Circumferential Cracking in Supercritical Waterwalls：在超临界水冷壁环向开裂.doc

Circumferential Cracking in Supercritical Waterwalls A recent EPRI report provides a review of the current understanding of circumferential cracking in the waterwalls of supercritical power plants. The report, entitled Root Causes of Circumferential Cracking in Waterwalls of Supercritical Units: State-of-Knowledge (1014205), summarizes what is known about the mechanisms behind circumferential cracking, methods of nondestructive examination (NDE), possible solutions, and areas of needed research. Qualified funders may click on the link below to view or download a copy of the report. How to Apply the Results Circumferential cracking in supercritical waterwalls has reappeared as a major issue in the industry. Plant staff responsible for system reliability can use this report to increase their understanding of the key causes of circumferential cracking. Armed with this knowledge, they will be able to assist plant operators in implementing practical, cost-effective solutions, which have the potential to significantly reduce failures and improve plant availability. Background Circumferential cracking on the waterwalls has again become a significant problem for many supercritical units, especially with the implementation of low-NOx systems. Damage typically consists of multiple, parallel cracks perpendicular to the longitudinal axis of the tube and to the direction of maximum tensile stress. There can be numerous potential causes, and the choice of the appropriate control strategy will depend on identifying the underlying cause(s) for a particular outbreak of damage. Research has shown that the causes of circumferential cracking are very site specific, and that often times multiple factors work to compound the damage. In many instances, the governing causes and mechanisms are steam side based (for example, growth of thermal oxides), while in other, more recent cases (especially given the implementation of low-NOx systems), combustion and fuel-related parameters are the pr