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Super heater and Reheater tubes offossil boilers, wherein creep is the major damage mechanism, are required to be assessed periodically (after one lakh hours) for remaining life. For remaining life estimation of these tubes, knowledge of... more
Super heater and Reheater tubes offossil boilers, wherein creep is the major damage mechanism, are required to be assessed periodically (after one lakh hours) for remaining life. For remaining life estimation of these tubes, knowledge of the operating tube metal temperature forms a very valuable input. Unfortunately , this information is hard to get, since measurement of tube temperature directly or indirectly through the measurement of steam temperature , are carried out only infrequently due to various technical and economic considerations. It is more convenient to estimate the operating tube metal temperature in service by examination of tube samples for thickness of steam side oxide scale , hardness and deterioration of microstructure. Since the changes in these parameters are fitnctions of time and temperature their current 43