Effect of geometry change on the creep failure life of a thick-walled CrMoV pipe with a circumferential weldment

Abstract

The influence of the geometry change on the failure life during creep of an internally pressurised thick-walled main steam pipe with a circumferential weldment was investigated, using finite element creep damage analyses. The pipe is subjected to a realistic internal pressure and a range of end (system) load levels, which are within the limits allowed by design codes. Actual material properties were used which were obtained from creep testing for a CrMoV pipe weldment at 640 °C. Damage calculations were conducted to investigate the deformation and strain behaviour and to obtain the failure life of the welded pipe. The plain pipe behaviour obtained previously is briefly reviewed. The results obtained from the welded pipe are compared with those obtained from the corresponding plain pipe. For the particular weldment properties used, the results obtained show that the life reduction, due to geometry change, for the welded pipe, is in the range 4.6–6.1%, which is much less significant than that for the corresponding plain pipe. The practical significance of these results is discussed.