Integrated methods to assess residual lifeand fitness for further service of hollowturbine and generator rotors

摘要

This paper deals with the development of specific tools (methods, equipment, software) forrnassessing the Fitness-for-Service (FFS) of turbine and generator rotors and their combinedrnapplication within an integrated approach, so as to improve the accuracy and reliability ofrnFFS and life consumption evaluations.rnThe outlined approach integrates the following aspects:rn? Accurate, quantitative and efficient defect detection, location and sizing in hollow rotorsrnby means of a boresonic system of non-conventional electro-mechanical design and withrnadvanced ultrasonic signal processing solutionsrn? Direct assessment of residual mechanical properties of the serviced rotor material in criti-calrnlocations by quasi - non invasive sample extraction and application of the “SmallrnPunch” method, using correlations of improved accuracy between standard and “SmallrnPunch” datarn? FEM analysis of thermal and mechanical stresses acting on the rotor under steady staternand typical transient (startup / shutdown) conditions and identification of highest stressrnvalues, locations and time ? Based on all the above inputs, automated screening and ranking of discontinuities de-tectedrnin the rotor, in terms of stability and growth rate under the rated operating condi-tionsrn/or the incoming service interval.rnThe benefits of this approach in terms of safe and reliable extension of the operation life ofrnserviced rotors savings are pointed out through a few selected examples.