Moisture and plastic contamination are among the most common causes of premature thermocouple failure in hot runner systems. Water vapor, oil, or cleaning agents can penetrate poorly sealed probes, damaging internal magnesium oxide insulation. Once contaminated, insulation resistance drops, causing signal noise, short circuits, or complete failure. This issue is especially severe in humid climates or facilities using water-based mold cooling.
Molten plastic infiltration through damaged seals or improper fitting also destroys thermocouple function. Resin solidifies around the junction, creating false temperature readings and accelerating corrosion. High-pressure injection can force small amounts of material into sensor mounts over time, leading to gradual performance decline.
Sealed mineral-insulated thermocouples with robust fittings provide the best protection. Proper installation, avoiding cracked sheaths, and using compatible sealing compounds prevent moisture entry. Regular inspection and cleaning around probe areas further reduce contamination risks. Understanding these damage mechanisms helps operators extend thermocouple life in challenging environments.
