Session: HT-03-01 Materials & Fitness for Service Methods for High-Pressure Vessels and Piping

Paper Number: 106355

106355 - Evaluation of the Api 579-1/asme Ffs-1 Kcsccl1 Global Bending Stress Intensity Factors 

Abstract:

The API 579-1/ASME FFS-1 2021 (API 579) Fitness-For-Service stress intensity factor solution for a cylinder with a long surface crack in the circumferential direction (i.e. 360 Degrees), subjected to Pressure, a Net-Section Axial Force and Global Bending (KCSCCL1) was independently investigated in this work. Linear elastic finite element models of cracked cylinders subjected to various applied global bending stress fields were created and used to estimate stress intensity factors (K), from which were determined the respective influence coefficient values for global bending (G₅). The comparison of the newly calculated values to the existing stress intensity factors shows reasonable agreement for larger internal radius to thickness ratios (R_i/t), but significant differences for low ratios representing thick wall cylinders. The new influence coefficients were also compared to values published by Maire et al (2007) for the parameter combinations that exactly overlap with API 579 for the R_i/t ≤ 10 parametric space. The new stress intensity factor equation and associated influence coefficient values presented in this work are recommended as an improvement for fitness for service assessments where R_i/t ≤ 10. For thin wall cylinders, the existing API 579 approach for KCSCCL1 is acceptable.

Presenting Author: Scott Bouse WJE Associates

Presenting Author Biography: Scott Bouse is a Senior Associate in the Metallurgy and Applied Mechanics group at Wiss, Janney, Elstner Associates, Inc. Scott's primary technical focus is on Fitness For Service of pressurized equipment and related maintenance concerns. He works with clients on new designs, fitness for service of existing assets, re-designs of existing assets to achieve improved mechanical performance, and forensic investigations. He has fourteen years of experience, primarily in the Downstream Oil & Gas and Chemical industries, and a M.S in Mechanical Engineering from Texas A&M University. He is a licensed professional engineer in Texas and four other states.

Authors:

Scott Bouse WJE Associates
Steven Altstadt WJE Associates