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Keywords:

  • creep rupture life;
  • steam-side oxide scales;
  • superheater tubes;
  • T91 alloy

A systematic probabilistic evaluation method for the long-term creep rupture life (LCL) of T91 alloy superheater tubes is proposed in this work. The effects of steam-side oxidation on the effective load-bearing thickness and temperature of tube wall are taken into account, and the latest assessment results of the creep rupture strength of T91 alloy are utilized. Since the uncertain factors including not only the geometry dimensions but also the operational conditions may hinder a reliable analysis, instead of usual deterministic methods, probabilistic life evaluation employing Monte Carlo simulation method is performed. The effects of initial inner tube diameter, steam temperature, and steam flow on the LCL of superheater tubes are analyzed, and simple fitting functions formulating the analysis results are obtained. The survival probability of the tubes, which reflects the possibility for the LCL to be longer than a given time, is calculated. It is found that when the initial inner tube diameter or the steam temperature increases, the survival probability of the tubes exhibits a decrease trend. However, the steam flow has an opposite effect. Based on the conclusions, feasible measures that can be adopted to improve the survival probability of high temperature steam generation components in coal-fired power plants are introduced.