Session: DA-08-01: Fitness for Service Evaluations - 1

Paper Number: 84922

84922 - Evaluation of the API 579-1/ASME FFS-1 KPECL and KCECLL Stress Intensity Factors 

The API 579-1/ASME FFS-1 2021 Fitness-For-Stress document’s stress intensity factor solution for a plate with an embedded crack, infinite length, through-wall fourth order polynomial stress distribution (KPECL) was independently investigated in this work. Finite element models of cracked plates subjected to various applied stress fields were created and used to estimate stress intensity factors (K), which were then used to calibrate the respective influence coefficient values (G_i). The comparison of the newly calculated values to the existing values shows reasonable agreement for some values and a substantial difference for others. The new values were also compared to values published by Delliou and Barthelet (2007) for the parameter combinations that exactly overlap with API 579-1/ASME FFS-1 2021. Excellent agreement was found with the new values presented herein. API 579-1/ASME FFS-1 2021 also indicates that the KPECL solution can be used for a cylinder with an embedded crack, longitudinal direction, infinite length, through-wall fourth order polynomial stress distribution (KCECLL) when the ratio of the internal radius (R_i) to wall thickness (t) is greater than 5. As part of this work, influence coefficient values were also calculated for R_i/t=5 and are included in this paper. A comparison of each KCECL value to its respective KCECLL value results in a difference of less than one percent. The new weight influence coefficient values are recommended for fitness for service assessments that involved the KPECL scenario or the KCECLL scenario where R_i/t≥5.

Presenting Author: Steven Altstadt Wiss Janney Elstner Assoc Inc

Presenting Author Biography: Dr. Altstadt is an associate principal at Wiss, Janney, Elstner Associates, Inc. where he helps clients with their technical challenges in the areas of fitness for service assessments, metal fatigue, non-linear finite element modeling, fracture mechanics, failure analysis, forensic investigation, laboratory testing, litigation support, integrity management programs, design review and non-standard engineering projects. Projects include pipelines, pressure vessels, tanks, silos, piping, metal structures (offshore/subsea/conventional onshore), and machinery. He is licensed professional engineer in 26 states.

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