Customized nitrogen vacuum furnace daily maintenance

The daily maintenance of customized nitrogen vacuum furnaces is the key to ensuring their long-term stable operation, extending their service life, and ensuring process quality. We provide professional and systematic maintenance guidelines from seven aspects: cleaning and maintenance, vacuum system maintenance, heating system maintenance, gas system maintenance, electrical system inspection, safety component calibration, recording, and training.

1. Cleaning and maintenance
Furnace cleaning
Frequency: After each batch of processing or once a week (depending on the degree of process pollution).
method:
Use a vacuum cleaner or soft bristled brush to remove metal debris, oxide scale, and other residues from the furnace.
Stubborn stains can be wiped with non-woven fabric dipped in alcohol (industrial grade), avoiding the use of hard tools to scrape the inner wall of the furnace (such as ceramic fiber insulation layer).
Case: After carburizing and quenching, a certain automotive parts factory promptly cleaned the residual carbides in the furnace, which extended the furnace life by 30%.
Seal inspection
Frequency: Once a month.
method:
Check if the sealing gasket of the furnace door is deformed, cracked, or contaminated with oil, and clean or replace it with alcohol if necessary.
Ensure that the sealing surface is free of foreign objects and the clamping force is uniform when the furnace door is closed (which can be monitored by a pressure gauge).
Key point: Poor sealing can lead to a decrease in vacuum degree, affecting the quality of coating or heat treatment.

2. Vacuum system maintenance
Vacuum pump maintenance
Oil change cycle:
Mechanical pump: every 200-500 hours (depending on the degree of oil contamination).
Diffusion pump/molecular pump: follow the manufacturer’s recommendations (usually every 1000-3000 hours).
method:
When discharging old oil, clean the oil mist filter at the same time.
Inject new oil to the centerline of the oil gauge to avoid excessive oil backflow.
Case: A certain aviation company regularly replaces vacuum pump oil, extending the lifespan of molecular pumps from 2 years to 4 years.
Vacuum pipeline cleaning
Frequency: Once every six months.
method:
Dismantle the pipeline and clean the inner wall with alcohol or acetone to remove adsorbed organic matter or metal vapor.
Check the sealing of the valve and replace the O-ring or valve core if necessary.

3. Heating system maintenance
Heating element inspection
Frequency: Once every quarter.
method:
Visually inspect whether the resistance wire/graphite rod is broken, deformed, or oxidized.
Measure the resistance value with a multimeter and compare it with the initial value (if the deviation is greater than 10%, it needs to be replaced).
Attention: Damage to the heating element can result in uneven temperature or inability to raise the temperature.
Thermocouple calibration
Frequency: Once a year.
method:
When comparing a standard thermometer (such as a platinum resistor) with a thermocouple, if the error is greater than ± 2 ℃, calibration or replacement is required.
Check if the thermocouple protective sleeve is damaged to prevent metal liquid from infiltrating and causing a short circuit.

4. Maintenance of pneumatic system
Nitrogen supply system
Pressure check: Before starting up daily, confirm that the nitrogen pressure is ≥ 0.4MPa (insufficient gas supply can cause unstable atmosphere).
Filter cleaning: Replace or clean the intake filter monthly to prevent particulate matter from blocking the air path.
Calibration of Mass Flow Meter (MFC)
Frequency: Once every six months.
method:
Compared with standard flow meters, if the error is greater than ± 1%, calibration is required.
Avoid prolonged exposure of MFC to high temperatures or corrosive gases.

5. Electrical system inspection
Tightening of wiring terminals
Frequency: Once every quarter.
method:
After turning off the power, use a torque wrench to check if all wiring terminals (such as heating power supply and vacuum pump motor) are loose.
Refer to the equipment manual for tightening torque (recommended 5-7N · m for copper terminals).
insulation test
Frequency: Once a year.
method:
Use a 500V megohmmeter to measure the insulation resistance of the heating circuit to ground, which should be ≥ 1M Ω.
Poor insulation can lead to leakage or short circuit.

6. Safety component verification
over temperature protection
Frequency: Once every six months.
method:
Simulate overheating conditions (such as short circuiting the temperature controller output) to verify whether the overheating alarm and power-off functions are normal.
The set value for overheating should be 50-100 ℃ lower than the maximum temperature resistance of the heating element.
pressure protect
Frequency: Once every quarter.
method:
Manually adjust the intake valve of the vacuum pump to verify the low limit vacuum alarm and shutdown function.
The pressure sensor needs to be cleaned regularly to avoid oil contamination and blockage.

Summarize
The daily maintenance of customized nitrogen vacuum furnaces should follow the principle of “prevention first, regular maintenance, and professional operation”. Through systematic cleaning, inspection, calibration, and recording, the failure rate (such as vacuum leakage and temperature runaway) can be significantly reduced, equipment life can be extended (usually by 30% -50%), and process quality (such as coating uniformity and heat treatment hardness stability) can be guaranteed. For high-value equipment, it is recommended to entrust the original factory or a professional third party for annual in-depth maintenance.