Routine maintenance of box type vacuum atmosphere muffle furnace

The box type vacuum atmosphere muffle furnace requires regular maintenance to ensure equipment performance, extend service life, and ensure experimental safety due to the involvement of high temperature, vacuum, and atmosphere control. The following outlines the key maintenance steps and precautions from five aspects: furnace cleaning, vacuum system maintenance, atmosphere system maintenance, electrical system inspection, and safety accessory maintenance.

1. Furnace cleaning and maintenance
Daily cleaning
Cleaning after cooling: After each experiment, wait for the furnace temperature to drop to room temperature (≤ 50 ℃), and use a vacuum cleaner or soft bristled brush to remove residual powder, oxides, and other impurities in the furnace.
Avoid scratching with hard objects: It is forbidden to use metal tools to clean the furnace to prevent scratching the alumina fiber or silicon carbide furnace, which may lead to a decrease in insulation performance.
Crucible residue treatment: If the crucible ruptures or the sample melts and adheres, special tools (such as ceramic shovels) should be used to carefully clean it to avoid damaging the furnace.
Regular in-depth maintenance
Alumina fiber replacement: If there are cracks, slag falling, or decreased insulation performance (such as slower heating rate) on the inner wall of the furnace, the alumina fiber module needs to be replaced. It is recommended to replace it every 2-3 years, depending on the frequency of use.
Thermocouple calibration: Use a standard thermometer to calibrate the thermocouple every six months to ensure that the temperature measurement error is ≤ ± 1 ℃. If the deviation is too large, the thermocouple needs to be replaced.
Heating element inspection: Regularly observe whether the heating wire (such as silicon molybdenum rod, silicon carbon rod) is aging, broken or deformed. If the resistance value changes by more than ± 10%, it should be replaced in a timely manner.

2. Vacuum system maintenance
Vacuum pump maintenance
Oil change cycle: Replace the vacuum pump oil (such as Fomblin Y-grade perfluoropolyether oil) every 300 hours or 3 months of operation to avoid oil emulsification or carbonization affecting the vacuum degree.
Oil mist filter cleaning: Clean the oil mist filter monthly to prevent oil mist from entering the furnace and contaminating the sample.
Pump body cleaning: Regularly wipe the surface of the pump body with a dust-free cloth to prevent dust from entering the pump.
Vacuum pipeline maintenance
Leak detection: Use a helium mass spectrometer leak detector every month to check the sealing of the furnace body, with a focus on inspecting the furnace door sealing ring, vacuum valve, and flange connections. If the leakage rate is greater than 1 × 10 ⁻⁸ Pa · m ³/s, the sealing ring or fastening bolt needs to be replaced.
Valve maintenance: Conduct on/off tests on vacuum valves every quarter to ensure flexible operation. If the valve is stuck, it needs to be disassembled, cleaned, and coated with vacuum grease.
Molecular sieve regeneration: If using molecular sieves to remove water, it is necessary to heat and regenerate them every six months (200-300 ℃, for 8 hours) to restore their adsorption capacity.

3. Atmosphere system maintenance
Gas pipeline inspection
Pipeline sealing: Check the gas pipeline connections for looseness every month and use soapy water to detect any leaks. If air leakage is found, tighten the joint or replace the sealing gasket.
Filter cleaning: Clean the gas filter quarterly to avoid impurities blocking the flow meter or valve.
Gas purity monitoring: Regularly check the purity of inert gases (such as nitrogen and argon) to ensure ≥ 99.999%; The purity of reducing gases (such as hydrogen) is ≥ 99.99%. If the purity is insufficient, the gas cylinder needs to be replaced.
Flow meter calibration
Calibrate gas flow meters with standard flow meters every six months to ensure an error of ≤ ± 1%. If the deviation is too large, the flowmeter needs to be adjusted or replaced.

4. Electrical system inspection
Power supply and grounding
Voltage stability: Use a multimeter to check the power supply voltage every month to ensure a fluctuation range of ≤± 5%. If the voltage is unstable, a voltage regulator needs to be installed.
Grounding resistance: Check the grounding resistance every six months to ensure it is ≤ 4 Ω. If the grounding is poor, the grounding wire needs to be reconnected.
Control cabinet maintenance
Cooling fan cleaning: Clean the dust of the cooling fan in the control cabinet every quarter to avoid component damage caused by overheating.
Relay and contactor inspection: Check the contacts of relays and contactors for oxidation or erosion every six months, and replace them if necessary.
Line aging inspection: Check the power and control lines for aging or damage every year and replace them in a timely manner.

5. Security Attachment Maintenance
Over temperature protection device
Functional testing: Simulate overheating situations every quarter and test whether the overheating protection device can automatically cut off power. If it fails, the temperature controller or thermocouple needs to be replaced.
Alarm threshold calibration: Calibrate the over temperature alarm threshold annually to ensure consistency with the set temperature.
Pressure sensors and safety valves
Pressure sensor calibration: Calibrate the pressure sensor every six months to ensure an error of ≤± 0.5%.
Safety valve inspection: Every year, manually test whether the safety valve can be opened normally to avoid excessive pressure inside the furnace.
Emergency stop button
Functional testing: Monthly testing of whether the emergency stop button can immediately cut off the power supply to ensure emergency response.

6. Maintenance records and archive management
Establish a maintenance ledger: record the time, content, replaced parts, and inspection data of each maintenance to facilitate problem tracing.
Develop maintenance plan: Based on the frequency of equipment usage, develop annual, quarterly, and monthly maintenance plans and strictly implement them.
Training and handover: Operators need to receive professional training and be familiar with maintenance procedures. Complete maintenance records must be provided during equipment handover.

Summarize
The daily maintenance of the box type vacuum atmosphere muffle furnace should follow the principle of “prevention first, regular maintenance, and traceable records”. Through furnace cleaning, vacuum system maintenance, atmosphere system maintenance, electrical system inspection, and safety accessory maintenance, the long-term stable operation of equipment can be ensured, the service life can be extended, and the reliability of experimental results and personnel safety can be guaranteed. It is recommended to develop personalized maintenance plans based on the equipment manual and actual operating conditions.