Predictive stress and crack growth monitoring in cracked superheater headers

This paper summarises the component life assessment strategy used by PowerGen to underwrite the continued operation of high capital cost components which contain defects, such as ligament cracking in boiler steam headers. The life assessment strategy consists of three separate stages, where at each stage more effort is expended and subsequently better, and generally longer, component life estimates are made. Benefits from this process are that the impact of changes in modes of operation, such as entering a two-shift mode of operation can be relatively easily assessed, and that cracked components can often be shown to be safe to remain in service, in some cases for many years.