Customized experimental rotary tube furnace temperature cannot rise

The inability to increase the temperature of a customized experimental rotary tube furnace may be caused by various factors such as heating system, control system, furnace structure, external conditions, or operating settings. The following is a detailed analysis of the reasons and corresponding solutions:

1. Heating system malfunction
Heating element damaged
Reason: Heating elements such as silicon carbon rods and silicon molybdenum rods have abnormal resistance due to aging, breakage, or poor contact, which prevents them from heating normally.
Inspection method:
Observe the appearance of the heating element for cracks, discoloration, or breakage;
Measure the resistance value of the heating element with a multimeter and compare it with the rated value;
If the resistance value is abnormal (such as infinite or far below the rated value), the heating element needs to be replaced.
Solution: Contact the manufacturer to replace the heating element with the same specifications and check if the wiring terminals are loose or oxidized.
Insufficient power
Reason: Unstable power supply voltage, insufficient selection of heating element power, or excessive furnace load (such as excessive material or insulation material failure).
Inspection method:
Use a voltmeter to measure whether the input voltage is stable;
Verify whether the rated power of the heating element meets the furnace design requirements;
Check if the amount of material in the furnace exceeds the recommended value.
Solution:
Stable power supply voltage (such as installing a voltage regulator);
Upgrade heating element power or optimize furnace structure (such as increasing insulation layer thickness);
Reduce material quantity or calcine in batches.

2. Control system issues
Temperature controller malfunction
Reason: Incorrect parameter settings of the temperature controller, damaged sensor or PID adjustment failure, resulting in abnormal output signals.
Inspection method:
Check whether the temperature displayed on the temperature controller is consistent with the actual temperature (such as using an infrared thermometer to assist in measurement);
Check whether the parameters of the temperature controller meet the process requirements;
Observe whether the output signal of the temperature controller changes with temperature.
Solution:
Reset the parameters of the temperature controller;
Replace the damaged temperature sensor;
Contact the manufacturer to calibrate or replace the temperature controller.
Solid state relay (SSR) or thyristor damaged
Reason: SSR or thyristor may break down due to overcurrent, overvoltage, or frequent switching, preventing normal conduction of heating current.
Inspection method:
Use a multimeter to measure the on/off status of the SSR input terminal (control signal) and output terminal (heating current);
Observe whether the SSR indicator light changes with the temperature controller signal (if the green light is on, it indicates conduction);
Check if the heating circuit current exceeds the SSR rated value.
Solution: Replace the SSR or thyristor with the same specifications and install heat sinks or fans for forced cooling.

3. Defects in furnace structure and design
Aging or damage of insulation materials
Reason: Thermal insulation materials such as alumina fibers and ceramic fibers in the furnace have decreased in insulation performance due to long-term high-temperature use or mechanical damage.
Inspection method:
Observe whether there are cracks, detachment or discoloration on the inner wall of the furnace;
Use an infrared thermometer to measure the temperature of the furnace shell;
Compare the heating curves of the new and old furnaces.
Solution: Contact the manufacturer to replace the insulation material, or temporarily use multi-layer aluminum foil to wrap the external auxiliary insulation of the furnace.
Poor furnace sealing
Reason: The furnace door, flange, or observation window is not tightly sealed, resulting in heat loss or cold air infiltration.
Inspection method:
After closing the furnace door, feel with your hands whether there is airflow in the gap;
Place paper sheets in the furnace and observe if they are blown by the airflow;
Vacuum to -0.1MPa, maintain pressure for 5 minutes, and observe if the pressure rises.
Solution: Replace the sealing ring (such as silicone rubber or fluororubber O-ring), or adjust the furnace door clamping mechanism (such as increasing spring pressure).

4. External condition interference
Low ambient temperature or poor ventilation
Reason: The laboratory environment temperature is less than 10 ℃ or the ventilation around the furnace is poor, resulting in rapid heat dissipation or reduced heating efficiency.
Inspection method:
Measure the laboratory environment temperature using a thermometer;
Observe whether there are any obstructions (such as experimental benches or cabinets) around the furnace that affect heat dissipation.
Solution:
Move the furnace body to an environment with a temperature ≥ 15 ℃;
Clean up obstacles around the furnace body to ensure the normal operation of the cooling fan;
Install insulation cover (such as asbestos cloth or aluminum foil) outside the furnace body.
Power line issue
Reason: Insufficient heating power due to thin power cord diameter, poor contact, or voltage fluctuations.
Inspection method:
Use a clamp ammeter to measure whether the heating circuit current has reached the rated value;
Check if the power cord is overheating;
Observe whether the voltmeter fluctuates.
Solution:
Replace the copper core power cord with an area of ≥ 6mm ²;
Tighten the wiring terminals and apply conductive paste;
Install a voltage regulator or UPS power supply.

5. Operation and setting errors
Improper setting of heating program
Reason: The user did not set a reasonable heating curve based on the material characteristics (such as too fast heating rate or insufficient segmented insulation).
Inspection method:
Check the temperature controller program settings (such as target temperature, heating rate, and holding time);
Refer to the calcination process parameters provided by the material supplier (e.g. aluminum hydroxide needs to be kept at 300 ℃ for 2 hours to remove crystal water).
Solution:
Reset the heating program (such as segmented heating: room temperature → 300 ℃ (10 ℃/min) → insulation for 2 hours → 300 → 1200 ℃ (5 ℃/min) → insulation for 3 hours);
Increase the holding time at key temperature points such as dehydration and phase transition temperature.
Material loading method error
Reason: Excessive accumulation or uneven distribution of materials can hinder heat transfer.
Inspection method:
Observe whether the materials in the furnace are evenly spread (recommended thickness<50mm);
Check if the material is in direct contact with the heating element (which may cause local overheating).
Solution:
Reduce the amount of materials and spread them evenly;
Use alumina crucibles or boats to carry materials and avoid direct contact with heating elements.