bluuebunny/crossref_metadata_2025 huggingface dataset:
Fitness for Service Analysis of the Circumferential Extent of Corrosion in Pipelines
Authors: Zhang Fan , Rosenfeld Michael , Gustafson Jeremy
Published: November 2018

The failure of a corroded pipe is generally controlled by the depth and the longitudinal extent of the metal loss area subjected to hoop stress. However, the failure of metal loss due to its circumferential extent under longitudinal stress is possible if significant longitudinal stress exists in the pipe or the metal loss has considerable circumferential extent and depth. If such circumstances exist, it is prudent to conduct a complementary analysis of pipe integrity to assess the potential for circumferential as well longitudinal failure. Most existing approaches for assessing circumferential metal loss, such as Miller’s equations, were derived by assuming the metal loss to be centered at the extreme stress position around the pipe circumference, i.e., the center of the metal loss is centered at the location of the maximum bending stress in the pipe. The assessment may be over-conservative if the metal loss area deviates from the extreme position related to the bending plane. Described in this paper is a new approach to assess the potential for circumferential failure of metal loss centered at an arbitrary angle from the location of maximum bending stress. The approach results in the same failure stress as existing models when the metal loss is centered at the location of maximum bending stress. The failure stress increases when the metal loss deviates from the location of maximum bending stress and reaches the maximum value when the metal loss is centered at the neutral axis. The equations of the model developed in this paper can be easily implemented into a spreadsheet tool for routine integrity assessment. Other considerations related to the assessment of circumferential metal loss are also discussed, including non-uniform corrosion, negligible corrosion, and the interaction of multiple corrosion areas in the same pipe cross section. The model developed in this paper can also be used to determine the cutoff line for plastic collapse in a failure assessment diagram (FAD) based approach for assessing circumferential cracks, such as API 1104 Appendix A and API 579.
Differences in Near-Neutral pH Crack Growth Behavior Between Oil Pipelines and Gas Pipelines and Corresponding Crack Growth Mitigation Strategies
Authors: Xu Zhezhu , Daniel Andrea , Chevil Karina , Gamboa Erwin , Chen Weixing
Published: November 2018

Oil pipelines and gas pipelines operations result in very different pressure fluctuation schemes due to different compressive properties of liquids and gases. Liquid fluids such as oil are less compressible and pressure fluctuations during oil pipelines operations are more frequent and vary over a wide range of magnitudes and frequencies, compared with those during gas pipelines operations. Despite the differences in operating conditions indicated above, both oil pipelines and gas pipelines are susceptible to stress corrosion cracking and corrosion fatigue failures. This investigation was initiated to understand the different crack growth rate behavior of pipeline steels characteristic to the type of pressure fluctuation schemes in near-neutral pH environment, that is, oil pipelines vs. gas pipelines. It was suspected that the similar range of service life between oil pipeline steels and gas pipeline steels could be attributed to a higher rate of direct dissolution at the tip of a crack during gas pipeline operation because of much higher mean pressures, despite their lower crack growth caused by corrosion fatigue. In the case of near-neutral pH stress corrosion cracking, corrosion makes minor contribution to crack growth but produces diffusible hydrogen that interacts with cyclic loading to make cracks grow. This study was performed using specimens with surface cracks, which simulated the following two environmental conditions: 1) fully exposed to the environment, 2) shielded from the environment, exposed to hydrogen only. In Case 1), the specimen surface, on which the surface cracks were made, was fully exposed to a near-neutral pH solution, allowing the occurrence of corrosion at the crack tip. In Case 2), a narrow strip of a coating was applied to prevent the cracks from direct contact with the corrosive solution; however, the cracks were affected by diffusible hydrogen which had been generated as a by-product of corrosion on the adjacent steel surface free of coatings. These specimens were mechanically loaded under different pressure schemes typical of both oil and gas pipeline operations. It has been found that crack growth caused by direct dissolution of crack tip materials is insignificant, regardless of pipeline operating conditions. A much higher crack growth rate, attributed to hydrogen embrittlement, was found under gas transmission conditions, while a higher corrosion fatigue crack growth was found under oil transmission conditions. Based on these findings, strategies on crack growth mitigation, characteristic to each type of pipeline operation are also proposed.
How Do We (Actually) Know Our Quality Is Improving?
Authors: Papp Justin R. , Forbes William H. , Yarmuch Matthew A. R.
Published: November 2018

We have all dealt with performance metrics in the pipeline industry. How do we measure operational excellence? Are we prioritizing the right corrective actions? Are our existing metrics fair and driving the right behaviors? Will they recognize success and actually show us and our clients that we are improving?

This paper describes how Enbridge Major Projects measures and knows our Quality is improving; how we prioritize, focus, and monitor Quality improvement.

Using our roadmap, your organization can transform existing data streams from anecdotal to well established facts that produce actionable results and drive business objectives.

To reach this outcome, Enbridge Major Projects quickly matured our Quality Culture by leveraging our strong Safety Culture and habits. On our journey to meaningful overall Quality metrics, Enbridge built a foundation through non-punitive incident reporting using incident resolution tools and a Cost of Quality model.

Cost of Quality models can be designed and executed in a variety of ways. This paper will focus on applying a model specifically suited for pipeline construction and operational activities. Key topics to be addressed include:

• basic common principles of an overall Cost of Quality model,

• various data collection methods to suit the model’s design, and

• how a Documented Defects Quality cost model allows Enbridge to identify, prioritize, and monitor Quality improvements focused on preventing recurrence and occurrence of Quality issues.

Examples will be provided for common pipeline applications, including valves, pipe, and other commodities and services. This approach has enabled Enbridge Major Projects to prioritize improvement actions and meet business objectives.

Applying a Cost of Quality model will enhance your operational excellence and greater adoption would provide the foundation for industry-wide Quality performance metrics that will recognize success and validate that Quality is improving in the pipeline industry.
Integration of Welding, NDT, Mechanical Testing and Field Control When Using an ECA Flaw Acceptance Criteria in Pipeline Construction
Authors: Lu Junfang , Huntley Bob , Ludwig Luke , Aulin Axel , Duncan Andy
Published: November 2018

The fracture mechanics based engineering critical assessment (ECA) method has been accepted as a fitness for service (FFS) approach to defining weld flaw acceptance criteria for pipeline girth welds. Mechanized gas metal arc welding (GMAW) processes are commonly used in cross country pipeline girth weld welding because of the advantages in good quality and high productivity. With the technical advancements of non-destructive testing (NDT) techniques, automated ultrasonic testing (AUT) has greatly improved flaw characterization, sizing and probability of detection during weld inspection. Alternative weld flaw acceptance criteria are permitted in pipeline construction code to assess the acceptability of mechanized girth welds using an ECA. The use of an ECA based weld flaw acceptance criteria can significantly reduce the construction cost. Mechanized girth weld acceptance criteria have been progressively transitioned from workmanship standards into using fitness for service based ECAs.

To successfully deliver an ECA on a pipeline project, a multidisciplinary approach must be taken during the welding design and construction stages. Welding, NDT, mechanical testing and field control are all integral elements of pipeline construction. All these four elements have to be fully integrated in order to implement the ECA and achieve the overall integrity of a pipeline. The purpose of this paper is to discuss the importance of the integration of these four elements necessary for proper implementation of the ECA weld flaw acceptance criteria.
Development of a Pipeline Post Seismic Response Screening Process
Authors: Warman David J. , Kendrick David Z. , Mackenzie John D.
Published: November 2018

US pipeline operators may receive USGS automated earthquake notifications. In most of these cases, the seismic event poses little threat to pipeline assets. However, until an analysis is performed there can be uncertainty as to when and what actions should be taken.

The paper describes the development and implementation of a simplified screening process to assess the effects of seismic events on buried pipelines. A design basis was established based on a literature review of seismic models, seismic-pipeline interactions, von Mises equivalent pipeline stress limits, standards, regulations, and practices that are currently used to assess seismic effects on buried pipelines. This design basis was used to develop a screening tool that provides a simple “pass/no pass” determination and is based on the readily obtained attributes (seismic magnitude and pipeline distance from the earthquake epicenter).

“No Pass” scenarios are sub-divided into medium or high threat categories, with the latter likely needing to be evaluated on a more detailed basis.

General guidelines and charts have been developed and incorporated into a general procedure to assess when and what actions should be taken.
A Method to Analyze the Impact of Inline Inspection Accuracy on Integrity Management Program Planning of Pipelines
Authors: Xie Mingjiang , Tian Zhigang , Sutherland Jeff , Fang Bingyan , Gu Bill
Published: November 2018

A pipeline integrity management program is greatly affected by integrity planning methods and inline inspection (ILI) tool performance. In integrity management program planning, inspection and maintenance activities are in common practice, determined from risk and integrity assessment practices with the objective to reduce risk and effectively exceed a reliability target for the safe operation of the pipeline. An efficient and effective integrity planning method can address the most significant risk and optimize the operational and maintenance costs.

In this paper, a method is presented for analyzing the impact of ILI tool accuracy on integrity planning for pipelines for fatigue cracks. Crack inspection and threat of fatigue cracking was used as the working case for the analysis although the approach could potentially be used for any pipeline threat type. The proposed method is based on the use of a Monte Carlo simulation framework, where initial crack defect size and ILI measurement errors are considered as key random variables.

The integrity (severity) assessment of the crack population scenarios used the CorLAS™ burst pressure model, and the Paris’ law crack growth model based on API 579. The subsequent pipeline reliability assessments also considered single and multiple cracks scenarios. Using a reliability / probability of failure (PoF) approach, the impact of ILI tool accuracy and initial crack size on when to set reinspection and reassessment intervals was investigated.

Furthermore, integrity program cost scenarios for pipeline integrity programs with multiple cracks was also evaluated with respect to different (crack) populations, pipe conditions and ILI accuracies. A sensitivity analysis was performed considering different inspection costs, maintenance costs and relative crack severity for pipelines with financial metrics. Various scenarios were discussed regarding maintenance and inspection planning and a “total cost rate” for different situations. The proposed method can support integrity management program planning by linking risks with integrity plan costs associated with ILI accuracies, and optimal re-assessment intervals.
Remaining Strength in Pressure Vessels With Pitting Type Metal Loss: Part 1
Authors: Trujillo-Tadeo J. J. , González-Velázquez J. L. , Rivas-López D. I.
Published: November 2018

This work proposes an assessment procedure for the determination of the remaining strength in pressure vessels with pitting type metal loss, trough the developed of integrity diagrams according to the pitting density, pitting depths and the internal pressure of the component using Finite Element Analysis simulations.

The simulations results indicate that the pitting density and depths according to the Gumbel Max Distribution, are the main factors that determine the mechanical integrity of the component; where 45% damaged area by pitting generates a stress concentration that multiplies at least ten times the stress compared with components without defects, since these variables present a synergistic behavior in the stress state.

The proposed assessment procedure facilitates the evaluation of the components that present pitting corrosion damage, due to the geometric and population effect of the pitting is considered in the finite element simulation.
Comparative Study on Atmospheric Temperature Models for the Buried Hot Oil Pipeline
Authors: Yuan Qing , Wu Zhiming , Li Wang , Yu Bo , Wu Changchun
Published: November 2018

In previous studies, the atmospheric temperature was generally assumed to be constant during a period (commonly a month) for the numerical simulation on the buried hot oil pipeline. The rationality of this assumption is controversial due to the absence of quantitative results, and thus it needs to be further verified or investigated to make atmospheric temperature approximation more convincing. In this study, based on the changing trend of actual atmospheric temperature, three mathematical models are established and their expressions are presented according to different approximations. And the relationships among these three expressions are obtained by utilizing mathematical derivation. On the basis of three atmospheric temperature models, the weakly unsteady single oil transportation and strongly unsteady batch transportation are numerically simulated, respectively. According to numerical results, the oil temperature at the pipeline ending point and the soil temperature field are compared for these three models. In order to make comparisons more convincing, the influences of the physical properties of crude oil, operation parameters, pipeline parameters and pipeline environments on the deviations of numerical results are compared and analyzed. Finally, based on all comparisons on the deviations of numerical results, the conclusions are drawn, which can provide beneficial reference for the choice of atmospheric temperature models in future numerical simulation study on the buried hot oil pipeline.
Numerical Simulation of Acoustic Resonance in Closed Side Branch With Different Cross-Section Shapes
Authors: LiuYi Jiang , Hong Zhang , QingQuan Duan
Published: November 2018

There are many closed side branches in the gas conveying pipeline system. When the gas passes through the closed side branch, the shear layer will arouse the acoustic resonance in the closed side branch, which is harmful to the safe operation of the pipeline. The research work is insufficient about the influence of the cross-section shape of the closed side branch on acoustic resonance. Using the Detached-Eddy Simulation (DES) model, the acoustic resonance characteristics caused by the side branch pipe with different square cross-sections are simulated at the inlet boundary conditions of 25 m/s, 30 m/s and 35 m/s. The results show that in the center axis of the side branch, a 1/4 wavelength standing wave was formed, and the acoustic resonance occurs at a higher Strouhal number in circular branch. The cross-section shape of the side branch does not affect the acoustic resonance frequency, but it has a certain influence on the amplitude of pressure fluctuation and has a significant influence on the high-order frequency components.
Structure Assessment Using Instrumented Indentation: Strength, Toughness and Residual Stress
Authors: Kwon Dongil , Kim Jong Hyoung , Kwon Ohmin , Kim Woojoo , Choi Sungki , Choi Seunghun , Kim Kwang-Ho , Ro Dongseong
Published: November 2018

The instrumented indentation technique (IIT) is a novel method for evaluating mechanical properties such as tensile properties, toughness and residual stress by analyzing the indentation load-depth curve measured during indentation. It can be applied directly on small-scale and localized sections in industrial structures and structural components since specimen preparation is very easy and the experimental procedure is nondestructive. We introduce the principles for measuring mechanical properties with IIT: tensile properties by using a representative stress and strain approach, residual stress by analyzing the stress-free and stressed-state indentation curves, and fracture toughness of metals based on a ductile or brittle model according to the fracture behavior of the material. The experimental results from IIT were verified by comparing results from conventional methods such as uniaxial tensile testing for tensile properties, mechanical saw-cutting and hole-drilling methods for residual stress, and CTOD test for fracture toughness.
Operational Experiences With Axial Strain Inline Inspection Tools
Authors: Dewar Douglas , Van Boven Greg , ElSeify Mohamed , Bjorn Paul , Bruce Nick
Published: November 2018

Axial Strain Inline Inspection has transitioned from an experimental to commercial technology that will develop significantly as the industry requires. Axial strain tool measures total elastic longitudinal strain on a pipeline including: imposed strains due to manufacturing; construction/cold bending; backfilling; and loading associated with abnormal forces such as ground movement and settlement. The technology is based on magnetostriction, which measures the permeability and magnetic induction of ferromagnetic materials. Magnetostriction is well understood, but the application of the technology to active pipelines is relatively recent. Currently, Inertial Measurement Unit (IMU) inline inspections (ILI) effectively identify areas of localized bending strains and can be used for monitoring of pipeline movements run to run, but they do not detect axial strain associated with either tensile or compressive loading. Currently, axial strain modules are mounted behind Magnetic Flux Leakage (MFL) platforms and have either 4 or 8 probes that provide circumferential readings typically at 0.5 to 1 m intervals. Data is either considered “trend” or “calibrated” depending on whether representative test samples are available. Interpretations are provided by the vendor in the form of Axial Strain Variation which is the averaged value of a set of readings with the hoop strain component removed. Additionally, data from each probe is analyzed to establish the maximum and minimal longitudinal strains (εmax/εmin) with locations around the circumference of the pipeline. Given the potential complexity of locked-in strains, simple calculations using sinusoidal bending relationships do not apply. Therefore, curve fitting analysis is required to determine the circumferential strains. This paper includes operational learnings from the analyses of data from eight (8) Axial Strain ILI runs within variable terrain on some natural gas transmission and gathering pipelines in British Columbia by verifying strains due to known abnormal loading as well as identifying previously unknown features (landslides, in particular). In addition, sources of error, data anomalies, current limitations and potential improvements of the technology are discussed.
Competency Standards for the Pipeline Industry
Authors: Unger Michelle , Hopkins Phil
Published: November 2018

Pipeline standards and regulations explicitly require personnel to be both competent and qualified to work on pipelines, but they neither define competent or qualified, nor provide methods or processes to demonstrate competence and qualifications.

This paper defines competence and qualification and introduces and describes “competency standards.” These standards are used to assess the competence of an individual and are an integral part of the process to qualify individuals as being competent. Individuals are proven to be qualified in a competency if they are successfully assessed against these standards.

The paper recommends the contents of a competency standard: the standard should clearly state its purpose and outcomes, and detail the knowledge, training, mentoring, and experience requirements, as well as an assessment method. Examples of these standards are presented, showing how competency standards provide a common definition of a competence and showing how competencies can be assessed against these standards. A case study of an assessment of an individual is also detailed.

The choice between a prescriptive and a performance-based competency standard is discussed, and it is shown that the choice is affected by the level of the competence, the complexity of the competence, the homogeneity of the industry, and the government regulator’s resources and capabilities to police the standard.

The paper explains that qualifications must be “portable”: as individuals move jobs, the qualifications they obtain need to be recognized by all companies. Portability is achieved by having the qualification “certified”. This certification is conducted by an independent body, which certifies that the processes followed (including any assessments) meet the requirements of the competency standard, and that the assessment and the award of the qualification have been audited and verified. Hence, a qualification is a two-step process: award and certification.
Prediction of Mechanical Properties of ERW Pipes Considering Manufacturing Process Through Numerical Analysis
Authors: Han Seong-Wook , Kang Soo-Chang , Yi Jiwoon , Kim Ho-Kyung
Published: November 2018

Along with the development of the energy industry, demand for oil and gas pipelines has increased, and as the low oil price era has been prolonged, more economical pipe design and construction are required. Especially, ERW pipe has been expanding its range of applications, which is advantageous in terms of productivity and price. ERW pipes are made by passing through continuous rollers, where unintentional plastic deformation such as the Bauschinger effect occurs. Since plastic deformation caused by repetitive loading and unloading changes the initial properties of steel, it is necessary to precisely predict the final properties of the pipe as well as an accurate understanding of the manufacturing process. So, this study focused on evaluating the effects of manufacturing process considering plastic deformation for high performance ERW pipe manufacturing.

In this paper, three manufacturing process stages of ERW pipe were simulated as 3D nonlinear finite element models using ABAQUS: forming stage, sizing stage, and flattening stage. And the ABAQUS model was verified by comparison with the outer diameter measured from full-scale size pipes. In order to maintain the continuity of analysis between each manufacturing process stage, PEEQ, Alpha and residual stress were obtained from each manufacturing process stage, and then these mechanical properties were mapped to the next manufacturing process stage. And change of mechanical properties during the each manufacturing process stage were examined. Finally, the change of material properties at the flattening stage where reverse bending occurs was evaluated, especially in influence of sizing ratio on the flattening stage. Through the developed analytical model, numerical prediction of the mechanical properties of ERW pipe is possible.
Crack Formation in Charpy Tests of the Heat-Affected Zone of Large-Diameter Linepipe Material
Authors: Schemmann Lars , Stallybrass Charles , Schröder Jens , Liessem Andreas , Zaefferer Stefan
Published: November 2018

Double submerged arc welding is an efficient process used during the production of longitudinally-welded large-diameter pipes. It is well known that the associated high heat input has a negative influence on the toughness of the heat-affected zone (HAZ). The toughness drop is related to changes in the HAZ microstructure compared to the base metal. The austenite grain size increases significantly and larger carbon-rich martensite/austenite particles (M/A-particles) are formed within a coarse bainitic matrix during the phase transformation compared to the as-rolled base material. The exact relationship between the microstructure, the processing conditions, base metal composition and the weld metal are at the focus of attention of materials development efforts at EUROPIPE and Salzgitter Mannesmann Forschung GmbH (SZMF).

In the present study, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to investigate the HAZ of X70 large-diameter pipe material as well as tested Charpy specimens from the same material. Secondary cracks in the direct vicinity of the primary fracture surface of tested Charpy specimens from the HAZ were analyzed by EBSD and SEM to investigate the damage mechanism in detail. It was found that these cracks originate at M/A-particles and that the dominant crack path depends on the crystallographic orientation of the surrounding matrix. The analysis of several EBSD measurements and a 3D-analysis of the propagation direction of the crack showed that secondary cracks frequently propagate parallel to {100} and rarely along {110}-planes. It is known from literature that these are preferred cleavage planes in ferritic steels. The SEM analysis performed in the HAZ of the investigated steel showed that the volume fraction of elongated M/A-particles is elevated close to the fusion line and decreases within the first few hundred micrometers distance from the fusion line. The EBSD measurements illustrate that the geometrically necessary dislocation density is significantly increased in the neighborhood of M/A-particles. This indicates that the bainitic matrix is work-hardened around the M/A-particles during testing and is therefore more prone to the formation of microcracks than other surrounding regions.
Experimental Measurement of CTOA During Ductile Crack Propagation in Pipeline Burst Tests
Authors: Shibanuma Kazuki , Yamaguchi Hikaru , Hosoe Takahiro , Suzuki Katsuyuki , Aihara Shuji
Published: November 2018

Dynamic measurement of drop-weight tear test (DWTT) and pipe burst test for 356 mm outer diameter and 9.5 mm wall thickness steel pipe were conducted using high-speed camera. Crack velocity in the DWTT were 10 m/s during the steady state. Crack Tip Opening Angle (CTOA) values measured in the DWTT showed the constant value of about 20.1° during steady state propagation. On the other hand, crack velocity in the burst test showed monotonically decreasing during crack propagation from 200 m/s but it was found that CTOA value kept constant value of about 13.2° until crack arrest irrespective of the crack velocity. These results showed the validation of the CTOA criterion for the high-pressure gas pipelines. The results also showed that CTOA in a burst test is generally different from that in a test using small-scale specimen. Future developments of the experimental procedure using a small-scale specimen to provide CTOA value corresponding with that in a burst test would be effective.
In-Line Inspection in Lieu of Hydrostatic Testing for Low Frequency Electric Resistance Welded Pipe
Authors: Krieg Matt , Nestleroth J. Bruce , Hennig Thomas , Haines Harvey
Published: November 2018

Hydrostatic testing is a costly, operationally-impactful method of verifying seam integrity in low frequency electric resistance welded (LF-ERW) line pipe. Pipeline operators seek an alternative seam assessment method that provides a sufficiently conservative integrity assessment without the potentially negative impacts of hydrostatic testing. As in-line inspection (ILI) and field nondestructive evaluation (NDE) improve, pipelines that have been historically hydrostatic tested can now use ILI to ensure operational integrity. The improved ILI technology assessed in this work is an enhanced ultrasonic crack ILI tool with higher circumferential resolution and finer axial sample intervals. Magnetic ILI data from previous assessments is used to assist in anomaly identification. In addition to utilizing NDE technologies such as phased array, the emerging full matrix capture (FMC) imaging method that quantifies the size, position, and orientation of seam weld anomalies was examined. This paper discusses the work performed to ensure the efficacy of the improved ILI and NDE methods to accurately detect and quantify all anomalies that could possibly fail a hydrostatic test. An early step in the process was removing three sections of pipe from service for technology calibration and assessment. Each spool was examined with ILI technology in a pump-through facility, inspected using many NDE methods and then destructively tested. These results were communicated to ILI analysts and used to calibrate and improve the interpretation of the inspection results. Then the pipeline was inspected as part of the scheduled integrity assessment. Using field evaluation of anomalies detected by ILI, pipes were selected for removal from service to examine destructively. This paper presents the inspection and destructive testing results in addition to prognosis for the use of the ILI in lieu of hydrostatic testing for LF-ERW pipe.
Statistical Analyses of Incidents on Onshore Hazardous Liquid Pipelines Based on PHMSA Database
Authors: Liu Shengli , Liang Yongtu , Wang Xiao , Han Dong
Published: November 2018

To improve the safety of a pipeline system, engineers use different methods to diagnose the hazardous pipeline accidents. However, most methods ignore the time dependence of pipeline failures. The aim of this paper is to provide a novel approach to analyzing the hazardous liquid pipeline incidents’ temporal structure. The database of hazardous liquid spillages from the US between 2002 and 2018 is collected by the Pipeline Hazardous Material Safety Administration of the US Department of Transportation. The result suggests that the whole oil pipeline incident sequence cannot be modeled as a Poisson (random and independent) process, which means that a hazardous liquid pipeline incident is not statistically independent from the time elapsed since the previous event. But the serious pipeline failures are random and unpredictable. The analysis also indicates that the equipment failure, corrosion, material failure and incorrect operation are the four leading failure causes, responsible for most of the total incidents. The study provides insights into the current state of hazard liquid pipelines in the US and baseline failure statistics for the quantitative risk assessments of such pipelines.
Root Cause Analysis of an Above-Ground Pipeline With Stress Corrosion Cracking
Authors: Ralston Kevin D. , Padgett Barbara N. , Norfleet David M. , Cao Liu , Delanty Burke S. , Klages Mark B. , Beavers John A. , Prewitt Thomas J.
Published: November 2018

A comprehensive metallurgical investigation of multiple, externally-initiated, in-service leaks on an above-ground, oil emulsion (multiphase) pipeline concluded that the crack-initiating mechanism was stress corrosion cracking (SCC). A technical root cause analysis (RCA) was performed, utilizing faults trees, to evaluate the potential contributors to the SCC from the time of construction through the identification of the first in-service leak. This paper outlines the RCA findings and current understating of the primary contributors given that SCC on above-ground, insulated carbon steel pipelines has not previously been reported.
Effect of Initial Bainite Microstructure on Tensile Properties After Long-Term Exposure at Elevated Temperature
Authors: Shimamura Junji , Ota Shusaku , Yokota Tomoyuki , Muraoka Ryuji
Published: November 2018

In the oil sand production field in Canada, steel pipes are used for injecting steam into the sands. Pipes for steam distribution are subjected to high operating temperature such as 350 degrees C for a long time. In this study, in order to insure the reliability of high strength pipe for steam distribution, long-term heating tests were conducted for X80 grade UOE pipe. To simulate the long-term operation at 350 degrees C for 40 years, accelerated tests were conducted at 400 degrees C for up to 4400 hours. The effect of initial bainite microstructure on tensile properties after long-term heat treatment was investigated by using two kinds of steel pipes with different bainite microstructure. One is accelerated cooling (ACC) type, and the other is heating on-line process (HOP) type just after accelerated cooling in plate manufacturing process.

It was revealed that strength decrease in ACC type steels produced by only accelerated cooling was mainly governed by decomposition of hard phase MA (Martensite-Austenite constituent) and recovery of dislocations. On the other hand, HOP type steels had small amount of MA and nanometer-sized carbides by applying HOP after accelerated cooling. The HOP type steels had almost the same initial strength in spite of small amount of MA. Fine niobium carbides gave enough precipitation strengthening. Formation of fine niobium carbides was promoted by the addition of niobium. The precipitates were stable after long-term heat treatment at 400 degrees C. It is confirmed that the fine niobium carbides in HOP type steels remained even after long-term heat treatment. The suppression of initial MA also lead to minimize the strength decrease by MA decomposition. Therefore, HOP type steels tend to have higher resistance to the strength decrease after long-term heat treatment.
A Sensitivity Study: Effects of Toughness Values on Fatigue Crack Growth Analysis of Just-Survived Flaws Following a Pressure Test
Authors: Ellinger Matt , Lutz Andy , Bubenik Tom , McMahan Tara
Published: November 2018

The Pipeline and Hazardous Materials Safety Administration (PHMSA) issued a Notice of Proposed Rulemaking (NPRM)1 on April 8, 2016 that is expected to have an impact on the pipeline industry’s approach to crack growth analyses. Specifically, the NPRM defines values for pipe toughness that should be used in analyzing crack anomalies that are subjected to fatigue growth for instances in which known or measured pipe toughness values are not available. Pipeline Operators conduct these types of analyses to derive remaining life values which can in turn be utilized to establish pipeline integrity reassessment intervals. Thus, the impacts of this NPRM are felt by all pipeline operators who own assets in which cracking is considered a threat. The goal of this paper is to quantify the effects of using the NPRM defined toughness values in pressure test assessments for scenarios where pipe toughness values are unavailable.
Exceeding Limitations: Ultrasonic Crack Inspections Become Feasible for Liquid Natural Gases
Authors: Hennig Thomas , Guajardo Rogelio , Suarez Ernesto , Haro Victor , Haberl Peter
Published: November 2018

Ultrasonic crack inspection services have become a standard solution for pipeline integrity programs, especially for liquid pipelines. ILI tools provide reliable and accurate data for assessment of axial and circumferential cracking defects to derive educated decisions on the integrity and maintenance of the asset. This technology inspects common media such as crude and light oils, water, diesel, benzene, or similar. Running tools in mediums used for commercial operations does not affect the throughput of the line. Crude and light oils, water, diesel, benzene etc. have relatively constant ultrasonic characteristics with varying pressures and temperatures and are very suitable for ultrasonic inspections, therefore called common media within the context of this paper.

If the medium in the pipeline does not fall within the common media, the situation changes. These media are called challenges media. Especially for liquefied natural gases (LNG) or liquefied petroleum gases (LPG) where temperature and pressure have a significant impact on the ultrasonic characteristics of speed of sound, density, and attenuation. LNGs and LPGs typically contain high amounts of propane, butane, and some other higher order alkanes. Due to the high variability of these components to external boundary conditions, inline inspections in these type of pipelines are usually performed by replacing the medium with a more feasible one, e.g. water or diesel. This causes significant impact to productivity and throughput and increases costs and efforts.

The authors will present the work performed to overcome and solve this workaround and run an ultrasonic crack inspection tool in LNG. This paper highlights the challenging aspects considered to successfully perform inline inspections in LNGs. We will present a standardized and systematic approach to overcome limitations of the technology in such media. Starting with the challenges and ideas for enhancement of the service, the paper will discuss the design of the experiment, the experiment itself, the results, and present the conclusions that resulted in the tool development and the analysis procedure. Finally, the authors will present the application of the enhanced service in a customer pipeline, including ILI preparation, execution, analysis, and in-the-ditch verifications.

The structured and systematic approach allows the inspection company to perform successful and reliable crack detection inspections in LNG lines. This includes axial and circumferential cracking threats.
Advanced Constitutive Model for the Accurate Evaluation of the Structural Performance of Welded Pipes in Offshore Applications
Authors: Cooreman Steven , Van Hoecke Dennis , Liebeherr Martin , Thibaux Philippe , Luccioni Hervé
Published: November 2018

To guarantee the structural integrity of oil and gas transporting pipelines, a detailed analysis of the pipe’s structural response has to be performed. This is of particular importance for offshore applications. As large scale testing is costly and time consuming, one often relies on FE (Finite Element) modelling to accomplish, at least, part of this task. Properties that typically need to be evaluated are compressive strain capacity, collapse resistance and ovalization during reel-lay installation. Furthermore, it can be assumed that those properties are influenced by the pipe forming process, as pipe forming will change the mechanical properties and the level of anisotropy and will modify/introduce residual stresses. Therefore, a first logical step is to simulate pipe forming before evaluating the pipe’s structural performance, to account for these effects.

The reliability of FE simulations largely depends on the capability of the constitutive model to accurately describe the mechanical behaviour of the material being studied. Most commercial FE codes only offer combined kinematic-isotropic hardening models. Those models cannot capture the so-called cross-hardening effect and can therefore not predict the evolution of anisotropy during pipe forming. The present paper discusses the implementation and calibration of a more advanced constitutive model, more specifically the Levkovitch-Svendsen model, which accounts for isotropic, kinematic and distortional hardening. The model was implemented in Abaqus/Implicit through a UMAT user subroutine. An inverse modelling approach was applied to calibrate the constitutive model, whereby an extensive set of mechanical tests, involving cyclic tension-compression tests and tests with changing strain paths, was conducted.

To assess the model’s performance, it was used in two case studies. The first study focused on the evolution of mechanical properties during spiral pipe forming. The results show that the Levkovitch-Svendsen model allows prediction of the properties in both the transverse and longitudinal direction on pipe. When applying a kinematic-isotropic hardening law only, the properties in the longitudinal direction are significantly underestimated. In the second study, different hardening models were used to predict the evolution of ovality during reel-lay installation. It was observed that the predictions made with the Levkovitch-Svendsen model were much closer to the experimental values than the results obtained by means of a kinematic-isotropic hardening model.
An ILI Based Program That Prevents Reoccurrence of Post ILI Failures Seen in Industry
Authors: Huang Terry , Kariyawasam Shahani
Published: November 2018

The pipeline industry has been using Inline Inspection (ILI) since the 1970s. High resolution tools have been available for inspecting corrosion from about the 1980s and related ILI-based programs have been evolving. In this study incident rate data from the last 30 to 40 years of experience was examined and trended.

Corrosion related incident rates have reduced where ILI programs have been implemented. Significant changes in programs have shown related incident reductions or positive trends. Throughout this time there have been a few post-ILI incidents and by taking a closer look at these incidents and learning from the findings the ILI-based assessments and programs were further improved.

In this study, all of the post-ILI corrosion related ruptures on the TransCanada system have been closely examined and trended. The effects of program changes and related changes to performance indicators have been examined. Some significant industry failures, where data is publicly available, have also been examined. These failures have been analyzed and trended to understand significant commonalities between these failures.

Data was analyzed with the intention of learning from them and applying this learning to avoid similar failures in the future. By understanding the uncertainties, technology limitations, and limits of applicability as well as the types of programs used and where these have not identified probable failures practical solutions were derived. All of the failures have been examined (as allowed by the data available) to find approaches which would have proactively identified these events, so that similar events can be avoided in the future.

ILI tools generate a wealth of information and appropriate use of this information has shown to be effective in managing pipelines. However, it is also important to understand the limitations of technologies, learn from the failures, and acknowledge uncertainties so that undesirable events can be avoided.
Development of Reliability-Based Criteria for Corrosion Assessment
Authors: Adianto Riski , Nessim Maher , Lu Dongliang
Published: November 2018

Reliability-based corrosion assessment criteria were developed for onshore natural gas and low vapor pressure (LVP) pipelines as part of a joint industry project. The criteria are based on the limit states design (LSD) approach and are designed to achieve consistent safety levels for a broad range of pipeline designs and corrosion conditions.

The assessment criteria were developed for two corrosion limit states categories: ultimate limit state, representing large leaks and ruptures; and leakage limit state, representing small leaks. For the ultimate limit state, a safety class system is used to characterize pipelines based on the anticipated severity of failure consequences as determined by pressure, diameter, product, population density and environmental sensitivity. Since the leakage limit state does not result in significant safety or environmental consequences, a single reliability target, applicable for all pipelines at all locations is used.

The assessment criteria formulations are characterized by three elements: the equations used to calculate the characteristic demand (i.e. operating pressure) and capacity (i.e. burst pressure resistance at a corrosion feature); the characteristic values of the key input parameters for these formulas (such as diameter, pressure and feature depth); and the safety factors defining the characteristic demand as a ratio of characteristic capacity. The process used to calibrate safety factors and characteristic input parameter values that meet the desired reliability levels is described, and an assessment of the accuracy and consistency of the resulting checks in meeting the reliability targets is included.

The assessment criteria include two methods of application: feature-based and section-based. The feature-based method divides the allowable failure probability equally between all features. It is simple to use, but conservative in nature. It is suitable for pipelines with a small number of corrosion features. The section-based method considers the failure probability of the corrosion features in a pipeline section as a group, and ensures that the total group failure probability is below the allowable threshold for the section. This method produces less conservative results than the feature-based method, but it requires more detailed calculations. It is suitable for all pipelines, and is particularly useful for those with a large number of features. The practical implications of the application of these criteria are described in the companion paper IPC2018-78608 Implementation of Reliability-based Criteria for Corrosion Assessment.
Experimental Evaluation of Blasting Near Pipelines
Authors: Gossard Justin , Waters Steven A. , Finneran Shane
Published: November 2018

Construction blasting was proposed as a technique to create a trench for a new pipeline within the right-of-way (ROW) of an existing vintage pipeline where soil conditions consisted primarily of rock. Several field experiments were conducted to assess the potential loading conditions that the vintage pipeline could experience due to various blasting configurations as part of the nearby construction process. Two test pipe segments were constructed from segments removed from the vintage pipeline for use in these experiments. Each test segment contained two vintage bell-bell chill ring girth welds (GW) and were pressurized to operating conditions of the vintage pipeline for the duration of all blasting. Groups of eight resistive strain gages were bonded around the exterior surface of three distinct locations on each test segment. The three locations include one pipe body location and each of the two welds on each segment.

Four separate experiments were conducted with each experiment focusing on a unique combination of trench backfill material, compaction level and separation distance from the test pipe segments and the explosive charges. The primary objective throughout these four experiments was to monitor and record the behavior of buried test pipe sections due to nearby blasting activities. Long range 3-dimentional (3D) laser scanning equipment was used to track movement of each test segment from test to test. High-speed video equipment was also employed to capture each blast. The high-speed video provided additional details on the blast energy transfer, verification of individual charge initiation as well as pipeline test segment movement where each pipeline segment was exposed. Peak particle velocity measurements were taken during each test blast. Strain data collected during each test was used to assess potential damage to the vintage pipeline test segments as a result of blasting.

The combined information collected from the in-field testing showed that elevated strains and stresses may be observed during blasting activities near pipelines.