Characterization of Tensile and Fracture Properties of X52 Steel Pipes and Their Girth WeldsReport as inadecuate




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Charpy V-notch impact test, X52 Steel, stress-strain curve, Norman Wells pipeline

Lin, Meng

Supervisor and department: Samer Adeeb Civil and Environmental J. J. Roger Cheng Civil and Environmental

Examining committee member and department: J. J. Roger Cheng Civil and Environmental Vivek Bindiganavile Civil and Environmental Marwan El-Rich Civil and Environmental Samer Adeeb Civil and Environmental

Department: Department of Civil and Environmental Engineering

Specialization: Structural Engineering

Date accepted: 2015-02-03T14:39:22Z

Graduation date: 2015-06

Degree: Master of Science

Degree level: Master's

Abstract: Enbridge vintage Norman Wells Pipeline made of X52 steels has transported crude oil from Norman Wells, Northwest Territories NWT to Zama, Alberta since 1985. It is the first fully buried pipeline that traverses permafrost regions in Canada, and is often subjected to adverse geotechnical conditions. It is significant to investigate the resistance of the buried X52 steel pipeline in response to the imposed substantial stresses and strains caused by impacts and displacements from geotechnical instability.In this thesis, tensile and fracture properties of X52 steel pipes and their girth welds are determined by small scale material tests. An original girth weld which was manufactured in 1980s and a new girth weld which was manufactured in 2013 are both studied and their material properties compared to the corresponding heat-affected zones and the pipe base metal. Tension tests are conducted to obtain stress-strain curves and determine the tensile properties of X52 pipe. The strain-hardening region of the true stress-strain curve is characterized into the empirical mathematical expressions otherwise known as the Hollomon equation and the Ramberg-Osgood equation. The stress-strain curve of X52 steel pipe is compared to curves obtained from higher grades of steel pipes and the comparison between the ductility of X52 steel pipe and other grades is discussed. Charpy V-notch impact tests are conducted to measure the energy required to fracture a V-notched specimen and determine the fracture properties of the pipe material. The decrease of the test temperature reduces the impact toughness and increases the probability of brittle fracture. The empirical correlation between the test CVN energy and the fracture toughness of X52 pipe is emphasized. Based on the test results, the tensile strain capacity of X52 pipe is predicted according to the empirical equation provided by CSA Z662-11. While the tensile strain capacity equations were developed based on tests conducted on higher grades of steel, the results of this work allowed the use of these equations to predict the amount of reduction of tensile strain capacity due to the presence of girth weld defects.

Language: English

DOI: doi:10.7939-R3X05XM68

Rights: Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.





Author: Lin, Meng

Source: https://era.library.ualberta.ca/


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Characterization of Tensile and Fracture Properties of X52 Steel Pipes and Their Girth Welds by Meng Lin A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Structural Engineering Department of Civil and Environmental Engineering University of Alberta © Meng Lin, 2015 Abstract Enbridge vintage Norman Wells Pipeline made of X52 steels has transported crude oil from Norman Wells, Northwest Territories (NWT) to Zama, Alberta since 1985.
It is the first fully buried pipeline that traverses permafrost regions in Canada, and is often subjected to adverse geotechnical conditions.
It is significant to investigate the resistance of the buried X52 steel pipeline in response to the imposed substantial stresses and strains caused by impacts and displacements from geotechnical instability. In this thesis, tensile and fracture properties of X52 steel pipes and their girth welds are determined by small scale material tests.
An original girth weld which was manufactured in 1980s and a new girth weld which was manufactured in 2013 are both studied and their material properties compared to the corresponding heat-affected zones and the pipe base metal.
Tension tests are conducted to obtain stress-strain curves and determine the tensile properties of X52 pipe.
The strain-hardening region of the true stress-strain curve is characterized into the empirical mathematical expressions otherwise known as the Hollomon equation and the Ramberg-Osgood equation.
The stress-strain curve of X52 steel pipe is compared to curves obtained from higher grades of steel pipes and the comparison between the ductility of X52 steel pipe and other grades is discussed.
Charpy V-notch impact tests are conducted to measure the energy required to fracture a V-notched specimen and determine the fracture properties of the pipe material.
The decrease of the test temperature reduces the impact toughness and increases the probability of brittle fracture.
The empir...





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