Session: CS-06-01 The Martin Prager Memorial Session on API 579/ASME Code Fitness-for-Service Activities

Paper Number: 122400

122400 - Evaluation of the Api 579-1/asme Ffs-1 Kstc Stress Intensity Factors 

The API 579-1/ASME FFS-1 2021 Fitness-For-Service stress intensity factor solutions for a sphere with a through-wall crack (KSTC) was investigated. Finite element models of through-thickness cracked spheres subjected to uniform crack face loading, linear crack face loading, and internal pressure induced stress fields were created and used to estimate stress intensity factors (K) along the various crack fronts, which were then used to establish influence coefficient values. Due to the extreme change in K near the vertex it is a common practice in engineering applications to extrapolate K to obtain an effective K at the inside and outside surface locations. The method of extrapolation used for this assessment is generally consistent with WRC 478, which established the basis for spheres and other through-thickness cracked shapes in API-579. The parametric space includes the current space covered in API 579-1 for KSTC plus new higher ratios of sphere internal radius to thickness. The comparison of the newly calculated stress intensity factors to the existing API 579-1 KSTC values showed good agreement in some cases and modest differences for the remaining cases. The differences are likely due to mesh refinement. The new influence coefficient values presented herein are recommended for fitness for service assessments that involve KSTC. 

Presenting Author: Scott Leakey Becht

Presenting Author Biography: Mr. Scott Leakey, P. Eng is an engineering advisor at Becht, based out of Alberta, Canada. His primarily technical focus is advanced simulation of pressurized equipment in the downstream oil and gas sector. Before joining Becht, he specialized in simulations for pipelines and pressurized components in offshore and subsea oil and gas applications. He is a registered professional engineer in Alberta and holds a Bachelors of Science Degree in Mechanical Engineering from the University of Alberta.

Authors:

Steven Altstadt Becht
Scott Leakey Becht