CHARACTERISATION AND QUANTIFICATION OF DEFECTS IN ROTORS AND CASINGS OF STEAM TURBINES

The loading situation of components in modern fossil-fired power plants is characterised by higher cyclic service in comparison to older plants. This leads in combination with larger units to increased stresses in the relevant components. To evaluate the risk of failure due to natural defects, life time approaches have been developed on the basis of advanced methods of fracture mechanics. The assessment of natural defects using fracture mechanics is, however, based on the following preconditions: • knowledge and data on the behaviour of such defects in terms of damage mechanism taking into account crack initiation and crack propagation under loading situations comparable to those in service,• data on the real size and geometry of defects,• data on the exact location of the defects.To create such a database an extensive joint research programme was started in the early eighties by German turbine manufacturers, steel makers and research institutes. The paper provides an overview of the results of these effo...