This paper describes the development of an assessment method to manage the integrity of numerous header end caps in an HRSG, some of which possess cracks. Following replacement of a P91 header, a subsequent inspection uncovered the presence of cracking in the end cap welds. There was evidence throughout of poor manufacturing quality and concerns over the end cap design, which analysis showed to be highly stressed. From a detailed assessment employing the methodology of the R5 procedure used in the UK, a life assessment provided a ranking list of end cap designs from which a targeted inspection strategy was devised. An NDE inspection procedure, using Phased Array and TOFD methods, was developed to inspect a sample of end caps. Further cracking across the header population was detected in both P91 other materials. Crack depths were compared to model predictions and an inspection strategy developed, taking account of both fatigue cracking as well as the perceived threat posed by Type IV cracking. Various recommendations are presented including the need for further materials data to support the process to enable the station to extend periods between re-inspections.

This content is only available via PDF.
You do not currently have access to this content.