bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Characteristics of Liquid Hydrocarbon Releases From Buried Pipelines: An Experimental Evaluation
Authors: Castellanos Fernando , van der Baan Mirko , Bussiere Mathew , Stephens Mark
Published: November 2018

Characterizing the acoustic energy associated with small pipeline leaks is of particular interest to pipeline operators who are considering deployment of acoustic based External Leak Detection (ELD) systems along their pipelines. Small leaks are defined here as product leaks having release rates and/or release volumes that fall below the detection threshold currently associated with conventional or traditional leak detection technologies, including but not limited to Computation Pipeline Monitoring (CPM) systems. Characterization of such acoustic energy could be used to predict and evaluate the performance of acoustic based ELD systems in a variety of candidate deployment locations. It could also be used to optimize system performance of existing or future deployed acoustic based ELD systems. This study focuses on investigating the transmission of acoustic energy caused by pressurized fluid releases through two different soil mediums (a dry soil and a saturated soil). Specifically, signal attenuation and frequency content as a function of sensor location from the release source were investigated. To accomplish this, geophones were placed within a large soil filled tank to listen passively to controlled releases of hydrocarbon liquids from a buried pipe segment. These releases were driven through circular shaped orifices ranging in diameter from 0.79 to 4 mm and by pressures ranging from 50 to 500 psi. Signal attenuation was observed in both the longitudinal and radial directions however the effect was more significant in the radial direction. This does not necessarily imply that anisotropic effects exist, but rather a possible explanation is that the acoustic waves traveling along the pipe walls (i.e. in the longitudinal direction) are less attenuated and can therefore carry the acoustic energy further in that direction. In addition, it was found that the dominant bandwidth of the leak signals (which is approximately 600 Hz but it can be as high as 1200 Hz) is inversely proportional to orifice diameter and proportional to the release pressure. Also, the dominant frequency was found to be slightly higher in the saturated soil environment. This study provides insights into expected acoustics characteristics of small liquid leaks, which can help in the selection and placement of appropriate acoustic based ELD systems.
The Effect of Ground Displacement and Stress Relief on Pipeline Behaviour: A Case Study
Authors: Karimian Hamid , Campbell Chris , Blackwell Chris , Dooley Colin , Barlow Pete
Published: November 2018

The Wapiti River South Slope is located 25 km southwest of Grande Prairie, AB. The slope is 500 m long and consists of a steep lower slope and a shallower upper slope, both of which are located within a landslide complex with ground movements of varying magnitudes and depths. The Alliance Pipelines Ltd. (Alliance) NPS 42 Mainline (the pipeline) was installed in the winter of 2000 using conventional trenching techniques at an angle of approximately 8° to the slope fall line. Evidence of slope instability was observed in the slope since the first ground inspection in 2007. Review of the available geotechnical data indicates two different slide mechanisms. In the lower slope, there is a shallow translational slide within a colluvium layer that is draped over a stable bedrock formation. In the upper slope, there is a deep-seated translational slide within glaciolacustrine and glacial till deposits that are underlain by pre-glacial fluvial deposits. Both the upper and lower slope landslide mechanisms have been confirmed to be active in the past decade.

Large ground displacements in the order of several meters between 2012 and 2014 in the lower slope led to a partial stress relief and subsequent slope mitigation measures in the spring and summer of 2014, which significantly reduced the rate of ground movement in the lower slope. Surveying of the pipeline before and after stress relief indicated an increase in lateral pipeline deformation (in the direction of ground movement) following the stress relief. This observation was counter-intuitive and raised questions regarding the effectiveness of partial stress relief to reduce stresses and strains associated with ground movements.

Finite element analysis (FEA) was conducted in 2017 to aid in assessing the condition of the pipeline after being subject to the aforementioned activities, and subsequent ground displacement from July 2014 to December 2016. This paper presents the assumptions and results of the FEA model and discusses the effect of large ground displacement, subsequent stress relief and continued ground displacement on pipeline behaviour. The results and findings of the FEA reasonably match the observed pipeline behaviour before and after stress relief. The FEA results showed that while the lateral displacement of the pipeline that was caused by ground movement actually increased following the removal of the soil loading, the maximum pipeline strain was reduced in the excavated portion. The results also indicated that ground displacement in the upper slope following the stress relief had minimal effect on pipe stresses and strains in the lower slope.
An Analysis Model and its Practical Applications in PG&E Gas Transmission Pipeline Strength Test Projects
Authors: He Chunlei , Stracke Edward
Published: November 2018

This article presents a complete set of calculations (referred to as Model) PG&E developed to monitor, assess and approve strength tests on insitu (pipelines currently in service) gas transmission pipelines. How the Model is used in the field, 2017 test results, and process improvements that resulted from the implementation of the model are also discussed.

In compliance with CPUC directives, the Code of Federal Regulations[1] and PG&E’s internal standards, PGE has performed strength tests on approximately 1,100 miles of insitu pipelines from 2011 through 2017. The model was specifically designed to assess the strength test of a closed section of gas pipeline for both leaks and ruptures.

The model was originally designed for strength tests using water as the test medium and updated to accommodate nitrogen as a test medium. A future enhancement will be to incorporate a blend of Nitrogen and Helium as the test medium. The model plots the pressure-temperature and pressure-volume curves over the test duration (field test measurements) and compares them to the theoretically calculated curves. The curves are used to determine if the change in pressure is due to temperature influence or leakage. When water is the test medium, the model calculates the net corrected medium volume change from start to end of the static test period. When nitrogen is the test medium, the model calculates and analyzes net mass change of the medium by considering nitrogen under both the real gas state and the ideal gas state.

By calculating restrained (buried) pipeline section and unrestrained (exposed) pipeline section separately, the model gains more accuracy. Accurate temperature measurements play a critical role in the model.

The model makes it possible for engineers to monitor, analyze and direct strength tests with real-time test data. The model is also used to evaluate the pipeline fill condition on the day prior to the actual test, which resulted in fewer test restarts due to incomplete fill or temperature stabilization issues. An additional benefit is the tests were typically completed earlier in the day. The model is utilized on all PG&E insitu pipeline strength projects today. Authors also provide improvement suggestions of this model in future application.
Non-Contact Geomagnetic Localization of Pipeline Defects Using Empirical Mode Decomposition and Magnetic Gradient Tensor
Authors: Zhang Tao , Wang Xinhua , Chen Yingchun , Ullah Zia , Zhao Yizhen
Published: November 2018

Non-contact geomagnetic anomaly detection, as one of passive non-destructive testing (NDT) techniques, can be used to locate pipeline defects, while its accuracy is affected by random noise and detection orientation. In order to extract effective geomagnetic anomaly signals of pipeline defects, a method based on empirical mode decomposition (EMD) and magnetic gradient tensor was studied. In order to filter random noise, EMD was performed to self-adaptively decompose magnetic field signals into a series of intrinsic mode functions (IMFs), and then Hurst exponent was implemented to exclude false modes; The calculation method of magnetic gradient tensor modulus (MGTM) was proposed to obtain precise defect locations according to tensor symmetry; Subsequently, the remote pipeline defect model was built based on the magnetic dipole theory, and the relationship between detection orientation and MGTM was discussed. The experimental results showed that the proposed method could realize high precision and reliable non-contact geomagnetic localization of pipeline defects.
Toughness of EW Pipe Seam Welds of Contemporary Steels
Authors: Xu S. , Laver A. , Liang J. , Tyson W. R. , Matsuno S.
Published: November 2018

An extensive experimental program to characterize the Charpy-V-notch (CVN) impact toughness of ten contemporary Electric Welded (EW) pipes was recently completed to establish a database to support the revision of the EW seam weld Charpy toughness testing requirements in Canadian Standards Association (CSA) Z245.1-14. The toughness in these welds is lowest at or near the weld bond line (BL) within a narrow zone ±≈0.5 mm wide. It is feasible and desirable to position the BL notch to a precision to match this width, i.e. ±0.5 mm from the BL. In this paper, typical results of microstructure, micro-hardness, CVN toughness (i.e. absorbed energy) as a function of temperature and notch location, and fractography will be presented. CVN absorbed energy requirements for EW welds in CSA Z245.1 have been determined using a failure assessment diagram (FAD) procedure. The values of required CVN estimated from the FAD are close to those specified in CSA Z245.1-14 but are higher than the specification in CSA Z245.1-18.
Comparison of Fracture Models to Quantify the Effects of Material Plasticity on the Ductile Fracture Propagation in Pipelines
Authors: Nonn Aida , Paredes Marcelo , Keim Vincent , Wierzbicki Tomasz
Published: November 2018

Various numerical approaches have been developed in the last years aimed to simulate the ductile fracture propagation in pipelines transporting CO2 or natural gas. However, a reliable quantification of the influence of material plasticity on the fracture resistance is still missing. Therefore, more accurate description of the material plasticity on the ductile fracture propagation is required based on a suitable numerical methodology.

In this study, different plasticity and fracture models are compared regarding the ductile fracture propagation in X100 pipeline steel with the objective to quantify the influence of plasticity parameters on the fracture resistance. The plastic behavior of the investigated material is considered by the quadratic yield surface in conjunction with a non-associated quadratic plastic flow potential. The strain hardening can be appropriately described by the mixed Swift-Voce law. The simulations of ductile fracture are conducted by an uncoupled, modified Mohr-Coulomb (MMC) and the micromechanically based Gurson-Tvergaard-Needleman (GTN) models. In contract to the original GTN model, the MMC model is capable of describing ductile failure over wide range of stress states. Thus, ductile fracture resistance can be estimated for various load and fracture scenarios. Both models are used for the simulation of fracture propagation in DWTT and 3D pressurized pipe sections. The results from the present work can serve as a basis for establishing the correlation between plasticity parameters and ductile fracture propagation.
Updates on Pipeline Integrity Reliability Targets
Authors: Nemeth Alex , Hassanien Sherif , Leblanc Len
Published: November 2018

The use of integrity reliability science is becoming a prevalent element in the pipeline integrity management process. One of the key elements in this process is defining what integrity reliability targets to achieve in order to maintain the safety of the system. IPC2016-64425 presented different industry approaches around the area of defining reliability target levels for pipelines. It discussed the importance of setting operators’ specific integrity target reliability levels, how to choose such targets, and how to determine the safety of a pipeline asset by comparing the probability of failure (PoF) against an integrity permissible probability of failure (PoFp) while keeping an eye on the estimated expected number of failures. Building upon the previous discussion, this paper reviews a risk-based approach for estimating integrity reliability targets that account for the consequence of a potential release. Given available technical publications, the as low as reasonably practicable (ALARP) concept, and operators’ specific risk tolerances, there is room for improving the communication of integrity reliability along with selected targets. The paper describes how codes, standards, and operators set reliability targets, how operator specific targets can be chosen, and how industry currently recommends liquid pipelines reliability targets. Moreover, the paper proposes different approaches to define practical reliability targets coupled with an integrity risk-informed decision making framework.
The Use of Sensitivity Analyses for Optimum Data Gathering in Risk and Threats Assessments
Authors: Ayello Francois , Chen Hao , Sridhar Narasi , Ruiz Lydia , Sera Travis , Shironishi Mari
Published: November 2018

Pipeline engineers routinely perform risk assessments using a linear approach that begins with data collection, progresses through threat identification, and concludes with risk assessment. This linear risk assessment process leads to some inefficiencies. For example, since all data is gathered in the first step, inconsequential data might be collected during the data gathering process that diverts resources from other pipelines. This paper presents a different approach, where data is gathered iteratively based on its risk reduction value derived from a sensitivity analysis and data collection cost. Each time data is gathered; future risk predictions become more certain. This process is stopped when the cost of data gathering activities outweighs the benefit to risk predictions.
Study on Transition of Stress Corrosion Cracking to Sharp Edge Corrosion for a Liquids Pipeline
Authors: Liang Jiajun (Jeff) , Dong Ziqiang (Alex) , Yu Mengshan , Dela Rosa Mariko , Nagra Gurwinder
Published: November 2018

Although stress corrosion cracking (SCC) growth is attributed to the synergistic effects of stress and corrosion, these two factors can just as easily become competing mechanisms, with stress cycles driving growth (hydrogen, the by-product of corrosion, may facilitate the growth), and corrosion working to blunt the crack tip and arrest growth. It follows that reducing the maximum pressure and cycling severity can slow down the crack growth or even stop it, and aggressive corrosion can further blunt the sharp crack tip. The Authors have observed, on a particular Polyethylene (PE) tape coated pipeline, instances where SCC has exhibited a propensity to corrode and convert into sharp edge corrosion. This is attributed to the combined effects of limited corrosion protection and low stresses. The focus of the paper is to assist operators in recognizing this phenomenon and integrate lessons learned into pipeline integrity management strategies.
Experimental-Numerical Assessment of Vintage Pipe and Girth Weld With a Geometrically Complex Corrosion Feature
Authors: Hertelé Stijn , Galle Timothy , Van Minnebruggen Koen , De Waele Wim , Huising Otto Jan
Published: November 2018

Standard pipe corrosion assessments are based on simplifying assumptions with respect to corrosion geometry and focus on pressure based loading. Moreover, when corrosion patches traverse girth welds, validity criteria to their assessment become impractically vague. The integrity of girth welds is additionally influenced by axial stresses, which may act in combination with hoop stress resulting from pressure. In an attempt to address these issues, the authors conducted a detailed assessment on a significant, highly irregular corrosion patch traversing a 12″ natural gas pipeline girth weld. The investigation comprises a full scale uniaxial tensile test and supporting detailed finite element (FE) analyses. Hereby, the model mesh adopts detailed geometrical characteristics resulting from a surface profile scan obtained from stereoscopic digital image correlation. The numerical model is validated based on the uniaxial tensile test, in the sense that plastic collapse and highly complex strain distributions are successfully reproduced. Finally, the FE model is used to explore axial tensile failure in presence of internal pressure.
Analysis of the National Energy Board Pipeline Integrity Performance Measures Data
Authors: Paviglianiti Joe , Shaw Sarah
Published: November 2018

The National Energy Board’s (NEB or the Board) top priorities are the safety of people and protection of the environment. NEB-regulated pipelines have a very good safety record; however, the NEB noticed an increased trend in some types of incidents. Therefore, after considerable stakeholder consultation, in March 2012 the NEB started requiring NEB-regulated companies to report annually on new pipeline performance measures. These performance measures were developed and introduced to promote continual improvement in the management of pipelines by allowing companies to compare their results with industry aggregate numbers. In addition, these metric results allow the NEB to both evaluate and demonstrate that pipeline companies are effective in managing pipeline safety and protection of the environment.

The NEB requires all regulated companies to report on incidents, such as releases of substances and serious injuries. Pipeline performance measures data provides the Board additional information such as lagging and leading indicators. These lagging indicators provide an historical view of company performance while the leading indicators provide forward looking data of potential future events. The NEB is of the view that an amalgamation of leading, lagging and qualitative measures can provide an overview of company effectiveness in meeting foundational management system program objectives.

This paper examines four years of reported integrity related performance and integrity inspection data to evaluate trends in activities taken by companies to maintain safe pipelines. This paper will briefly discuss the challenges encountered when developing the measures, obtaining consistent data and evaluation of the data to identify trends.

The paper will conclude by summarizing select results of the integrity performance measures and integrity inspection information data and discuss any potential future actions related to the pipeline performance integrity measures.
Pipeline Rupture Detection Using Real-Time Transient Modelling and Convolutional Neural Networks
Authors: Smith Joel , Chae Jaehee , Learn Shawn , Hugo Ron , Park Simon
Published: November 2018

Demonstrating the ability to reliably detect pipeline ruptures is critical for pipeline operators as they seek to maintain the social license necessary to construct and upgrade their pipeline systems. Current leak detection systems range from very simple mass balances to highly complex models with real-time simulation and advanced statistical processing with the goal of detecting small leaks around 1% of the nominal flow rate. No matter how finely-tuned these systems are, however, they are invariably affected by noise and uncertainties in a pipeline system, resulting in false alarms that reduce system confidence. This study aims to develop a leak detection system that can detect leaks with high reliability by focusing on sudden-onset leaks of various sizes (ruptures), as opposed to slow leaks that develop over time. The expected outcome is that not only will pipeline operators avoid the costs associated with false-alarm shut downs, but more importantly, they will be able to respond faster and more confidently in the event of an actual rupture. To accomplish these goals, leaks of various sizes are simulated using a real-time transient model based on the method of characteristics. A novel leak detection model is presented that fuses together several different preprocessing techniques, including convolution neural networks. This leak detection system is expected to increase operator confidence in leak alarms, when they occur, and therefore decrease the amount of time between leak detection and pipeline shutdown.
Overcoming Difficult to Inspect Multi-Diameter, Low Pressure Gas Transmission Pipeline Challenges
Authors: Dauby Frank , Vages Stefan
Published: November 2018

Pacific Gas and Electric Company owns and operates an extensive network of over 10,700 km (6,700 miles) of gas transmission pipelines, much of which is under 16″ diameter and operates at less than 27.5 bar (400 psig), making them difficult to inspect with free swimming in-line inspection (ILI) tools. Additionally, many piggable pipeline sections are multi-diameter and have numerous 1.5D fittings, some of these in back to back configuration, requiring tools that are not currently available. Following several failed attempts to inspect PG&E’s 12″ × 16″ pipelines in 2015 using existing ILI tools, and after working to modify a 12″ × 18″ tool for lower pressure service in 2016, PG&E and ROSEN decided to collaboratively develop new, specially designed, 12″ × 16″ geometry and axial MFL tools.

The goal of this project was to develop tools that could meet both the PG&E pipeline passage requirements and allow for an acceptable speed profile. The need to inspect a total of 16 pipeline sections in the long-term ILI Upgrade Plan, in this size range, justified the investment in these new tools. The service provider embarked on a new ILI tool design process including design, manufacturing, fabrication and testing at their facilities in Germany. Through this process, a number of unique ILI tool design features to lower tool drag and improve ease of collapsibility were implemented, resulting in a tool that far exceeds existing industry capabilities. To confirm the tools’ capabilities before their first use in a live gas transmission pipeline, pump testing in water, as well as in compressed air, was performed. In late 2017, using these tools, PG&E inspected two previously unpiggable 12″ × 16″ low-pressure pipelines successfully. In this paper, the process of developing these tools will be discussed. The test program will be reviewed comparing findings under controlled conditions in water and compressed air with pig run behavior in the live pipelines. The analysis also provides an assessment of the operating conditions that are deemed necessary for the inspection tool to gather a good quality data set.
Algorithms for the Strain Based Analysis of Dented Pipelines
Authors: Okoloekwe Chike , Kainat Muntaseer , Langer Doug , Hassanien Sherif , Adeeb Samer
Published: November 2018

Pipeline integrity management commonly leverages nondestructive inspection of pipeline defects via inline inspection (ILI) and assessment of the resultant data. Key parameters for dent analysis include the feature geometry measured by caliper tools and the presence/severity of any interacting features (such as cracks or areas of corrosion) which can be measured with a variety of technologies (such as magnetic flux leakage or ultrasonic tools). Dent profile measurements can be especially susceptible to noise due to the measurement techniques employed, signal quality, and overall tool performance. Analytical methods for strain assessment of dents can employ curve/surface fitting techniques to estimate the curvature and calculate the strain of the dent based on the fitted curve/surface. Noise in the measured profile can result in local areas of high perceived strain, which could lead to misinterpretation of a dent’s true severity, especially when using automated or purely analytical assessment methods.

A deterministic strain-based approach for evaluating the severity of dented pipelines has been presented previously which leverages multi-dimensional B-spline functions to more accurately apply the non-mandatory ASME B31.8 equations for dent assessment. The approach presented previously requires relatively smooth dent profile information to minimize the effects of signal noise. While low pass filters can effectively eliminate noise in the signal, they may also lead to loss of accuracy (e.g. excessive smoothing can reduce the depth and sharpness of a measured dent’s profile). This paper discusses how low pass filters can be optimally used to smooth the raw ILI signals to allow for analytical representation of the dent shape without underestimating its severity.

The conclusion of this venture is a detailed workflow for the analytical assessment of dented pipelines for the rapid characterization of the severity of deformation in pipelines with limited computational demand. This type of assessment allows for initial ranking and assessment of large and complex pipeline systems to select features requiring more detailed assessment or mitigation.
Landslide Pipe-Soil Interaction: State of the Practice
Authors: Eichhorn Geoffrey N. , Haigh Stuart K.
Published: November 2018

Current understanding of pipe-soil interaction during large ground movement events is insufficient due to their infrequency and the complexity of the infrastructure. Pipeline operators currently rely on a fully coupled continuum model of a landslide and pipeline interaction, or, more commonly, on a simplification of this interface using structural beam style soil-springs to transfer soil loads and displacements to the pipeline.

The basis for soil-springs are laboratory studies based largely on clean sand or pure clay, and flat ground. Owing to the use of manufactured soils and flat ground, the soil-pipe interface modelling may not be valid for landslides.

The loading of a pipeline in a landslide, and how the soil-spring factors should change with space and time are reviewed and may differ from commonly adopted guidelines. Physical modelling in research is emerging to study landslides and pipelines utilizing fully instrumented scale models. In the absence of fully instrumented field pipelines, physical modelling should be used to validate continuum models.
Integrity of Longitudinal Welds in Pipelines: Bridging Scales
Authors: Erdelen-Peppler Marion , Kalwa Christoph , Schröder Jens
Published: November 2018

Toughness testing of the heat affected zone (HAZ) of longitudinal welds is increasingly often required in pipeline standards and specifications. This includes simple tests such as the Charpy impact test that was designed to serve as quality test as well as enhanced methods including crack tip opening displacement (CTOD) tests that are necessary to conduct an engineering critical assessment (ECA). If occasional low toughness values are observed, the question turns towards assessing the impact of such numbers and how representative they are of the behavior of a pipe in service. The significance of low toughness values measured in laboratory testing can be judged on basis of ring expansion and hydraulic burst tests.

The current study summarises an extensive test series to quantify the toughness of submerged arc welds (SAW) obtained by different test methods. The tested pipes cover a wide range of material including medium strength X70 up to high strength X100. Their welds are characterized in terms of fracture toughness properties with single edge notch tension (SENT) and single edge notch bending (SENB) tests. Different constraint levels are obtained within each series by introducing notches of standard depth as well as shallow notches. Structural behavior is characterized with burst tests as well as ring expansion tests containing notches in the longitudinal weld.

The experimental results are assessed within dedicated finite element studies. The assessment is conducted for pipes serving as pressure containment, thus having circumferential stress resulting from internal pressure. Based on the results achieved the conclusion can be drawn that the standard route including high constraint CTOD leads to overly conservative results concerning the integrity of longitudinal welds. A better representation of structural behavior is observed in ring expansion tests.
Application of Wide-Band Ultrasound for the Detection of Angled Crack Features in Oil and Gas Pipelines
Authors: Vos Willem , Norli Petter , Vallee Emilie
Published: November 2018

This paper describes a novel technique for the detection of cracks in pipelines. The proposed in-line inspection technique has the ability to detect crack features at random angles in the pipeline, such as axial, circumferential, and any angle in between. This ability is novel to the current ILI technology offering and will also add value by detecting cracks in deformed pipes (i.e. in dents), and cracks associated with the girth weld (mid weld cracks, rapid cooling cracks and cracks parallel to the weld). Furthermore, the technology is suitable for detection of cracks in spiral welded pipes, both parallel to the spiral weld as well as perpendicular to the weld. Integrity issues around most features described above are not addressed with ILI tools, often forcing operators to perform hydrostatic tests to ensure pipeline safety.

The technology described here is based on the use of wideband ultrasound inline inspection tools that are already in operation. They are designed for the inspection of structures operating in challenging environments such as offshore pipelines. Adjustments to the front-end analog system and data collection from a grid of transducers allow the tools to detect cracks in any orientation in the line. Description of changes to the test set-up are presented as well as the theoretical background behind crack detection.

Historical development of the technology will be presented, such as early laboratory testing and proof of concept. The proof of concept data will be compared to the theoretical predictions. A detailed set of results are presented. These are from tests that were performed on samples sourced from North America and Europe which contain SCC features. Results from ongoing testing will be presented, which involved large-scale testing on SCC features in gas-filled pipe spools.
CO2SAFE-ARREST: A Full-Scale Burst Test Research Program for Carbon Dioxide Pipelines — Part 3: Dispersion Modelling
Authors: Godbole Ajit , Liu Xiong , Michal Guillaume , Lu Cheng , Huéscar Medina Clara
Published: November 2018

The ‘CO2SafeArrest’ Joint Industry Project (JIP) was set up with the twin aims of: (1) investigating the fracture propagation and arrest characteristics of steel pipelines carrying anthropogenic carbon dioxide (CO2), and (2) investigating the dispersion of CO2 following its release into the atmosphere. The project involves two full-scale burst tests of 24-inch, X65 buried line pipes filled with a mixture of CO2 and nitrogen (N2). An overview of the CO2SafeArrest JIP and details of the fracture propagation and arrest investigation appear elsewhere in two companion papers.

This paper presents the experimental investigation and computational fluid dynamics (CFD) simulations of the dispersion of CO2 following its explosive release into the atmosphere over the terrain at the test site in the first test.

The setting up of the experiment and the CFD model is described in detail, including the representation of terrain topography and weather (wind) conditions, and the condition at the ‘inlet to the dispersion domain’. The modelling was carried out prior to the actual event, and simulated the dispersion of the CO2 cloud for different wind speeds and directions. This analysis confirmed that the sensor layout set up to obtain spot measurements CO2 concentration over the terrain at the site was adequate.

The predicted and experimental values of CO2 concentration at the nominated locations over the duration of the dispersion were found to be in good agreement. Results of this study are expected to be used in developing a generalized model for the dispersion of CO2 and for estimating the ‘consequence distance’ for such events. It is noted that this distance is necessarily a function of time due to the highly transient nature of the event.
Implementation of a New Tool for Pipelines Integrity Evaluation: A Correlation Between Local Strains and Hardness
Authors: Soret Clément , Djouda Joseph Marae , Bonnaudet Mélissandre , Zarea Murès , Madi Yazid
Published: November 2018

Due to external interference, pipelines used for onshore as well as offshore operations can present dent and gouge defects. As such defects can seriously impair facilities’ integrity and performance, it is necessary to evaluate the strains in the vicinity of these defects. The development of non-destructive approaches to assess defects severity remains an issue in the pipeline industry. In the present study, micro-hardness - strain relationships are established for three steel grades of pipeline materials: API X52 modern, API X52 vintage and API X63 vintage. The micro-hardness – strain correlations of the three pipe materials are analyzed in order to verify if they can be described by a master curve. For that purpose, Notched Tensile (NT) tests are performed in Longitudinal (L) and Transverse (T) directions for each grade in order to reach high strain values (up to 70%). The relationship proposed by Tabor was improved with the introduction of three new parameters that allow considering actual material behavior.
Complex Circumferential Stress Corrosion Cracking: Identification, Sizing and Consequences for the Integrity Management Program
Authors: Johnson Brett , Tesfaye Bereket , Wargacki Cory , Hennig Thomas , Suarez Ernesto
Published: November 2018

Since the late 1980’s Ultrasonic tools have been used for the detection and sizing of crack like indications. ILI service providers developed inspection technologies for liquid and gas lines that are widely used nowadays. In comparison to axial cracking, circumferential cracking is not a prevalent risk to most pipelines and therefore is not as well understood. Nevertheless, pipeline Operators observe from time to time circumferentially oriented defects, often in combination with circumferential welds or local stress/strain accumulations. These are often caused by pipeline movement, which may especially occur in mountain areas.

With the introduction of Ultrasonic circumferential crack inspection tools in the late 2000’s the knowledge has steadily increased over time. Extensive data collected from in-ditch NDE validations has provided NDT Global with an increased knowledge of the morphology of single cracking and stress corrosion cracking defects both in the axial and circumferential orientations. Field verifications have shown that not all features have the same morphology. Some of the challenges with circumferential cracking are for features that fall outside of the industry standard specifications. These types of features can exhibit characteristics such as being sloped, skewed or tilted. In 2016 NDT Global was approached by Plains Midstream Canada to complete inspections utilizing the 10″ Ultrasonic Circumferential crack inspection technology. The pipeline system spans 188km within Canada and consists of 2 segments. The pipeline traverses several elevation changes and crosses several creeks and roads. Circumferential cracking was identified during dig campaigns performed for other threats, therefore the need to inspect each pipeline segment with the Ultrasonic circumferential technology was identified.

Plains Midstream Canada and NDT Global formed a close collaboration to assess the severity of circumferential crack features in this line. This paper will discuss integrity aspects from an Operator and Vendor perspective. Challenges identified due to the morphology of the circumferential crack like indications and derived analysis rules and interpretation methodologies to optimize characterization and sizing are presented. Finally, potential opportunities to maintain the integrity of similar assets by applying some of the findings and enhance the management and decision making process are suggested.
InSAR and the Pipeline Geohazards Toolbox: Instructions for Use As of 2018
Authors: Guthrie Richard , Reid Emma , Richmond John , Ghuman Parwant , Cormier Yves
Published: November 2018

Interferometric Synthetic Aperture Radar (InSAR) is a type of active remote sensing whereby a satellite transmits electromagnetic radiation (microwaves) at the ground and measures the differential phase of the reflected signal over multiple images (or multiple antennas on a single satellite). InSAR has the potential to provide centimeter and even millimeter-scale measurements of displacement over time, but is sensitive to vegetation, topography, and atmospheric effects. We consider herein, the application of InSAR at two known landslides on the Enbridge pipeline system, and discuss the strengths, weaknesses, values, and limitations of its application in the Geohazard Management of landslides impacting pipeline ROW’s. We compare information provided at each site by InSAR (both L-band and X-band) to data derived by mapping using Light Detection and Ranging (LiDAR) or air photographs, to differential LiDAR techniques, and to data derived from subsurface measurements (slope inclinometers). In doing so we find that L-Band data can be an effective tool to establish the extent or footprint of movement (or lack of movement) at known landslide locations, extending the interpretive power of a specialist and the understanding of event magnitude, and potentially affecting the mitigation options. Further, L-Band InSAR can be used in a supporting role to pre-screen areas for active landslides along the right of way (ROW), however, data gaps, a lack of explanatory power, and considerable noise in the results mean that a user step that further considers the terrain, other sources of data, and the identified magnitude, is essential. X-Band InSAR appeared impractical for ROW monitoring where vegetation prevented coherence between images, however, X-Band InSAR was able to detect small displacements at above ground infrastructures.
Reducing Excavation Damage in the Natural Gas Industry Using Real-Time GIS and Sensors
Authors: Rezendez Aaron , Marros Robert J. , Farrag Khalid , Acharya Saurav
Published: November 2018

Excavation damage is one of the top causes of incidents in both the transmission and distribution pipeline sectors. Damage caused from insufficient notification of one-call centers or careless digging near gas pipelines can potentially result in property damage, significant injury, and/or loss of life. Pacific Gas and Electric Company (PG&E) and the Gas Technology Institute (GTI) have developed the framework for an Excavation Encroachment Notification (EEN) system to support damage prevention efforts to reduce damage from excavation activity. The research was funded by the California Energy Commission (CEC) and Operations Technology Development (OTD).

The system utilizes real-time Geographic Information System (GIS) technology and cellular-connected location and motion sensors placed on excavation equipment. Controlled and field-based testing and training of machine learning algorithms were conducted to aid in characterization of excavation equipment. Additionally, a GIS system populated with pipeline information allowed operators of excavation equipment and utilities to receive an alarm and indication when equipment is adjacent to or excavating in the vicinity of a gas pipeline. More broadly, the utility stakeholder has increased situational awareness of excavation activities within its service territory with access to the real-time activity of excavation equipment through a mobile-compatible dashboard, reducing excavation damage risk and improving safety. Lastly, the project offers historical data archiving for data analysis and trend identification.
Application of Machine Learning to Distributed Temperature Sensing (DTS) Systems
Authors: Araujo Maria S. , Spidle Heath A. , Siebenaler Shane P. , Blaisdell Samantha G. , Vickers David W.
Published: November 2018

The timely detection of small leaks from liquid pipelines poses a significant challenge for pipeline operations. One technology considered for continual monitoring is distributed temperature sensing (DTS), which utilizes a fiber-optic cable to provide distributed temperature measurements along a pipeline segment. This measurement technique allows for a high accuracy of temperature determination over long distances. Unexpected deviations in temperature at any given location can indicate various physical changes in the environment, including contact with a heated hydrocarbon due to a pipeline leak.

The signals stemming from pipeline leaks may not be significantly greater than the noise in the DTS measurements, so care must be taken to configure the system in a manner that can detect small leaks while rejecting non-leak temperature anomalies. There are many factors that influence the frequency and intensity of the backscattered optical signal. This can result in noise in the fine-grained temperature sensing data. Thus, the DTS system must be tuned to the nominal temperature profile along the pipe segment. This customization allows for significant sensitivity and can utilize different leak detection thresholds at various locations based on normal temperature patterns. However, this segment-specific tuning can require a significant amount of resources and time. Additionally, this configuration exercise may have to be repeated as pipeline operating conditions change over time. Thus, there is a significant need and interest in advancing existing DTS processing techniques to enable the detection of leaks that today go undetected by DTS due to their signal response being too close to the noise floor and/or requiring significant resources to achieve positive results.

This paper discusses the recent work focused on using machine learning (ML) techniques to detect leak signatures. Initial proof-of-concept results provide a more robust methodology for detecting leaks and allow for the detection of smaller leaks than are currently detectable by typical DTS systems, with low false alarm rates. A key use of ML approaches is that the system can “learn” about a given pipeline on its own without the need to utilize resources for pipeline segment-specific tuning. The potential to have a self-taught system is a powerful concept, and this paper discusses some key initial findings from applying ML-based techniques to optimize leak detection capabilities of an existing DTS system.
Evaluation of Crack Growth and Material Toughness Effects on Probability of Pipeline Failure
Authors: Riccardella Pete , Dedhia Dilip , Riccardella Scott , Manning Tyson
Published: November 2018

Probabilistic fracture mechanics (PFM) analysis can provide insights into the relative benefits of various pipeline integrity management options in reducing the probability of a pipeline failure. For example, a prior analysis (1) showed that In-Line Inspection (ILI) technology can achieve a greater level of safety, at longer reassessment intervals, than other integrity management techniques such as Hydrostatic Pressure Testing in a line subject to an aggressive Stress Corrosion Cracking (SCC) environment in relatively high toughness pipe base material.

This paper extends that study to evaluate the effects of different crack growth mechanisms, such as fatigue crack growth (FCG) in gas and liquid pipelines as well as materials with differing fracture toughness levels (i.e. Seam Welds vs. Base Metal). PFM analysis can address these growth mechanisms and toughness distributions and serve as a valuable tool for weighing the effects of different assessment techniques, repair criteria and reassessment intervals on pipeline integrity. The analysis can also be used to study the effects of probability of detection (POD) of the ILI techniques as well as enhanced repair (dig) criteria. This paper presents a series of case studies to illustrate the utility of the PFM approach for comparing integrity management options for pipelines subject to different crack growth mechanisms and fracture toughness properties.
Improving Fitness-for-Purpose Methodology and Safety Target Definitions on Geohazard Related Pipe Deformation
Authors: Yoosef-Ghodsi Nader , Baraniecki Kurt , Hill Mike , Hubert Yvan
Published: November 2018

Previous practices at Enbridge Pipelines Inc. regarding allowable deformation and/or strain in pipelines were closely mirrored to current North American standards and did not effectively manage the time dependent aspect of active slope movement and other similar progressive external force phenomena applied to a pipeline. In addition, variability in soil spring values and/or soil displacements utilized in FEA assessments can lead to significant variability between predicted pipeline strain demand and actual conditions. Furthermore, the risk tolerance of a potential and significant deformation that could impact the serviceability of one pipeline in a Right of Way (ROW) including multiple pipelines was not well defined. Shutting down several pipelines in a ROW until it could be proven that they are fit-for-service is time consuming. In addition, it requires a good amount of engineering work to address the significant uncertainty in confirming if a pipeline has not deformed beyond a safe limit when the latest deformation in-line inspection predates significant soil movement.

A better tool was required to allow a more precise assessment. A better fitness-for-purpose approach has been developed and used to both predict when a timely repair would be required and conservatively set the In-line Inspection (ILI) re-inspection interval to monitor the condition of the pipe. This approach allowed to step away from the greater uncertainty associated with understanding the impact of soil movement on the pipe integrity. This paper presents the methodology used by Enbridge to redefine its fitness-for-purpose methodology using proven strain-deformation correlation models and strain rates estimated through multiple arrays of strain gauges. The discussion will include how the safety targets were re-engineered to account for multiple pipelines in a ROW.