ISBN : 81 - 87053 - 73-1 Remaining L4fe Assessment of Aged Components in Thermal Power Plants and Petrochemical Industries, Vol. 2 Eds. A. K. Ray, S. Chaudhuri, N. G. Goswami and R. N. Ghosh ©NML Jamshedpur 831007, India, 2008, pp. 43-56 3 Residual life estimation of high temperature tubings based on oxide scale thickness measurement B. B. JHA, S. N. OJHA' and B . K. MISRA Institute of Minerals and Materials Technology, Bhubaneswar-751015, India 'Dept. of Met. Engineering, Institute of Technology, Banaras Hindu University, Varanasi-221 005 Abstract : Super heater and Reheater tubes of fossil 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