Creep damage in long-term grade 91 steel component tests

This paper describes specific results from a unique study which involves design, manufacture and internal pressure testing of two Grade 91 steel vessels. The vessel results which are the focus of this paper relate to the creep behaviour of the closures and the associated pressure boundary welds. All the end fittings used in the vessels were consistent with arrangements allowed by typical design codes. Similar parts can be found in power boilers and other high energy components. The results are discussed in terms of creep crack initiation and the potential for fast fracture for the individual geometries.