WRC 613 PDF

The Plausible Profiles (Psqr) method has been proposed as a means for improving the accuracy and precision of Level 2 Fitness-For-Service evaluations of corrosion damage. The method has been published as an alternative, Level 2(b), procedure in the ASME B31.G 2023 edition and, at the time of publication, is being evaluated for inclusion in an upcoming edition of API 579-1/ASME FFS-1 (API 579). ASME B31.G also permits the use of the API 579 Level 2 Assessment method within its scope. Thus, even if the Psqr method is not adopted directly by API 579, the scenario may arise where the Psqr method is used in conjunction with the API 579 Level 2 Assessment method. However, all validation studies for the Psqr method thus far have used the Modified ASME B31.G (RSTRENG) method as their basis.

This report presents an independent review of the Psqr method, including detailed verification, validation, and sensitivity studies. Novel contributions in this report include a comparison of the Psqr method with detailed elastic-plastic finite element analysis, an independent validation study, and the first documented use of the Psqr method with the API 579 Level 2 Assessment method. This report demonstrates that, due to the use of an improved model for the burst pressure of an undamaged cylinder, the API 579 Level 2 Assessment method yields more accurate predictions for the burst pressure of corroded cylinders than the RSTRENG method. As a result, the benefits of the Psqr method are shown to be limited when combined with the API 579 Level 2 Assessment method, for the cases considered. Further extension of the validation dataset would be required to demonstrate the benefit of combining the Psqr method with the API 579 Level 2 Assessment method.