Probabilistic Fracture Analysis of Pipelines

2002 ◽  
Author(s):  
Shahani Kariyawasam ◽  
Mark Stephens ◽  
Wytze Sloterdijk
Keyword(s):  
Fracture Initiation ◽  
Crack Arrest ◽  
Small Samples ◽  
Mixed Mode Fracture ◽  
Line Pipe ◽  
Initiation And Propagation ◽  
Probabilistic Characterization ◽  
Fracture Control ◽  
Added Uncertainty

Many pipelines were built before the industry developed material specifications for fracture control. For these older pipelines an essential first step in fracture control is to estimate the existing likelihood of fracture initiation and propagation. It is also desirable for operators to know the size of defects the pipeline can tolerate without causing pipeline fracture. This paper describes a methodology developed for the probabilistic characterization of the fracture initiation and propagation susceptibility of older pipeline segments, made from line pipe exhibiting (by today’s standards) low to moderate strength and low notch toughness. It is applicable to ductile, brittle and mixed-mode fracture behaviour. A probabilistic analysis approach is ideally suited to the problem since it offers a way to quantitatively address both the inherent variability in the mechanical properties of line pipe and the uncertainties associated with the various models currently available to determine the conditions necessary to cause crack initiation or to force crack arrest. The method described addresses both of these forms of uncertainty, and also reflects the added uncertainty inherent in trying to estimate material properties for existing lines from small samples of data.

Fracture Control for the Alliance Pipeline

2000 ◽  
Author(s):  
Bob Eiber ◽  
Lorne Carlson ◽  
Brian Leis
Keyword(s):  
Natural Gas ◽  
New Technology ◽  
Fracture Initiation ◽  
Line Pipe ◽  
Control Plan ◽  
High Toughness ◽  
Pipe Burst ◽  
Fracture Control ◽  
Pipe Fittings ◽  
Fracture Arrest

This paper reviews the fracture control plan for the Alliance Pipeline, which is planned for operation in 2000. This natural-gas pipeline is 2627 km (1858 miles) long, running from British Columbia, Canada to Illinois, USA. Interest in the fracture control for this pipeline results from its design, which is based on transporting a rich natural gas (up to 15% ethane, 3% propane) at a relatively high pressure 12,000 kPa (1740 psi). This break from traditional pressures and lean gases, which frequently are constrained by incremental expansion, is more efficient and more economical than previous natural gas pipelines. Use of higher pressures and rich gas requires adequate fracture control for the line pipe, fittings, and valves. This fracture control has been achieved for the Alliance Pipeline by specifying high-toughness steels, in terms of both fracture-initiation and fracture-propagation resistance for the line pipe, fittings and heavy wall components. While beneficial from an economics viewpoint, the need for higher toughnesses raised concern over the validity of the fracture control plan, which was based on existing and new technology. The concern focused on fracture arrest using high toughness steels. The concern was associated with characterizing fracture arrest resistance using Charpy V-notch impact toughness, the most commonly used method to measure fracture arrest resistance. Developments were undertaken to address problems associated with the use of higher-toughness steel and these were validated with full-scale pipe burst tests to demonstrate the viability of the fracture control plan. The solution involved extending existing methods to address much higher toughness steels, which provided a significantly improved correlation between fracture arrest predictions and experimental results. In the burst tests, data was collected to validate the Alliance design and also to extend the database of fracture arrest data to assist future pipelines. Data such as the pressure between the pipe and soil as the gas escapes from the pipe, the sound levels in the atmosphere, the movement and strains in the pipe ahead of the running fracture were instrumented in the test and the available results are presented.

Relationships Between Mechanical Properties and the Extension and Arrest of Unstable Cracks in Line Pipe Steels

1980 ◽  
Vol 102 (3) ◽  
pp. 309-313 ◽  
Author(s):  
A. K. Shoemaker
Keyword(s):  
Transmission Lines ◽  
Large Diameter ◽  
Fracture Initiation ◽  
Crack Arrest ◽  
Crack Size ◽  
Operating Conditions ◽  
Design Parameters ◽  
Critical Crack ◽  
Line Pipe ◽  
Stress Dependent

With the increasing need for high-strength, high-pressure, large-diameter, gas-transmission lines, considerable attention has been given, in recent years, to the aspects of fracture initiation, propagation and crack arrest in line pipe. This paper presents an overview of the interrelations between material properties and design parameters that can lead to the initiation of a running fracture and the interrelationships which are necessary to arrest a running fracture. It is shown that if the pipe has ductility such that CVN/YS ≥ 0.6 ft-lb/ksi, further increases in Charpy toughness would not have a significant effect upon the critical crack size because fracture initiation becomes flow-stress dependent. Moreover, the length of a stable through-the-wall crack at operating conditions would be about two orders of magnitude longer than the current rejectable weld defect length specified by API. For “conventional” transmission-line applications CVN ≥ 0.024 σh1.5D0.5 assures arrest of running shear fractures.

Applicability of Existing Fracture Initiation Models to High-Strength Steel Line Pipe

2010 ◽  
Author(s):  
Do-Jun Shim ◽  
Gery Wilkowski ◽  
Frederick Brust ◽  
David Horsley ◽  
Max Toch
Keyword(s):  
High Strength Steel ◽  
High Strength ◽  
Fracture Initiation ◽  
Failure Behavior ◽  
Surface Cracks ◽  
Test Results ◽  
Fracture Criteria ◽  
Line Pipe ◽  
Steel Pipes

The original fracture criteria developed by Maxey/Kiefner for axial through-wall and surface-cracked pipes have worked well for many industries for a large variety of low strength and low toughness materials. However, newer line-pipe steels have some unusual characteristics that differ from these older materials. One example is a single test that has demonstrated that X100 line-pipe with an axial through-wall-crack can fail at pressures about 30 percent lower than predicted with commonly used analysis methods for older steels. Thus, it is essential to review the currently available models and investigate the applicability of these models to newer high-strength line pipe materials. In this paper, the available models for predicting the failure behavior of axial-cracked pipes (through-wall-cracked and external surface-cracked pipes) were reviewed. The applicability of these models to high-strength steel pipes was investigated by analyzing limited full-scale pipe fracture initiation test results and the shortcomings were identified. For both through-wall and surface cracks, the major shortcomings were related to the characterization of the material toughness, which generally leads to non-conservative predictions in the J-T analyses. The findings in this paper may be limited to the test data that was consider for this study. The requisite characteristics of a potential model were also identified.

scholarly journals Prediction of Ductile Fracture in Metal Blanking

1999 ◽  
Vol 122 (3) ◽  
pp. 476-483 ◽  
Author(s):  
A. M. Goijaerts ◽  
L. E. Govaert ◽  
F. P. T. Baaijens
Keyword(s):  
Finite Element ◽  
Tensile Test ◽  
Ductile Fracture ◽  
Experimental Error ◽  
Fracture Initiation ◽  
Fracture Model ◽  
Ductile Fracture Model ◽  
Blanking Process ◽  
Ductile Fracture Initiation

This study is focused on the description of ductile fracture initiation, which is needed to predict product shapes in the blanking process. Two approaches are elaborated using a local ductile fracture model. According to literature, characterization of such a model should take place under loading conditions, comparable to the application. Therefore, the first approach incorporates the characterization of a ductile fracture model in a blanking experiment. The second approach is more favorable for industry. In this approach a tensile test is used to characterize the fracture model, instead of a complex and elaborate blanking experiment. Finite element simulations and blanking experiments are performed for five different clearances to validate both approaches. In conclusion it can be stated that for the investigated material, the first approach gives very good results within the experimental error. The second approach, the more favorable one for industry, yields results within 6 percent of the experiments over a wide, industrial range of clearances, when a newly proposed criterion is used. [S1087-1357(00)02202-4]

Probabilistic characterization of subsurface stratigraphic configuration with modified random field approach

2021 ◽  
pp. 106138
Author(s):  
Chao Zhao ◽  
Wenping Gong ◽  
Tianzheng Li ◽  
C. Hsein Juang ◽  
Huiming Tang ◽  
...  
Keyword(s):  
Random Field ◽  
Field Approach ◽  
Probabilistic Characterization
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