The Procedure for Determining the Time of Safe Service beyond the Design Service Time Based on Creep Testing

Abstract

This article describes the method for determination of residual life and disposable residual life based on long-and short-term creep tests for different temperature levels above the operating one and stress level equal to the operating one. The method for determination of the share of disposable life in total life and the time of safe service beyond the design service time was proposed. These characteristics of the steel are used for the evaluation of the structural changes and mechanical properties of the material after long-term operation. The result of this study is the database of material characteristics representing the mechanical properties related to the structure analysis, and it can be used for diagnosis of the components of pressure part of power boilers.

Service Life of Steam Turbine Rotor Material Made of Low-Alloy Cr-Mo-V Steels after Long-Term Use outside the Design Operating Time of Power Unit

“…Detailed locations from which the material for destructive testing was taken and their operational parameters are shown in Figure 1 (material No. [1][2][3][4][5].…”

“…Based on the results of many years of own research, patterns of structure were developed, illustrating the successive stages of its changes defined in the prepared classifications, including for the tested steel [1][2][3][4][5][6][7][8][9][10]. The structure change model related to the degree of exhaustion defined as the ratio of service life t e to expected time to failure t r for low-alloy ternary ferritic-bainite steels is shown in Figure 3.…”

“…Łukasiewicz Research Network -Upper Silesian Institute of Technology (formerly Łukasiewicz Research Network -Institute for Ferrous Metallurgy) has been carrying out research for several decades, aimed at creating diagnostic rules, developing methods and methodology for assessing the service life of critical components of the pressure part of power units, i.e. those operating in the most difficult temperature and stress conditions in a time significantly exceeding the design time [1][2][3][4][5][6][7][8][9][10]. These works cover various issues, including the development of a methodology to assess the condition of these components and forecast their further safe operation.…”