Residual Life Assessment of F12 Main Steam Pipe System in Thermo-Power Plant

The health assessment of an exposed main steam pipe of X20CrMoV12.1(F12) in a thermal power plant was made by accelerated stress rupture and tensile tests and microstructure examinations.Results show that the main pipe has been degraded obviously after 165 000 hours in service.The pipe,especial the elbow part,displays embrittlement tendency in property.Corresponding microstructure exhibits the characteristics of granule boundary weakening and creep damage,but no evidence of localized damage in the form of cavitation or surface crack was found,the results of accelerated stress rupture tests and stress analysis by finite element method show that this steam pipe,from re-design viewpoint,is not safe in operation for next 100 000 hours under normal service condition,and its residual life is assessed from the results as well.