Precautions for daily maintenance of box type annealing atmosphere furnace

As a precision heat treatment equipment, the daily maintenance of the box type annealing atmosphere furnace directly affects the equipment life, process stability, and production safety. From the three dimensions of core component maintenance, safety operation standards, and environmental management, the key precautions for daily maintenance are systematically summarized as follows:

1. Core component maintenance
a. Heating system
Inspection of electric heating elements
Visually inspect the oxidation degree of the heating wire/rod every week. If there is uneven redness or local breakage, it should be replaced in a timely manner.
Use an infrared thermometer to check the temperature uniformity in each area every month. If the deviation exceeds ± 5 ℃, adjust the power distribution.
Insulation performance test
Use a megohmmeter to measure the insulation resistance of heating elements to ground every quarter, with a requirement of ≥ 1M Ω to prevent leakage risks.
b. Vacuum and Atmosphere System
Vacuum pump maintenance
Drain the condensate inside the pump daily to avoid corrosion of the pump body.
Replace the pump oil monthly (special oil is required for Roots pumps), and if the oil turbidity exceeds level 3 (NAS 1638 standard), it must be replaced.
Seal inspection
Check the sealing ring of the furnace door every week and maintain it with fluorine rubber special lubricating grease. If cracks or permanent compression deformation exceeding 20% are found, it needs to be replaced.
Tighten the flange bolts monthly, with torque values in accordance with the equipment manual (such as 50-60N · m for M16 bolts).
c. Temperature control system
Thermocouple calibration
Compare the thermocouple error with a standard thermometer every six months. If it exceeds ± 1 ℃, recalibration or replacement is required.
Avoid direct contact between thermocouples and furnace walls to prevent measurement distortion.
pid parameter optimization
After replacing the process or material, it is necessary to readjust the PID parameters (such as P=10-30%, I=30-120s, D=5-30s) to avoid temperature overshoot.

2. Safety operation standards
a. Pre operation inspection
Air path sealing
Inject 0.1MPa nitrogen gas daily and maintain pressure for 10 minutes. If the pressure drop exceeds 0.005MPa, check for leaks (soap water detection method).
Electrical safety
Check the grounding resistance to be ≤ 4 Ω every month, and ensure that the emergency stop button is functioning properly.
b. Process monitoring
Atmosphere purity control
A hydrogen leak alarm should be installed for hydrogen containing atmosphere, and the gas source should be automatically cut off when the concentration exceeds 1%.
The oxygen content analyzer is calibrated quarterly to ensure a reading error of ≤ 0.1%.
pressure protect
Set the safe pressure range (such as -0.1~0.05MPa), and the mechanical safety valve will automatically release pressure when overpressure occurs.
c. Emergency response
power-off protection
Configure UPS power supply to ensure that the vacuum pump and control system can maintain operation for ≥ 15 minutes during power outage.
After a sudden power outage, it is necessary to wait for the furnace temperature to drop below 300 ℃ before resuming gas supply.
Fire contingency plan
CO ₂ fire extinguishers are equipped inside the furnace, and water-based fire extinguishers are prohibited (which may cause the furnace to explode).

3. Environmental and Auxiliary System Management
a. Furnace body cleaning
Internal cavity cleaning
After each annealing, use a vacuum cleaner to remove the oxide skin, wipe stubborn stains with alcohol swabs, and prohibit the use of metal shovels.
Rust prevention of shell
Check the surface paint layer of the furnace every month, and polish the corroded areas to St3 level before applying anti rust paint.
b. Maintenance of cooling system
water quality management
The closed cooling water system needs to be tested monthly for pH value (6.5-8.5) and conductivity (≤ 500 μ S/cm), and deionized water should be replaced if it exceeds the standard.
Scale cleaning
Clean the cooling pipeline with a 5% citric acid solution every six months to remove scale.
c. Recording and tracing
Maintenance file
Establish an electronic maintenance ledger to record maintenance time, projects, replacement part models, and supplier information.
Spare parts Management
The inventory of key spare parts (such as thermocouples and sealing rings) should be ≥ 2 sets and stored in a dry environment (humidity ≤ 40%).

Through the above systematic maintenance measures, the failure rate of the box type annealing atmosphere furnace can be effectively reduced (measured data: MTBF ≥ 3000h when maintained properly), the equipment life can be extended to more than 15 years, and the process repeatability can be guaranteed (CPK ≥ 1.33). It is recommended to develop an Equipment Maintenance SOP and provide regular skill training for operators (once every quarter).