Signal distortion in reduced-bore thermocouples is generally irreparable. It is recommended to replace the probe directly, as its miniaturized structure and high-sealing design do not allow for disassembly and repair.
1. Why Repair is Generally Not Recommended
Irreversible Structure: After reduction, the outer diameter is only Φ0.25–3mm. The internal thermocouple wire and magnesium oxide insulation layer are highly densely bonded through forging/drawing processes, making non-destructive disassembly impossible.
High Welding Requirements: Re-welding requires inert gas protection, and the weld joints must be spherical and free of pores, which is difficult to achieve with ordinary equipment.
High Insulation Risk: The disassembly and repair process can easily introduce moisture or impurities, leading to a decrease in insulation resistance and affecting temperature measurement stability.
Length Change: After repair, the probe length becomes shorter, which may not meet the original installation depth requirements (e.g., hot runner systems are sensitive to insertion length).
Even with temporary repair, its mechanical strength and thermal cycle life are significantly reduced, posing a risk of field failure.
2. Only Feasible Emergency Handling Method
If signal distortion is caused by a terminal problem (e.g., oxidation, loosening), and the probe body is intact, try the following:
Cut off the damaged section: Only if the breakage or corrosion is located at the terminal and the remaining length still meets installation requirements;
Re-strip the wire and crimp the terminals;
Use a dedicated thermocouple extension cable of the same index number to ensure correct polarity and firm contact.
This is only suitable for temporary replacement and is not recommended for long-term use in critical operating conditions.
3. Correct Response Strategy
Situation Handling Recommendation
Signal distortion at the measuring end Replace immediately, cannot be repaired
Insulation failure in the middle section or damage to the thermocouple wire Replace with a new probe to avoid signal drift
Poor contact at the terminal Can be cut and rewired, but insulation and thermoelectric potential must be verified
Industry Practice: High-end applications (such as injection molding hot runners) adopt a "replace the fault" strategy to ensure system reliability.
