Behavior of X60 Line Pipe Subjected to Axial and Lateral Deformations

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Navid Nazemi ◽  
Sreekanta Das
Keyword(s):  
Laboratory Tests ◽  
Structural Integrity ◽  
Pipe Wall ◽  
Lateral Load ◽  
Test Method ◽  
Line Pipe ◽  
Test Setup ◽  
Steel Pipes ◽  
Sustained Loads ◽  
The University

Buried pipelines may be subjected to various complicated combinations of forces and deformations. This may result in localized curvature, strains, and associated deformations in the pipe wall. As a result, wrinkle may form. The wrinkled pipeline may then develop a rupture in the pipe wall and lose its structural integrity if it is subjected to further sustained loads or deformations. Recently, laboratory tests on NPS6 steel pipes were undertaken at the University of Windsor to study the wrinkling and post-wrinkling behaviors of this NPS6 pipe when subjected to lateral load in addition to internal pressure and axial load. Four full-scale laboratory tests were conducted, and it was found that the application of lateral load on wrinkled pipe produces a wrinkle shape similar to that occurred in a field NPS10 line pipe. Complex test setup was designed and built for successful loading and completion of these tests. This paper makes a detailed discussion on the test setup, test method, loading and boundary conditions, instruments used, and test results obtained from this study.

Revisiting ASME Strain-Based Dent Evaluation Criterion

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Abu Naim Md Rafi ◽  
Sreekanta Das ◽  
Hossein Ghaednia ◽  
Jorge Silva ◽  
Richard Kania ◽  
...  
Keyword(s):  
Laboratory Tests ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Pipe Wall ◽  
Effective Strain ◽  
Evaluation Criterion ◽  
Lateral Loads ◽  
Finite Element Analyses ◽  
Cyclic Pressure ◽  
Long Run

Oil and gas transmission pipelines can be subjected to concentrated lateral loads and as a result, a dent can form. A dent is a localized defect in the pipe wall in the form of a permanent inward plastic deformation. This kind of defect is a matter of serious concern for the pipeline operator since a rupture or a leak may occur. Dent may not pose an immediate threat to the structural integrity of a pipeline. However, it can possibly hinder the operational and inline inspection activities. In the long run, it can cause a leak or rupture in the pipeline under sustained or cyclic pressure load. Hence, AMSE B31.8 recommends a strain-based criterion for the assessment of dents. This strain-based criterion was developed based on several assumptions. This study was undertaken using full-scale laboratory tests and finite element analyses to review and revisit the ASME strain-based dent evaluation criterion and its assumptions. It was found that some of these assumptions are incorrect, and hence, this dent evaluation criterion can lead to inaccurate estimations of critical (effective) strain values in dents, which in turn can lead to inaccurate assessments of the dents.

Strength of Line Pipe With Dent and Crack Defect

2010 ◽  
Author(s):  
Abu Rafi ◽  
Jorge Silva ◽  
Sara Kenno ◽  
Sreekanta Das ◽  
Richard Kania ◽  
...  
Keyword(s):  
Test Data ◽  
Pipe Wall ◽  
Test Procedure ◽  
Line Pipe ◽  
Research Organizations ◽  
Pressure Tests ◽  
The University ◽  
Crack Defect ◽  
Pipe Lines

Pipeline industry and various research organizations have been undertaking studies to understand how the pressure strength of line pipes reduces as the defects in the line pipes grow. Defect in pipe lines can be in the form of corrosion, dent, wrinkle, gouge, crack, and combinations of these. A large number of studies have been completed in developing methods for determining the pressure strength of line pipes with dent and gouge defects and also in the form of combined dent-gouge defect. Some of these studies were undertaken with the intention of determining the pressure strength of line pipes when a combined dent and crack (dent-crack) defect has formed. However, in these studies no cracks were simulated in the test pipe specimens; instead, a gouge (machined cut or notch) was produced and considered as a crack. Therefore, it is not realistic to call this defect a dent-crack defect; rather, it should be called dent-gouge defect. Hence, the current project is being undertaken at the University of Windsor to study how the dent-crack defect influences the pressure strength of line pipes. In this study, a crack in true sense was introduced in the pipe wall. Two different techniques were used to simulate the crack in the pipe wall. This paper discusses the procedures used in this study to simulate crack and dent. In addition, the test procedure and test data obtained from denting and pressure tests are discussed.

scholarly journals Mechanical Behavior of Steel Pipes With Local Wall Distortions Under Cyclic Loading

2012 ◽  
Author(s):  
Aglaia E. Pournara ◽  
Spyros A. Karamanos
Keyword(s):  
Cyclic Loading ◽  
Large Scale ◽  
Structural Integrity ◽  
Oil And Gas ◽  
Pipe Wall ◽  
Local Stress ◽  
Local Strain ◽  
Design Guidelines ◽  
Repeated Loading ◽  
Steel Pipes

Evaluating the severity of pipe wall distortions is a crucial step towards safeguarding the structural integrity of aging hydrocarbon pipeline infrastructure. The present research refers to the remaining life of oil and gas transmission steel pipelines with local wall distortions (i.e. dents and buckles) under repeated loading. The research described in this paper constitutes the first part of a large numerical/experimental research project, aimed at developing methodologies and relevant design guidelines towards assessing and repairing structural pipeline damages in the form of local wall distortions. The paper describes numerical research aimed at investigating the residual structural integrity of smooth dented and buckled steel pipes, with respect to repeated loading that causes fatigue, with the purpose of designing large-scale experiments. Finite element models are developed to simulate the formation of dents and buckles on the pipe wall at various sizes (depths). The deformed steel pipes are further subjected to cyclic pressure or cyclic bending loading in order to estimate the remaining fatigue life of the deformed pipe. The local stress and strain variations due to cyclic loading application are calculated numerically at the deformed area of the pipe wall. In addition, the local strain variations are expressed in terms of strain concentration factors (SNCF) at the critical region of the pipe.

Ovalization Defect in Energy Pipes Caused by Concentrated Load

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Hossein Ghaednia ◽  
Sreekanta Das
Keyword(s):  
Structural Integrity ◽  
Complex Loading ◽  
Outer Wall ◽  
Buried Pipelines ◽  
Element Analysis ◽  
Cross Sectional ◽  
Concentrated Load ◽  
Engineering Research ◽  
Steel Pipes ◽  
The University

Steel pipes are used to build pipelines that carry gas and oil across a country or a continent. The majority of onshore pipelines run underground; hence, they are called buried pipelines. These buried pipelines must endure external interferences and complex loading that result from geotechnical causes, aggressive environments, and operational requirements. Many segments of an underground pipeline may rest on rock tips and other localized hard surfaces, resulting in concentrated reaction load acting on small area of the outer wall of the operating pipeline. As a result, permanent inward deformations in the pipe wall, known as dent defect, can form. In addition, a resulting cross-sectional irregularity, known as an ovalization defect, can also occur. Pipe ovalization defects are a concern of pipeline operating companies, as the defect may challenge a pipeline's operation and/or structural integrity and safety. This research was completed by the Centre of Engineering Research in Pipelines located at the University of Windsor to examine the effects that rock tip shape, operating (internal) pressure, and a pipe's diameter-to-thickness ratio (D/t) have on an NPS30 X70-grade pipe's ovalization defect when it is subjected to such a concentrated load. This article discusses the lab-based full-scale examinations, finite element analysis (FEA) simulations, results, and discussions.

Elastic-Plastic Fracture Mechanics Analysis of Cast Stainless Steel Pipes (Influence of Axial Load on Z-Factor of Pipes With Circumferential Crack Under Bending Load)

2013 ◽  
Author(s):  
Masayuki Kamaya ◽  
Kiminobu Hojo
Keyword(s):  
Stainless Steel ◽  
Axial Load ◽  
Power Plants ◽  
Structural Integrity ◽  
Term Operation ◽  
Steel Pipes ◽  
Integrity Assessment ◽  
Plastic Failure ◽  
Elastic Plastic ◽  
Bending Load

Since the ductility of cast austenitic stainless steel pipes decreases due to thermal aging embrittlement after long term operation, not only plastic collapse failure but also unstable ductile crack propagation (elastic-plastic failure) should be taken into account for the structural integrity assessment of cracked pipes. In the ASME Section XI, the load multiplier (Z-factor) is used to derive the elastic-plastic failure of the cracked components. The Z-factor of cracked pipes under bending load has been obtained without considering the axial load. In this study, the influence of the axial load on Z-factor was quantified through elastic-plastic failure analyses under various conditions. It was concluded that the axial load increased the Z-factor; however, the magnitude of the increase was not significant, particularly for the main coolant pipes of PWR nuclear power plants.

Evaluation of Hydrogen Cracking Susceptibility in X120 Girth Welds

2004 ◽  
Author(s):  
M. L. Macia ◽  
D. P. Fairchild ◽  
J. Y. Koo ◽  
N. V. Bangaru
Keyword(s):  
Laboratory Tests ◽  
High Strength ◽  
Test Method ◽  
Laboratory Studies ◽  
Long Distance ◽  
Hydrogen Cracking ◽  
Girth Welding ◽  
Groove Test ◽  
Girth Welds ◽  
The Cost

To reduce the cost of long distance gas transmission, high strength pipeline steels are being developed. Implementation of high strength pipeline materials requires the avoidance of hydrogen cracking during field girth welding. A study of hydrogen cracking in X120 girth welds has been conducted. Cracking resistance of both the weld metal and heat affected zone (HAZ) were investigated. The laboratory tests included the controlled thermal severity (CTS) test, the WIC test and the Y-groove test. In addition, multi-pass plate welds and full pipe welds were completed and examined for the presence of hydrogen cracks. The suitability of each test method for predicting cracking in X120 girth welds is determined. The morphology of hydrogen cracks in X120 girth welds is described, and the conditions necessary to prevent hydrogen cracking are identified. Following the laboratory studies, construction of X120 pipelines without cracking was demonstrated through a 1.6 km field trial.

Issues in Welding of HSLA Steels

2011 ◽  
Vol 365 ◽  
pp. 44-49 ◽  
Author(s):  
Sandeep Jindal ◽  
Rahul Chhibber ◽  
N.P. Mehta
Keyword(s):  
Structural Integrity ◽  
Hsla Steel ◽  
Weight Ratio ◽  
Welding Process ◽  
Pressure Vessels ◽  
Carbon Steels ◽  
Low Carbon ◽  
Line Pipe ◽  
Hsla Steels ◽  
Selection Of

The application of High Strength Low Alloy (HSLA) steels has expanded to almost all fields viz. automobile industry, ship building, line pipe, pressure vessels, building construction, bridges, storage tanks. HSLA steels were developed primarily for the automotive industry to replace low-carbon steels in order to improve the strength-to-weight ratio and meet the need for higher-strength materials. Due to higher-strength and added excellent toughness and formability, demand for HSLA steel is increasing globally. With the increase of demand; other issues like the selection of filler grade and selection of suitable welding process for the joining of these steels have become very significant. This paper discusses the various issues regarding selection of suitable grade and selection of suitable welding process for joining of HSLA steels and issues concerning the structural integrity of HSLA steel welds.

Self-lubricated transport of bitumen froth

1999 ◽  
Vol 386 ◽  
pp. 127-148 ◽  
Author(s):  
DANIEL D. JOSEPH ◽  
RUNYAN BAI ◽  
CLARA MATA ◽  
KEN SURY ◽  
CHRIS GRANT
Keyword(s):  
Pressure Gradient ◽  
Oil Sands ◽  
Pipe Wall ◽  
Extraction Process ◽  
Hot Water ◽  
Turbulent Pipe Flow ◽  
University Of Minnesota ◽  
Lubricating Layer ◽  
Direct Measurements ◽  
The University

Bitumen froth is produced from the oil sands of Athabasca using the Clark's Hot Water Extraction process. When transported in a pipeline, water present in the froth is released in regions of high shear, namely at the pipe wall. This results in a lubricating layer of water that allows bitumen froth pumping at greatly reduced pressures and hence the potential for savings in pumping energy consumption. Experiments establishing the features of the self-lubrication phenomenon were carried out in a 25 mm diameter pipeloop at the University of Minnesota, and in a 0.6 m diameter pilot pipeline at Syncrude, Canada. The pressure gradient of lubricated flows in 25 mm, 50 mm and 0.6 m diameter pipes closely follow the empirical law of Blasius for turbulent pipe flow; the pressure gradient is proportional to the ratio of the 7/4th power of the velocity to the 5/4th power of the pipe diameter, but the constant of proportionality is about 10 to 20 times larger than that for water alone. We used Reichardt's model for turbulent Couette flow with a friction velocity based on the shear stress acting on the pipe wall due to the imposed pressure gradient to predict the effective thickness of the lubricating layer of water. The agreement with direct measurements is satisfactory. Mechanisms for self-lubrication are also considered.

Investigation of an on-line pipe wall defect monitoring sensor

2010 ◽  
Vol 33 (1-2) ◽  
pp. 639-647 ◽  
Author(s):  
Akihiro Tagawa ◽  
Kazunari Fujiki ◽  
Fumio Kojima
Keyword(s):  
Pipe Wall ◽  
Line Pipe ◽  
Wall Defect ◽  
On Line
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