specific maintenance points and operational recommendations:

1. Safety inspection and protection
Electrical system inspection
Wiring tightening: Check the wiring terminals of the heating element, controller, and power cord every month, use a torque wrench to tighten the bolts, and avoid poor contact that may cause local overheating.
Insulation testing: Use a megohmmeter to test the insulation resistance of the heating element to ground every six months, with a standard value of ≥ 10M Ω. If the resistance is lower than 5M Ω, the insulation layer or heating element should be replaced immediately.
Emergency stop test: Test the function of the emergency stop button every week to ensure that the power is cut off within 0.5 seconds after pressing, in order to prevent the equipment from losing control.
Gas system inspection
Leak detection: Apply soapy water to gas interfaces (such as flanges and valves) every month and observe the generation of bubbles. The hydrogen system requires the use of a helium mass spectrometer leak detector to ensure no leaks.
Pressure verification: Use a pressure gauge to check the pressure inside the furnace every quarter to ensure that it does not exceed the design value (such as conventional tube furnaces ≤ 0.1MPa), and to avoid seal failure.
Gas purity: Before each experiment, use a gas purity analyzer to test the inlet purity (such as high-purity nitrogen ≥ 99.999%). Excessive impurity content can lead to experimental failure or equipment corrosion.

2. Component maintenance and replacement
Heating element maintenance
Appearance inspection: Visually inspect the heating wire (silicon molybdenum rod/resistance wire) monthly for oxidation, fracture, or localized melting. If the diameter of the heating wire shrinks by more than 20% of its original size, or if the resistance value changes by more than ± 10%, it needs to be replaced immediately.
Cleaning method: Clean the surface dust of the heating element with a soft brush or compressed air every quarter, avoiding scratching with metal tools to prevent damage to the element.
Furnace tube cleaning
Physical cleaning: After each experiment, use a vacuum cleaner or compressed air to remove residual powder from the furnace tube to prevent high-temperature carbonization and corrosion of the furnace tube.
Chemical cleaning: For carbon deposition, soak the furnace tube in 10% dilute hydrochloric acid for 2 hours every six months and rinse it (to confirm compatibility of furnace tube materials, quartz tube is usable, and neutral cleaning agent is required for ceramic tube).
Placement of furnace plugs: During heating, alumina furnace plugs (2 on each end, 450mm apart) must be placed inside the furnace tube to form a balanced temperature field and avoid flange O-ring failure due to high temperature.
Seal replacement
O-ring inspection: Check the O-ring at the furnace door and flange for aging, hardening, or cracking every 6 months. If there is a decrease in elasticity or leakage of the sealing surface, it should be replaced immediately (using a fluororubber O-ring for high temperature environments, with a temperature resistance of ≥ 250 ℃).
Vacuum pump maintenance: Replace the vacuum pump oil every 200 hours (it is recommended to use mineral oil or synthetic oil) to avoid carbonization of the oil causing a decrease in pumping speed. At the same time, check the sealing of the pump body to prevent air leakage.

3. Environmental Control and Operating Standards
Environmental Requirements
Temperature and humidity control: The ambient temperature around the equipment should be controlled between 5-40 ℃, with a relative humidity of ≤ 85%, to avoid condensation water corroding electrical components.
Ventilation conditions: The laboratory needs to install an exhaust system (with a ventilation rate of ≥ 6 times/hour) to promptly discharge toxic gases such as CO and H ₂ S.
Cleaning requirements: Keep no flammable materials (such as alcohol, organic solvents) within 1 meter around the furnace, regularly wipe the surface of the equipment with a damp cloth to prevent dust accumulation.
Operating Specifications
Oven drying procedure: When used for the first time or after long-term disuse, oven drying must be carried out. The program is: room temperature → 200 ℃ (4 hours, open the furnace door) → 200 ℃ → 600 ℃ (4 hours, close the furnace door) → 600 ℃ → 800 ℃ (2 hours, close the furnace door), to avoid cracking of the furnace due to thermal stress.
Heating rate: The heating rate of quartz furnace tube is ≤ 10 ℃/min, and the heating rate of alumina furnace tube is ≤ 15 ℃/min, to prevent sudden temperature changes from causing furnace tube rupture.
Cooling method: Natural cooling or program-controlled cooling (cooling rate ≤ 5 ℃/min) to avoid cracking of the sample due to rapid cooling.

4. Regular calibration and recording
temperature calibration
Standard substance method: Use high-precision thermocouples (such as S-type) to calibrate the temperature measurement points inside the furnace every six months. If the error exceeds ± 5 ℃, adjust the PID parameters (typical values: P=30%, I=120 seconds, D=30 seconds).
Program testing: Run a step heating program (such as increasing from 20 ℃/min to 1000 ℃), record the deviation between the actual temperature curve and the set value, and ensure temperature control accuracy.
Maintenance Record
Equipment archives: Establish equipment archives to record maintenance time, component replacement, and calibration data for easy traceability of issues.
Operation log: Record the parameters (temperature, time, gas flow rate), abnormal phenomena, and handling measures of each experiment, providing a basis for troubleshooting.