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Recently updated on Maggio 11th, 2021 at 08:59 am
The conventional thermal power generation infrastructure in Italy is largely obsolescent, many steam cycle units still in operation dating back to the late ’70s and before. On the other hand, the large on-going effort in converting obsolescent steam cycle units to gas-fired combined–cycle units points out the problem of safe and economically viable re-use of some high-value components of the old units, typically the steam turbine. Finally, the opening of the electric market and the competitive energy bidding determines an increasing trend towards flexible, on-demand, cyclic operation of medium merit conventional steam units. All the above factors stress the importance of reliable and accurate methods to assess life consumption and fitness for further service (FFS) of turbine and generator rotors (hollow rotors in most of the oldest steam turbines) under combined creep and thermal fatigue conditions. This paper deals with the development of specific tools (methods, equipments, software) for assessing the FFS of turbine and generator rotors and their combined application within an integrated approach, so as to improve the accuracy and reliability of life consumption and FFS evaluations. The approach outlined in the paper integrates the following aspects: • Accurate, quantitative and efficient defect detection, location and sizing in hollow rotors by means of a boresonic system of non-conventional electro-mechanical design and with advanced ultrasonic signal processing solutions • Direct assessment of residual mechanical properties of the serviced rotor material in critical locations by quasi – non invasive sample extraction and application of the “Small Punch” method, using correlations of improved accuracy between standard and “Small Punch” data • FEM analysis of thermal and mechanical stresses acting on the rotor under steady state and typical transient (startup / shutdown) conditions and identification of highest stress values, locations and time • Based on all the above inputs, automated screening and ranking of discontinuities detected in the rotor, in terms of stability and growth rate under the rated operating conditions /or the incoming service interval. An actual example of application is discussed in detail in the paper, pointing out the benefits of this approach in terms of safe and reliable extension of the operation life of serviced rotors and of the related savings. PUBBLICATO A5032652 (PAD – 675666)
31 Dicembre 2005
Una generazione sostenibile di Energia Elettrica per il XXI secolo (GEN 21)