Residual lifetime assessment of cold-reheater pipe in coal-fired power plant through accelerated degradation test

Non-destructive testing (NDT) is the process of evaluating and inspecting materials without damage. The purpose of present study is to evaluate the residual lifetime of materials by proposing a new concept of non-destructive testing. The residual lifetime of service-exposed 1.25Cr-0.5Mo (P11) steel cold-reheater pipes in a coal-fired power plant, which were used for approximately 23 years at 310 °C, was investigated with accelerated degradation tests of a fresh P11 steel. The hardness and the microstructure of the P11 steel aged at 550 °C for 1000 h were similar to those of the service-exposed cold-reheater pipe. The creep-rupture tests of the steel aged at 550 °C for 1000 h were performed under various temperature and stress conditions together with the fresh steel. The creep-rupture properties analyzed using a Larson–Miller parameter (LMP) approach suggested that the residual lifetime of the service-exposed pipes is approximately 53% at the current conditions. The proposed methodology is expected to serve as a useful tool to check the timing of materials replacement and to maintain safety in a coal-fired power plant.