Session: DA-09-02 Piping and Equipment Dynamics and Dynamic Response Analysis-2

Paper Number: 122678

122678 - Using Asme B31j Stress Intensification Factors (Sifs) to Improve a Bs 7608 Fatigue Analysis 

Standards like ASME B31J-2017 describe a methodology for calculating stress intensification factors (SIFs) for metallic piping components like branch connection fittings and elbows. These SIFs are based on fatigue tests done on commercially available metallic components, and relate the stress that causes a through-wall crack in the component to the fatigue strength of straight butt-welded pipe. The SIFs consider many different variables of the geometry including component diameter and wall thickness.
Fatigue standards like BS 7608:2015 do not account for fitting geometry directly, focusing instead on weld joint details required for fatigue calculations. Standards like BS 7608:2015 are widely used and appear to more accurately simulate the fatigue failure of welded structures.
The goal of this paper is to outline a method to utilize the fatigue testing that is embedded in the ASME B31J SIF calculations to improve the accuracy of a fatigue analysis done using standard BS 7608:2015. Some consideration is required before using the standards together, due to different methodologies and S-N curves.
The paper includes several finite element analyses which test the conclusions of the paper. Additionally, calculations are done using the original testing data contained in ASME STP-PT-073 Annex E by A. W. Paulin.
The approach outlined in this paper is being considered for use in the new API 579 Part 15 – Assessment of Piping Vibration.

Presenting Author: Chris Harper Wood

Presenting Author Biography: Chris Harper is a principal consulting engineer with Wood’s vibration, dynamic and noise division and has 25 years’ experience in the fields of piping/machinery vibration, stress/fatigue analysis, AIV/FIV, transient analysis, small bore connections (SBCs), and finite element analysis (FEA). He has led several research projects for the Gas Machinery Research Council (GMRC), has contributed to guidelines such as ISO 20816-8 Annex E, the upcoming API 579 Part 15, the upcoming 3rd edition of the Energy Institute AVIFF document, and written several papers for ASME International Pipeline Conference (IPC), Gas Machinery Conference (GMC), European Forum for Reciprocating Compressors (EFRC), and CompressorTech2 magazine.

Authors:

Chris Harper Wood
Lyle Breaux Stress Engineering Services, Inc.