Creep-Fatigue Design Studies for Process Reactor Components Subjected to Elevated Temperature Service as per ASME-NH

A number of process reactors in refinery and petrochemical industry are constructed using low chrome alloys which are operating in the creep range and are in cyclic service. ASME B&PV Section VIII Code provides allowable stresses at elevated temperatures for design of reactor components, which are controlled by creep properties. However, fatigue design rules and fatigue exemption rules are not applicable, precluding construction of reactors using low chrome alloys at temperatures above 371 °C (7000F). ASME B&PV Section III Division 1 - Subsection NH (ASME-NH) Code considers cyclic failure modes at elevated temperatures and provides creep-fatigue interaction rules and damage limits. In this paper, creep-fatigue damage under elevated temperatures is investigated for process reactor components using elastic analysis method of ASME-NH Code for a defined representative load cycle. Also the complexities in application procedures of ASME-NH rules with thermal and structural analysis results are described in detail.