A comparative study on determining primary and secondary stress levels in boiler valve bodies between FEA simulations, RemLife, and the ASME BPVC Section III Division I NB approach

Remington, Callum (2021) A comparative study on determining primary and secondary stress levels in boiler valve bodies between FEA simulations, RemLife, and the ASME BPVC Section III Division I NB approach. [USQ Project]

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A comparative study was undertaken to assess the primary and secondary stress levels in various boiler valve body designs between finite element analysis in ANSYS, following the ASME BPVC Section III Division I NB approach and through the RemLife software developed by ANSTO (Australian Nuclear Science and Technology Organisation). The purpose of the research was two-fold. First, to assess the correlation in results between these three assessment methods, primarily aimed at identifying the levels of conservatism embodied in the ASME and RemLife assessments. Then, using the same results, it aimed to assess the accuracy of the RemLife software.

This dissertation provides a background on the area of research, particularly in relation to the significance of primary and secondary stresses in the pressure equipment industry. This is followed by a comprehensive literature review, beginning with understanding the formulation of the current ‘Design by Analysis’ method adopted in the ASME BPVC codes, stress categorisation, stress linearisation, and the nature of stresses encountered in valve bodies.

The stresses derived from the ASME approach and RemLife software were compared to the exact solutions obtained from finite element analysis. The methodology for each of the three assessment methods are described in sufficient detail, including a description of how they were implemented. The finite element method followed the stress linearisation procedure for decomposing total equivalent stress fields into the individual stress categories outlined in the ASME BPVC codes. A total of five valve body designs were modelled and assessed in this study, all of which are commonly encountered in the power generation industry.

In the ASME assessments, it was found that there was a good correlation to ANSYS, with the primary stresses averaging 9.03% higher than ANSYS and the secondary stresses 12.40% across the various valve designs. A key finding from this study, however, was that the ASME approach is highly constrained to assessing secondary stresses at a steady-state operating temperature of 260℃ and a specific ramp rate of 56℃/ℎ, with the code providing no guidance or method of varying this loading condition. Nevertheless, the correlation in results at this temperature validated the accuracy of the ANSYS models.

In the RemLife assessment, the software initially returned primary and secondary stress results with a significant discrepancy to that obtained from ANSYS and ASME. In some cases, the error margins compared to ANSYS were as high as 53.14% and 120.87% for the primary and secondary stresses, respectively. However, during the undertaking of this project, the results were released to ANSTO for review and comment, where several errors in the RemLife software were identified. Consequently, with the aid of the present research, ANSTO employed several updates to the RemLife software to correct these inaccuracies. Following the updates, the RemLife software returned results with average error margins of 2.90% and 5.35% for the primary and secondary stresses, respectively.

Overall, it was identified that the ASME assessment and updated version of the RemLife software contained a level of conservatism of approximately 8-10% and 3-5%, respectively. In addition, the accuracy of the RemLife software was confirmed.

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Item Type: USQ Project
Item Status: Live Archive
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 Jul 2013 - 31 Dec 2021)
Supervisors: Yousif, Belal
Qualification: Bachelor of Engineering (Honours) (Mechanical)
Date Deposited: 03 Jan 2023 04:09
Last Modified: 26 Jun 2023 01:53
Uncontrolled Keywords: RemLife, ASME, boiler, valve, finite element analysis, assessment, methods, correlation
URI: https://sear.unisq.edu.au/id/eprint/51834

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