After a power piping system has begun commercial operation, it is recommended that the initial nondestructive examination (NDE) of the welds should be developed and executed to reveal possible fabrication and early service-related material damage. The identified indications and other possible anomalies should be thoroughly documented, evaluated, and dispositioned.
Additional early service-related cracks may initiate and propagate several years after the first examination. This paper considers historical early service-related cracks in weldments of power piping systems operating in the creep regime. Factors that dominate these early service-related cracks are discussed in this paper.
This paper provides a list of more than 20 historical examples of power piping Grade 91 material macrocracks (partial wall or through-wall) that were not present immediately after construction and propagated substantially in service. Five of the examples are discussed in more detail. The study only includes cases where propagating cracks were confirmed. It does not include examples where NDE reportable indications have not propagated in service to large macrocracks. Due to the time-dependent nature of these girth weld cracks, the results of this study may be used to assist in the selection of Grade 91 reexamination locations after the power piping system (e.g., main steam, hot reheat, high pressure, or intermediate pressure) has been several years in service.