A Methodology for Evaluating the Integrity of Longitudinally Seam-Welded Steam Pipes in Fossil Plants

Two recent catastrophic failures of steam pipes have generated great concern about the integrity of steam pipes in fossil power plants. In the wake of these failures, extensive pipe inspections have been carried out by utilities. Numerous flaws have been found, but the methodologies for disposition of flawed piping have varied widely. The failure scenario has emerged to be one involving creep crack growth of preexisting flaws located at the weld fusion line. The crack growth susceptibility itself has been found to be a function of the metallurgical condition of the steel. Based on creep damage initiation and crack growth methodologies developed by Electric Power Research Institute under a variety of projects, an overall approach to assessing pipe integrity and for determining inspection intervals has been constructed. This paper will report on the details of this approach.