Failed Type J Thermocouple Analysis
The Customer’s Problem
The customer submitted a failed Type J Thermocouple reported to have developed an open circuit after extended time at temperature. Initial evaluation confirmed the open circuit.
The Findings / Analysis
Sectioning of the thermocouple probe confirmed that the thermocouple wires remained intact. Further examination revealed the breaks to be in the extension wire portion of the probe.
Further sectioning of the extension wire isolated the open circuit to be adjacent to the transition section shown in Figure 1. Removal of the armoring and insulation reveled the break within one inch of the transition.
Figure 2 shows comparison between the un-corroded negative leg and the heavily corroded positive leg.
At higher magnification (Figure 3) shows the degree of corrosion in the positive leg.
In conclusion, it was determined the leg corroded because of oxidation. Recommended to client to swap wire for non-oxidizing material(s).
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