Review of Fracture Control Technology for Gas Transmission Pipelines

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Ductile Fracture ◽  
Fracture Propagation ◽  
High Strength ◽  
Fracture Initiation ◽  
Alternative Methods ◽  
Opening Angle ◽  
Pipeline Steels ◽  
Control Plan ◽  
Fracture Control ◽  
Arrest Toughness

A fracture control plan is often required for a gas transmission pipeline in the structural design and safe operation. Fracture control involves technologies to control brittle and ductile fracture initiation, as well as brittle and ductile fracture propagation for gas pipelines, as reviewed in this paper. The approaches developed forty years ago for the fracture initiation controls remain in use today, with limited improvements. In contrast, the approaches developed for the ductile fracture propagation control has not worked for today’s pipeline steels. Extensive efforts have been made to this topic, but new technology still needs to be developed for modern high-strength pipeline steels. Thus, this is the central to be reviewed. In order to control ductile fracture propagation, Battelle in the 1970s developed a two-curve model (BTCM) to determine arrest toughness for gas pipeline steels in terms of Charpy vee-notched (CVN) impact energy. Practice showed that the BTCM is viable for pipeline grades X65 and below, but issues emerged for higher grades. Thus, different corrections to improve the BTCM and alternative methods have been proposed over the years. This includes the CVN energy-based corrections, the drop-weight tear test (DWTT) energy-based correlations, the crack-tip opening angle (CTOA) criteria, and finite element methods. These approaches are reviewed and discussed in this paper, as well as the newest technology developed to determine fracture arrest toughness for high-strength pipeline steels.

Ductile Fracture Control for High Strength Steel Pipelines

2006 ◽  
Author(s):  
Andrea Fonzo ◽  
Andrea Meleddu ◽  
Giuseppe Demofonti ◽  
Michele Tavassi ◽  
Brian Rothwell
Keyword(s):  
Ductile Fracture ◽  
High Strength Steel ◽  
Driving Force ◽  
Empirical Relationship ◽  
Fracture Propagation ◽  
High Strength ◽  
Operating Conditions ◽  
Resistance Force ◽  
Fracture Control ◽  
Material Fracture

The determination of the toughness values required for arresting ductile fracture propagation has been historically based on the use of models whose resulting predictions can be very unreliable when applied to new high strength linepipe materials (≥X100) and/or different operating conditions. In addition, for the modern high strength steels a methodology for determining the material fracture resistance for arresting running shear fracture starting from laboratory data is still lacking. The work here presented (developed within a PRCI sponsored project) deals with the use of CSM’s proprietary PICPRO® Finite Element code to develop methodologies for ductile fracture propagation control in high grade steel pipes. The relationships providing the maximum crack driving force which can be experienced in a pipe operated at known conditions have been determined, for different types of gas. On the other side, an empirical relationship has been found to correlate the critical Crack Tip Opening Angle (CTOA) determined by laboratory testing, to the critical CTOA on pipe (which represents the material fracture propagation resistance) with the aid of devoted simulations of past full-scale burst tests. By comparing Driving Force and Resistance Force, ductile fracture control for high strength steel pipelines can be achieved.

Existing Methods in Ductile Fracture Propagation Control for High-Strength Gas Transmission Pipelines

2013 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Fracture Toughness ◽  
High Pressure ◽  
Ductile Fracture ◽  
Engineering Design ◽  
Fracture Propagation ◽  
High Strength ◽  
Control Analysis ◽  
Battelle Memorial Institute ◽  
Pipeline Steels ◽  
Transmission Pipelines

Ductile fracture propagation control is one of the most important technologies adopted in engineering design for high-pressure, high-strength gas transmission pipelines. In the early 1970s, Battelle Memorial Institute developed a two-curve model that is now commonly referred to as BTCM for dynamic ductile fracture control analysis. The BTCM has been applied successfully for determining the minimum fracture toughness required to arrest a running ductile fracture in a gas transmission pipeline in terms of Charpy vee-notched (CVN) impact energy. Practice showed that BTCM is accurate only for pipeline grades up to X65, and becomes invalid for high strength pipeline steels like X70, X80 and X100. Since 1990s, different correction methods for improving the BTCM have been proposed. However, a commonly accepted method is not available yet for the high strength pipeline steels in grades X80 and above. This paper reviews and evaluates the primary existing methods in determination of fracture arrest toughness for ductile pipeline steels. These include the CVN energy-based methods, the drop-weight tear test (DWTT) energy-based methods, the crack-tip opening angle (CTOA) method, and finite element numerical analysis methods. The purpose is to identify a method to be used in engineering design or to be investigated further for determining the minimum fracture toughness to arrest a ductile running crack in a modern high-pressure, high-strength gas pipeline.

Applicability of Existing Models for Predicting Ductile Fracture Arrest in High Pressure Pipelines

2006 ◽  
Author(s):  
John Wolodko ◽  
Mark Stephens
Keyword(s):  
High Pressure ◽  
Ductile Fracture ◽  
High Pressures ◽  
Fracture Propagation ◽  
High Strength Steels ◽  
High Strength ◽  
Full Scale ◽  
Stage Of Development ◽  
Fracture Arrest ◽  
Arrest Toughness

The ductile fracture arrest capability of gas pipelines is seen as one of the most important factors in the future acceptance of new high strength pipeline steels for high pressure applications. It has been acknowledged for some time that the current methods for characterizing and predicting the arrest toughness for ductile fracture propagation in high strength steels are un-conservative. This observation is based on the inability of existing models to predict the required arrest toughness in full-scale ductile fracture propagation tests. While considerable effort is currently being applied to develop more accurate methods for predicting ductile facture arrest, the resulting models are still in a preliminary stage of development and are not immediately amenable for use by the general engineering community. As an interim solution, a number of authors have advocated the empirical adjustment or reformulation of the existing models for use with the newer, high strength pipe grades. While this approach does not address the fundamental issues surrounding the fracture arrest problem, it does provide methods that can be used in the near term for analysis and preliminary design. The desire to use these existing methods, however, is tempered by the uncertainty associated with their applicability in situations involving high pressures and/or high toughness materials. In an attempt to address some of these concerns, a statistical analysis was conducted to assess the accuracy of a number of available fracture arrest models by comparing predictions to actual values determined from full-scale fracture propagation experiments. From the results, correction factors were developed for determining the required toughness levels in high pressure applications that account for the uncertainty in the theoretical prediction methods.

The Practical Application of Fracture Control to Natural Gas Pipelines

2008 ◽  
Author(s):  
K. A. Widenmaier ◽  
A. B. Rothwell
Keyword(s):  
Natural Gas ◽  
Large Scale ◽  
High Strength ◽  
Fracture Initiation ◽  
Opening Angle ◽  
Pipe Material ◽  
Design Factor ◽  
Line Pipe ◽  
Natural Gas Pipelines ◽  
Crack Tip Opening

The use of high strength, high design-factor pipe to transport natural gas requires the careful design and selection of pipeline materials. A primary material concern is the characterization and control of ductile fracture initiation and arrest. Impact toughness in the form of Charpy V-notch energies or drop-weight tear tests is usually specified in the design and purchase of line pipe in order to prevent large-scale fracture. While minimum values are prescribed in various codes, they may not offer sufficient protection in pipelines with high pressure, cold temperature, rich gas designs. The implications of the crack driving force arising from the gas decompression versus the resisting force of the pipe material and backfill are examined. The use and limitations of the Battelle two-curve method as the standard model are compared with new developments utilizing crack-tip opening angle and other techniques. The methodology and reasoning used to specify the material properties for line pipe are described and the inherent limits and risks are discussed. The applicability of Charpy energy to predict ductile arrest in high strength pipes (X80 and above) is examined.

CVN and DWTT Energy Methods for Determining Fracture Arrest Toughness of High Strength Pipeline Steels

2012 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Nonlinear Models ◽  
High Strength ◽  
Correction Method ◽  
Gas Pipeline ◽  
Pipeline Steels ◽  
Curve Model ◽  
Drop Weight Tear Test ◽  
Viable Approach ◽  
Fracture Arrest ◽  
Arrest Toughness

Battelle two curve model (BTCM) was developed in the 1970s and successfully used for determining arrest toughness for ductile gas transmission pipelines in terms of Charpy vee-notched (CVN) impact energy. Practice has shown that the BTCM is accurate only for pipeline grades up to X65, but not for high strength pipeline grades X70 and above. Different methods to improve the BTCM were proposed over the years. This paper reviews the BTCM and its modified methods in terms of CVN energy or drop weight tear test (DWTT) energy for determining arrest toughness of ductile gas pipeline steels, particularly for high strength pipeline steels X80 and beyond. This includes the often-used Leis correction method, the CSM factor method, Wilkowski DWTT method and others. The CVN and DWTT energy-based methods are evaluated and discussed through the critical analysis and comparison with full-scale experimental data. The objective is to identify reasonable methods to be used for determining the minimum fracture toughness required to arrest a ductile running crack in a modern high strength, high pressure gas pipeline. The results show that available nonlinear models to correlate the standard DWTT and CVN energies are questionable, and the Leis correction method is a viable approach for determining arrest toughness for high strength pipeline steels, but further study is needed for ultra-high pipeline grades. Suggestions for further improving the BTCM are discussed.

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.

Evaluation of Ductile Cracking Criterion for Grade X100 Linepipe and Relationship to Large Scale Fracture Behavior

2003 ◽  
Author(s):  
Nobuyuki Ishikawa ◽  
Shigeru Endo ◽  
Alan Glover ◽  
David Horsley ◽  
Masao Toyoda
Keyword(s):  
Plastic Strain ◽  
Ductile Fracture ◽  
Fracture Behavior ◽  
Large Scale ◽  
Notch Root ◽  
Equivalent Plastic Strain ◽  
High Strength ◽  
Fracture Initiation ◽  
Linepipe Steels ◽  
Ductile Fracture Initiation

Recent developments in the manufacturing process of steel plate for high strength linepipe have enabled superior toughness to prevent brittle fracture of the pipe body. Techniques for non-destructive inspection have also improved, and large flaws that could lead to brittle fracture are highly unlikely in recent high strength pipelines. However, large amounts of plastic deformation can be expected in seismic or permafrost regions. Prevention of ductile fracture of the pipe body or weldment therefore becomes a key issue in defining the tensile strain limit. Ductile fracture is considered to occur by growth and coalescence of voids, and is affected by stress triaxiality and plastic straining at the cracked region. Although many studies have been carried out to evaluate ductile cracking criteria, its transferability to large-scale fracture behavior has not been thoroughly investigated. In this study, ductile cracking of high strength linepipe steels, Grade X80 and X100, was investigated. Notched round bar specimens with different notch root radii were tested to determine the precise conditions for initiation of ductile fracture. Stress and strain conditions at the notch regions were evaluated by FE analysis, and the “critical equivalent plastic strain” was defined at conditions corresponding to ductile fracture initiation in the experimental small specimen tests. Ductile crack initiation behavior was also determined for wide plate test specimens by making close observations of the notch root area. 3-D FE analysis of the wide plate tensile test showed that the equivalent plastic strain at the point of ductile fracture initiation was in close agreement with that in the notched round bas specimen. Thus, the “critical equivalent plastic strain,” determined by small notched round bar specimens, can be considered as a transferable criterion to predict large-scale fracture behavior in wide plate tests. Concepts of strain based design in terms of preventing ductile failure from a surface flaw by applying critical strain to cracking were also discussed in this paper. Results were compared to conventional grade linepipe steels and structural steels, showing that recent high strength linepipe steels have higher resistance to ductile cracking than conventional structural steels. In addition, 3-D FE analyses were used in a parametric study to determine the effects of Y/T and uniform strain on the onset of ductile cracking behaviour. The results of these analyses show the relative importance of materials properties on the resistance to ductile cracking.

Parameter Calibration for Continuum Damage Mechanics Models to Simulate Ductile Fracture of High Strength Pipeline Steels

2019 ◽  
Author(s):  
Filip Van den Abeele
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Damage Mechanics ◽  
Void Nucleation ◽  
High Strength ◽  
Continuum Damage Mechanics ◽  
Continuum Damage ◽  
Pipeline Steels ◽  
Gtn Model ◽  
Input Parameters

Abstract The ability to arrest a running crack is one of the key features in the safe design of pipeline systems. In the industry design codes, the crack arrest properties of a pipeline should meet two requirements: crack propagation has to occur in a ductile fashion, and enough energy should be dissipated during propagation. While the first criterion is assessed by the Battelle Drop Weight Tear Test (BDWTT) at low temperatures, the latter requirement is converted into a lower bound for the impact energy absorbed during a Charpy V-notch (CVN) impact test. However, the introduction of high strength pipelines steels (X70 and beyond) has revealed that the commonly used relations based on BDWTT and CVN no longer hold. For such scenarios, Continuum Damage Mechanics (CDM) models provide promising potential to obtain a more profound understanding of the mechanisms that govern ductile crack propagation in high strength pipeline steels. In recent years, different types of CDM models have been used to simulate ductile fracture of pipeline steels. This paper focuses on two of these models, i.e. the Gurson-Tvergaard-Needleman (GTN) model and the Modified Bai-Wierzbicki (MBW) model. The GTN model is based on the computation of void growth according to Rice and Tracey, and account for the local softening of the material due to void nucleation, growth and subsequent coalescence. The MBW model is a fully coupled damage model, where the yield surface depends on both the stress triaxiality and the Lode angle. Although both models can predict ductile fracture propagation, their widespread application in pipeline design is hampered by the large number of input parameters to be calibrated. The GTN model requires 10 input parameters, i.e. 3 Tvergaard damage parameters, 4 porosity parameters and 3 parameters to describe void nucleation. Whereas the Modified Mohr-Coulomb model originally proposed by Bai and Wierzbicki uses merely 2 parameters, the extended MBW model requires no less than 18 parameters to be calibrated: 11 plasticity parameters (5 stress + 3 strain rate + 3 temperature) and 7 damage parameters (4 initiation + 1 propagation + 2 failure). In this paper, different numerical/experimental strategies to calibrate these parameter sets are reviewed and compared. Sensitivity analyses are performed to assess the influence of the different input parameters on the model predictions. For both GTN and MBW models, the robustness and uniqueness of the calibrated parameter sets is investigated. Recommendations on optimum parameter values are derived, with special emphasis on high strength pipeline steels.

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