Long-term exposure to high temperatures in hot runner systems gradually changeHow Are Thermocouples Affected by Long-Term High-Temperature Operation?
s the physical and electrical properties of thermocouples. The alloy wires used in temperature sensing can undergo grain growth, oxidation, and elemental migration, leading to increased drift and reduced accuracy. Insulation materials may also degrade, allowing moisture or contaminants to enter and cause signal instability.
Type K thermocouples, widely used in hot runners, are especially susceptible to oxidation at sustained temperatures above 350°C. This phenomenon, known as green rot, can cause sudden signal shifts and inaccurate readings. Special high-temperature alloys and surface treatments help reduce these effects, but no sensor remains completely unaffected over time. Mineral-insulated construction slows degradation by protecting internal components from air and contaminants.
Regular calibration is necessary to detect drift caused by long-term high-temperature operation. Many mold shops schedule calibration quarterly or semi-annually to maintain accuracy. Using thermocouples rated for higher temperatures than required can also extend service life. Understanding the effects of prolonged heat allows operators to select appropriate sensors, schedule maintenance, and avoid unexpected failures during critical production runs.
