Pressure Correction Factor for Strain Capacity Predictions Based on Curved Wide Plate Testing

2012 ◽  
Author(s):  
Matthias Verstraete ◽  
Wim De Waele ◽  
Rudi Denys ◽  
Stijn Hertelé
Keyword(s):  
Correction Factor ◽  
Large Scale ◽  
Strain Capacity ◽  
Defect Assessment ◽  
Ductile Crack Growth ◽  
Large Scale Testing ◽  
Weld Defect ◽  
Girth Welds ◽  
Assessment Procedures ◽  
Tensile Strain Capacity

Strain-based girth weld defect assessment procedures are essentially based on large scale testing. Ever since the 1980’s curved wide plate testing has been widely applied to determine the tensile strain capacity of flawed girth welds. However, the effect of internal pressure is not captured in curved wide plate testing. Accordingly, unconservative predictions of strain capacity occur when straightforwardly transferred to pressurized pipes. To address this anomaly, this paper presents results of finite element simulations incorporating ductile crack growth. Simulations on homogeneous and girth welded specimens indicate that a correction factor of 0.5 allows to conservatively predict the strain capacity of a pressurized pipe through wide plate testing under the considered conditions.

Large Scale Experimental Data for Improved Strain-Based Design Models

2010 ◽  
Author(s):  
Mark Stephens ◽  
Randy Petersen ◽  
Yong-Yi Wang ◽  
Robin Gordon ◽  
David Horsley
Keyword(s):  
Large Scale ◽  
State Of The Art ◽  
Weld Strength ◽  
Design Models ◽  
Testing Program ◽  
Weld Material ◽  
Large Scale Testing ◽  
Girth Welds ◽  
Improved Strain ◽  
Tensile Strain Capacity

This paper provides an overview of a large-scale testing program that is associated with an ongoing, joint government/industry funded research program, which is intended to advance the state-of-the-art in strain-based design as it pertains to the tensile capacity of girth welds in steel pipelines. The testing program has exercised a number of parameters that are known to have a significant impact on tensile strain capacity including: the effects of internal pressure, the strain hardening characteristics of the pipe body and weld material, the degree of weld strength overmatch and the location of the assumed flaw. This paper describes the type of tests performed and the instrumentation plan; it also provides a summary and discussion of the results obtained to date.

Evaluation of Girth Weld Defect Acceptance Criteria for Grade X100 Pipelines

2012 ◽  
Author(s):  
Troy Swankie ◽  
Vinod Chauhan ◽  
Ian Wood ◽  
Richard Espiner ◽  
Max Kieba ◽  
...  
Keyword(s):  
Analytical Methods ◽  
Large Scale ◽  
Charpy Impact ◽  
Assessment Methods ◽  
Test Facility ◽  
Weld Defect ◽  
Girth Welds ◽  
Assessment Procedures ◽  
Large Scale Tests ◽  
Pipeline Design

There are a number of methods that are commonly used for the assessment of a girth weld containing a ‘fabrication’ defect. These range from the more generic workmanship limits through to more complex pipeline specific Engineering Critical Assessment (ECA) methodologies. The workmanship limits stipulated in pipeline design codes can be very conservative, resulting in un-necessary and costly repairs. The ECA approach is being increasingly used to derive girth weld defect acceptance limits specific to a pipeline. These limits have been derived using either semi-analytical methods or from the results of large-scale tests conducted on pipeline girth welds. However, at present there is no one standardized method. The guidance produced by the European Pipeline Research Group (EPRG) is an example of an established methodology based on the results of large-scale tests, while commonly used pipeline specific semi-analytical assessment methods include API 1104 and CSA Z662. Other commonly used analytical methods, which are more generic in application, include BS 7910 and API 579-1/ASME FFS-1. Application of these methods to girth welds in grade X100 pipelines has not yet been validated. The US Department of Transportation, Pipeline and Hazardous Materials Safety Administration (PHMSA) commissioned Electricore, Inc and GL Noble Denton to investigate the applicability of these ‘commonly used’ girth weld assessment procedures to grade X100 pipelines. To facilitate this project, BP provided 10 girth welds from a full-scale operational trial of two grade X100 48in diameter pipeline test sections, following completion of the trial at GL Noble Denton’s Spadeadam test facility, Cumbria, UK. The girth welds were selected to enable the effects of material variability between abutting pipes, different heats and different manufacturers (pipe was sourced from two world class pipe mills, with the plate supply for one mill coming from two sources) to be investigated. A substantial test program has been undertaken to fully characterize the mechanical properties of each girth weld, comprising curved wide plate (CWP), tensile, Charpy impact and fracture mechanics tests. The results from the CWP tests have been analyzed using the procedures given in API 1104 (Option 2), EPRG, CSA Z662, BS 7910 and API 579-1/ASME FFS-1. This paper presents an overview of the tests undertaken and a comparison of the actual test results with the predictions from the assessment methods.

Application of State of the Art Assessment for Pipeline Girth Weld

2017 ◽  
Vol 898 ◽  
pp. 1063-1068
Author(s):  
Deng Zun Yao ◽  
Zhi Wen Li ◽  
Jian Wu Liu ◽  
Lin Chen
Keyword(s):  
State Of The Art ◽  
Axial Stress ◽  
Construction Cost ◽  
Assessment Methods ◽  
Weld Repair ◽  
Defect Assessment ◽  
Weld Defect ◽  
Key Points ◽  
Welding Defects ◽  
Girth Welds

In the pipeline construction, the girth welds tend to be the weakness because of defects and microstructural heterogeneities. The importance of suitable assessment of various defects in the weld is not only to prevent the cracks from unstable growth to cause catastrophic accident but also can effectively reduce the weld repair to reduce construction cost. Although many welding defects assessment methods and codes have been applied in this field, there are many differences among them. In this paper, the application of weld defect assessment methods was extensively studied. The key points of ECA applications, such as the pipeline axial stress and toughness, have been introduced. Furthermore, some suggestions were given on the application of girth weld ECA assessment.

Estimation of Tensile Strain Capacity of Vintage Girth Welds

2021 ◽  
Author(s):  
Banglin Liu ◽  
Bo Wang ◽  
Yong-Yi Wang ◽  
Otto Jan Huising
Keyword(s):  
Tensile Strain ◽  
Strain Capacity ◽  
Girth Welds ◽  
Tensile Strain Capacity

Effects of Biaxial Loading on the Tensile Strain Capacity of Girth Welds With Weld Strength Undermatching and HAZ Softening

2020 ◽  
Author(s):  
Banglin Liu ◽  
Yong-Yi Wang ◽  
Xiaotong Chen ◽  
David Warman
Keyword(s):  
Internal Pressure ◽  
Tensile Strain ◽  
Biaxial Loading ◽  
Reduction Factor ◽  
Pressure Level ◽  
Weld Strength ◽  
Strain Capacity ◽  
Weld Region ◽  
Girth Welds ◽  
Tensile Strain Capacity

Abstract The ability to accurately estimate the tensile strain capacity (TSC) of a girth weld is critical to performing strain-based assessment (SBA). A wide range of geometry, material, and loading factors can affect the TSC of a girth weld. Among the influencing factors, an increase in the internal pressure level has been shown to have a detrimental effect on the TSC. The overall influence of internal pressure is usually quantified by a TSC reduction factor, defined as the ratio of the TSC at zero pressure to the lowest TSC typically attained at pressure factors around 0.5–0.6. Here the pressure factor is defined as the ratio of the nominal hoop stress induced by pressure to the yield strength (YS) of the pipe material. A number of numeric and experiment studies have reported a TSC reduction factor of 1.5–2.5. These studies generally focused on strain-based designed pipelines with evenmatching or overmatching welds, minimum heat affected zone (HAZ) softening, and a surface breaking flaw at the weld centerline or the fusion boundary. This paper examines the effects of pipe internal pressure on the TSC of girth welds under the premise of weld strength undermatching and HAZ softening. The interaction of biaxial loading and the local stress concentration at the girth weld region was quantified using full-pipe finite element analysis (FEA). The relationship between TSC and the internal pressure level was obtained under several combinations of weld strength mismatch and HAZ softening. Results from the FEA show that the effects of the internal pressure on the TSC are highly sensitive to the material attributes in the girth weld region. Under less favorable weld strength undermatching and HAZ softening conditions, the traditionally assumed reduction factor or 1.5–2.5 may not be applicable. Further, the location of tensile failure is found to depend on both the weld material attributes and the internal pressure. It is possible for the failure location to shift from pipe body at zero internal pressure to the girth weld at elevated internal pressure levels. The implications of the results for both girth weld qualification and integrity assessment are discussed.

Framework for Key Influences on Tensile Strain Capacity of Flawed Girth Welds

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Stijn Hertelé ◽  
Rudi Denys ◽  
Anthony Horn ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Tensile Strain ◽  
Influence Factor ◽  
Weld Strength ◽  
Strain Capacity ◽  
Strain Behavior ◽  
Weld Geometry ◽  
Girth Welds ◽  
Tearing Resistance ◽  
Tensile Strain Capacity ◽  
Element Study

A key influence factor in the strain-based assessment of pipeline girth weld flaws is weld strength mismatch. Recent research has led to a framework for tensile strain capacity as a function of weld flow stress (FS) overmatch. This framework is built around three parameters: the strain capacity of an evenmatching weldment, the sensitivity of strain capacity to weld FS overmatch, and the strain capacity at gross section collapse (GSC). A parametric finite element study of curved wide plate (CWP) tests has been performed to identify the influence of various characteristics on each of these three parameters. This paper focuses on flaw depth, tearing resistance of the weld, stress–strain behavior of the base metal, and weld geometry. Influences of these characteristics are mostly found to be limited to one or two of the three framework parameters. A preliminary structure is proposed for equations that further develop the strain capacity framework.

Buckling and Tensile Strain Capacity of Girth Welded 48″ X80 Pipeline

2013 ◽  
Author(s):  
Satoshi Igi ◽  
Mitsuru Ohata ◽  
Takahiro Sakimoto ◽  
Junji Shimamura ◽  
Kenji Oi
Keyword(s):  
Crack Growth ◽  
Tensile Strain ◽  
Compressive Strain ◽  
Bending Test ◽  
Ductile Crack ◽  
Pipe Surface ◽  
Strain Capacity ◽  
Ductile Crack Growth ◽  
Strain Limit ◽  
Tensile Strain Capacity

This paper presents the experimental and analytical results focused on the compressive and tensile strain capacity of X80 linepipe. A full-scale bending test of girth welded 48″ OD X80 linepipes was conducted to investigate the compressive strain limit regarding to the local buckling and tensile strain limit regarding to the girth weld fracture. As for the compressive buckling behavior, one large developing wrinkle and some small wrinkles on the pipe surface were captured relatively well from observation and strain distribution measurement after pipe reaches its endurable maximum bending moment. The tensile strain limit is discussed from the viewpoint of competition of two fracture phenomena: ductile crack initiation / propagation from an artificial notch at the HAZ of the girth weld, and strain concentration and necking / rupture in the base material. The ductile crack growth behavior from the girth weld notch is simulated by FE-analysis based on the proposed damage model, and compared with the experimental results. In this report, it is also demonstrated that the simulation model can be applicable to predicting ductile crack growth behaviors from a circumferentially notched girth welded pipe with internal high pressure subjected to post-buckling loading.

Enhancing Tensile Strain Capacity Through the Optimization of Weld Profiles

2014 ◽  
Author(s):  
Yong-Yi Wang ◽  
Yaoshan Chen ◽  
Mamdouh Salama
Keyword(s):  
Tensile Strain ◽  
High Strength Steels ◽  
High Strength ◽  
Recent Analysis ◽  
Strain Concentration ◽  
Strain Capacity ◽  
Weld Defects ◽  
Weld Region ◽  
Girth Welds ◽  
Tensile Strain Capacity

In order to optimize cost and performance of high pressure gas pipelines by reducing the wall thickness, pipeline companies are considering the use of higher grade (X70 or above) steels or a composite pipe of thin steel liner and fiber wrap. The use of high strength steels and thinner pipes can result in challenges when the pipe is installed in areas imposing high strain demand such as discontinuous permafrost regions. For high strength steels, the difficulty of ensuring the strength overmatching of the weld metal and the potential softening of the heat affected zone (HAZ) can result in gross strain concentration in the weld region and thus reduce the strain capacity of the pipeline in the presence of weld defects. Also, a thinner pipe has lower strain capacity than a thicker pipe for the weld defect of the same dimensions. One of the economical and effective ways of mitigating the possibility of gross strain concentration and increasing the strain capacity of a weld region containing weld defects is through the use of appropriate weld profiles. For instance, adding a smooth and wide layer of weld reinforcement (termed weld overbuild) can increase the effective strength of the weld. The effectiveness of the weld overbuild in improving the tensile strain capacity of girth welds is evaluated using the Level 4a approach of the PRCI-CRES tensile strain models. The crack-driving force is obtained through finite element analysis (FEA) of welds with planar weld and HAZ flaws of various sizes. It was demonstrated that weld overbuild with appropriate dimensions is an effective method to increase the tensile strain capacity (TSC) of girth welds which may have limited TSC without the overbuild. The role of weld profiles in girth weld integrity is discussed from the perspectives of historical evidence and more recent analysis and experimental tests.

Influence of pipe steel heterogeneity of the upper bound tensile strain capacity of pipeline girth welds: A validation study

2016 ◽  
Vol 162 ◽  
pp. 121-135
Author(s):  
Stijn Hertelé ◽  
Koen Van Minnebruggen ◽  
Matthias Verstraete ◽  
Rudi Denys ◽  
Wim De Waele
Keyword(s):  
Validation Study ◽  
Upper Bound ◽  
Tensile Strain ◽  
Pipe Steel ◽  
Strain Capacity ◽  
Girth Welds ◽  
Tensile Strain Capacity

Tensile Strain Capacity of X80 and X100 Welds

2012 ◽  
Author(s):  
Yong-Yi Wang ◽  
Fan Zhang ◽  
Ming Liu ◽  
Woo-Yeon Cho ◽  
Dong-Han Seo
Keyword(s):  
Tensile Strain ◽  
Large Diameter ◽  
High Strength ◽  
Experimental Tests ◽  
Mechanical Tests ◽  
Strain Capacity ◽  
Girth Welds ◽  
Energy Products ◽  
Tensile Strain Capacity ◽  
Potential Use

High-strength pipelines (API 5L grade X70 and above) provide viable economic options for large-diameter and high-pressure transmission of energy products. To facilitate the understanding and potential use of high-strength pipelines, the tensile strain capacity (TSC) of X80 and X100 girth welds was evaluated through a series of mechanical tests and analytical/computational modeling. The experimental tests include tensile, Charpy, SENT, and curved-wide-plate (CWP) tests. The TSC measured from CWP tests is compared with the prediction from TSC models developed at CRES. The TSC of the girth welds is assessed by comparing experimentally measured values with the expected TSC from similar welds. The assessment confirms that this particular set of X80 and X100 girth welds provide very good tensile strain capacity.

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