bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaluation of Fatigue in Gas Pipelines
Authors: Semiga Vlad , Tiku Sanjay , Dinovitzer Aaron , Wagster Wendy 
Published: November 2016

There is a commonly held belief that internal operational pressure fluctuations of a gas pipeline is less likely to result in fatigue cracking than a liquid pipeline. A defensible engineering analysis process, demonstrating that this observation remains valid for all gas pipeline systems regardless of operation (i.e. transmission, bi-directional flow at storage facilities), existing features (i.e. dents or preexisting cracks), material properties (i.e. pipe vintage, grade) and pipeline geometry, needs to be developed. The work reported in this paper describes the work sponsored by the Interstate Natural Gas Association of America (INGAA) to support gas pipeline operators in completing Integrity Verification Programs (IVP) by defining which pipeline segments can reasonably be considered to be at risk of fatigue damage accumulation and which are not.
This paper presents an overview of the work completed to develop a defensible approach to demonstrate the conditions under which pipeline pressure fluctuation induced fatigue is not a concern. The development of this approach, presented in this paper, considers the results of a survey of the range of cyclic severities experienced by gas pipeline operators, typical feature types and sizes that could exist in a pipeline system (i.e. mechanical damage, cracking) and the role of material properties on these assessments. The paper includes the development of directions as to the collection and analysis of SCADA pressure data to produce a pressure spectrum severity indicator (SSI) characterizing the fatigue damage potential of an operational history. This SSI is used along with fatigue susceptibility tables indicating the conditions for which fatigue would not be a concern for a pipeline segment. The susceptibility criterion relates a pipelines operation, in terms of SSI to the maximum feature size that can exist in the system before fatigue is considered a threat to pipeline integrity.
The information presented in this paper would be of interest to pipeline operators, maintainers, consultants and regulators. The technical work presented in this paper was completed to support compliance with regulatory requirements and may also be used to influence the application of integrity management regulatory requirements on gas pipeline systems by providing information and processes to eliminate the need to consider fatigue as a damage accumulation process or integrity threat.
Evaluating Dents With Metal Loss Using Finite Element Analysis
Authors: Gossard Justin , Bratton Joseph , Kemp David , Finneran Shane , Polasik Steven J. 
Published: November 2016

Dents created by third party mechanical damage are a severe integrity threat to onshore and offshore transmission pipelines. This type of damage is often associated with metal loss, which can be introduced during the initiation of a dent or develop as a result of the presence of a dent and associated coating damage. Once a dent has been found to be associated with metal loss through excavation, there is little guidance to determine the serviceability of the anomaly.
In this study, dents with associated metal loss due to corrosion examined in the field are evaluated to determine the contribution of the interacting dent and metal loss features to the associated burst pressure of the feature. Twenty dents with metal loss flaws were identified through an ILI survey while in service to capture dimensions of the dent and metal loss features. Each site was excavated and measured using a laser scanner. The laser scanner produced 3D imaging with sufficient resolution of both the dent and metal loss areas as a 3D surface mesh. The 3D surface mesh was transformed into a 3D solid mesh and analyzed using a finite element analysis software package in order to determine a predicted internal pressure that would cause failure. A subsequent statistical assessment was performed to analyze the relationship between the ILI measurements and the predicted burst pressure resulting from finite element analysis of each dent with metal loss feature. Statistical analyses were used to evaluate the prediction capabilities of burst pressures of dent with metal loss features identified through ILI, prior to excavation and direct examination.
ILI to ILI Comparisons: Quantifying the Impact of Multiple Inspections
Authors: Moreno Pamela J. , Ellinger Matthew A. , Bubenik Thomas A. 
Published: November 2016

Det Norske Veritas (U.S.A.), Inc. (DNV GL) prepared this paper in order to study the repeatability of inspection results between subsequent in-line inspections. DNV GL has access to a significant amount of data that spans many different pipeline operators, ILI vendors, inspection years, and inspection technologies. DNV GL is well suited to complete this study as a result of our access to these various data sets.
Over 55,000 one-to-one metal loss defect comparisons were assembled from ILI-to-ILI analyses. Reported metal loss defect depths, lengths, and widths spanning from 2003 through 2015 from 13 pipeline operators and 36 pipeline segments were compiled to meet the objectives of this paper. Inspection technologies include axial magnetic flux leakage (MFL), ultrasonic wall thickness (UTWT), spiral MFL, and circumferential MFL ILI.
From analyses of these data, the following conclusions were generated:
• Effect of ILI vendor: ILI repeatability is generally improved when the same ILI vendor is used (when compared to using two different ILI vendors in subsequent inspections), but this is not always true.
• Reported metal loss depths: ILI repeatability decreases with increasing metal loss depth.
• Pipe geometry and type: ILI repeatability is better in larger diameter pipelines and with increasing wall thickness.
• POF classification: ILI repeatability is better for pitting, general corrosion, and axial grooving defects as compared to the other POF classifications.
Based on these insights, the authors make the following recommendations:
• Pipeline operators should consider using the same ILI vendor and tool if the goal is to identify change and/or corrosion growth in the pipeline segment. A raw signal review is encouraged in order to verify the presence, or lack thereof, changes in metal loss morphologies. The raw data review is especially important when comparing inspections from two different ILI vendors.
• If the goal is to identify corrosion growth, and a pipeline operator uses different ILI vendors, it is recommended that a statistical review of one-to-one matched metal loss features take place to identify candidate locations that are more likely to be growing. The candidate locations should have a raw signal review in order to verify whether or not growth is taking place.
Study of a Plastic Strain Limit Damage Criterion for Pipeline Mechanical Damage Using FEA and Full-Scale Denting Tests
Authors: Arumugam Udayasankar , Gao Ming , Krishnamurthy Ravi , Wang Rick , Kania Richard 
Published: November 2016

Pipeline constructed in rocky terrain is vulnerable to damages such as denting, gouging and other mechanical damages. In-line inspection (ILI) of these pipelines often reported several hundreds or even thousands of dents. Although most of these reported dents are well below 6% outside diameter (OD) depth limit as per ASME B31.8, few dents (sharp rock dents) with high strain could pose threat to integrity of the pipeline. Recently, strain-based models have been proposed to assess mechanical damage severity in pipelines. Attempts have also been made to characterize cracking susceptibility in rock dents using the critical strain based ductile failure damage indicator (DFDI) model. The objective of this study is to validate this model using full-scale denting tests conducted at the laboratory. Additionally, validation also extends to against the simplified DFDI model without finite element analysis (FEA).
In this paper, the existing ASME strain limit and strain limit damage models are reviewed. The critical strain based strain damage model known as Ductile Failure Damage Indicator (DFDI) is then presented. The theoretical aspect of this model, including early work by Hancock and Mackenzie on strain limit (εf, reference failure strain) for ductile failure, is reviewed. The experimental aspect of material critical strain and its measurement using uni-axial tensile testing are then described. An elastic-plastic finite element analysis is employed to calculate DFDI, which is used to quantify the accumulated plastic strain damage and its susceptibility to cracking, and is validated using six full scale denting tests.
Finally, the simplified strain limits for plain dent is proposed and validated.
Implementation of CSA Z662-15 Annex K Option 2 on a 610mm Liquid Pipeline
Authors: Belanger Rory , Sarafinchan Derrick 
Published: November 2016

For more than two decades, CSA Z662 Annex K has provided a method for developing alternative acceptance criteria for weld flaws in mechanized welded pipelines. Increasingly, over the years, fracture mechanics practitioners have found the method overly conservative and restrictive with respect to brittle fracture criteria when compared to other accepted fracture mechanics-based engineering critical assessment ECA codes and methods. These limitations rendered the CSA Annex K method difficult to implement on pipelines constructed with materials not possessing optimal toughness and in cases requiring consideration of fracture toughness at temperatures lower than the typical minimum design metal temperature (MDMT) of −5°C. This paper presents experiences implementing CSA Z662-15 Annex K Option 2 methodology on a 610 mm diameter liquids pipeline and compares and contrasts the utility and benefits of the code revision. This pipeline required consideration for installation during winter months, necessitating installation temperatures as low as −30°C. In addition to evaluation of actual ECA results, analytical evaluations of the Option 2 methodology were also conducted considering parameters outside those used on the project.
The new Annex K Option 2 method was found to be of considerable benefit in preparation of a practical ECA. Since fracture toughness testing was conducted at the anticipated lowest installation temperature, the flaw criteria were, as expected, principally controlled by elastic/plastic crack growth consideration. The failure assessment diagram implemented into the CSA Z662-15 Annex K Option 2 provided tolerance for both longer and deeper flaws than that afforded by Option 1 (which resorts to the former 2011 Annex K method). Furthermore, the reduced restriction to the surface interaction ligament (p distance) offers additional advantages including increased flexibility in weld profile design and weld pass sequencing.
Fracture toughness (CTOD) testing of TMP pipeline steels used in the project at −30°C often produced transitional fracture toughness results. It was found that the particular project materials were quite sensitive to the level of test specimen pre-compression (an acceptable plastic straining method to reduce residual stress gradients) applied to the CTOD specimens to enhance fatigue crack-front straightness. It was found that optimizing the level of pre-compression (to achieve acceptable pre-crack straightness while minimizing plastic pre-strain) achieved a balance between fully satisfying testing requirements, providing a conservative assessment of CTOD, and facilitating a functional Annex K ECA.
Hydrostatic Pressure Testing as Part of an Integrity Management Program: A Case Study
Authors: Keane Sean , Rosenfeld Michael , Heise Larry 
Published: November 2016

Integrity management tools must be fit for their intended purpose and a hydrostatic pressure test is no exception to this. A hydrotest can be designed to demonstrate an industry recognized safety factor, or an alternate safety factor that aligns with a target reliability. Hydrostatic pressure tests are a destructive test, but they can be designed and executed to minimize likelihood of unnecessary damage to otherwise benign manufacturing anomalies. In order to determine a risk balanced design, a hydrostatic pressure test must be engineered to achieve fitness-for-service goals, risk goals, as well as asset goals.
This paper presents a risk balanced design to a hydrostatic pressure test. Key technical aspects related to the science of hydrostatic pressure testing are summarized as to the affect on fitness-for service goals, risk goals and asset goals. The approach to designing a hydrostatic pressure test is demonstrated through a case study on a 326 mile (525 km) NPS 26 (DN 650 mm) pipeline manufactured using 1950’s vintage flashweld longseam.
A Study of Crack Detection Ultrasonic Attributes to Manage Leak Threats Associated With Short Crack-Like Flaws in ERW Pipelines
Authors: Korol Kaitlyn , Hubert Yvan , Fredine Gordon , Senf Petra , Koon Koon Sherry-Ann 
Published: November 2016

Inline Inspection (ILI) tools along with hydrostatic testing have been the primary identification and mitigation techniques for cracking threats on liquids pipelines. Each technique faces detection challenges in relation with the weld type, geometry, and feature types, sizes and orientations. Low frequency electric resistance welds (LF ERWs) are subject to a number of crack-like defects due to the ERW manufacturing process. These defects may include fatigue cracks, lack of fusion, burned metal defects, stitched welds, cold welds, cracks in hard HAZ, surface breaking hook cracks near the weld and selective seam corrosion [1].
Within a population of features in a pipeline, a subpopulation can exist of short, deep defects (>50% wt) that may be undersized by the ILI tool or not detected by a hydrostatic test due to the length of the flaw. For ILI tools, a length detection threshold is set based on the tool speed (which is dictated by the tool type and configuration). A feature may be undersized by the ILI tool if its length is below this tool threshold. For hydrostatic testing, through-wall flaws may be undetected if the flaw length is below the critical length for a significant leak. Through detailed ILI data analysis, Enbridge along with PII Pipeline Solutions has been able to consistently identify short and deep crack-related defects on LF ERW pipe through means other than feature dimensions provided by the ILI tool.
In-ditch non-destructive examination and destructive laboratory testing has confirmed these features are critical and fall below current ILI tool’s detection thresholds. This paper discusses unique ILI data attributes that may identify a more severe feature than would conventional ILI sizing practices, and how the identification and selection procedure is being applied across Enbridge’s pipeline system. This analysis effort aligns with Enbridge’s goal to continuously improve its integrity management processes and further enhance the safety of its pipelines.
Modified Two-Curve Model for Predicting Fracture Arrest Toughness and Arrest Distance of Full-Size Burst Tests
Authors: Zhu Xian-Kui 
Published: November 2016

Running fracture control is a very important technology for gas transmission pipelines with large diameter and high pressure. The Battelle two-curve (BTC) model developed in the early 1970s has been widely used in pipeline industry to determine arrest toughness in terms of the Charpy energy. Because of its semi-empirical nature and calibration with test data only for grades up to X65, the BTC does not work for higher grades. Simple corrections were thus proposed to extend the BTC model to higher grades, but limited to those grades considered. Moreover, the BTC model only predicts the minimum arrest toughness, but not arrest distance.
To fill the technical gaps, this paper proposes a modified two-curve (MTC) model and a fracture arrest distance model in reference to the Charpy energy. The MTC model coupling with an arrest distance algorithm can predict fracture arrest toughness and arrest distance in one simulation of numerical integration for a single pipe or a set of multiple pipes with given toughness. Two sets of full-scale burst test data for X70 and X80 are used to validate the proposed model, and the results show good agreements between the predictions and full-scale test data of arrest toughness and arrest distance as well. The MTC model is then applied to optimize a design of pipe segment arrangements for a mockup full-scale burst test on a high-strength pipeline steel. The MTC simulation results confirm the experimental observation that different pipe arrangements determine different arrest toughness and arrest distance for the same grade pipes.
Advanced Integrity Management Framework for Pipelines
Authors: LeBlanc Len , Kresic Walter , Keane Sean , Munro John 
Published: November 2016

This paper describes the integrity management framework utilized within the Enbridge Liquids Pipelines Integrity Management Program. The role of the framework is to provide the high-level structure used by the company to prepare and demonstrate integrity safety decisions relative to mainline pipelines, and facility piping segments where applicable. The scope is directed to corrosion, cracking, and deformation threats and all variants within those broad categories. The basis for the framework centers on the use of a safety case to provide evidence that the risks affecting the system have been effectively mitigated. A ‘safety case’, for the purposes of this methodology is defined as a structured argument demonstrating that the evidence is sufficient to show that the system is safe.[1]
The decision model brings together the aspects of data integration and determination of maintenance timing; execution of prevention, monitoring, and mitigation; confirmation that the execution has met reliability targets; application of additional steps if targets are not met; and then the collation of the results into an engineering assessment of the program effectiveness (safety case). Once the program is complete, continuous improvement is built into the next program through the incorporation of research and development solutions, lessons learned, and improvements to processes.
On the basis of a wide range of experiences, investigations and research, it was concluded that there are combinations of monitoring and mitigation methods required in an integrity program to effectively manage integrity threats. A safety case approach ultimately provides the structure for measuring the effectiveness of integrity monitoring and mitigation efforts, and the methodology to assess whether a pipeline is sufficiently safe with targets for continuous improvement. Hence, the need for the safety case is to provide transparent, quantitative integrity program performance results which are continually improved upon through ongoing revalidations and improvement to the methods utilized. This enables risk reduction, better stakeholder awareness, focused innovation, opportunities for industry information sharing along with other benefits.
The Benefits of Accurate ILI Performance on Pipeline Integrity Programs for Axial Crack and Metal Loss Corrosion Threats
Authors: Adianto Riski H. , Skow Jason B. , Sutherland Jeffrey 
Published: November 2016

An analysis describing the benefits of an accurate in-line inspection (ILI) system performance is presented in this paper. A good ILI performance is characterized as an accurate description of the condition of an inspected pipeline. Information from a better ILI performance, as compared to a poorer one, can be used to reduce the number of required digs and/or extend the re-inspection interval without compromising the pipeline’s integrity. As a result, these parameters can be used to assess the benefits of the improved inspection performance.
For this analysis, the ILI performance was represented by the depth sizing accuracy as the depth of a feature is one of the most critical parameters in assessing the pressure containment capacity at the feature location. This work utilized a sensitivity analysis in which the impact of various levels of ILI performance on a pipeline integrity program in terms of the number of required repairs for a given reliability threshold was examined. The number of required repairs associated with each inspection performance was calculated using a reliability based assessment method. This method was selected because it fully accounts for the statistical characteristic of the ILI performance.
The sensitivity analysis considered two pipeline condition scenarios for two pipeline systems. The first pipeline condition scenario was characterized as having a high number of features, many of which were severe in size, while the second condition scenario consisted of fewer features that were less significant in size. The analysis was carried out for both axial stress corrosion cracking and metal loss corrosion features.
The results of the analysis show that a more accurate ILI depth measurement leads to a more accurate pipeline reliability estimate, and therefore, a reduction in the number of required repairs. However, the benefit associated with continued ILI measurement accuracy improvement exhibits a diminishing trend.
The Influence of the Bourdon Effect on Pipe Elbow
Authors: Abdulhameed Diana , Adeeb Samer , Cheng Roger , Martens Michael 
Published: November 2016

Pipe elbows are frequently used in a pipeline system to change the directions. Thermal expansion and internal pressure results in bending moments on the bends causing ovalization of the initial circular cross-section. The ability of the bend to ovalize will result in an increase in the bend flexibility when compared to straight pipes [1]. In case of bends subjected to internal pressure, the pipe will start to straighten out due to the difference between the intrados and extrados surface areas. The internal pressure causes unbalanced thrust forces tending to open up the elbow depending on its stiffness and surrounding constraints. These forces tending to cause ovalization of the cross section and causing the tendency of pipe bends to open up are termed the “Bourdon effect”. If these unbalanced thrust forces are not taken into consideration, unanticipated deformations and high stress levels could occur at the elbow location that may not be accounted for in traditional stress analysis [2]. A better understanding of the influence of the Bourdon effect on the elbow design parameters is required. Past studies have investigated the behaviour of pipe elbows under closing bending moment and proposed factors that account for the increased flexibility and high stress levels resulted from ovalization. These factors are used in the current design codes [3],[4] &[5] and known as the flexibility factor and stress intensification factor.
In this investigation, pipe elbows with different nominal pipe size and various bend radiuses to internal pipe radius ratios (R/r) are studied to get a better understanding of the Bourdon effect and its influence on the pipe stresses and deformations. Differential equilibrium equations are solved to derive a mathematical model to evaluate the unbalanced thrust forces resulted from the Bourdon effect on a pipe elbow. The forces evaluated from the derived model are compared to finite element model results and showed excellent agreement. A comparison between the CSA-Z662 code and the FEA results is conducted to investigate the applicability of the stress intensification factors used in the current design code for different loading cases. The study showed that the external bending moment direction acting on the pipe has a significant effect on the distribution of stresses on the pipe elbow and significantly depending on the level of applied internal pressure.