Following the catastrophic failures of seam-welded hot reheat piping at two power stations in 1985/86, the industry, with the assistance of the Electric Power Research Institute (EPRI) embarked on an aggreesive inspection and evaluation effort to minimize the apparent risk associated with operating seam-welded hot reheat piping. This effort resulted in the EPRI Guidelines for the Evaluation of Seam-Welded Steam Pipes issued in 1987. Since 1987, more data and plant experience relating to seam weld cracking have become available. The data and experience have furthered our understanding of the in-service damaging process, and have helped assess the field effectiveness of the EPRI-recommendedprocedure for in-service seam-wealded pipe inspection. Based on metallurgical evaluation and mechanicla tests of weldments, the factors contribudting to failures have bene identified to be some or all of the following: excess stress and temperature; pre-existing flaws; nonmetallic inclusion; sharp weld cusps and creep strength mismatch; impurity segregation; weld roof-angle; etc. Since exceptions exist in every case, attempts to develop screening criteria for pipes "at risk" have been less than cussessful. This ppaer presents an overview of the current state-of-knowledge with regard to the integrity of hot reheat seam-welded piping in the USA, with summary guidance on quantitative application of this knowledge to the life prediction of in-service piping.
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