Precautions for maintenance of high-temperature vacuum atmosphere tube furnace

The maintenance of high-temperature vacuum atmosphere tube furnace is the key to ensuring long-term stable operation of equipment, extending service life, and ensuring experimental safety. The following are detailed maintenance precautions, covering daily maintenance, regular inspections, and safety operation standards:

1. Daily maintenance and cleaning
Furnace body cleaning
External cleaning: After each use, wipe the surface of the furnace body with a soft cloth to avoid the accumulation of dust or corrosive substances. Do not use organic solvents (such as alcohol, acetone) for direct wiping to prevent damage to the coating of the shell.
Internal cleaning:
After cooling (recommended to cool to room temperature), use a soft bristled brush or vacuum cleaner to clean the residual powder, particles, or oxides in the furnace to avoid scratching the inner wall of the furnace with hard objects.
If there are refractory materials (such as alumina fiberboard) in the furnace, their integrity should be checked regularly. If there is any damage or detachment, they should be replaced in a timely manner.
Furnace tube cleaning:
Choose a cleaning method based on the properties of the experimental residue:
Metal oxides: Soak in dilute hydrochloric acid or oxalic acid solution and rinse with deionized water.
Carbon deposition: High temperature air burning under an inert atmosphere (such as maintaining at 800 ℃ for 2 hours), or cleaning by mechanical methods (such as a soft bristled brush).
Do not use strong acids (such as hydrofluoric acid) or strong bases to clean furnace tubes to prevent corrosion of materials (such as corundum and quartz).
Seal inspection
Before each start-up, check whether the sealing rings (such as fluororubber, silicone rubber) of the furnace door, flange, observation window and other parts are intact, whether they are aged, cracked or deformed.
Regularly apply vacuum silicone grease to maintain sealing, but avoid excessive application that may contaminate the furnace.
Vacuum system maintenance
Vacuum pump oil:
Regularly check the oil level (usually located at 1/2~2/3 of the oil window), and replace it promptly if the oil color turns black or contains water.
Different types of vacuum pump oil (such as mineral oil and synthetic oil) cannot be mixed and should be selected according to the equipment manual.
Vacuum gauge:
Regularly wipe the surface of the gauge with a dust-free cloth to avoid dust affecting measurement accuracy.
If the regulatory display is abnormal (such as large fluctuations in readings), calibration or replacement is required.
Gas system:
Check if there is any air leakage at the intake valve and pipeline connections (which can be detected by applying soapy water).
Regularly replace gas filters (such as molecular sieves and activated carbon) to prevent impurities from entering the furnace.

2. Regular maintenance and calibration
Temperature control system calibration
Every 6 months, calibrate the furnace temperature with a standard thermometer (such as a platinum rhodium platinum thermocouple) to ensure that the displayed temperature deviates from the actual temperature by ≤± 5 ℃.
Check if the thermocouple protective sleeve is damaged, and replace it if it is severely oxidized or corroded.
Furnace tube deformation inspection
Visually inspect furnace tubes (such as corundum, quartz) monthly for bending, cracking, or discoloration.
Measure the diameter of the furnace tube with a micrometer, and replace it if the deformation exceeds 1% of the original size.
Electrical system inspection
Check whether the power cord and heating elements (such as silicon carbide rods and silicon molybdenum rods) are loose, and whether there are signs of overheating or erosion.
Measure the insulation resistance (≥ 1M Ω) with a megohmmeter. If it is lower than the standard value, maintenance is required.
Lubrication of mechanical components
Regularly apply high-temperature resistant lubricating grease (such as molybdenum disulfide) to the furnace door lifting mechanism, vacuum pump transmission components, etc., to reduce wear and tear.

3. Safety operation standards
Temperature control
Strictly follow the temperature rise and fall rate specified by the equipment (such as alumina tube ≤ 5 ℃/min) to avoid cracking of the furnace tube due to thermal stress.
It is prohibited to rapidly heat up an empty furnace to high temperatures (such as directly rising to 1600 ℃), and inert gas protection must be introduced first.
atmosphere control
Before the experiment, confirm that there is no residual gas (such as oxygen) in the furnace to avoid mixing with experimental gas (such as hydrogen) and causing an explosion.
When replacing gas, first empty the original gas and then introduce new gas to prevent cross contamination.
Emergency situation handling
Equip with fire extinguishers (such as carbon dioxide fire extinguishers) and gas masks, and prohibit the stacking of flammable materials in the experimental area.
If there is a furnace tube rupture or vacuum leak, immediately turn off the power and gas valves, and evacuate personnel.

4. Long term disuse maintenance
Furnace protection
After cleaning the furnace, place desiccants (such as silica gel) and seal the furnace door to prevent damage to refractory materials caused by moisture.
If there are metal parts in the furnace, rust proof oil can be applied to prevent oxidation.
Furnace tube preservation
Remove the furnace tube from the furnace and place it vertically on a dedicated support to avoid deformation.
If the furnace tube material is quartz, it needs to be stored away from light to prevent UV aging.
Vacuum system maintenance
Before turning off the vacuum pump, introduce dry nitrogen gas to break the vacuum and prevent the pump oil from being sucked back.
When not in use for a long time, start the vacuum pump and run it for 10 minutes every week to maintain component lubrication.

5. Maintenance records and archive management
Establish an equipment maintenance ledger to record the maintenance time, content, replacement parts, and operator information for each maintenance.
Save equipment manuals, maintenance manuals, and calibration certificates for easy traceability and retrieval.
Through systematic maintenance, the failure rate of high-temperature vacuum atmosphere tube furnaces can be significantly reduced, and the service life can be extended to more than 10 years, while ensuring the repeatability and safety of experimental results.