COMPARISON OF CANDIDATE STEADY LOADING ELEVATED TEMPERATURE DESIGN-BY-ANALYSIS METHODS

Design-by-Analysis is distinguished from Design-by-Formula or Design-by-Rule in that specific failure modes are identified, and detailed analysis of each failure mode is compared to criteria specific to each failure mode. Several ASME Boiler and Pressure Vessel code committees continue to work on design-by-analysis methods in the elevated temperature range, where creep rupture is a failure mode with steady loading. The Subgroup on Elevated Temperature Design, which reports to Section I and Section VIII and collaborates with Section III, has been evaluating eight different analysis methods for six example problems. The two Design-by-Formula methods are from Section I and Section VIII Division 1 and the Design-by-Analysis methods are (1) Linear Elastic Analysis with revised stress limits, (2) Isochronous Curve Limit Load, (3) STP-PT-070 Limit Load Analysis, (4) Detailed Inelastic Methods using the MPC Omega creep models, (5) ASME CC2843 (simplified NH method),and (6) Section III Division 5 Draft Code Case for Limit Load Analysis. The test cases include (1) Grade 11 Steam Outlet Header, (2) Grade 91 Header Endplate, (3) Grade 91 Steam Outlet Header, (4) Grade 91 Steam outlet Header 2, (5) Grade 91 Steam Piping Lateral and (6) Type 304 Stainless Spherical Vessel/Nozzle. To ensure a common comparison, a common material definition was used based on the ASME FFS-1/API579 material models. Each of the analysis methods and examples will be described along with a comparison of the maximum pressure predicted by each method for each problem.