Abstract
Present study extends the investigation previously carried out on a P91 tee to two of the three component’s welds. Previous studies included both creep analysis and infield tests; component considered is the outflow tubing / manifold tee of the superheater harp, steam generator high-temperature-section. Creep simulation requires extraction of constituent law’s coefficients for the P91 weld metal. Analytical methods base on creep strain and strain rate data. As an alternative to their experimental derivation from an ex-service welded-material sample, present study benefits from literature data availability. Specifically, they come from rupture creep-tests on cross-weld P91 specimens at 600°C and 650°C; the weld sample consisted of as-fabricated P91 two plates, welded by a V-butt joint. Stresses selected are above, close to the operation maximum considered in the analysis. Coherently, instead of the outflow-tube / manifold tee-weld, study now considers the butt joint weld on manifold and the outflow tube. It adopted this choice also for economy of the simulation, weld creep damage calculated through both Larson-Miller theory and Monkman-Grant relation. Comparison of LMP (stress) data from literature sources (base-metal minimum-LMP and weld-metal) shows good consistency. For the manifold’s weld, API 579-1 and FEM stress analysis have predicted expended life percentage of 24%. For the outflow tube’s weld, master curve method and manual stress analysis have predicted similar expended life percentage.
