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Comparison of BS 7910 and API 579-1/ASME FFS-1 Solutions With Regards to Leak-Before-Break

[+] Author Affiliations
Renaud Bourga, Bin Wang

Brunel University London, Uxbridge, UK

Philippa Moore, Yin Jin Janin

TWI Ltd, Great Abington, UK

Paper No. PVP2016-63876, pp. V06AT06A077; 21 pages
  • ASME 2016 Pressure Vessels and Piping Conference
  • Volume 6A: Materials and Fabrication
  • Vancouver, British Columbia, Canada, July 17–21, 2016
  • Conference Sponsors: Pressure Vessels and Piping Division
  • ISBN: 978-0-7918-5042-8
  • Copyright © 2016 by ASME


One of the ways to aid the decision whether or not to live with defects in pressurised components is through the demonstration of Leak-Before-Break (LBB). In this paper, three of the main solutions to carry out the LBB assessment, namely Stress Intensity Factor (SIF), Reference Stress (RS) and Crack Opening Area (COA) have been evaluated and compared for both BS 7910 and API 579/ASME FFS-1 standards. Differences with respect to the choice of solutions and boundary conditions are illustrated and discussed. The same applied loads and material properties have been used when applying each procedure. Different geometries for potential pressurised components which are of interest with regards to LBB have been considered for each solution. Focus is made on cylinders where axially and circumferentially oriented through-wall and surface cracks were analysed. While SIF solutions produce similar results for both standards, reference stress solutions show greater differences in the results. However, in LBB assessments it is the reference stress solution which is more relevant, since most LBB assessments pre-suppose the material to be ductile. In terms of COA, solutions are not given exactly equivalent, however they seem to agree well within the common range of applicability. Differences in the assessment route between the standards is also discussed. Experimental data from literature has also been compared to the different standard predictions, to illustrate the accuracy of the solutions for axially oriented surface cracks. The ability of solutions to predict the boundary between leak and break is discussed, in relation to how this shows the level of conservatism.

Copyright © 2016 by ASME



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