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.

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.

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

Application of Tensile Strain Models to Multiple Grades of Pipelines

2014 ◽  
Author(s):  
Wenwei Zhang ◽  
Zhenyong Zhang ◽  
Jinyuan Zhang ◽  
Peng Yang
Keyword(s):  
Tensile Strain ◽  
Large Diameter ◽  
High Strength ◽  
Slope Movement ◽  
Experimental Database ◽  
Mine Subsidence ◽  
The Past ◽  
Discontinuous Permafrost ◽  
China National Petroleum Corporation ◽  
Tensile Strain Capacity

China National Petroleum Corporation (CNPC) has constructed large-diameter high-strength pipelines (X70 and X80) in the past decades in areas of seismic activities, mine subsidence, and slope movement using strain-based design (SBD) technology. More pipelines being constructed now traverse regions of active seismic activities, mine subsidence, slope movement, and discontinuous permafrost. CNPC is also interested in moving to linepipe grades higher than X80. In view of the recent development of various tensile strain models, work was undertaken to evaluate those models and determine the most appropriate models for current and future applications. In this paper, selected tensile strain models are reviewed and evaluated against an experimental database. The database of 80 tests from public-domain publications contains both full-scale pipe tests and curved wide plate tests with 46 tests from high strength pipes (X80 and above). The calculated tensile strain capacity from the selected models was compared with the test data. The models were evaluated and the applicability of the models to the linepipes of different strength levels was discussed.

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.

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

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

2013 ◽  
Author(s):  
Stijn Hertelé ◽  
Rudi Denys ◽  
Anthony Horn ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Flow Stress ◽  
Tensile Strain ◽  
Influence Factor ◽  
Weld Strength ◽  
Strain Capacity ◽  
Weld Geometry ◽  
Strain Behaviour ◽  
Girth Welds ◽  
Tearing Resistance ◽  
Tensile Strain Capacity

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 overmatch. This framework is built around three parameters: the strain capacity of an evenmatching weldment, the sensitivity of strain capacity to weld flow stress overmatch and the strain capacity at gross section collapse. A parametric finite element study of curved wide plate 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 behaviour 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.

A Quantitative Approach to Tensile Strain Capacity of Pipelines

2006 ◽  
Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
David Horsley ◽  
Joe Zhou
Keyword(s):  
Quantitative Determination ◽  
Tensile Strain ◽  
Limit State ◽  
Ultimate Limit State ◽  
Strain Capacity ◽  
Closed Form Solutions ◽  
Number Of Factors ◽  
Girth Welds ◽  
Tensile Strain Capacity

Tensile strain rupture is an ultimate limit state. A limit state is stated in generic terms of “load” and “resistance” or alternatively termed “demand” and “capacity.” The “demand” of tensile rupture limit state is mostly related to displacement-controlled loading, such as that induced by frost heave, landslide, and seismic activities. The “capacity” is most often controlled by girth weld tensile strain limits, as girth welds tend to be the weakest link in pipelines experiencing high tensile strains. The tensile strain limits of girth welds are affected by a large number of factors: tensile and toughness properties of the pipe and weld, weld geometry, stress state, defect size and location. Consequently, closed-form solutions for tensile strain limits of girth welds do not yet exist in codes and standards. PRCI and TransCanada have funded a number of projects in recent years to develop fracture-mechanics-based procedures aimed at quantitative determination of girth weld tensile strain limits. The results of these projects, along with the reviews and examination of available experiment data by the authors, have culminated in a set of recommended procedures that enable the quantitative determination of the tensile strain capacity of pipelines. The required input parameters, formulae for the computation of tensile strain limits, limits of applicability, and suggested methods of applications are specified in the proposed procedures. This paper covers the technical basis of the procedures. Particular emphasis is placed on the validation of these procedures. The limitations of the procedures and future directions of improvements are suggested. It is believed that these procedures may lay the initial groundwork towards the eventual code implementation of a comprehensive set of tools for quantitative strain-based design of pipelines.

A Case Study of Predicting Tensile Strain Capacity of In-Service Pipelines

2020 ◽  
Author(s):  
Junfang Lu ◽  
Ali Fathi ◽  
Nader Yoosef-Ghodsi ◽  
Debra Tetteh-Wayoe ◽  
Mike Hill
Keyword(s):  
Material Properties ◽  
Tensile Strain ◽  
Large Diameter ◽  
Ground Movement ◽  
Capacity Assessment ◽  
Pipe Material ◽  
Strain Capacity ◽  
Welding Processes ◽  
Tensile Strain Capacity

Abstract Strain-based design (SBD) method has evolved over the years for use in the construction of large-diameter, high pressure gas and liquid transmission pipelines. It has not been widely materialized for major construction projects because of the technical complexity which requires multidisciplinary expertise including, but not limited to, pipeline material properties, welding processes, mechanical testing, field construction, and weld inspection. The industry has been showing more interest in using this methodology for strain capacity assessment of in-service stress-based pipelines, especially those that are subjected to ground movement. The strain capacity assessment of the stress-based pipelines is essential to ensure structural integrity and operational safety of the pipeline. This has become more apparent due to recent incidents in pipeline industry caused by geotechnical hazards. This paper provides a case study of assessing the tensile strain capacity (TSC) of existing modern linepipes manufactured through thermomechanical controlled process (TMCP). The TSC was predicted using two main methodologies in the public domain: the CSA Z662-11 Annex C approach and the PRCI-CRES TSC model. Actual pipeline information and construction data are used to perform TSC assessment when possible. This includes pipe material properties, welding procedures qualified on the project pipe, and test weld properties. The predicted TSC and the estimated strain demand will allow for effective remediation decisions. This work helps to enhance pipeline strain management systems in response to the geotechnical and hydrotechnical issues and therefore fills the gaps in present day’s pipeline threat management programs in addition to crack, corrosion and mechanical damage threats. Through such a program, prevention, monitoring and mitigation strategies can be deployed to existing stress-based pipelines, especially in areas where pipeline strain is identified as a potential risk.

Estimation of Tensile Strain Capacity of Vintage Girth Welds

2020 ◽  
Author(s):  
Bo Wang ◽  
Banglin Liu ◽  
Yong-Yi Wang ◽  
Otto Jan Huising
Keyword(s):  
Driving Force ◽  
Tensile Strain ◽  
Software Tool ◽  
Ground Movement ◽  
Small Scale ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Girth Welds ◽  
The Impact ◽  
Tensile Strain Capacity

Abstract Being able to estimate the tensile strain capacity (TSC) of vintage girth welds is sometimes necessary for the integrity management of vintage pipelines. Assessing girth weld integrity could be a top priority after a confirmed ground movement event. Decisions may also be needed about the disposition of a girth weld when weld anomalies are found. Typical fitness-for-service (FFS) procedures, such as API 1104 Annex A and API 579/ASME FFS-1, generally target materials under nominally elastic conditions and strain demands less than 0.2%. These procedures may produce overly conservative results when the strain demand exceeds 0.2%. This paper summarizes the development and validation of a TSC estimation tool for vintage girth welds under PRCI funding. The work consisted of three components: the development of a TSC model for vintage girth welds, the implementation of the model into a software tool, and the experimental validation of the performance of the tool using curved wide plate (CWP) tests. The TSC model was developed following the procedures established through a previous PRCI-PHMSA cofounded work. Finite element analyses (FEA) were performed to obtain a crack-driving force database while considering the salient features of vintage girth welds, such as larger weld caps and weld strength mismatch levels. The TSC model was then derived from the crack-driving force database using apparent toughness values representative of vintage girth welds. A graphical user interface (GUI) and a user manual were developed to facilitate the application of the TSC model. The software tool produces TSC estimates based on geometry, material, loading, and flaw characteristics of a girth weld. For inputs that might not have readily available values, recommended values are provided. The tool allows the evaluation of the impact of various input parameters on TSC. The performance of the TSC estimation tool was evaluated against eight purposely designed CWP tests. Accompanying small-scale material characterization tests, including chemical composition, round bar tensile, microhardness, and Charpy impact tests, were performed to provide additional inputs for the evaluation of the tool. The tool is shown to provide reasonably conservative estimates for TSC. An example problem is presented to demonstrate the application of the tool. Gaps and future work to improve the tool are highlighted at the end of the paper.

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