Influence of thermal-varying material properties on stress calculation for creep life assessment of seamless medium-carbon steel boiler tubes

Abstract Seamless medium-carbon steel boiler tubes from a thermoelectric plant are studied to predict their remanent life. An alternative for stresses calculation in creep life-assessment method is presented. The proposed stress calculation incorporates not only material dimensions and working pressure but also thermal-varying properties of the material and the radial temperature gradient in the tube wall. The methodology for creep life prediction established by ISO / TR 7468-1981 is used. It is compared with the API std 530 to show that the predicted creep rupture times can result longer when thermal-varying properties and the radial temperature gradient in the tube wall are considered. This enhanced creep failure prediction method may favour a cost reduction avoiding premature maintenance and unnecessary plant shutdowns.