Daily maintenance of box type tempering furnace

As a key equipment for metal heat treatment, the daily maintenance of the box type tempering furnace directly affects the equipment life, process accuracy, and production safety. The following outlines the key points of daily maintenance from four modules: cleaning and maintenance, core component inspection, safety protection, and operation monitoring, and provides practical operation guidelines in accordance with industry standards:

1. Cleaning and maintenance: eliminate pollution and corrosion
Furnace cleaning
Cycle: After processing each batch of workpieces
method:
Use a vacuum cleaner to remove oxide scale and metal debris (to avoid scratching the inner wall of the furnace);
Stubborn stains should be wiped with a soft cloth dipped in alcohol, and sharp tools should not be used for scraping;
Regularly check the ash accumulation at the bottom of the furnace (it is recommended to clean it once a month).
Case: A certain mold factory experienced a 15% decrease in heating efficiency and a 20% increase in energy consumption due to failure to clean up furnace dust in a timely manner.
Maintenance of furnace door sealing strip
Cycle: Weekly inspection, monthly in-depth maintenance
method:
Check whether the sealing strip is aged or cracked (there should be no loss of elasticity when pressed by hand);
Clean the oil stains on the surface of the sealing strip with a neutral cleaner, air dry and apply silicone grease for lubrication;
Replace the sealing strip every six months (shortened to three months in high temperature environments).
Data: Failure of sealing strips can lead to a 10% -15% decrease in temperature uniformity inside the furnace.
Cleaning of shell and control panel
Cycle: After daily operation
method:
Wipe the dust off the casing with a dry cloth to prevent water stains from entering the electrical box;
Disable organic solvents on the control panel, wipe gently with a slightly damp soft cloth and immediately dry.

2. Core component inspection: Ensure equipment performance
Heating element (electric heating wire/silicon carbide rod)
Cycle: Monthly visual inspection, quarterly resistance testing
method:
Observe whether the heating element is unevenly red, broken, or deformed (especially in the corners of the furnace);
Measure the resistance value with a multimeter, and replace it if the deviation from the initial value exceeds ± 10%;
The silicon carbide rod needs to be checked for looseness or cracking of the cold end ceramic head.
Risk: Abnormal heating elements may lead to uncontrolled furnace temperature, resulting in workpiece scrap or fire.
Thermocouples and Temperature Control Systems
Cycle: Quarterly calibration, annual inspection
method:
Compare the readings of the thermocouple with a standard thermometer, and calibrate if the error exceeds ± 2 ℃;
Check if the temperature controller displays flashing or garbled text, and if the wiring terminals are loose;
Backup PID parameters to avoid process control caused by misoperation.
Case: A certain aviation parts factory caused a batch of titanium alloy workpieces to exceed the hardness tolerance due to a thermocouple offset of 5 ℃.
Fan and circulation system
Cycle: Monthly inspection, lubrication every six months
method:
Manually rotate the fan blades and confirm that there is no jamming or abnormal noise;
Clean the fan inlet filter (monthly), and add high-temperature lubricating grease to the bearings every six months;
Use an anemometer to measure the circulating wind speed inside the furnace. If it is lower than 0.5m/s, maintenance is required.
Impact: Poor circulation can lead to poor uniformity of furnace temperature, and local overheating or underheating of the workpiece.

3. Safety protection: prevent accident risks
Electrical system inspection
Cycle: Monthly
method:
Check if the insulation layer of the power cord is damaged and the grounding resistance is ≤ 4 Ω;
Test the leakage protector (once a month), with an action time of ≤ 0.1s;
Clean the dust inside the electrical box and prohibit the stacking of debris.
Standard: Complies with the requirements of GB/T 5959.1-2019 “Safety of Electric Heating Devices”.
Maintenance of pneumatic system (if equipped with atmosphere protection)
Cycle: Before each batch is used
method:
Check if there is any air leakage at the air circuit joint (soap water test);
Confirm gas purity (such as nitrogen ≥ 99.99%) and regularly replace filter cartridges;
Test the emergency shut-off valve function to ensure that the gas source is cut off within 3 seconds.
Risk: Gas leakage may cause explosion or poisoning accidents.
Safety device testing
Cycle: Quarterly
method:
Manually trigger the over temperature alarm and confirm that the sound and light alarms are normal;
Simulate power outage situation and test the endurance time of UPS uninterruptible power supply (≥ 30 minutes);
Check the furnace door interlock device to ensure that heating cannot be powered on when the furnace door is not closed.
Regulations: Must comply with TSG 07-2019 “License Rules for Special Equipment Production and Filling Units”.

4. Operation monitoring: data-driven preventive maintenance
Key parameter record
Content:
Daily recording of heating rate, insulation temperature, and cooling time;
Monthly statistics on energy consumption (kW · h/batch) and workpiece qualification rate;
Analyze temperature uniformity test data quarterly using the nine point method.
Tool: Use a thermocouple multi-point inspection instrument to automatically collect data.
Abnormal situation handling
technological process:
When the temperature fluctuation is found to be greater than ± 5 ℃, immediately stop the machine and check the thermocouple and heating element;
When hearing abnormal noise or smelling burnt smell, cut off the power and check the fan and electrical box;
Establish a ‘Equipment Exception File’ to record fault phenomena, handling measures, and preventive suggestions.
Case: A certain enterprise discovered a problem of shortened lifespan of heating elements through abnormal records, traced back to voltage fluctuations in the power supply. After installing a voltage regulator, the lifespan of the elements was extended by 30%.
Spare parts Management
detailed list:
Common spare parts: thermocouple, heating element, sealing strip, fan bearing;
Key spare parts: temperature controller, solid-state relay, leakage protector.
Inventory strategy: Manage according to the principle of “1 set in use+1 set on standby+1 set in transit”.

5. Maintenance Schedule (Example)
Time consumption of the executor of the periodic maintenance project
Daily furnace/shell cleaning and control panel inspection by operators for 15 minutes
30 minutes of weekly furnace door seal inspection and gas path testing equipment maintenance personnel
2 hours of monthly heating element inspection and electrical system maintenance by a professional electrician
Quarterly temperature control system calibration, safety device testing, third-party testing agency 4 hours
8 hours of annual overhaul (replacement of vulnerable parts, repair of inner walls) for equipment manufacturers

6. Summary
The daily maintenance of the box type tempering furnace should follow the principle of “prevention first, data-driven”. Through standardized cleaning, precise inspection, and intelligent monitoring, the equipment failure rate can be reduced by more than 40%, and the service life can be extended by 2-3 years. Enterprises should develop a “Box type Reflux Furnace Maintenance Manual” based on their own process characteristics, and regularly train operators to ensure that maintenance work is implemented effectively.