bluuebunny/crossref_metadata_2025 huggingface dataset:
Identifying Initial Imperfection Patterns of Energy Pipes Using a 3D Laser Scanner
Authors: Kainat Muntaseer , Adeeb Samer , Cheng J. J. Roger , Ferguson James , Martens Michael
Published: July 2013

Measurement of initial imperfections of energy pipes and incorporating them in analytical models has been a major focus of research in the pipeline industry as well as at the University of Alberta. Researchers at the University of Alberta have devised various techniques to measure initial imperfection of pipes prior to testing. The analytical imperfection models developed based on these techniques have proven to be effective in predicting pipe behavior. These techniques, however, are time consuming, error prone to some extent, and yield limited data, in addition to their limitations regarding the size of the pipes that can be measured. The objective of the current study is to overcome the limitations of the previous measurement techniques by utilizing advanced surface profiling technology. A high accuracy 3D laser scanner is used to create three dimensional models of energy pipes. Commercially available reverse engineering and inspection software is used to measure the different geometric attributes of the pipes that are of interest. This new technique enables us to overcome the previous limitations by acquiring data in the field at a faster rate and creating high resolution point clouds. The actual pipe surfaces are compared with the model of a perfect cylinder of uniform nominal diameter. It is possible to locate the axes of the scanned pipes and use these axes as references for measurements. Outer diameter variation, thickness variations, weld geometry variations and deviations from a perfect cylinder are measured. Results indicate that the deviations from a perfect cylinder can be used to describe the pattern of radii variations around the perimeter of the pipes. When described with respect to the seam weld location, distinct patterns of radii variations were identified. Thickness variations showed identical behavior in all the pipes when viewed with respect to the seam weld location.
Calculation of Dynamic Stress Intensity Factors for Pipes During Crack Propagation by Dynamic Finite Element Analysis
Authors: Mitsuya Masaki , Motohashi Hiroyuki , Oguchi Noritake , Aihara Shuji
Published: July 2013

A dynamic finite element analysis method was proposed for calculating the dynamic stress intensity factors for pipes during crack propagation. The proposed method can directly calculate the stress intensity factors without the simplification used in theoretical analyses, and it can consider the effects of the crack velocity and gas decompression. It was found that the stress intensity factors of long propagating cracks in pipes saturated at a certain value in the case of a high crack velocity. However, although the stress intensity factors for pipes were in good agreement with those of band plates in the case of a high crack velocity, the stress intensity factors for pipes were different from those of band plates in the case of a low crack velocity. This result could be explained by the effect of bulging on the stress distribution around a crack tip. The effect of bulging was more prominent for pipes with smaller diameters. In contrast, the dynamic stress intensity factors for band plates were in good agreement with the theoretical values that consider the dynamic effects and tended to decrease monotonically with increasing crack velocity. Additionally, the effects of gas decompression, caused by leakage from opened cracks, on the stress intensity factors for pipes were investigated. An explanation of crack deviation, which is observed in actual pipeline fractures, was provided by analyzing the ratio of the longitudinal stress to lateral stress.
Development of an Ultrasonic Phased Array Testing System That Can Evaluate Quality of Weld Seam of High-Quality ERW Pipes
Authors: Matsui Yutaka , Iizuka Yukinori , Suzuki Masahito , Urahata Eiichi , Inoue Tomohiro , Kumazawa Shintarou , Oka Masaru
Published: July 2013

A high sensitivity ultrasonic testing system for inspection of the weld seam of ERW pipes was developed. The factors that affect the quality of the weld seam were investigated using an ultrasonic C-scan method with a focused probe and samples sliced from weld seams. As the result, it was found that a scattered-type penetrator consisting of micro oxides is a key factor in the quality of the weld seam. Absorbed energy in the Charpy impact test can be evaluated by the ultrasonic echo amplitude with the optimized focused beam size (about 1mm2) to detect the scattered-type penetrator.

In order to evaluate the density of the scattered-type penetrator in weld seams with the optimum focused beam size for pipe, a point focused beam tandem method was developed by applying the ultrasonic phased array technique. The sensitivity of the developed method is 20dB higher for a standard artificial through drilled hole whose diameter is 1.6mm. A precise seam tracking system was also developed for application of the point focused beam tandem method to the actual ERW pipe manufacturing process. Since the allowance for applying the focused beam to the weld seam is very narrow, i.e., about 1mm, a circumference multi-point simultaneous receiving technique and thermal image-type seam detection technique were developed. The developed ultrasonic testing system has been in operation at the 24″ ERW mill at East Japan Works (Keihin District) of JFE Steel Corporation since March 2011. The combination of the ultrasonic testing system and an oxide control technique now contributes to production of high-performance, high-quality ERW pipe “Mighty Seam®” for use in frigid environments.
Development of a New Optical Monitoring System of Welding Conditions for Producing HF-ERW Line Pipes With High Weld Seam Toughness: Advanced Welding Process of HF-ERW 2
Authors: Hasegawa Noboru , Hamatani Hideki , Mizuhashi Nobuo , Fukami Toshisuke , Karube Yoshifumi , Miura Takao , Tanaka Kimiharu , Nakaji Tomohiro , Yamamoto Kazuto , Hasegawa Yasushi
Published: July 2013

To improve the weld seam quality of HF-ERW (high frequency-electric resistance welded) pipes, a monitoring system that combines optical and electrical measurement techniques is developed. In the welding process, it is known that there are type 1, 2, and 3 phenomena depending on the welding speed, the input power and the Vee convergence angle. We found that type 2 phenomena can be subdivided into three conditions, normal type 2, instable (type 3) and the two phased reduction of the Vee convergence angle (type 2′) regions in production processes, caused by the facing angle of the edge surfaces, which may not have the I-shape. Among them, only the condition under a narrow range of type 2′ allows to prove melting in the whole area of the edge surfaces and to excrete the oxide inclusions from the weld seam. Following the welding mechanism, the defect rate in the weld seam is kept at minimum. Accordingly, we developed a monitoring system to control the welding condition to the type 2′ range. An optical image processing and an electric impedance measurement method are combined into this system, which is based on remote photographing, high-precision V point detection, temperature measurement techniques with image processing, and a multi-frequency filtering method of the transient impedance waveform. Furthermore, operational indices are constructed through the analysis of the welding mechanism and the experimental data. We find that the weld defect area ratio lower than ever is steadily achieved in the trial products, as a result of continuously controlling the heat-input condition.
Strain Softening and Rate Effects on Soil Shear Strength in Modeling of Vertical Penetration of Offshore Pipelines
Authors: Dutta Sujan , Hawlader Bipul , Phillips Ryan
Published: July 2013

Offshore pipelines play a vital role in the transportation of hydrocarbon. In deep seas, pipelines laid on the seabed usually penetrate into the soil a certain amount. These pipelines might experience significant lateral movement during the operational period. The resistance to lateral movement depends on vertical penetration and berm formation around the pipe. Vertical penetration is a large deformation problem. Finite element modeling of vertical penetration of offshore pipeline in soft clay seabed in deep water is presented in this study. The modeling was performed using ABAQUS finite element software. Soil was modeled in an Eulerian framework and the pipe in a Lagrangian framework. Strain softening behavior and strain rate effects on undrained shear strength of clay was incorporated in ABAQUS FE software using user subroutines written in FORTRAN. The variation of undrained shear strength with depth is also considered. The results are compared with centrifuge test results and also with available solutions.
Predicting the Failure Pressure of SCC Flaws in Gas Transmission Pipelines
Authors: Fessler Raymond R. , Batte David , Rosca Gabriela , Van Boven Greg , Vervake Gary , Limon Sergio
Published: July 2013

An important requirement for the management of stress-corrosion cracking (SCC) in natural gas transmission pipelines is the ability to predict accurately the burst failure pressure of flaws that have been discovered, particularly those found by crack detection in-line inspection (ILI). ASME B31.8S contains guidance for categorization of SCC based on predicted failure pressure for the cracks. Assessment of the segments is based on the severity category of SCC.

As part of a Joint Industry Project (JIP) addressing the management of SCC in gas transmission pipelines, eight operators have assembled information relating to 85 in-service failures, hundreds of hydrostatic test failures, and dozens of pipe burst tests in which failure was due to SCC. Within the database are a wide range of pipe grades and sizes. Failures are due to both high pH and near-neutral pH SCC, and the flaws that initiated failure range from simple thumbnails to complex groups of cracks in a three-dimensional cluster.

This paper presents some of the results from a comprehensive comparative study of the failure pressure predictions obtained using API 579 Level II, ln-secant, CorLAS® and PAFFC methods for around 40 of the best-characterized datasets within the above database. From the results obtained, the sensitivities of the calculations to the calculation method used and to the input data, such as flaw profile, are examined. The results provide useful guidance to all those involved in predicting failure pressures as part of their threat management activities.
The Effects of Temper Bead Welding Technique on Weld Integrity for In-Service Welding of Carbon Steels
Authors: Meszaros K. , Vrolyk C. , Pepin J. , Yarmuch M. , Mah-Paulson T.
Published: July 2013

The maintenance of pipeline infrastructure is a significant integrity consideration for the pipeline industry. Employing traditional repair techniques, whereby to conduct repairs when the pipeline is shut-down and drained, can result in significant losses to revenue and production. There is industry demand for repair techniques that allow both scheduled and emergency ‘in-service’ weld repair techniques to be developed. As a result, in-service welding with the temper bead technique is becoming increasingly common for repair operations.

During in-service welding, the two most prevalent metallurgical concerns are burn-through and hydrogen induced cracking (HIC). The risk of burn-through can be limited through appropriate welding parameter and heat input control during welding. The temper bead welding technique utilizes special bead placement to ensure appropriate heat flow throughout the weld zone to metallurgically improve resistance to HIC.

In this study, a series of shielded metal arc welding (SMAW) coupons were produced on 0.250″ thick carbon steel plates subjected to water-cooling. Single and double-layer deposits were made. The second layer tempering bead heat input was purposely varied from plate to plate. The first layer of the welds were all performed using similar welding parameters, so the “tempering” effect from the second weld layer on the metallurgical properties of the resultant welds could be examined. To further expand the understanding of important procedural variables for in-service welding applications, this study investigates the effect of welder technique on the weldment properties achieved during temper bead welding.
Calculating Probability of Detection Using Excavation Data
Authors: Skow Jason , Nessim Maher A.
Published: July 2013

The key to estimating the probability of detection (POD) of an inline inspection tool is to count existing defects that have not been detected by the tool. In an ideal experiment, the number of defects in the pipeline is known before running the tool and the rate of detection is calculated by comparing the number of defects detected by the inline tool with the total number of defects in the pipeline. In reality, the inline inspection is often the first method of identifying defects. Undetected defects are found during excavation only if they are near defects called by the inline tool.

This paper describes a new model for probability of detection based on a combination of excavation data and the vendor claim. It addresses the limitations of existing models by assuming undetected defects can occur anywhere in the tool run. This is accomplished by modeling the rate of undetected defects using a Poisson distribution.

Its main advantages are a more accurate representation of the probability of detection that considers all the available data, the flexibility to update the model with additional data sets as they become available and ability to quantify changes in the uncertainty of POD as additional data is uncovered through excavations.

Overall, a more accurate and defensible process for determining probability of detection is proposed which can be used for managing pipeline integrity and risk.
Design of Parallel Pipelines in Second West-East Natural Gas Pipeline Project
Authors: Shi Hang , Wu Wen , Zhang Wenwei , Yu Zhifeng , Huang Liuqun
Published: July 2013

The Second West-East Gas Pipeline (2nd WEP) Project, consisting of one trunk line and eight branches, has a total length of 8,704 km and a designed annual transportation capacity of 30 billion cubic meters. The outside diameter of trunk line is 1,219 mm (48″). According to the plan, 2nd WEP will parallel with several existing or planning pipelines in long distance, some will even be located in rocky area. However, there are neither requirements of separation distance nor other related provisions of parallel pipelines in current domestic regulation and codes in China. It is an urgent critical problem to reasonably design, construct and operate multiple pipelines in same corridor.

In order to design 2nd WEP in parallel with other existing and planning pipelines, a series of technical studies were carried out. This paper describes the main work. First of all is the literature review, including regulation, standards, codes etc. and similar work on parallel pipelines and applicable practices in other countries. Second, for the primary concern-separation distance, the main factors are considered. Then, the computational results of some 2nd WEP paralleling with other pipelines based on the impact of the failure of natural gas pipeline to adjacent pipelines are introduced. Third, the experiments and some related researches in rocky areas where 2nd WEP parallels with existing pipelines are introduced. Forth, analysis of Direct Current (DC) stray current interference resulted from Cathodic Protection (CP) Systems located along each parallel pipeline is briefly introduced. Then is the mitigation and monitoring requirements for unbounded (separate) CP system.

According to the works above together with engineering practices as well as experiences, the design guideline of parallel pipelines is established. When 2nd WEP parallels with other pipelines not locating in rocky areas, the reasonable separation distance is based on integrated considerations of adjacent pipeline’s survival in the event of failure of gas transmission pipeline, easiness to construct, less CP interferences, adequate space requirements for maintenance and repair. For other paralleling cases, engineering requirements are established separately. This guideline has been applied in design of parallel pipelines and provides management requirements for future operation in 2nd WEP project.
Accurate Short Period Corrosion Growth Rates From Combined MFL-UT Inline Inspection: A Case Study
Authors: Palmer Johannes , Hennig Thomas
Published: July 2013

Inline inspection (ILI) identifies most significant anomalies - at the time of inspection. To recognize those individual features, which have the highest potential to enter these ranks, perhaps soon, is a challenging question, which is not necessarily covered with established ILI approaches.

Whether the circumstances permit the identification and reliable description of individual corrosion hot spots depend on the ILI quality, the specific feature shape-dependent sizing, the comparability of the data and the time-dependent development of the anomaly.

This case study demonstrates the enormous benefits of the combination of two technologies. The robust, indirect Magnetic Flux Leakage (MFL) methodology and the direct Ultrasonic Testing (UT) ILI tool. The intelligent interpretative combination of the two ILI information sources exceeds significantly the straight forward statistical combination benefit. The presented approach demonstrates how to:

• identify features not suitable to UT stand alone sizing.

• compensate systematic errors from MFL sizing models and calibration assumptions.

• introduce UT shape information as major improvement to MFL sizing.

• apply MFL amplitude based depth sizing.

• reduce the subsequent sizing tolerance to values, which allow corrosion prediction based on even short term repeated ILI intervals.

Applied to the identified group of pinholes and embedded pinholes with an average maximum depth of more than 50% the method delivered a depth sizing accuracy of ±6.0% wall thickness at 80% certainty. The fact, that even smaller corrosion growth rate values become resolvable, allows for the equivalent shortening of the re-inspection intervals and for the prolongation of the validity of prediction, whatever may be advisable in specific cases. Also it is shown, that this approach does not require to rerun similar tools, because systematic errors can be compensated absolutely with this approach.

The optimization of inspection strategies and methods with regard to specific pipeline problems can have monetary benefit even at higher inspection costs. More sophisticated ILI systems requiring specialist data analysis become justified for equivalent pipeline use cases. The presented combination of the two independent ILI methodologies bears significant useful potential to approach aggressive corrosion mechanisms, e.g. microbial corrosion or CP shielding.
Pipeline Material Strain Monitoring System in Permafrost of MoHe-DaQing Pipeline
Authors: Chen Pengchao , Zhang Shibin , Yang Shimei , Li Zhengbin , Ren Yanguang
Published: July 2013

Mohe-Daqing pipeline is the first pipeline to be buried, passing through the permafrost regions of North China where the temperature in winter is about minus thirty degrees Celsius. This pipeline has been transporting large quantities of crude oil per day to northern markets of China since January 1st, 2011. It’s a significant cooperation for both Russia and China.

This paper reviews the design, construction, and operational challenges of the first pipeline buried in the permafrost regions of North China. The pipeline is in so complicated geography environment that many kinds of geotechnical disaster could happen easily, including frost heave, thaw settlement, slope instabilities, and collapse and so on. Monitoring pipeline material strain in specific region is important and significant. Ground movement of the pipeline induces sufficiently large strains to the pipeline, which would cause wrinkling on the compression side of the pipe, or alternatively tensile fracture on the tensile side of the pipe. Brag fiber sensors have been located and composed on the surface of the pipe, which were used to monitor material strain real-time data at any time.

Finite element pipe soil interaction and ground movement models in specific sites have been developed according to the monitoring data. Whether the generated pipeline strain is exceeded the strain capacity or not could be estimated by comparing with the strain capacity of the pipeline, which can help us to make decision for pipeline safety management and prevent pipeline damage from geotechnical disaster.
The Formal Adoption of a Process Safety Management Methodology Within an International Oil and Gas Pipeline Company
Authors: Urra Susan
Published: July 2013

Process Safety Management (PSM) is an integrated approach to managing loss prevention. At Enbridge, as with many organizations, several PSM elements of practice have been implemented with different levels of rigor, maturity and/or alignment with best practices.

This paper presents Enbridge Liquid Pipelines’ approach to assess a strategy to adopt a formal PSM system. A description of the current regulation framework for PSM and the drivers for adoption are presented to explain the considerations during the scoping and design of a PSM system for an international oil and gas pipeline system that operates across numerous state and provincial boundaries, and one international border.

The paper also discusses the requirements for organizational governance to ensure accountability for and ownership of individual elements of a PSM program throughout a large, geographically diverse organization such as Enbridge.

Finally, a strategy to develop and potentially implement and manage PSM in a large organization such as Enbridge is proposed.
Evolution of Process Hazard Analysis in an Oil and Gas Pipeline Company: From Ad-Hoc to an Enterprise Standard Practice
Authors: Urra Susan
Published: July 2013

Enbridge’s decision to formalize a Process Hazard Analysis (PHA) program has taken the organization through a journey from an informal/ad hoc practice to a rigorous, standardized, best-practice-based process with selected methodologies and tools being applied to all capital and operation projects in the company.

This paper begins with a description of past hazard practices in the oil and gas pipeline industry in relation to the application of a hazard analysis. The oil and gas pipeline industry is governed by PHMSA, NEB, TSB, and provincial OHSA regulations, but is not regulated by OSHA or EPA RMP. Using this regulatory framework as a reference, a standard corporate PHA at Enbridge was developed and implemented. The paper describes the process, the methodologies, and the associated templates and tools. The implementation strategy is also discussed, including training deployment and communication plans. Finally, a road map for continuous improvement describes how to make the process sustainable by closing the current process gaps in relation to best practices and achieving a maturity stage of execution.
Managing and Addressing Fitness for Service of Vintage Pipelines
Authors: Nanney Steven V. , Lee Kenneth Y.
Published: July 2013

Recent pipeline accidents in the United States have highlighted concerns with older vintage natural gas and hazardous liquid pipelines. The United States Department of Transportation (USDOT) Pipeline and Hazardous Materials Safety Administration (PHMSA) is performing a comprehensive review to determine the fitness for service of vintage pipelines, and if the risks associated with vintage pipelines can be better managed by changes to US pipeline safety standards and regulations. Concerns with vintage pipelines include weld seam manufacturing issues, such as low frequency electric resistance welding (LF-ERW) and submerged arc welding (SAW), cast iron pipe, plastic pipe and certain coatings. This paper presents findings from vintage pipeline failure investigations, recent PHMSA actions, and some approaches to address key vintage pipe concerns. These approaches include knowledge assurance (adequacy and quality of historical data), methods to systematically obtain missing data, and processes and criteria for determining fitness-for-service, including assessment, remediation, and replacement programs.
A New Focus With Leak Detection for US Pipelines
Authors: Merritt James , Jasion Patricia , Kieba Max
Published: July 2013

The United States (U.S.) Department of Transportation’s Pipeline and Hazardous Materials Safety Administration (PHMSA) is exploring methods for increasing usage and improving leak detection systems in both hazardous liquid and natural gas pipelines. This is a critical focus for PHMSA in the wake of several recent pipeline incidents where more effective and redundant leak detection systems may have lessened the experienced consequences. The U.S. Congress and the National Transportation Safety Board (NTSB) have recommended deploying more leak detection systems into the U.S. pipeline infrastructure to address increasing public safety and environment impact concerns. PHMSA has taken a number of actions to work toward this goal including increased operator guidance, fostering technology research, information gathering, and reports on state of the art technologies. This paper discusses PHMSA’s actions regarding leak detection systems and the progress in advancing the dialogue amongst hazardous liquids and natural gas pipeline operators, other regulators, and the public, so that considerations in deploying systems on vintage and new construction pipelines can be identified.
Rational Stress Limits and Load Factors for Finite Element Analyses in Pipeline Applications: Part II — Limit-State Load Factor Development
Authors: Lin Bisen , Biel Richard C.
Published: July 2013

In this paper, a load factor for use in a limit-load analysis of a pipeline and its components is established. The load factor is based on the ASME pipeline Code’s design margin for the service and location of the installation [1, 2]. These Codes are recognized by 49 CRF192 [3].

A load factor for internal pressure loads can be derived analytically based on the equations of determining design pressure and wall thickness in the ASME B31 piping Codes. Once the load factor is established, the limit-load methodology may be used in a Finite Element Analysis (FEA) of pipelines and related components.

Two application examples are presented showing analyses done with Abaqus [4], a commercial, general purpose FEA software package. The first example calculates the design pressure of an X65 pipe given the pipe dimensions (outer diameter and wall thickness). Second example deals with the re-certification of a Y-connector.

This paper is not intended to revise or replace any provision of ASME B31.4 and/or B31.8 [1, 2]. Instead, it provides a limit-load approach for assessment with same design margin as the ASME B31 Codes for use in a detailed FEA of pipelines and the associated components.
Research and Development Into Low Temperature Toughness of Large Diameter Heavy Wall X80 Pipeline Steel at Shougang Steel
Authors: Ding Wenhua , Jiang Zhonghang , Li Jiading , Li Shaopo , Zha Chunhe , Bai Xuejun , Li Qun , Zhang Guodong , Stalheim Douglas
Published: July 2013

In recent years the trend in oil and gas transmission pipelines has been toward higher operating pressures. This trend, while the desire to keep steel costs low, has resulted in an increased demand for large diameter heavy wall X80 with good low temperature toughness. It is well known that improving the low temperature toughness with increasing wall thickness of the pipeline is very difficult. To overcome the difficulty of producing consistent low temperature toughness in heavy wall pipe Shougang Steel Research in cooperation with the Shougang Steel Qinhuangdao China (Shouqin) 4.3 m heavy wide plate mill research was conducted.

This paper describes the background, composition design and process strategy to produce good low temperature toughness in heavy wall API plate. The importance of the slab reheating schedule and recrystallized rolling process/schedule that occurs during the roughing process will be discussed. The effect of per pass reductions and work roll speed rotation on the strain introduced was analyzed by means of the numerical simulation technology. Furthermore, the center thickness microstructure and low temperature toughness of plate under the different rolling schedules were researched. The results showed a low reheating temperature and slow rough rolling speed should be implemented. The per pass reductions during recrystallized rough rolling should be increased in a steady fashion, with special emphasis on the reduction of the final roughing pass prior to the intermediate hold (transfer thickness for finishing). When the final roughing pass had a per pass reduction of more than 15%, the main microstructure of plate consists of uniform (surface to center) fine ferrite/acicular ferrite with a small volume fraction of M-A constituent. This fine uniform microstructure results in good low temperature fracture toughness in heavier plate thicknesses. Results of this research and development work will be discussed.
Model Error Assessment of Burst Capacity Models for Defect-Free Pipes
Authors: Zhou W. , Huang G. (Terry)
Published: July 2013

The model errors associated with 19 burst pressure prediction models for defect-free thin-walled pipes are evaluated using a total of 76 full-scale burst test data of perfect pipes and pressure vessels collected from the literature. The considered models are based on the Tresca yield criterion, the von Mises yield criterion, or the average shear stress yield criterion. The probabilistic characteristics of the model error, i.e. the mean, coefficient of variation and best-fit probability distribution, are obtained based on the test-to-predicted ratios. The applicability of an empirical equation for estimating the strain hardening exponent in the burst capacity models is also evaluated. The model errors obtained in this study can be used in the structural reliability analysis of energy pipelines with respect to the limit state of burst of defect-free pipes and will facilitate the reliability-based design and assessment of pipelines.
The ‘Eckert Number Phenomenon’ in Pipeline Decompression
Authors: Godbole Ajit , Venton Philip , Lu Cheng , Colvin Philip
Published: July 2013

The Eckert number emerges as an important non-dimensional parameter, in addition to the Reynolds number and the Prandtl number, in problems involving heat transfer in compressible flows. The Eckert number is considered to represent a ratio of the flow kinetic energy at the wall and the specific enthalpy difference between the wall and the fluid, and is important when viscous dissipation is significant. This paper investigates the role played by the Eckert number during rapid decompression of high pressure gas pipelines. During such processes, the gas temperature attains very low values corresponding to sonic flow at the vent location, and it is often assumed that the pipeline material is also cooled to a comparable degree (‘Low Temperature Excursions’). This has often led to over-specification of the properties required of the pipeline material. In this paper, it is shown using Computational Fluid Dynamics (CFD) simulations that the highly complex flow during rapid decompression of high-pressure gas pipelines leads to significant frictional dissipation (heating) adjacent to the pipe wall. This prevents the pipeline from attaining excessively low temperatures. It is shown that frictional heating may sometimes lead to a heat transfer reversal. This finding may help pipeline designers in making appropriate recommendations regarding the properties required of the pipeline materials. The paper also describes a preliminary experiment designed carried out to validate the CFD simulations. More detailed experiments are under way.
Experiment Study of Pigging Characteristics in Horizontal Gas-Liquid Flow Pipeline With Different Pig Sizes
Authors: Duan Ruixi , Yu Da , Wu Haihao , Gong Jing , Hu Shanwei , Zhou Tong , Zheng Lijun
Published: July 2013

During pigging process of long-distance pipeline, pig seals wear due to abrasion on pipe wall, the diameter of seal decreases and even to be smaller than pipe inner diameter as a result. This study has researched the characteristics of pigging processes using pigs different in diameter in horizontal experimental pipe. In the study, mandrel pig with two seals was chosen for experiment. Five pigs different in size were used, and pigging experiments under various flow conditions were carried out in a horizontal air-water flow experimental loop. During experiment, the features of pigging process from pig launcher to trap were observed, the liquid holdup and pressure were detected and collected, pig velocities in different sections of pipe were measured, the velocity of pigging slug front and length of the slug were also measured. The relationship between pig movement and flow conditions was analyzed, the methods to calculate velocity of pigging slug front and length of the slug were obtained and the results calculated were similar to the results measured. Based on the results of experiment, some suggestions were proposed for pigging operation in real pipeline.
Phase Field Modelling of Microstructure Evolution in the HAZ of X80 Linepipe Steel
Authors: Toloui Morteza , Militzer Matthias
Published: July 2013

The heat affected zone (HAZ) during welding experiences a very steep temperature gradient which results in significant microstructure gradients. Thus, model approaches on the length scale of the microstructure, i.e. the so-called mesoscale, are useful to accurately simulate microstructure evolution in the HAZ. In this study, a phase field model (PFM) is employed to simulate austenite grain growth and austenite decomposition in the HAZ of an X80 linepipe steel microalloyed with Nb and Ti. The interfacial mobilities and nucleation conditions are obtained by benchmarking the PFM with experimental data from austenite grain growth and continuous cooling transformation tests. An effective grain boundary mobility is introduced for austenite grain growth to implicitly account for dissolution of NbC. Subsequently, austenite decomposition into polygonal ferrite and bainite is considered. For this purpose the PFM is coupled with a carbon diffusion model. Ferrite nuclei are introduced at austenite grain boundaries and suitable interfacial mobilities are selected to reproduce experimental ferrite formation kinetics. Bainite nucleation occurs for a sufficiently high undercooling at available interface sites (i.e. austenite grain boundaries and/or austenite-ferrite interfaces). For simplicity, the formation of carbide-free bainite is considered and a suitable anisotropy approach is proposed for the austenite-bainite interface mobility. The model is then used to predict austenite grain growth and phase transformation in the HAZ.
Application of SEM-EBSD for Measurement of Plastic Strain Fields Associated With Weld Metal Hydrogen Assisted Cold Cracking
Authors: Brown I. H. , Costin W. L. , Barbaro F. , Ghomashchi R.
Published: July 2013

The requirement for more efficient use of materials for pipelines has lead to the application of high strength low alloy steels such as X70 and X80 in pipelines. As the strength of these alloys has increased so has the risk of hydrogen assisted cold cracking (HACC). In Australia to minimize construction time, the root runs of girth welds are produced by shielded metal arc welding using cellulosic electrodes without either pre or post heating. Well defined welding criteria have been developed and are incorporated into the weld procedures for the elimination of HACC in the heat affected zone but the risk of cracking to the weld metal is still of concern.

It has been reported that plastic deformation occurs prior to the formation of hydrogen cracks in weld metal. Therefore the evaluation of plastic strains at the micro- and nano-scale and their relationship to the weld metal microstructure could be of great significance in assessing the susceptibility of welds to weld metal hydrogen assisted cold cracking (WMHACC).

A method for analysing plastic strains on the micro- and nano-scales using electron backscattered diffraction (EBSD) has been developed. This technique is based on the degradation and rotation of diffraction patterns as a result of crystallographic lattice distortion resulting from plastic deformation. The analysis can be automated to produce an Image Quality (IQ) map in order to relate the spatial distribution of plastic deformation to microstructural features e.g. grains or cracks.

The development and assessment of techniques using Scanning Electron Microscopy (SEM) and EBSD for the determination of local plastic strain distribution in E8010 weld metal used for the root pass of X70 pipeline girth welds is discussed.
Evaluation of Girth Weld Defect Acceptance Criteria for Grade X100 Pipelines
Authors: Swankie Troy , Chauhan Vinod , Wood Ian , Espiner Richard , Kieba Max , Quong Spencer
Published: July 2013

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.
Mechanical Anisotropy of Hot Rolled Line Pipe Steel Coil
Authors: Sanchez Nuria , Van Hoecke Dennis , Liebeherr Martin
Published: July 2013

The mechanical anisotropy of hot rolled coils for linepipe grades in the range between X52 and X80 have been investigated in terms of tensile strength and Charpy impact toughness. Samples were taken in different orientations with respect to the strip rolling direction: 0, 30, 45, 60 and 90 degrees. Tensile tests were performed on round tensile specimens to avoid the need for strip levelling. Results from this investigation reveal that the hot rolled coils display different degrees of anisotropy varying as function of strength level and thickness. The material anisotropy is reflected in variations in yield, tensile strength and ovality of the gauge section after fracture. At the same time, variations of the CVN absorbed energy in the upper shelf energy and in the ductile to brittle transition temperature were also observed. Finally, detailed texture studies revealed a relation between mechanical anisotropy and crystallographic texture.
Full Ring Evaluation of X70 Grade UOE Line Pipes for Sour Service
Authors: Kobayashi Kenji , Omura Tomohiko , Hamada Masahiko , Nagayama Hiroyuki , Minato Izuru , Nishi Yuki
Published: July 2013

High-strength large-diameter UOE line pipes over X70 grade are difficult to apply to actual fields, including H2S, because of a deterioration of sour resistance and a lack of past performance. However, API X70 grade large-diameter UOE line pipes for sour service have been manufactured stably by optimizing the continuous casting process, controlling the shape of inclusions and decreasing coarse precipitates. A full-ring test can simulate fairly well the actual applied conditions of line pipes and evaluate hydrogen induced cracking (HIC), sulfide stress cracking (SSC) and stress oriented hydrogen induced cracking (SOHIC) of line pipes for sour service simultaneously. It was confirmed that the X70 grade UOE line pipes have a good sour resistance from standard HIC tests, four-point bent beam SSC tests and the full-ring test including a seam weld under severe sour conditions (NACE solution A with 0.1 MPa H2S). In addition, the SSC resistance of a girth welded portion was also investigated by using simulated HAZ.
Full Scale Cyclic Fatigue Testing of Dented Pipelines and Development of a Validated Dented Pipe Finite Element Model
Authors: Tiku Sanjay , Semiga Vlado , Dinovitzer Aaron , Vignal Geoff
Published: July 2013

Dents in buried pipelines can occur due to a number of potential causes; the pipe resting on rock, third party machinery strike, rock strikes during backfilling, amongst others. The long-term integrity of a dented pipeline segment is a complex function of a variety of parameters, including pipe geometry, indenter shape, dent depth, indenter support, pressure history at and following indentation. In order to estimate the safe remaining operational life of a dented pipeline, all of these factors must be accounted for in the analysis.

The paper discusses the full-scale dent testing being completed to support the development of pipeline integrity management criteria and is a continuation of the work discussed in previous IPC papers [1,2]. The material and structural response of the pipe test segments during dent formation and pressure loading has been recorded to support numerical model development. The full scale experimental testing is being completed for pipe test specimens in the unrestrained and restrained condition using different indentation depths and indenter sizes. The dents are pressure cycled until fatigue failure in the dent. This paper presents typical data recorded during trial including indentation load/displacement curves, applied pressures, strain gauges along the axial and circumferential centerlines, as well as dent profiles.

The use of the full-scale mechanical damage test data described in this paper in calibrating and validating a finite element model based integrity assessment model is outlined. The details of the integrity assessment model are described along with the level of agreement of the finite element model with the full scale trial results. Current and future applications of the integrity assessment model are described along with recommendations for further development and testing to support pipeline integrity management.
Pipeline Mechanical Damage Integrity Management Framework
Authors: Semiga Vlado , Tiku Sanjay , Dinovitzer Aaron
Published: July 2013

With the resolution and capabilities of the latest generation multi-sensor in-line inspection tools, detection and sizing of mechanical damage (i.e. dents, metal loss, etc) and their interaction is becoming more prevalent. As a result, the number of features requiring consideration in terms of integrity assessment is ever increasing.

The following paper presents a mechanical damage integrity management framework, intended to allow the assessment of a large number of features to support maintenance planning decisions. The framework is centred around organizing and collecting features into groups that share similar integrity driving parameters. An example demonstration of the framework is also presented using the results of a single ILI run on a small diameter pipeline. The example assessment focuses on shallow dents interacting with metal loss features where the metal loss features are treated as localized, gouge-like features.
Metallugical Design and Performance of ERW Linepipe With High-Quality Weld Seam Suitable for Extra-Low-Temperature Services
Authors: Toyoda Shunsuke , Goto Sota , Okabe Takatoshi , Kimura Hideto , Igi Satoshi , Matsui Yutaka , Yabumoto Satoru , Sato Akio , Suzuki Masahito , Inoue Tomohiro
Published: July 2013

To clarify the effect of inclusions on the Charpy impact properties, the 2 mm V-notched Charpy properties of X60 – X80-grades steel were numerically simulated using the finite element method code ABAQUS. The yield strength and the tensile strength of the steel were 562 MPa and 644 MPa, respectively. The striker’s velocity and the temperature dependency of the stress-strain curve were taken into account. To estimate the effect of nonmetallic inclusions, a 200 μm long virtual inclusion with a 1 μm edge radius was situated at the maximum point of the stress triaxiality. Four types of micro crack initiation were determined: (a) ductile void generation in the matrix, (b) cleavage crack generation in the matrix, (c) void generation by inclusion fracture and (d) void generation by matrix-inclusion interface debonding. Without inclusions, a ductile micro void was generated when the striker stroke was 3.3 mm, independent of the temperature. With inclusions, an inclusion fracture occurred when the striker stroke was 0.6 mm at room temperature. The striker stroke decreased as the temperature decreased.

Based on the above numerical estimation results, electric resistance welded (ERW) Linepipe with high-quality weld seam MightySeam® has been developed. Controlling the morphology and distribution of oxides generated during the welding process by means of temperature and deformation distribution control is the key factor for improving the low-temperature toughness. The Charpy transition temperature of the developed ERW pipe was much lower than −45°C. Based on the low-temperature hydrostatic burst test with a notched weld seam at −20 °C, the MightySeam® weld provides a fracture performance that is the same as UOE Double Submerged Arc Welded pipe. The pipe has been used in actual, highly demanding, severe environments.