Residual lifetime estimation by scatter band analysis of an E911 pipe bend of an USC power plant

The ex-service behaviour of an ultra-supercritical (USC) power plant pipe bend operated at 260 bar and 580 °C is analysed. For analysis of E911 material residual lifetime properties, a pipe bend from a live steam line was uninstalled and tested under advanced conditions (460 bar at 600 °C). The creep deformation was measured with high-temperature strain sensors and modelled by the flexible logistic creep strain predication (LCSP) deformation model together with a model for diffusive creep deformation. This modified model had been adjusted to creep data of different E911 batches. The batch dependence of E911 creep strength is addressed with a so-called scatter band factor, which is adjusted with respect to ECCC data for E911 average creep strength. The scatter band factor of the pipe bend material is identified comparing strain sensor measurements from the component surface with finite element calculations using the modified LCSP deformation model. This allows the determination of the components material scatter band factor and hence improved residual lifetime estimate by comparison of service deformation to calculated strains. The lifetime usage of the pipe bend was estimated and compared to creep damage assessment by surface replicas during the 25 000 hours of ex-service loading.