Analysis of Frequent Tube Burst of High Temperature Reheater in 600 MW Unit

The reasons of frequent tube burst of the high temperature reheater in a supercritical 600 MW unit were systematically investigated via the examination of macroscopic inspection, chemical composition, mechanical properties, microstructures, scanning electron microscope and energy disperse spectroscopy detection. It is demonstrated that the tube burst of the high temperature reheater results from not only design factors, but also manufacture quality. Due to the absence of solid solution treatment in spare elbow, the inner dislocations and residual stress increase obviously, which accelerates the precipitation of carbide containing Cr and the formation of Cr depleted zone on grain boundary(GB) subsequently, leading to the decrease of GB corrosion resistance and the final leakage of high temperature reheater tube induced by intergranular corrosion.