The actual operating conditions of a component may vary from the original design conditions either constantly or variably as a consequence of deviation from design parameters. Hence, the knowledge of operating temperatures and stresses, both historically and for anticipated future operation is required for an accurate life assessment. A number of high temperature and high stress components of Indian thermal power utilities are being monitored round-the-clock for damage assessment by acquiring real-time process data using an on-line damage monitoring system BOSSES, developed by BARC, Mumbai. A number of surface replicas have been obtained from the critical location of a shell-nozzle junction of a super-heater header and analyzed by quantitative metallographic methods. The aim of these activities is to assess service damage of critical components to prevent any unforeseen failure based on a closed loop on-line damage monitoring system-cum-surveillance-cum-life management programme.