ON LINE FATIGUE LIFE MONITORING METHODOLOGY FOR POWER-PLANT COMPONENTS

Fatigue is one of the most important aging effects of power plant comp onents. Information about fatigue helps in assessing structural degrad ation of the components and so assists in planning in-service inspecti on and maintenance. It may also support the future life extension prog ramme of a power plant. In the present paper, the development of a met hodology for on line fatigue life monitoring using available plant ins trumentation is presented. The Green's function technique is used to c onvert plant data to stress-time data. Using a rainflow cycle counting method, stress-time data are analysed and the fatigue usage factor is computed from the material fatigue curve. Various codes are developed to generate Green's functions, to convert plant data to stress-time d ata, to find the fatigue usage factor and to display fatigue informati on. Using the developed codes, information about the fatigue life of v arious components of a power plant can be updated, stored and displaye d interactively by plant operators. Three different case studies are r eported in the present paper. These are the fatigue analyses of a thic k pipe, of a nozzle connected to a pressure vessel and of a reducer co nnecting a heat exchanger to its piping system.