Factors for Improving Reliability in Large Industrial Gas Turbines

Abstract

The use of aero engine design methods and experience including higher temperature materials and protective coatings have significantly increased thermal efficiency, and output capability of large industrial gas turbines such as the F, G and H class. As a result the gas path components operate at much higher gas temperatures over significantly longer maintenance intervals, as compared to aero engine experience. Therefore, it is essential that the hardware durability can effectively endure longer periods of attack by oxidation, creep and fatigue because of longer operating intervals between scheduled maintenance periods. Another factor that has become increasingly important is the need for greater flexibility in power plant operation. Specifically, the power plants must operate reliably under more frequent cyclic operation, including partial load cycling. This is in addition to the normal dispatch cycle of the power plant (i.e. daily-start-stop, weekly-start-stop, etc). Gas Turbine reliability is directly dependent on hardware performance and durability. Therefore, the gas turbine must have sufficient design margin to sustain the synergistic effect of higher firing temperature, and the operational challenges associated with greater partial load cycling. This paper discusses Mitsubishi’s approach for achieving the above mentioned objectives so that the overarching goals of higher reliability and durability of hot components are achieved in large advanced gas turbines.