Application of the Multi-Axial Creep Failure Method on Double Reheat Thermodynamic Cycle Turbine

Abstract

With the development of higher efficiency and lower consumption plants, higher steam parameters to 600/620/620°C and 33/10.6/3.5MPa and double reheat thermodynamic cycle system are adopted for the power plant. Thus, it is believed that the safety of high temperature components in the steam turbine system is a critical issue that could not be circumvented in the period of modern industrial development. To achieve a reliable design, manufacture and the desired long-term operation of the high temperature components in steam turbine, many fundamental research concerning design criteria and life prediction has been studied. However, for the steam turbine original equipment manufacturer (OEM) which design criteria and life prediction model are suitable for their product and how to accurately assess the components’ life under long-term operation is still a critical issue. For all confronted problems, the multi-axial creep failure is one of the major problems in the life prediction for high temperature components, and it is an important factor to be considered in the high temperature components design. In this paper, the creep failure mechanisms of high temperature components in steam turbine which under multi-axial stress states are analyzed, and the design criteria for creep strain and stress are presented which are based on cavity growth theory. The application of the method and design criteria in a medium pressure turbine which is included in a double reheat thermodynamic cycle plant is presented.