Common faults and solutions of bell type lifting high-temperature muffle furnace

The common faults and solutions of bell type lifting high-temperature muffle furnace can be summarized into the following five categories, covering heating, temperature control, sealing, electrical and mechanical systems, as follows:

1. Heating system malfunction
Fault phenomenon
The temperature cannot rise or the heating rate significantly slows down.
Localized uneven heating (such as overheating or undercooling in certain areas).
The heating element turns red abnormally or breaks.
Possible reasons
Heating element aging: The resistance value of silicon carbon rod/silicon molybdenum rod changes greatly, or the surface is oxidized and peeled off (which is easily caused by long-term overheating of silicon carbon rod).
Wiring issues: Loose terminals, oxidation, or uneven installation stress.
Improper installation: The spacing between heating elements does not meet the standard.
solution
Testing resistance: The resistance of the silicon carbide rod exceeds the range and needs to be replaced.
Tighten the wiring: Polish the oxidized terminals with sandpaper and tighten them with a torque wrench to the standard torque.
Standardized installation: Ensure that the heating elements are parallel and evenly stressed, and use stepped heating when heating up.

2. Temperature control system malfunction
Fault phenomenon
The temperature fluctuates greatly.
Display abnormal temperature (such as displaying “—-” or jumping).
PID control failure, unable to maintain the set temperature stably.
Possible reasons
Thermocouple malfunction: wire breakage, oxidation, or installation position deviation.
PID parameter drift: Control parameters need to be readjusted after long-term use.
Solid state relay damage: abnormal output resistance.
solution
Calibration thermocouple: Use K-type (<1200 ℃) or B-type (>1600 ℃) thermocouples to ensure insertion depth.
Adjust PID parameters: perform automatic tuning function or manually set reference values.
Replace SSR: Check whether the relay is on or off. If it is damaged, replace it and strengthen heat dissipation.

3. Sealing system malfunction
Fault phenomenon
Furnace door leakage (atmosphere experiment failed).
Severe heat loss and slower heating rate.
Possible reasons
Aging of sealing strip: large compression deformation or long-term high temperature leading to hardening.
Mechanical structural deformation: Loose hinge of furnace door or deformation of furnace chamber.
solution
Replace sealing strip: Use ceramic fiber sealing tape (temperature resistance>1300 ℃), maintain compression during installation, and verify sealing performance using A4 paper testing method (if the paper cannot be pulled out after closing the door, it is qualified).
Calibrate the mechanical structure: tighten the furnace door hinge, adjust the track for foreign objects, and apply high-temperature resistant grease if necessary.

4. Electrical system malfunction
Fault phenomenon
The device has no response or frequent tripping when powered on.
Abnormal fluctuations in current during heating process.
Possible reasons
Power issue: Main power circuit breaker tripped, fuse blown.
Component short circuit: The insulation resistance of the heating element to ground is less than the standard value.
Control board malfunction: capacitor bulging, relay burnout.
solution
Check the power supply: Confirm that the input voltage is stable, reset the emergency stop button.
Repair short circuit: Replace the heating element or silicone high-temperature wire with damaged insulation.
Replace control board: Check the status of capacitors and relays, and replace industrial grade capacitors that can withstand 105 ℃ if necessary.

5. Mechanical structural failure
Fault phenomenon
The furnace door is stuck and cannot be fully closed.
The device prompts’ furnace door not closed ‘but it is actually closed.
Possible reasons
Door magnetic switch malfunction: sensor sensitivity decreases or dust accumulates in the sensing area.
Safety interlock failure: The interlock circuit is open or has poor contact.
solution
Clean the door magnetic sensor: Clean the sensing area with electronic cleaner and test its sensitivity.
Check the interlocking circuit: Use a multimeter to detect the continuity of the circuit, repair the broken point or replace damaged components.
Preventive maintenance recommendations
Regular inspection: Check the status of thermocouples and sealing strips monthly, and calibrate the temperature controller quarterly.
Cleaning and maintenance: Clean the interior of the furnace after each use to prevent sample residue from corroding the heating element.
Operating standards: Avoid overloading operation, set the temperature rise and fall rate reasonably, and prevent thermal stress damage to equipment.