High temperature component integrity in turbines required for flexible operation – evaluating assessment effectiveness

ABSTRACT In recent years, there has increasingly been the requirement for turbine generators to operate more efficiently, and in a more flexible way. Traditionally, the effectiveness of assessment procedures used to predict component integrity has been established on the basis of service experience. As the demand has increased for new materials to be adopted after increasingly shorter development periods, and more efficient and flexible operation to complement the availability of renewable energies has become the norm, it has no longer been possible to evaluate assessment effectiveness on the basis of prior operating experience, since it did not exist. The solution has been to use the results of component-feature specimen tests. Initially, these were full section isothermal benchmark tests conducted at the maximum operating temperature. Now the verification of assessment effectiveness using component-feature specimen, service-cycle TMF testing has become more realistic and economically viable, with (i) component-feature specimens of a more conventional laboratory testing size, but meeting prior defined geometry and damage mechanism requirements, and (ii) service-cycle details based on the results of operation-based non-linear (elastic-plastic-creep) finite element analysis.