The LP Economiser Pressure Relief Valve had been incorrectly installed on a horizontal gas path / vertical tube HRSG. Heating of the isolated volume of water resulted in excessive pressure and rupture of one of the lower headers.Access for repairs was difficult as the header was within a bundle. It was eventually repaired by lowering the whole harp, cutting out the damaged section (see photo), and welding in a new section of header and tube stubs.
