Failure analysis of a high-temperature thermocouple |
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Authors: | K. Gates S. Benhaddad |
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Affiliation: | (1) Thermex Metal Treating, 4734 18 St., T6P 1N8 Edmonton, AB, Canada;(2) Versa Power Systems, 4852 52 St. SE, T2B 3R2 Calgary, AB, Canada |
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Abstract: | A solid oxide fuel cell unit operates at high temperatures of 700 to 800°C. The operation of the unit is controlled by a set of instrumentation including sensors, thermocouples, and voltage leads. Two S-thermocouples were inserted in the after-burner where temperature is constantly at 1000°C. During operation of one prototype unit and after 1000 h, the thermocouples started to give erratic readings and led to complete shutdown of the unit. Analysis of the thermocouples revealed a series of events may have occurred due to stress induced by the design, materials and operating conditions, contamination during manufacturing, or a reducing environment caused by sheathing. The specification from S-type to B-type may remove the risk of reoccurrence. A design change in platinum burner thermocouples to ensure an oxygen-rich environment for the platinum was also recommended. |
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Keywords: | catastrophic failure contamination failure analysis high temperature materials selection metallurgical investigation nonferrous metals |
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