bluuebunny/crossref_metadata_2025 huggingface dataset:
Fracture Toughness of X100 Pipe Girth Welds Using SE(T) and SE(B) Tests
Authors: Park Dong-Yeob , Tyson William R. , Gianetto James A. , Shen Guowu , Eagleson Robert S.
Published: July 2013

Extensive single-edge notched tension (SE(T)) and single-edge notched bend (SE(B)) tests were performed to apply the SE(T) procedure developed at CANMET and the standard SE(B) procedure of ASTM E1820 to pipeline girth welds as a contribution to a broader project on strain-based design (SBD) for pipeline girth weld integrity. Specimens were precracked from the pipe inner surface to target lengths of 3 and 6 mm to represent surface-breaking weld flaws of single- and double-pass height, respectively. It was found that resistance curves for weld metal (WM) were much lower than those for base metal (BM) or heat affected zone (HAZ) specimens even though the WM strength overmatched the BM, owing to effects from the WM microstructure. The small crack-tip opening angle observed in post-test WM specimens was consistent with the low crack propagation resistance, which in turn results in small tearing resistance, TR. In general, toughness decreases with increase in initial crack length. J values and tearing resistance are found to be influenced by loading mode; toughness is higher in tension, SE(T), than in bending, SE(B) for a given crack length and test temperature.
Effect of Plastic Constraint on Anisotropic Crack Extension in a Grade X63 Line Pipe Steel
Authors: Burlot Philippe , Besson Jacques , Madi Yazid , Batisse Rémi , Hertz-Clémens Stéphane
Published: July 2013

The purpose of this work was to evaluate the fracture toughness for different plastic constraint levels of a grade X63 line pipe representative of in-service line pipes in France. This study was carried out for high constraint levels using Compact Tensile (CT) specimens and low constraint levels using Single Edge Notched Tensile (SENT) specimens. Moreover, in order to reduce the amount of tested samples, silicone replicas of crack advance were made all along the test. The results show that the loss of plastic constraint induces J–values about 70% higher compared to high constraint tests. A strong crack growth resistance anisotropy was observed at high constraint. This anisotropy is significantly reduced at low constraint.
Testing and Analysis of the Soil Thermal Conductivity in Tropical Desert and Grassland of West Africa
Authors: Li Yutian , Wu Changchun , Xing Xiaokai , Yue Mingliang , Shang Yun
Published: July 2013

Thermal conductivity is one of the basic thermal properties of soil. For a buried pipeline, the thermal conductivity of the surrounding soil is the most important factor determining the overall heat transfer from the pipeline, and plays an important role in assessing the safety and energy consumption of pipeline operation. For providing reliable basic data for the commissioning and the operation of a waxy crude oil pipeline stretching in southwest Sahara Desert, six phases of thermal conductivity testing were performed along the pipeline route, respectively in February, March, April, May, July and September, 2011. The pipeline is 462.5km long and 323.9mm outside diameter. The pipeline route crosses tropical desert and grassland. Test points are located at roughly equal spaces along the pipeline route, and additional test points are located in seasonal river beds and rugged terrains. The soil temperature and thermal conductivity were tested simultaneously at a depth of about130cm below soil surface, which is also near to the pipeline centerline. The test equipment used was a field thermal needle system FTN01 for thermal conductivity made in Holland. For a given location along the pipeline route, the soil thermal conductivities have different values in dry season and rainy season. The average soil thermal conductivities for the pipeline route between two stations ranges from 0.5 to 1.1W/(m·°C) in rainy season, and from 0.4 to 0.8 W/(m·°C) in dry season. The test results show that the change of soil moisture content has significant impact on soil thermal conductivity. Because other properties of the tested soil along the pipeline route such as soil mineral composition, particle size distribution and density have no significant change, these factors have little effect on soil thermal conductivity.
Why Reliability-Based Approaches Need More Realistic Corrosion Growth Modeling
Authors: Huyse Luc , Brown Katherine A.
Published: July 2013

Deterministic design and assessment methods are by definition conservative. Although no claim is made regarding the actual reliability level that is achieved using deterministic, i.e. safety-factor based approaches, the safety factors have been selected such that generally sufficient conservatism is maintained. Reliability-based methods aim to explicitly quantify the aggregated conservatism in terms of failure probabilities or risk. Accurate reliability estimates are not possible without accurate computational prediction models for the limit states and adequate quantification of the uncertainties in both the inputs and model assumptions. Although this statement may seem self-evident, it should not be made light-heartedly. In fact, just about every analysis step in the pipeline integrity assessment procedures contains an inherent, yet unquantified, level of conservatism. One such example is the application of a “maximum” corrosion growth rate that is constant in time.

A reliability-based framework holds the promise of a more consistent and explicitly quantified safety level. This ultimately leads to higher safety efficiency for an entire pipeline system than under safety factor based approaches. An accurate prediction of the true likelihood of an adverse event is impossible without significant research into determining and understanding the, usually conservative, bias in the engineering models that are currently employed in the pipeline integrity state-of-the-practice. This paper highlights some of the challenges that are associated when porting the “maximum corrosion rate” approach used in a deterministic approach to a reliability-based paradigm. Issues associated with both defect and segment matching approaches will be highlighted and a better corrosion growth model form will be proposed.
The Critical Path Method for Assessment of Pipelines With Metal Loss Defects
Authors: Freire José L. F. , Vieira Ronaldo D. , Fontes Pablo M. , Benjamin Adilson C. , Murillo C. Luis S. , Miranda Antonio C.
Published: July 2013

The Critical Path (CP) Method (CPM proposes a set of rules allowing the drawing of failure lines that represent adjacent areas positioned along selected circumferential and longitudinal directions of pipelines that contain colonies of corrosion defects. Failure pressures are calculated for each of those lines to determine the most critical one. This selected line is considered as the most probable path of rupture, and it corresponds to the minimum calculated internal pressure to take the pipeline to fracture. The proposed method was checked against twelve burst pressure tests performed on pipeline tubular specimens. Three specimens were labeled as control specimens — one was a pipe without defect and the other two had single small base defects of different depths. Nine of the specimens contained interacting corrosion defects, which were composed of the combinations of two or more base defects. Comparisons were made of the measured burst pressures with those predicted by the CPM, by one recently proposed method called MTI, version 1, or MTI V1, and by four other Level-1 or Level-2 assessment methods, namely the American Society of Mechanical Engineers (ASME) B31G method, the Det Norske Veritas (DNV) RP-F101 for single and for complex and interacting defects, and the RSTRENG Effective Area method. The CPM and MTI V1 methods predicted the failure pressures closest to the actual test failure pressures, with the CPM presenting suitable small mean error of evaluation as well as very low standard deviation error for its predictions.
Evaluation of Wireless Tools for Determining Contact Status Between a Casing and the Carrier Pipe
Authors: Song Fengmei , McFarland John , He Xihua
Published: July 2013

For more than half a century, cased crossings have been used to support oil and gas steel pipes for crossing highways, railways, or rivers. Leaks or ruptures of cased crossings have occurred that resulted in casualties and property damage. Unlike uncased pipes buried in soils, which can be assessed for external corrosion directly and indirectly, the presence of a steel casing wall makes it challenging, even if possible, to conduct these assessments. The effect of the casing wall on the external corrosion of the carrier pipe inside the annulus is not well understood; it is unclear what tools can be used to effectively inspect the cased pipes. Empirical experience from the pipeline industry has shown that a few tools can be used to detect the contact status between a casing and the carrier pipe, which can help assess the severity of the carrier pipe external corrosion. Unfortunately, the criteria used to detect a contact status vary by user for the same tool and thus, the effectiveness of these criteria is uncertain. This paper reports results from a recent study aimed at evaluating the effectiveness of AC current attenuation, AC voltage gradient, and close interval (potential) survey as tools for detecting the contact status between a casing and the carrier pipe.
Investigation of the Effects of Pipe Wall Roughness and Pipe Diameter on the Decompression Wave Speed in Natural Gas Pipelines
Authors: Lu C. , Michal G. , Elshahomi A. , Godbole A. , Venton P. , Botros K. K. , Fletcher L. , Rothwell B.
Published: July 2013

The shock tube experimental results have shown clearly that the decompression wave was slowed down in a pipe with a rough inner surface relative to that in a smooth pipe under comparable conditions. In the present paper a one-dimensional dynamic simulation model, named EPDECOM, was developed to investigate the effects of pipe wall roughness and pipe diameter on the decompression wave speed. Comparison with experimental results showed that the inclusion of frictional effects led to a better prediction than that of the widely used model implemented in GASDECOM. EPDECOM simulation results showed that the effect of roughness on the decompression wave speed is significant for pipe diameters less than 250 mm. However the decompression wave speed is nearly independent of the roughness for diameters above 250 mm as the frictional effect becomes negligible at such diameters.
The Contribution of Aboriginal Traditional Ecological Knowledge to the Environmental Assessment Process for Canadian Pipelines
Authors: Lewis Wanda
Published: July 2013

Northern British Columbia (BC) and Alberta are sparsely populated forested lands under provincial jurisdiction (also known as Crown land) which are under intensive oil & gas exploration and pipeline development. Local Aboriginal people continue to implement traditional practices that maintain viable land and productive ecosystems by annual rotation of trap lines, hunting and gathering areas and similar activities. Aboriginal people can exert tremendous influence on pipeline projects through various means. Regulators and enlightened pipeline companies recognize the value of assessing traditional knowledge that has been collected over generations and passed down from the Elders to contribute to final routing, siting and project design identifying effects on environmental resources and traditional land and resource use and developing mitigation opportunities. Traditional knowledge includes experiential and secondary knowledge as well as accepted scientific research in the context of environmental assessments. Robust applications consider sources from all land users while being mindful of the intricacies inherent with Aboriginal engagement in order to gather substantive input for projects on Crown land.

This paper explores the contribution of Aboriginal Traditional Ecological Knowledge (TEK) in the environmental assessment process on selected case studies involving recent natural gas pipeline projects in northern BC and Alberta from a balanced perspective. It also describes the evolution of a program developed by the author from its initial emphasis on Traditional Land Use (TLU) studies to the present day application of TLU studies, and TEK studies, focusing on lessons learned and regulatory and engagement challenges and successes.
Effect of Thermal Aging on Strain Capacity of X80 SAW Pipes
Authors: Shitamoto Hidenori , Hamada Masahiko , Takahashi Nobuaki , Nishi Yuki
Published: July 2013

Application of API X80 grade line pipes has been promoted to increase the operating pressure. It is generally known that the deformability of submerged arc welding (SAW) pipes is decreased by increasing strength of the pipes. The assessment of the strain capacity of X80 SAW pipes is required for strain-based design (SBD). In the assessment of the strain capacity, one of the important issues is the effect of thermal aging during the anti-corrosion coating on the yielding phenomenon. In this study, full-scale pipe bending tests of X80 SAW pipes produced by UOE process were performed to evaluate the effect of thermal aging on the strain capacity.
A Model of Hydrogen Assisted Cold Cracking in Weld Metal
Authors: Kotousov Andrei , Borkowski Krzysztof , Fletcher Leigh , Ghomashchi Reza
Published: July 2013

Due to significant cost and productivity advantages, low heat inputs, high welding speeds, severe loading conditions and the use of cellulosic electrodes in the construction of oil and gas pipelines are unavoidable in Australia. Another significant cost reduction directly related to the tonnage of steel pipe dictates the wider use of higher grade steels, such as X70, X80 or X100. These current tendencies raise a serious concern regarding potential problems associated with weld metal hydrogen assisted cold cracking, HACC. Although there are industry standards and guidelines for the avoidance of hydrogen cracking in the heat affected zone, this is not the case for the weld metal, which is now more likely source of crack initiation in modern pipeline steels. The current paper develops a simplified mathematical model to predict the risk of hydrogen cracking in weld metal. A sensitivity study is conducted to evaluate the effect of various welding parameters and geometry, such as heat input, preheat and ambient temperatures and wall thickness on the risk of hydrogen cracking.
Development of Optimum Welding Heat Input Device Based on Welding Frequency and Spark Detection
Authors: Eun Sung-Soo , Cho Min-Hyun , Kim Ki-Hong , Lee Hyun-Seung
Published: July 2013

According to the previous researches, the welding frequency increases as the load impedance decreases when the narrow gap shorts out during ERW welding process. The proper welding frequency is theoretically calculated and also measured for OCTG pipe manufacturing. Also, to assure the quality of ERW tube, the spark detection device developed. According to signals from the spark detection device, there are two types of sparks found as a single-shot spark and sustainable spark. The formation of single-shot spark is too short to recognize the existence of spark with operator’s naked eyes during ERW process. Thus, the paint spraying system was used to mark the sparking location for screening at the inspection unit. Therefore, spark detecting devices (bad signal detection) are used to increase the productivity of products and improve its quality. In addition, the database server system developed according to the accumulated data can provide the cost savings and the creation of new demands.
PIRAM: Pipeline Ice Risk Assessment and Mitigation Program Overview
Authors: Phillips Ryan , King Tony , Bruce Jim
Published: July 2013

The Pipeline Ice Risk Assessment & Mitigation JIP (PIRAM) developed a set of engineering models and design procedures for implementation into industry best practices for risk mitigation and protection of pipeline infrastructure from ice keel loading. The models established the pipeline mechanical behaviour in response to ice keel load events, and assessed engineering concepts for protection and risk mitigation strategies. Improved methodologies for contact frequency and ice keel loads determination formed part of the integrated model.

This paper presents an overview of this multiyear program and examples of the application of the models in pipeline burial depth assessment in pressure ridge ice gouged seabeds.
Development and Production of Helical-Two-Step (HTS) Pipes: Grades Up to API X70 for Sour Service Application
Authors: Mirković Djordje , Flaxa Volker , Knoop Franz Martin
Published: July 2013

Within the corresponding commercial and R&D projects five microalloyed pipeline steel grades have recently been developed and processed to spiral-welded pipes. For steel grades X52, X65, and X70 the aimed tensile properties, improved sour service resistivity, and low temperature toughness up to −40°C were reliably achieved.

Influence of steel cleanliness, the non-metallic inclusions in particular, on sour gas resistibility has been investigated by means of ultrasonic testing of hydrogen charged HIC (Hydrogen Induced Cracking) samples and SEM (Scanning Electron Microscope) analyses of HIC fracture surfaces. The results have been used to optimize the applied process parameter in steel production and coil processing. The ladle metallurgical treatment and soft reduction were consistently applied within narrow process tolerances enabling high steel cleanness and slab centerline quality, which are both indispensable for sour service application. Subsequent TMCP (Thermo Mechanical Processing) wide strip hot rolling and cooling parameters were selected to prevent a two-phase finish rolling and to obtain a predominating acicular ferritic microstructure. For pipe production, attention was paid to minimize the residual stresses, due to both pipe-forming and welding.

The alloying approach is based on the classical sour lean NbTi steel composition, modified by varying Cu, Ni, Cr, and Mo contents to achieve the targeted specification.

The processed spiral-welded pipes were formed to diameters between 762 and 1372 mm with a wall thickness of 13.7 to 16.0 mm. CVN (Charpy V-Notch) values were higher than 360 J/cm2 and DWTT (Drop Weight Tear Test) higher than 60% SA (Shear Area) at −40°C. The samples also showed outstanding HIC resistivity. Being proved with standard test conditions according to NACE TM0284 solution A, the CAR (Crack Area Ratio) average value of pipe samples was less than 1% for grades up to X65 and less than 5% for X70 grades. The 4-point-bending SSC (Sulphide Stress Cracking) tests at 80% of SMYS according to NACE TM0177 and ASTM G39 showed no SSC cracks for all projects.

Finally, the results of one specific R&D project are presented to demonstrate that even for API X70 grade spiral-welded pipes (OD 1016×16 mm) mechanical properties, e.g. high-strength, ductility, and low temperature toughness has been successfully combined with sour service resistivity.
Field Experience With a Model for Determining Hydrostatic Re-Test Intervals
Authors: Fessler Raymond R. , Rapp Steve C. , Marr Jim E.
Published: July 2013

At IPC 2006, a model was described that provided a scientific basis for determining hydrostatic re-test intervals for SCC in gas pipelines.[1,2] The model involves determining the maximum possible crack growth rate based upon previous hydrostatic-test intervals and pressures. It resulted in intervals that initially are short and subsequently get longer and longer. Compared to uniform intervals, this sequence is predicted to result in an equivalent level of safety with fewer re-tests. Several pipeline companies have adopted the model, and, in general, the model has been successful. The 2006 paper pointed out that the model was applicable to ruptures but not leaks. In addition, the model did not consider two possible, but unlikely, conditions. One is the possibility that a coating defect could develop after the first hydrostatic test and a severe chemical environment might develop under the defective coating. This possibility has never been observed. The second is the possibility that two or more nearly co-linear sub-critical cracks could coalesce to form a critical size flaw. That would cause a discontinuous step in the growth curve, which is not consistent with the model. The one and only exception to the model that has been observed to date was of this nature. Since this latter condition can occur for cracks at the toe of a double-submerged arc weld under tented tape coating, a special re-test schedule has been devised for this condition. The original assumption of the model that the failure pressure of a growing crack varies linearly with time was verified from a fracture surface that had markings corresponding to the position of the crack front at various known times during the history of the pipeline.
Limit States Design and Assessment of Onshore Pipelines
Authors: Nessim Maher
Published: July 2013

In 2005, guidelines for the application of reliability-based design and assessment (RBDA) to natural gas pipelines were developed under PRCI sponsorship. The methodology underlying these guidelines has since been adopted as a non-mandatory Annex in the CSA Z662 standard (Annex O). The benefits of reliability-based methods include consistent safety levels, optimized solutions that make best use of available resources and flexibility in addressing non-standard problems. The key limitations of the methodology are that it requires specialized expertise, good data and a significant analysis effort.

One approach that has been successfully used to simplify the application of reliability-based methods is to develop simple design and assessment rules that are designed to meet specified safety levels. In this approach, which is referred to here as limit states design and assessment, the checking rules incorporate safety factors that are “calibrated” to meet pre-selected reliability targets, within a specified tolerance, over a wide range of possible design and assessment cases. Probabilistic analyses are performed as part of the development stage, but the resulting checks are deterministic.

The basic elements required to calibrate limit states design and assessment checks have been developed as part of the RBDA methodology, making the development of a limit states approach feasible. This paper provides an overview of an ongoing Joint Industry Project to develop a limit states design and assessment standard that addresses the key threats to the safety of onshore pipelines. The benefits and limitations of this approach are discussed in comparison to the full RBDA approach, and the expected outcomes of the project are described.
Safety Levels Associated With the Ultimate Limit State Reliability Targets in Annex O of CSA Z662
Authors: Nessim Maher , Stephens Mark , Adianto Riski
Published: July 2013

In 2005, guidelines for the application of reliability-based design and assessment (RBDA) to natural gas pipelines were developed under PRCI sponsorship. The methodology underlying these guidelines has since been adopted as a non-mandatory Annex in the CSA Z662 standard (Annex O). Because the methodology is based on the concept of consistent risk, it is more restrictive than current design standards for some pipelines and less restrictive for other pipelines. Specifically, the RBDA reliability targets for ultimate limit states (ULS) are lower than the reliability levels achieved by current design standards for large diameter, high pressure pipelines in Classes 2 to 4 (referred to in this paper as high consequence pipelines) and for all pipelines in Class 1. This has naturally led to questions among users and reviewers of RBDA regarding the adequacy of the ULS reliability targets for these pipelines.

For high consequence pipelines, the safety levels associated with the ULS reliability targets are compared to risk tolerance criteria from three published European standards. The comparison demonstrates that the targets are generally more conservative than all three standards. For Class 1 pipelines, the average failure probability for pipelines designed to the RBDA methodology is compared to the average failure probabilities for pipelines designed to ASME B31.8 and Clause 4 of CSA Z662. This shows that there is no significant difference in overall failure probability because the wall thickness for most Class 1 pipelines with low ULS targets are governed by other criteria, such as minimum permitted wall thickness and maximum diameter-to-thickness ratio for standard line pipe. Recognizing the potential difficulties with reliability targets that do not govern any designs, a possible modification to align the targets with the actual reliability levels is proposed.
Professional Qualification Program in Natural Gas Transmission at Transpetro
Authors: Tomaz Luciane G. , Real Vicente J. C.
Published: July 2013

This article describes the conception, implementation and management of the training program in the natural gas division established by Transpetro to prepare its workforce to deal with the increasing operational complexity of the company’s systems while maintaining high levels of safety and ensuring continuous delivery. The main objective of the development of the program was to train field technicians spread all over the country in a short time frame and in standardized form. The results so far have been highly satisfactory.
Techno-Economic Modelling and Analysis of CO2 Pipelines
Authors: Ghazi Nima , Race Julia M.
Published: July 2013

The main focus of this paper is on techno-economic modeling and analysis of CO2 pipelines, as it strives to develop a thorough understanding of the essential fluid-mechanics variables involved in modeling and analysis of such pipelines. The authors investigate and analyze the reasons behind the variations in the techno-economic results generated from seven different techno-economic models which are commonly used for construction and operation of CO2 pipelines. Such variations often translate into tens or, at times, hundreds of millions of dollars in terms of initial financial estimates at the Pre-FEED (Front End Engineering Design) or FEED stages for Carbon Capture and Storage (CCS) projects. Variations of this magnitude can easily bring much unwanted uncertainty to the feasibility of a CO2 pipeline project and they can potentially cause a major over or under estimation of the project’s true costs. The summary of a detailed analysis and assessment for these seven existing techno-economic models for CO2 pipeline transport has been presented in this paper. The analysis conducted indicates that some of these models are essentially identical and are rooted in similar fluid mechanics theories and assumptions. This type of analysis assists with explaining and narrowing down the variability of the models’ results. Based on these analyses, a refined and more accurate model was established and the development process was explained. The refined model uses the Reynolds number, Colebrook-White equation using the Darcy friction factor, and the Darcy-Weisbach pressure drop equation to establish the most accurate measure for the pipe’s diameter. To assess the CO2 pipeline’s total capital cost, total annual cost, and the levelized transport cost, a statistical regression analysis approach was suggested and the adjusted-r2 measure was proposed to assess the goodness-of-the-fit of the generated cost function. The accuracy of the new techno-economic model was validated with the figures of a proposed CO2 infrastructure project in the United Kingdom and also through hydraulic modeling.
The Decompression Behaviour of Carbon Dioxide in the Dense Phase
Authors: Cosham Andrew , Jones David G. , Armstrong Keith , Allason Daniel , Barnett Julian
Published: July 2013

Pipelines can be expected to play a significant role in the transportation infrastructure required for the successful implementation of carbon capture and storage (CCS). National Grid is undertaking a research and development programme to support the development of a safety justification for the transportation of carbon dioxide (CO2) by pipeline in the United Kingdom.

The ‘typical’ CO2 pipeline is designed to operate at high pressure in the ‘dense’ phase. Shock tube tests were conducted in the early 1980s to investigate the decompression behaviour of pure CO2, but, until recently, there have been no tests with CO2-rich mixtures.

National Grid have undertaken a programme of shock tube tests on CO2 and CO2-rich mixtures in order to understand the decompression behaviour in the gaseous phase and the liquid (or dense) phase. An understanding of the decompression behaviour is required in order to predict the toughness required to arrest a running ductile fracture.

The test programme consisted of three (3) commissioning tests, three (3) test with natural gas, fourteen (14) tests with CO2 and CO2-rich mixtures in the gaseous phase, and fourteen (14) tests with CO2 and CO2-rich mixtures in the liquid (or dense) phase. The shock tube tests in the liquid (dense) phase are the subject under consideration here.

Firstly, the design of the shock tube test rig is summarised. Then the test programme is described. Finally, the results of the dense phase tests are presented, and the observed decompression behaviour is compared with that predicted using a simple (isentropic) decompression model. Reference is also made to the more complicated (non-isentropic) decompression models. The differences between decompression through the gaseous and liquid phases are highlighted.

It is shown that there is reasonable agreement between the observed and predicted decompression curves.

The decompression behaviour of CO2 and CO2-rich mixtures in the liquid (dense) phase is very different to that of lean or rich natural gas, or CO2 in the gaseous phase. The plateau in the decompression curve is long. The following trends (which are the opposite of those observed in the gaseous phase) can be identified in experiment and theory:

• Increasing the initial temperature will increase the arrest toughness.

• Decreasing the initial pressure will increase the arrest toughness.

• The addition of other components such as hydrogen, oxygen, nitrogen or methane will increase the arrest toughness.
An Efficient Methodology for the Reliability Analysis of Corroding Pipelines
Authors: Zhang S. , Zhou W.
Published: July 2013

This paper describes an efficient methodology that utilizes the first order reliability method (FORM) and system reliability approaches to evaluate the time-dependent failure probabilities of a pressurized pipeline at a single active corrosion defect considering three different failure modes, i.e. small leak, large leak and rupture. The criteria for distinguishing small leak, large leak and rupture at a given corrosion defect are established based on the information in the literature. The wedge integral and probability weighting factor methods are used to evaluate the probabilities of small leak and burst, whereas the conditional reliability index method is used to evaluate the probabilities of large leak and rupture. Two numerical examples are used to illustrate the accuracy, efficiency and robustness of the proposed methodology. The proposed methodology can be used to facilitate reliability-based corrosion management programs for energy pipelines.
Tensile and Fracture Properties of X80 Steel Microstructures Relevant to the HAZ
Authors: Gaudet Michael J. , Poole Warren J.
Published: July 2013

The girth welding of steel pipelines creates a substantial heat affected zone (HAZ) within the base pipeline steel. The HAZ can be considered to be a complex graded microstructure. While there is significant concern as to the fracture and mechanical properties of the HAZ as whole, detailed knowledge about the mechanical properties of the individual microstructures is lacking. For this study, X80 is heat treated in a Gleeble simulator to create samples of bulk microstructures with differing amounts and morphologies of bainite, ferrite and martensite-retained austenite (MA) with a total of 8 microstructures being investigated. The heat treatments were selected specifically to control the level of niobium in solid solution; that is to control whether niobium was fully in solution or contained mainly in niobium carbonitride precipitates. From the heat treated samples a matching tensile and fracture specimens were made. The strongest microstructure proved to be the finest bainitic microstructure, while the lowest strength microstructure was the coarsest bainite sample containing a significant amount of martensite-retained austenite connected along grain boundaries. The fracture behaviour at ambient temperature was studied using the Kahn tear test. The Kahn tear test is a machine notched, thin-sheet, slow strain rate fracture test which has the advantage of being a simple test to conduct. All Kahn tests failed in a ductile manner and it showed that the sample with the coarse bainite, with a connected martensite-retained austenite phase had the lowest unit propagation energy and tear strength while the fine, fully bainitic sample had the highest unit propagation energy and tear strength. Further investigation using SEM measurements of the final fracture surface from the tensile test to determine the tensile toughness. A comparison of the tensile toughness and unit propagation energies showed that there was a complex relationship between the two measurements. However, the samples which had the highest content of MA gave the in lowest unit propagation energy.
Microstructure and Properties of High Strength Steel Weld Metals
Authors: Gianetto J. A. , Goodall G. R. , Tyson W. R. , Fazeli F. , Quintana M. A. , Rajan V. B. , Chen Y.
Published: July 2013

With an industry trend towards application of modern high strength steels for construction of large diameter, high pressure pipelines from remote northern regions there is a need to develop high-productivity welding processes to reduce costs and deal with short construction seasons. Achieving the required level of weld metal overmatching together with adequate ductility and good low temperature toughness is another major challenge for joining high strength X80/100 pipes. It is important to develop an improved understanding of weld metal systems that are required for the successful production of high strength pipeline girth welds that are needed for such demanding pipeline construction. In this investigation a range of weld metal (WM) compositions based on (i) C-Mn-Si-Mo, (ii) C-Mn-Si-Ni-Mo-Ti and (iii) C-Mn-Si-Ni-Cr-Mo-Ti was selected for more detailed evaluation of experimental plate welds complemented by specimens simulated by Gleeble® thermal cycling. Five specially-designed experimental plate welds were made with a robotic single torch pulsed gas metal arc welding (GMAW-P) procedures with wire electrodes applicable for joining X100 pipe. The procedures consisted of three initial fill passes deposited at 0.5 kJ/mm and a final deep-fill pass at 1.5 kJ/mm to just fill the narrow-gap joint. An important part of the research focused on development of WM Continuous Cooling Transformation (CCT) diagrams to establish the influence of composition and thermal cycle (cooling time) on formation of fine-scale, predominantly martensite, bainite and acicular ferrite (AF) microstructures. For the relatively wide range of cooling times investigated (Δt800−500 = 2 to 50 s), the lowest-alloyed WM (LA90) exhibited microstructures dominated by bainite with martensite to AF, whereas the highest-alloyed WM (PT02) formed large fractions of martensite with bainite to AF. Weld metal toughness was evaluated using both through-thickness notched 2/3 sub-size Charpy-V-notch (CVN) specimens as well as full-size surface-notched specimens. Post-test metallographic and fractographic examinations of selected fractured specimens were used to correlate WM microstructure and notch toughness.
Neutron Diffraction Studies of Residual Stresses Around Gouges and Gouged Dents
Authors: Clapham Lynann , Babbar Vijay , Gnaeupel-Herold Thomas , Batisse Remi , Zarea Mures
Published: July 2013

The residual stress pattern surrounding gouges is complex and, to date, has not been accurately modeled using stress modeling software. Thus measurement of these stress distributions is necessary. Neutron diffraction is the only experimental method with the capability of directly evaluating residual strain throughout the entire thickness of a pipe wall, in and around dent or gouged regions.

Neutron diffraction measurements were conducted at the NIST reactor on three gouged dents in X52 pipeline sections. These were part of a larger sample set examined as part of the comprehensive MD4-1 PRCI/DOT PHMSA project. Gouges contained in pipeline sections were termed BEA161 (primarily a gouge with little denting), and BEA178 (mild gouging, very large dent). Measurements were also conducted on a coupon sample – P22, that was created as part of an earlier study.

For the moderate gouges with little or no associated denting (BEA161 and P22) the residual stress field was highly localized around the immediate gouge vicinity (except where there was some denting present). The through wall stress distributions were similar at most locations — characterized by neutral or moderate hoop and axial stresses (50–100MPa) at the outer wall surface (i.e. at the gouge itself) gradually becoming highly compressive (up to −600MPa) at the inner wall surface. The other sample (BEA178) exhibited a very mild gouge with significant denting, and the results were very different. The denting process associated with this kind of gouge+dent dominated the residual stresses, making the residual stress distribution very complex. In addition, rather than having a residual stress field that is localized in the immediate gouge vicinity, the varying stress distribution extends to the edge of the dented region..
Comparison of Pipeline Girth Weld Defect Acceptance at the Onset of Yielding According to CSA Z662 and EPRG Guidelines
Authors: Verstraete Matthias , De Waele Wim , Denys Rudi , Hertelé Stijn
Published: July 2013

Within a stress-based design context, different codified engineering critical assessment procedures are available for defect assessment. This paper aims at comparing the recently updated EPRG Tier 2 guidelines with the Canadian CSA Z662 Annex K procedure. Therefore, the requirements for both procedure are discussed and the maximum allowable defect dimensions are graphically compared. It is observed that the use of the EPRG guidelines is significantly more restricted in terms of steel grades and pipe geometry. However, within the limits of the EPRG’s applicability, the CSA procedure requires significantly more material testing, while resulting in (extremely) low defect acceptance.
Investigation Into the Failure of a 40” Diameter Crude Oil Pipeline
Authors: Dafea Mohamed , Hopkins Phil , Palmer-Jones Roland , de Bourayne Patrick , Blin Lionel
Published: July 2013

In August 2009, there was a 2.5 m long rupture in the longitudinal seam weld of a crude oil pipeline in France. The failure caused a spillage of approximately 2000 cubic metres in a protected area. This rupture caused the authorities to withdraw the permit to operate a 260 km long section of this pipeline.

The pipeline had a similar failure in August 1980. The 1980 failure was attributed to a fatigue crack initiating at the inner side of the longitudinal weld. There was evidence of ‘roof topping’ along this weld.

Penspen Ltd., UK were contracted by the pipeline operator Societe du Pipeline Sud Europeen (SPSE) to carry out an independent investigation into the cause of the 2009 failure, review and confirm the actions needed for safe short term operation to allow internal inspection, and determine a safe future life for the pipeline.

The failed pipe specimen was not immediately available for inspection. An initial analysis indicated that purely an analytical evaluation would not provide conclusive results, due to variability in material properties, geometry and loading. It was decided that a better understanding of the behaviour of defects in the pipe, and the fatigue performance, was required.

A detailed laboratory programme of burst and fatigue testing on a section of line-pipe was recommended. The tests were carried out on a combination of ‘defect-free’ ring specimens, and ring specimens with initial Electric Discharge Machined (EDM) slits to represent crack-like defects. These tests showed:

1. BURST TESTS: The failure pressures of the burst tests could be predicted using a recognised industry model. Roof topping, laminations and inclusions, and toughness variations were found to have no noticeable effect on the defect size at failure.

2. FATIGUE TESTS: The fatigue test results showed that defect-free rings had a fatigue life one order of magnitude longer than those containing an EDM slit, and that the fatigue life of a defect-free ring could be predicted using a standard S-N method. In addition, it was found that crack growth was conservatively predicted using standard fatigue fracture mechanics.

The fatigue test results showed that the 1980 and the 2009 failures were caused by a combination of cyclic pressure loading, roof topping, and a pre-existing weld defect (probably present when the pipeline went into service in 1972).

This paper provides an overview of the failure investigation, with a discussion of the ring testing, supporting tests, and fracture surface inspection.
Emerging Technology: Remote Controlled Hot Tap System for Subsea Pipelines
Authors: Lim George
Published: July 2013

Subsea hot tapping of pipelines is performed for a variety of reasons, including tie-ins, pipeline repair, insertion of instrumentation, facilitating chemical injection or providing access for temporary isolation tools.

The full hot tap process — that is, installing the hot tap assembly, performing the tap and recovering the hot tap machine — is normally conducted with diver assistance. After bolting the assembly of the machine, isolation valve and fitting to the pipeline (or machine and isolation valve to a pre-installed flanged membrane on the pipeline), the divers then operate the machine to perform the tap, under instructions from — and supervision — by hot tap technicians located on deck of the diving support vessel (DSV). Subsequent unbolting and removal of the hot tap machine is also carried out by the divers.

The demands of deep water have necessitated development of a totally diver-less, remote-controlled system. Diver operations are limited to a maximum of 300 meters of water depth, whereas a significant portion of existing subsea field infrastructure, as well as projected future developments, are in deeper waters in depths up to 3,000 meters. In addition, diver safety concerns in shallow water, as well as impaired diver efficiency in difficult environmental conditions such as wave breaking zones, prompts the call for a reduction of diver exposure or complete elimination of diver assistance.

The recent completion of a remote-controlled hot tap machine (Subsea 1200RC) is an important step toward developing a totally diver-less system. The installation of the hot tap assembly and subsequent removal of the machine still require diver assistance, but the performance of the tap itself is remotely controlled by a hot tap technician from the deck of the DSV. The concept is a topside-driven hot tap machine with “passive Remotely Operated Vehicle (ROV) interface”, which means a stationary ROV with its hydraulics and control system is attached to the hot tap machine and operated from an onboard laptop. This results in a light weight hot tap frame and total direct control of the cutting process. The machine has been designed, built, tested and successfully deployed on a recent subsea tap for a pipeline operator in Asia.

This technology promotes the “separation of man and machine” proposition. It reduces risk by reducing diver exposure, enhances safety, provides direct control and visibility from a laptop and facilitates fast and accurate execution. Ultimately, the concept may be extended toward onshore hot tap applications in risky environments calling for remotely operated systems. Diverless tapping is now also qualified and offered by others.
Finite Element Modeling of the Dynamic Response of a Steel Pipe During Water Hammer
Authors: Suárez Juan C. , Pinilla Paz , Alonso Javier
Published: July 2013

Water hammer imposes a steep rise in pipe pressure due to the rapid closure of a valve or a pump shutdown. Transversal strain waves propagate along the pipe wall at sonic velocities, and dynamic stresses are developed in the material, which can interact with discontinuities and contribute to an unexpected failure. Pressure increase has been modeled as a simple step front in a finite element model of a short section of a steel pipe. Boundary conditions have been considered to closely resemble the conditions of longer pipe behavior. The shock traveling along the length of the fluid-filled pipe causes a vibration response in the pipe wall. Dynamic strains and stresses follow the water hammer event with a certain delay, as is shown from the results of the FEA. Response of the material is strain rate dependent and dynamic peak stresses are substantially larger than the expected from the static pressure loads. Damping of the waves, neither by the material of the pipe nor by the interaction fluid-pipe, has not been considered in this simple model. Hoop, axial, radial, and Von Mises equivalent stresses have been evaluated both for the overshooting and the following phase of decompression of a pipe without discontinuities. However, dynamic stresses can be enhanced in the presence of discontinuities such as laminations, thickness losses in the pipe wall due to corrosion, changes in the wall thickness in neighboring pipe sections, dents, etc. These dynamic effects are able to explain how certain discontinuities that were reported as passing an Engineering Critical Assessment can eventually cause failure to the integrity of the structure. Deflections in the pipe wall can be altered by the welded transition from a pipe with a certain thickness to another with a smaller thickness, and wavelength changes of one order of magnitude can be expected. This can result in different approaches towards the risk assessment for discontinuities in the proximity of changes in wall thickness.
Assessment of Hydrostatic Collapse of Submarine Pipelines: Historical Review of the Classic Methods
Authors: Benjamin Adilson C. , Cunha Divino J. S.
Published: July 2013

In this paper the assessment of the hydrostatic collapse of submarine pipelines is addressed. Initially an overview of the classical approach is presented. Then a historical review of the classic methods is carried out. Seven assessment methods are reviewed: six well-known classic methods (the Southwell method, the Timoshenko method, the Shell method, the Murphey method, the Haagsma-Schaap method and the DNV method) and one newly developed classic method (the RCA method). Finally the collapse pressures previously calculated using Finite Element (FE) models are compared with those predicted by the seven methods.
Evaluation on Dependence of Ductile Crack Propagation Resistance on Crack Velocity
Authors: Aihara Shuji , Shibanuma Kazuki , Imai Yasuhito , Fujishiro Taishi , Hara Takuya
Published: July 2013

Plastic strains were measured near a propagating ductile crack in drop-weight tear tests (DWTT). Plastic work evaluated from the plastic strains agreed with crack propagation energy evaluated from dynamic load versus displacement curve. Furthermore, plastic strains were measured near a propagating ductile crack in a full-scale burst tested pipes. Plastic work of the burst pipe was found to be much larger than that of the DWTT. Values of the plastic work of the DWTT and the burst pipe were plotted against crack velocity to construct crack resistance curve. Reason to the increased crack resistance with crack velocity was understood as a dependence of plastic strain distribution on crack velocity by elasto-plastic dymanic finite element analysis.