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Thermocouple Service and Maintenance

Protect Thermocouples in Service - Evaporation, diffusion, oxidation, corrosion, and contamination induce EMF drift due to their effect on the composition of the thermocouple alloys. These environmental factors are destructive to all common thermocouple alloys. It is essential that proper protection be provided anytime adverse conditions are encountered.

In many applications this can be done by using sheath style elements. If bare wire elements are used, the thermoelement must be properly installed in suitable protection tubes or thermowells. When the interior of the protection tube or thermowell is free of sulfur bearing medias and when they are of the proper diameter to length ratios to permit adequate ventilation, they server very well in overcoming the harmful effects of a corrosive atmosphere.

Preventative Maintenance - Thermocouples, protection tubes, and extension wires should be checked periodically. Experience largely determines the frequency of inspection but once a month is normally sufficient.

Check out extension wire by making certain that it meets the established external resistance required.

Damaged or burnt out protection tubes and thermowells should be replaced to prevent damage to the thermocouple.

Thermocouples should be checked in place if possible. If removing the element is necessary, it should be to the same depth or deeper to avoid errors arising from placing an inhomogeneous segment of wire in a steep temperature gradient.