Atmosphere tube electric furnace is a device that achieves material heat treatment by precisely controlling the temperature and gas environment inside the furnace, and is widely used in fields such as semiconductors, new energy, metallurgy, etc. Its core components include a heating module, a temperature control system, a gas delivery unit, and a sealed chamber.

1、 Typical fault classification analysis

1. Temperature runaway phenomenon

-Appearance features: The measured temperature deviates from the set value by more than ± 5 ℃, and the heating rate is abnormal (such as dropping from the original 10 ℃/min to 3 ℃/min).

-Root cause positioning:

-Thermocouple failure: The thermocouple wire breaks or the compensating wire ages, causing distortion of the feedback signal.

-PID parameter mismatch: oscillation caused by narrow proportional band, and steady-state error caused by improper integration time.

-Heating element open circuit: Local erosion of molybdenum wire/silicon molybdenum rod, sudden change in resistance causing a sharp drop in power output.

-Disposal process:

① Cross validation of furnace temperature using an infrared thermometer; ② Replace the thermocouple with the same model and recalibrate it; ③ Reset PID parameters to factory default values; ④ Disconnect the main circuit and use a multimeter to check the continuity of the heating element.

2. Gas leakage crisis

-Risk level: Hydrogen medium leakage reaching the explosive limit constitutes a major safety hazard.

-Traceability method:

-Soap water spraying method: Spray on the flange interface and needle valve, and determine the leakage point when bubbles bulge.

-Positive pressure leak detector: Fill with 0.02MPa nitrogen gas and maintain pressure for 30 minutes. If the pressure drop is less than 1%, it is qualified.

-Emergency repair:

-O-ring deformation → replace with fluororubber sealing ring;

-Thread sliding wire → Wrap PTFE raw material tape;

-Weld crack → argon arc welding repair and polishing treatment.

3. Deterioration of vacuum degree

-Negative pressure performance: Vacuum gauge reading>5Pa and continuously rising, vacuum pump abnormal noise accompanied by heating.

-Root cause analysis:

-Pre stage pump oil emulsification → replace with dedicated diffusion pump oil;

-Twisted deformation of corrugated pipe → correction of pipeline support frame;

-Leakage of furnace liner sand holes → Penetrating detection to locate defects.

-Deep maintenance: Perform high-temperature baking and degassing once a week, replace pump oil and clean the filter screen monthly.

4. Transmission mechanism stuck

-Movement disorders: The push rod shakes significantly when pushing materials, and the buffering at the end of the stroke fails.

-Lubrication optimization: Apply molybdenum disulfide grease to the guide rail and spray WD-40 rust inhibitor on the gear meshing surface.

-Gap adjustment: When the reverse clearance of the ball screw is greater than 0.05mm, the nut needs to be pre tightened, and the tension of the synchronous belt should refer to the torque value in the manual.

5. Program logic disorder

-Symptoms of system crash: Touch screen malfunction, process curve jumps to the initial section midway.

-Reset strategy:

-Hard restart: Cut off the main power supply and wait for the capacitor to discharge completely;

-Soft reset: Press and hold the 'Reset' button on the PLC panel until all indicator lights are off;

-Firmware upgrade: Flash in the latest stable firmware through the USB port.

-Anti interference enhancement: Use shielded twisted pair cables for signal lines, with a grounding resistance of<4 Ω.

6. Damaged insulation layer

-Energy consumption surge: The surface temperature of the shell exceeds 60 ℃, and the heat dissipation loss exceeds the design value by 30%.

-Repair process:

-Collapse of ceramic fiber module → removal of old cotton and laying of new module, filling of aluminum oxide hollow balls at the joints;

-Cracking of refractory castable → Welding reinforcement of anchor nails, pouring of high-temperature resistant castable for formwork support;

-Oxidation and peeling of reflective screen → sanding the substrate with sandpaper and spraying high emissivity coating.

7. Cooling system paralysis

-Overheating alarm: Circulating water temperature rise>10 ℃, flow meter shows a 50% decrease in flow rate.

-Clearing plan:

-Scale blockage → Soak in citric acid solution and rinse with high-pressure water gun;

-Electromagnetic valve stuck → Disassemble and clean the pilot hole, grind the sealing surface of the valve core;

-Ice formation in heat exchanger → switch to ethylene glycol antifreeze and add electric heat tracing strip.

8. Insufficient purity of atmosphere

-Impurities source: Compressed air containing oil mist, argon gas cylinder residual pressure<0.5MPa.

-Purification measures:

-Third level filtration: pre filter+activated carbon adsorption tower+precision filter element;

-Gas replacement: Three pumps and three rows method (vacuum pumping inert gas filling air bursting), repeated three times;

-Catalytic deoxygenation: The palladium catalyst bed is heated to 300 ℃ for activation.

9. Failure of safety protection

-Interlock failure: Heating can still be started even if the furnace door is not tightly closed, and the over temperature alarm is silent.

-Mandatory improvement:

-Install mechanical limit switches to ensure power-off when opening the door;

-The sound and light alarm is independently powered, and the test button simulates a fault;

-Directional guidance for explosive devices, avoiding personnel operation areas.

10. Data collection drift

-Record deviation: The historical data curve shows a step like jump, and the log file is missing key periods.

-Diagnostic tool: oscilloscope captures RS485 bus waveform and verifies baud rate matching; Rollback the database transaction log to a normal node.

2、 Special working condition response plan

-Sudden power outage: Immediately close the gas main valve and manually rotate the fan to prevent deformation.

-Toxic gas release: Activate the spray absorption device and evacuate with a positive pressure respirator.

-Earthquake disaster: Emergency power cut off and fix the furnace body to the seismic base.