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.

Multi-Tier Tensile Strain Models for Strain-Based Design: Part 2 — Development and Formulation of Tensile Strain Capacity Models

2012 ◽  
Author(s):  
Ming Liu ◽  
Yong-Yi Wang ◽  
Yaxin Song ◽  
David Horsley ◽  
Steve Nanney
Keyword(s):  
Driving Force ◽  
Tensile Strain ◽  
Weld Strength ◽  
Experiment Data ◽  
Pipe Wall Thickness ◽  
Crack Driving Force ◽  
Strain Capacity ◽  
Welding Processes ◽  
Tensile Strain Capacity

This is the second paper in a three-paper series related to the development of tensile strain models. The fundamental basis of the models [1] and evaluation of the models against experiment data [2] are presented in two companion papers. This paper presents the structure and formulation of the models. The philosophy and development of the multi-tier tensile strain models are described. The tensile strain models are applicable for linepipe grades from X65 to X100 and two welding processes, i.e., mechanized GMAW and FCAW/SMAW. The tensile strain capacity (TSC) is given as a function of key material properties and weld and flaw geometric parameters, including pipe wall thickness, girth weld high-low misalignment, pipe strain hardening (Y/T ratio), weld strength mismatch, girth weld flaw size, toughness, and internal pressure. Two essential parts of the tensile strain models are the crack driving force and material’s toughness. This paper covers principally the crack driving force. The significance and determination of material’s toughness are covered in the companion papers [1,2].

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.

Tensile Strain Models for Strain-Based Design of Pipelines

2012 ◽  
Author(s):  
Yong-Yi Wang ◽  
Ming Liu ◽  
Yaxin Song ◽  
David Horsley
Keyword(s):  
Material Properties ◽  
Tensile Strain ◽  
Weld Strength ◽  
Limit States ◽  
Design Models ◽  
Strain Capacity ◽  
Strain Design ◽  
Level 3 ◽  
Tensile Strain Capacity

This paper covers the development of tensile strain design models using a multidisciplinary approach, including fundamental fracture mechanics, small-scale material characterization tests, and large-scale tests of full-size pipes. The tensile strain design models are formulated in a four-level format. The Level 1 procedure provides estimated tensile strain capacity (TSC) in a tabular format for quick initial assessment. The initiation toughness alternatively termed apparent toughness is estimated from upper shelf Charpy impact energy. The Level 2 procedure contains a set of parametric equations based on an initiation-control limit state. The tensile strain capacity can be computed from these equations with the input of a pipe’s dimensional and material property parameters. The apparent toughness is estimated from either upper shelf Charpy energy or upper shelf toughness of standard CTOD test specimens. The Level 3 procedure uses the same set of equations as in Level 2 and the toughness values are obtained from low-constraint tests. In the Level 3 procedure, two limit states based on either initiation control or ductile instability can be used. The Level 4 procedure allows the use of direct FEA calculation to develop crack driving force relations. The same limit states as those in Level 3 may be used. The Level 4 procedures should only be used by seasoned experts in special circumstances where lower level procedures are judged inappropriate. The tensile strain design models may be used for the following purposes: (1) The determination of tensile strain capacity for a given set of material properties and flaw size. (2) The determination of acceptable flaw sizes for a given set of material properties and target tensile strain capacity. (3) The selection of material properties to achieve a target strain capacity for a given flaw size. (4) The optimization of the tensile strain capacity by balancing the requirements of material parameters, such as weld strength (thus weld strength mismatch level) versus toughness. The application of the tensile strain design models is given in a companion paper.

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.

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

2021 ◽  
Author(s):  
Junfang Lu ◽  
Ali Fathi ◽  
Nader Yoosef Ghodsi ◽  
Debra Tetteh-Wayoe ◽  
Mike Hill
Keyword(s):  
Tensile Strain ◽  
Strain Capacity ◽  
Tensile Strain Capacity

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

Probabilistic Fatigue Reliability of Large Diameter Steel Catenary Risers (SCR) for Ultra-Deepwater Operations

2007 ◽  
Author(s):  
U. O. Akpan ◽  
T. S. Koko ◽  
P. A. Rushton ◽  
A. Tavassoli ◽  
M. Else
Keyword(s):  
Fatigue Strength ◽  
Case Studies ◽  
Material Properties ◽  
Large Diameter ◽  
Random Variables ◽  
Fatigue Reliability ◽  
Strength Parameters ◽  
Stress Levels ◽  
Steel Catenary Risers

For deepwater development in the Gulf of Mexico, steel catenary risers (SCRs) supported from both SPAR and semi-submersible platforms have proven to be successful solutions for in-field flowlines, tie-backs, and export systems. It is envisaged that this will continue to be a promising solution in ultra deep-water applications, up to and beyond 10,000 ft. The study, commissioned by the Mineral Management Service (MMS), investigated the reliability of large-diameter SCRs in ultra-deepwater operations. The primary damage mode considered is fatigue failure. A probabilistic methodology for fatigue reliability is developed, which utilizes deterministic cumulative fatigue damage indicators, namely the stress levels and cycles associated with the various sea states and the fatigue strength of the members. Uncertainties in structural load and material properties are accounted for by assigning probability distributions and standard deviations to the deterministic stress levels. Furthermore, fatigue strength parameters, Miner’s indices, and capacities are modeled as random variables. First order reliability method (FORM) is employed for estimating fatigue reliability. The methodology is applied to three deterministic case studies presented by Intec Engineering (2006a, 2006b). The case studies involved either a SPAR or a semi-submersible platform. For the sake of brevity, a case study involving only a SPAR platform is presented in this paper. The effect of uncertainties in parameters on fatigue reliabilities is investigated. It is observed that the fatigue reliability estimates followed similar trends as the deterministic cumulative damage results, and hence can be used to complement deterministic estimates. Additional benefit and insight gained from the probabilistic study, which can be used for design decisions, include information regarding probabilistic importance and probabilistic sensitivity analysis. For case study presented here, it is seen that in general, uncertainty in the fatigue strength exponent (m) has the highest impact on fatigue reliability of SCRs. The second most important random variable is the stress range (S), which captures uncertainties in parameters such as loads and material properties. Parametric sensitivity studies on the fatigue strength parameters indicate that SCR reliability is sensitive to both the standard deviation and probability distribution of the parameters, thus highlighting the need for accurate probabilistic calibration of the random variables.

Design of the Full Scale Experiments for the Testing of the Tensile Strain Capacity of X52 Pipes With Girth Weld Flaws Under Internal Pressure and Tensile Displacement

2014 ◽  
Author(s):  
Celal Cakiroglu ◽  
Samer Adeeb ◽  
J. J. Roger Cheng ◽  
Millan Sen
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Tensile Strain ◽  
Oil And Gas ◽  
Full Scale ◽  
Element Analysis ◽  
Simultaneous Application ◽  
Strain Capacity ◽  
Tensile Strain Capacity

Pipelines can be subjected to significant amounts of tensile forces due to geotechnical movements like slope instabilities and seismic activities as well as due to frost heave and thaw cycles in arctic regions. The tensile strain capacity εtcrit of pipelines is crucial in the prediction of rupture and loss of containment capability in these load cases. Currently the Oil and Gas Pipeline Systems code CSA Z662-11 0 contains equations for the prediction of εtcrit as a function of geometry and material properties of the pipeline. These equations resulted from extensive experimental and numerical studies carried out by Wang et al [2]–[6] using curved wide plate tests on pipes having grades X65 and higher. Verstraete et al 0 conducted curved wide plate tests at the University of Ghent which also resulted in tensile strain capacity prediction methods and girth weld flaw acceptability criteria. These criteria are included in the European Pipeline Research Group (EPRG) Tier 2 guidelines. Furthermore Verstrate et al 0 introduced a pressure correction factor of 0.5 in order to include the effect of internal pressure in the tensile strain capacity predictions in a conservative way. Further research by Wang et al with full scale pipes having an internal pressure factor of 0.72 also showed that εtcrit decreases in the presence of internal pressure [10]–[15]. In their work, Wang et al presented a clear methodology for the design of full scale experiments and numerical simulations to study the effect of internal pressure on the tensile strain capacity of pipes with girth weld flaws [10]–[15]. However, there has been limited testing to enable a precise understanding of the tensile strain capacity of pipes with grades less than X65 as a function of girth weld flaw sizes and the internal pressure. In this paper the experimental setup for the testing of grade X52 full scale specimens with 12″ diameter and ¼″ wall thickness is demonstrated. In the scope of this research 8 full scale specimens will be tested and the results will be used to formulate the tensile strain capacity of X52 pipes under internal pressure. The specimens are designed for the simultaneous application of displacement controlled tensile loading and the internal pressure. Finite element analysis is applied in the optimization process for the sizes of end plates and connection elements. Also the lengths of the full scale specimens are determined based on the results from finite element analysis. The appropriate lengths are chosen in such a way that between the location of the girth weld flaw and the end plates uniform strain zones could be obtained. The internal pressure in these experiments is ranging between pressure values causing 80% SMYS and 30% SMYS hoop stress. The end plates and connection elements of the specimens are designed in such a way that the tensile displacement load is applied with an eccentricity of 10% of the pipe diameter with the purpose of increasing the magnitude of tensile strains at the girth weld flaw location. The results of two full scale experiments of this research program are presented. The structural response from the experiments is compared to the finite element simulation. The remote strain values of the experiment are found to be higher than the εtcrit values predicted by the equations in 0.

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