Abbott Furnace Spare Parts & Components

What types of thermocouples are commonly used in thermal processing equipment?
Thermal processing equipment typically uses two categories of thermocouples: base metal and noble metal.
Base metal thermocouples include Types K, N, J, and E. These are commonly used at lower temperatures and are relatively economical.
Noble metal thermocouples include Types B, R, and S. These are used at higher temperatures, are more expensive, and offer improved accuracy. Noble metal thermocouples are also available with special limits of error for applications requiring the highest precision.

Why do thermocouples need to be replaced or recalibrated?
Many current manufacturing standards, including CQI-9, CQI-29, and AMS 2750, require periodic replacement or recalibration of thermocouples to ensure process accuracy and repeatability. Over time, thermocouples drift due to exposure to heat, atmosphere, and thermal cycling, which can impact temperature measurement accuracy.

How often should thermocouples be replaced or recalibrated?
While requirements vary by specification, a common guideline is:

• Base metal thermocouples must be replaced at least annually and cannot be recalibrated.
• Noble metal thermocouples typically require replacement or recalibration every two years and can often be recalibrated by the manufacturer.

Always confirm the specific requirements of the governing specification for your process. Specific replacement and calibration intervals are defined by the applicable specifications, furnace class, and usage types.

What is included in a temperature controller calibration?
Calibration of temperature controllers and instruments is typically performed by an ISO 17025–accredited calibration provider. This calibration verifies the accuracy of the temperature instrument by simulating the millivolt signal of a thermocouple using a calibrated reference device.

Does controller calibration verify the accuracy of the thermocouple itself?
No. Controller calibration only verifies the accuracy of the temperature instrument. It does not evaluate the condition or accuracy of the installed thermocouple. This is why standards require separate thermocouple replacement or recalibration at defined intervals.

What is a common compliance risk related to thermocouples?
A frequent issue occurs when controller calibrations are performed as required, but thermocouples are not replaced or recalibrated at the specified frequency. This can lead to inaccurate temperature control and noncompliance with applicable standards.

Who is responsible for thermocouple replacement?
Thermocouple replacement may be handled by your internal maintenance team or by an external service provider. Regardless of who performs the work, it is critical that thermocouples are replaced or recalibrated in accordance with the applicable specifications.