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Fracture assessment method for girth welds of high-grade steel pipelines considering strength matching

Oil & Gas Storage and Transportation[ISSN:1000-8241/CN:13-1093/TE] Issue: 2021年09期Page: 1008-1016 Research Field: Publishing date: 2021-09-25
Title:

Fracture assessment method for girth welds of high-grade steel pipelines considering strength matching

Author(s):

WU Kai1;  ZHANG Hong1;  YANG Yue1;  LIU Xiaoben1;  SUI Yongli2;  CHEN Pengchao3

1. China University of Petroleum (Beijing) // National Engineering Laboratory for Pipeline Safety // MOE Key Laboratory of Petroleum Engineering // Beijing Key Laboratory of Urban Oil and Gas Distribution Technology; 2. China Petroleum Pipeline Research I

Keywords:

girth welds;  high-grade;  strength matching;  Failure Assessment Diagram (FAD);  fracture assessment

CLC:
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DOI:
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DocumentCode:

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Abstract:

The actual strength under-matching of pipeline girth welds is a principal cause for the fracture failure of welds. The current Failure Assessment Diagram (FAD) method for the applicability assessment of pipeline welds cannot accurately consider the influence of weld strength matching. Thus, accurate inclusion of strength matching becomes critical to broaden the FAD method to apply to the crack defect assessment for the girth welds of high-grade steel pipelines. Based on the nonlinear finite element method, a numerical simulation model of the crack driving forces for the girth welds of high-grade steel pipelines was established, and the general failure assessment curve of girth weld cracks was plotted with the equivalent stress-strain relationship method. Then, a series of finite element assessment points under different load levels were determined with the finite element calculation results of the crack driving forces in combination with the recommended methods in Guide to methods for assessing the acceptability of flaws in metallic structures (BS 7910-2019). Further, the assessment accuracy of BS 7910- 2019 to the crack defects of girth welds was determined, and the critical causes affecting the accuracy of the assessment results were investigated. On this basis, the optimized ultimate load calculation model of the pipeline girth welds and the improved FAD method were put forward with the crack depth, the crack length and the weld strength matching coefficient considered, and the weld strength matching was accurately included into the FAD method. Thereby, the assessment accuracy of the girth weld crack defects of the high-grade steel pipelines was further enhanced. Generally, the method could provide reference for the applicability assessment of the girth weld cracks of in-service high-grade steel pipelines. (11 Figures, 24 References)


References

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Memo

Received date: 30 Apr. 2021. Revised date: 11 Aug. 2021; Edited by: ZHANG Xueqin
Foundation item: supported by the National Natural Science Foundation of China, "Study on Buckling Evolution and Ductile Failure Mechanism of X80 Pipeline under Reverse Fault" (No.52004314) and Xinjiang Tianshan Youth Program "Ductile Fracture and Post-buckling Failure Behavior of High-grade Steel Pipelines under Complex Load" (No.2019Q088).
About the author: WU Kai, male, born in 1994, is a doctoral student. He graduated from China University of Petroleum (Beijing) with a master's degree in Safety Engineering in 2018. Now he is mainly engaged in the research on failure analysis and integrity management of oil and gas equipment. Address: China University of Petroleum (Beijing), No.18, Fuxue Road, Changping District, Beijing, 102249. Tel: 13691133698. Email: wk0609@126.com

Last Update: 2022-09-25