bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Microstructural Change on Fracture Behavior in Heat-Affected Zone of API 5L X65 Pipeline Steel
Authors: Ju Jang-Bog , Jang Jae-il , Kim Woo-sik , Kwon Dongil
Published: October 2016

Reliability evaluation of welded structures by mechanical testing of weld heat-affected zones (HAZs) has become general practice throughout the world. HAZs of steel welded joints show a gradient of microstructure from the fusion line to the unaffected base metal. This study is concerned with a correlation between the microstructural change and the fracture characteristics in HAZs of both seam and girth welds of API 5L X65 pipeline steel, which is generally used for natural gas transmission pipelines in Korea. The focus in present study was the investigation of macroscopic fracture behavior of the various regions within HAZ. Changes in microstructure and impact toughness were observed using synthetic HAZ specimens as well as actual HAZ specimens. To evaluate the macroscopic toughness of actual HAZ, Charpy V-notch impact test was performed.
Microstructure of Microalloyed Linepipe Steels
Authors: Sharma Udit , Ivey Douglas G.
Published: October 2016

The aim of this study was to characterize the microstructure of microalloyed linepipe steels. The steels investigated were X70 (0.04 wt% C - 0.02 wt% Ti - 0.07 wt% Nb) and X80 (0.04 wt% C - 0.025 wt% Ti - 0.09 wt% Nb) steels, where the numbers refer to their specified minimum yield strength (SMYS) in ksi. This class of steels has the advantage of high strength and good toughness combined with minimal wall thickness (15.5 mm for X70 steel). These attributes result in considerable cost savings when installation of several hundreds of kilometers of pipeline is required for oil and natural gas recovery and transport.

The present study focused on phase identification and quantification, distribution of alloying elements and inclusions and segregation effects. Both steels were primarily composed of a mixed ferrite structure, i.e., polygonal ferrite and acicular ferrite/bainite, with characteristic low angle grain boundaries and high dislocation densities. The proportion of acicular grains was higher for the X80 steel. Pockets of retained austenite, exhibiting a Kurdjumov-Sachs orientation relationship (KS-OR) with the adjoining ferrite, were found in both steels.

Five general classes of precipitates were identified in both steels: 1) Very large (2–10 μm) cuboidal TiN particles nucleated on inclusions; 2) large (0.1–1.0 μm) cuboidal TiN particles; 3) medium sized (30–50nm), irregular shaped Nb-Ti carbonitrides; 4) fine (<20nm), rounded precipitates of Nb carbonitrides with traces of Mo; 5) very fine dispersed precipitates (<5 nm in size). For X80 steels many of the large TiN precipitates were observed with Nb-rich carbonitrides precipitated epitaxially on them.

Inclusion content and morphology were analyzed in both steels. The inclusions in X70 steels were found to be primarily CaS with significant amounts of Al, O, Ti, Fe and Mn. They were essentially spherical in shape with small elliptical distortions along the rolling direction and across the width of the plate. The morphology of the inclusions in the X80 steel was very similar, however, they showed higher Mn levels.
Performance of Insulated Pipelines in Sub-Arctic Conditions
Authors: Alexander Mike , D’Agostino Carmine
Published: October 2016

In the conditions of sub-Arctic winter it is not unusual for the ambient temperatures to drop as low as −40°C. Insulated pipes overcoated with extruded polyethylene may fail, sometimes drastically due to mechanical impact which can rupture the outer polyethylene layer and damage the polyurethane foam.

A systematic investigation into the main reasons for this failure mode was conducted, resulting in specific recommendations to permanently solve this problem.
Wear- and Corrosion-Resistant Ceramics for Protection of Pipelines and Rotating Equipment
Authors: Medvedovski Eugene , Marchant David D.
Published: October 2016

Engineering ceramics have a growing application potential for the wear- and corrosion protection of piping systems and for manufacturing of working parts of rotating equipment in mining and -mineral industries, including oil, gas, coal, ores, and others. The alumina, zirconia, alumina-zirconia, and silicon carbide-based engineering ceramics developed and manufactured by Ceramic Protection Corporation used for extraction, processing, conveying, and dust collection equipment are reviewed. These ceramics have high hardness (greater than the majority of processed materials) and mechanical strength, moderate fracture toughness (fracture toughness of zirconia ceramics is close to metal fracture toughness), excellent wear- and corrosion resistance, ability to withstand high temperatures (greater than 1000°C) and thermal shocks. These ceramics successfully withstand various solid and liquid abrasive media transported at high velocity and turbulence, under high pressure and cavitation. In terms of wear- and corrosion resistance ceramics are significantly stronger than hard steels widely used in the piping systems, and may successfully replace hard metals such as tungsten carbide. The features of the compositions, microstructure, and properties of these ceramics are considered. The wear test results are discussed; the factors effected wear resistance are emphasized. In dependence on the working conditions and the product design, a ceramic material may be chosen or developed in each particular case.

The manufacturing processes of the considered ceramics and the installation technique are described. These ceramics are produced on the large-scale basis, and the parts may be manufactured in accordance with the customer design and requirements. The ceramic components may be manufactured as monolithic bodies, including bodies with the complicated shapes, or as tiles; in both cases they are easily installed into equipment. The main features of the ceramic product design are discussed. Pipe lining, including elbows, T- and Y-sections, cyclones and reducers, nozzles, pump parts, seals, valves, and others made from these ceramics are successfully used in the most important sections of piping systems and rotating equipment. The use of the ceramics reduces the wear- and corrosion problems, increases the life cycle of equipment without damage and shutdowns.
The Application of the Battelle “Short Formula” to the Determination of Ductile Fracture Arrest Toughness in Gas Pipelines
Authors: Rothwell A. B.
Published: October 2016

Many models and formulae have been put forward, over the years, for the determination of the toughness necessary for the arrest of propagating ductile fracture in gas pipelines. One of the first, and most prominent, was that developed by Battelle Columbus Laboratories for the Pipeline Research Committee of the American Gas Association. As originally embodied, the model involved the comparison of curves expressing the variation of fracture velocity and of decompression wave velocity with pressure (the “two-curve model” — TCM). To aid in analysis, at a time long before a computer was available on every desk, a “short formula” (SF) was developed that provided a good fit to the results of the TCM for a substantial matrix of conditions. This SF has subsequently been adopted by several standards bodies and used widely in the analysis of the results of full-scale burst tests. Since the original description of the derivation of the SF is to be found only in a report to the PRC dating back to the Seventies, many in the pipeline industry today are left without a full appreciation of its range of validity. The present paper briefly discusses the original intent of the SF as a substitute for the TCM, and presents the results of extensive calculations comparing the results of the two. It can be concluded that the SF provides an excellent estimate of the results of the TCM over a very wide range of design and operating parameters, within the limitations inherent in the method.
An Interim Approach to Determine Dynamic Ductile Fracture Resistance of Modern High Toughness Pipeline Steels
Authors: Pussegoda N. , Malik L. , Dinovitzer A. , Graville B. A. , Rothwell A. B.
Published: October 2016

The ductile fracture toughness of steel is used to assess the ability of a pipeline to resist long running ductile fractures in a burst event. In modern low carbon clean steels with high toughness, conventional measures of ductile fracture toughness (standard Charpy and DWTT energy) are under review, and alternatives are being studied. The major factor causing concern is the inability of these tests to isolate the energy associated with crack propagation from the total energy absorbed during the specimen fracture. This is significant in modern high toughness steels because their initiation toughness is extremely high.

To resolve crack propagation energy, a novel modification was evaluated for both Charpy and DWTT specimens by employing a back-slot including a snug fitting shim to replace the removed material. In most cases, this modification was effective in curtailing the load-displacement trace when the propagating crack interacted with the slot on the backside of the specimen, without affecting the initial portion of the trace; this allowed crack propagation energies to be resolved. The propagation energy determined by this method is compared with the total energy and conventional test parameters. The crack propagation energy values inferred based on this should be validated, in future burst test.
Review of CTOA as a Measure of Ductile Fracture Toughness
Authors: Pussegoda L. N. , Verbit S. , Dinovitzer A. , Tyson W. , Glover A. , Collins L. , Carlson L. , Beattie J.
Published: October 2016

The ductile fracture toughness of steel is used to assess the ability of a pipeline to resist long running ductile fractures in a burst event. With the introduction of modern low carbon clean steels with ultra high toughness, conventional measures of ductile fracture toughness (standard Charpy and DWTT energy) are under review, and alternatives are being studied. The crack tip opening angle (CTOA) was investigated to evaluate its appropriateness as a measure of modern pipeline steel ductile fracture toughness. At first, fracture mechanics tests at quasi-static rate were analyzed to examine the constancy of CTOA with crack growth. The results of this initial review are based on four pipeline steels with a range of ductile fracture toughness. The CTOA values are also compared with appropriate parameters from conventional tests to examine potential relationships that may be used to indicate the relative resistance of pipeline steels to ductile fracture propagation. The final objective is to compare CTOA values determined by the simple two specimen method and those developed through a formal fracture mechanics based technique.
Effects of Prestrain on Fracture Toughness and Fatigue-Crack Growth of Line Pipe Steels
Authors: Hagiwara Naoto , Masuda Tomoki , Oguchi Noritake
Published: October 2016

To investigate the failure mechanism of pipelines subjected to mechanical damage, Charpy impact, crack-tip-opening displacement (CTOD) and fatigue-crack growth tests were carried out for six series of line pipe steels with uniaxial plastic prestrain, εpr. The Charpy absorbed energy and critical CTOD (δc) decreased with increasing |εpr|; ln δc = α εpr + β. The derivative, dδc/dεpr, was dependent on the ductile-to-brittle transition temperature of the steels. In the CTOD tests, the prestrain caused ductile-to-brittle transition for the steels with a higher transition temperature. The effects of the compressive εpr on both the reduction of δc and ductile-to-brittle transition were larger than those of the tensile εpr. The compressive εpr accelerated both the fatigue-crack initiation and growth.
On Longitudinal Propagation of a Ductile Fracture in a Buried Gas Pipeline: Numerical and Experimental Analysis
Authors: Berardo G. , Salvini P. , Mannucci G. , Demofonti G.
Published: October 2016

The work deals with the development of a finite element code, named PICPRO (PIpe Crack PROpagation), for the analysis of ductile fracture propagation in buried gas pipelines. Driving force estimate is given in terms of CTOA and computed during simulations; its value is then compared with the material parameter CTOAc, inferred by small specimen tests, to evaluate the toughness of a given line pipe. Some relevant aspects are considered in the modelling with the aim to simulate the real phenomenon, namely ductile fracture mechanism, gas decompression behaviour and soil backfill constraint. The gas decompression law is calculated outside the finite element code by means of experimental data from full-scale burst tests coupled with classical shock tube solution. The validation is performed on the basis of full-scale propagation experiments, carried out on typical pipeline layouts, and includes verification of global plastic displacements and strains, CTOA values and soil-pipe interaction pressures.
Design, Development and Confirmation of a High Toughness Gas Line Pipe for Alliance Pipeline at Camrose Pipe Company
Authors: Afaganis Alex J. , Mitchell James R. , Carlson Lorne , Gilroy-Scott Alan
Published: October 2016

Through 1999, Camrose Pipe Company manufactured ∼152 km (∼45 000 tonnes) of 1067 × 11.4mm pipe for Alliance Pipeline Partnership Ltd. This section of Alliance’s pipeline was manufactured to a design whose pipe fracture toughness requirements was significantly beyond those historically manufactured in Canada and initiated a major leap in plate/pipe manufacturing toughness capability. The development of line pipe toughness in Canada culminating in this order will be profiled.

Further, this high toughness design is at the far reaches of the traditional fracture arrest models. Besides the traditional Charpy energy measure, and to confirm Alliance’s confidence in their fracture arrest design, another two sets of fracture assessment tests were used on a trial and production basis: the API chevron notch drop weight tear test (CN DWTT) energy and the energy of a similar test using an Alliance notch modification. The results of these tests will be reviewed and compared.
Pipeline Maintenance in Geotechnically Unstable Areas: A Case Study
Authors: Sorensen Michelle L.
Published: October 2016

The 22″ Alberta Oilsands Pipeline transports synthetic crude oil from Syncrude Canada Limited in Fort McMurray to Edmonton, Alberta. The pipeline crosses the House River approximately 100 kilometers south of Fort McMurray.

The slope has been monitored since 1991 by three slope indicators. A finite element stress analysis indicated that total ground movement since installation in 1977 could correspond to pipeline compressive strains in excess of 0.32%, a level of risk unacceptable to the pipeline owner.

A probability-based model was developed to determine cost and benefit of risk mitigation options. Parameters such as soil movement and pipe strain were input as probability distributions. The mitigation options included: reduce slope instability; reduce pipe stress; reduce pipe-to-soil interaction; implement long term monitoring; determine current pipe strain level (to decrease data uncertainty); do nothing.

A Monte Carlo simulation was used to establish probability of failure and probable cost distributions for each option. The results were presented as a combined cost of failure and mitigation over 10 years.

The analysis indicated that the optimum solution was to remove the existing soil traction loading on the pipe and mitigate long-term slope movement. The decision was made to relieve the pipe strain by excavating. Current pipe strain was measured in situ using residual strain measurement. Long term strain gauges were installed. Slope mitigation was deferred until the strain gauges indicate total pipeline strain levels approaching 0.32%.
Wave Propagation Versus Transient Ground Displacement as a Credible Hazard to Buried Oil and Gas Pipelines
Authors: Honegger Douglas G.
Published: October 2016

In 1997, a research project was initiated by Southern California Gas Company, Pacific Gas and Electric Company, with support from Tokyo Gas, Osaka Gas, and Toho Gas, to investigate the cause of natural gas pipeline damage during the 1994 Northridge earthquake. As part of this research activity, extensive field and laboratory investigations were performed on a 1925 gas pipeline that suffered several girth weld failures in Potrero Canyon, a remote and unpopulated area just north of the Santa Susana Mountains. The pipeline is operated by the Southern California Gas Company, one of the principle sponsors of the gas utility research project.

The investigations into the performance of the pipeline were largely prompted by questions regarding the cause of pipeline damage. Although ground cracking and sand boils were observed in Potrero Canyon following the Northridge earthquake, there were no clear signs of permanent ground deformation near the locations of pipeline damage. Pipeline damage, consisting predominantly of girth weld tensile failure and two instances of buckling of the pipe wall, indicated that significant relative pipe-soil deformation might have occurred. Field investigations were unable to identify surface evidence of permanent ground deformation near the locations of pipeline damage and attention focused on the possibility that the damage could have been caused by wave propagation. This focus was based on the assertions of past researchers that pipelines with poor-quality oxyacetylene girth welds are susceptible to damage from wave propagation. The detailed investigation of The pipeline has concluded that wave propagation was not a significant factor in the pipeline damage and raises questions regarding wave propagation effects as a causative mechanism for pipeline damage in past earthquakes.

A simple analytical model of the transient ground deformation that may have occurred in the vicinity of the pipeline damage was found to provide insight into the cause of the ground cracking observed at the margins of Potrero Canyon, approximate magnitudes of differential ground displacements that may have occurred during the earthquake, and the reasons for the spatial distribution of pipeline damage. This model is proposed as the basis for identifying locations where similar earthquake effects can be identified in future hazard assessment studies.
Remedial Protection of a Pipeline Crossing of the River Wye, UK
Authors: Dean K. Bruce , Ade Femi , Sawatsky Les , Gray R. , Cutler John , Wheeler Neil
Published: October 2016

This project is of interest to those involved in construction, siting and repair of pipeline crossings of rivers, streams and estuaries. In early 1999, Mainline Pipelines Limited discovered that their pipeline crossing of the River Wye had been exposed by river scour. Originally laid in 1972, the line provides petroleum products main supply from the port at Milford Haven to the Midlands, England, and operates at a high pressure. A break in or temporary shutdown of the pipeline would have had serious implications. Remedial protection options were needed rapidly, to ensure the integrity of the pipeline. A review of historical air photographs and maps, dating back to 1888, showed that the meandering channel of the River Wye has shifted to the north at an average rate of 0.65m per year. Thus, the remedial works would have to account for ongoing vertical and lateral scour. It was recognized that river training works would be required at the site to ensure continued protection of the pipeline in the long-term. The recommended design and remedial construction techniques allowed for safety issues, the potential impact on the river ecology, recreational river users, the river hydrology and restricted access to the steep northern riverbank. The design comprised filling of the eroded riverbed and bank with rock aggregate and placing a protective layer of graded rock riprap. Grout filled fabric formwork bags were placed beneath the pipeline to minimise deflection and the development of unacceptable stresses in the exposed length during rock placement. Rock filled wire mattresses were placed immediately on top of the pipeline to protect it from point loading of the angular riprap. A satellite guided positioning system was used to control material placement, and environmental monitoring of river water quality was carried out continuously during construction.
Integrating GIS and GPS Into Today’s Pipeline
Authors: Hobbs David , Rummell Keith
Published: October 2016

Today’s tools and technologies allow the pipeline industry to collect information and describe company pipeline assets in a productive way. Rooney Engineering, Inc. recently completed a 130-mile crude oil pipeline in the greater Los Angeles area of California with which wide ranges of technologies were utilized over an 8-year period. Review of all phases of this pipeline project offers a unique glimpse of managing and integrating traditional survey and Global Positioning System (GPS) techniques with a Geographic Information System (GIS). While the first portion of the project used traditional methods of photogrammetry and Computer Aided Drafting (CAD) to complete the conceptual design and construction drawings, the second portion utilized a combination of CAD, GIS and GPS technologies to assist the construction team during construction and as-built. Geographically organized data was later applied beyond the phases of pipeline construction; data was later used in one-call, contingency planning and emergency response.

This paper will give an overview of the project, including pre-construction drawing preparation, construction zones, terrain types, political jurisdictions, and original staff assignments for data collection. The paper will discuss data dictionary design and management of collected field data, equipment and personnel requirements, and accuracy trade-off. The paper will examine the verification of data for attribute integrity and assignment of positional accuracy tags, along with specific methods of GPS and traditional data collection, while also exploring data management of incoming field data from multiple sources over an extensive timeline. Additionally, the paper will focus on the use of GIS to support construction monitoring and cost reconciliation analysis. Finally, we will review preparation of final drawings, summarize lessons learned, and discuss what the future offers in enhancing pipeline-mapping productivity.
Special Problems in Pipeline Risk Assessment
Authors: Bercha Frank G.
Published: October 2016

The paper presents case studies of pipeline risk assessments for special situations such as multiple pipelines in a common trench, pipelines adjacent to other hazardous facilities, and segments of special construction such as major water crossings. For such situations, the relatively straightforward risk assessment applicable to single pipelines in normal conditions is not applicable. Rather, one must generate a special analytical approach case by case to deal with those aspects of the risk assessment which vary from those of the normal situation. In this paper, following a brief introduction, a series of case studies for special problems in pipeline risk assessment based on real projects completed by the authors, is given, followed by conclusions and recommendations.
Determination of Pipe Roughness and Heat Transfer Coefficient in Pipeline Networks Using Multidomain Solution Method
Authors: Jelen Jaroslaw A. , Golshan Hossein
Published: October 2016

The multidomain model, which has already been developed for the simulation of large networks, is being used to determine the surface roughness and heat transfer coefficient for two parts of the TransCanada system.
Use of Robotic Technology for Cast Iron Pipeline Repair
Authors: Elliott Ron , Szilard Steve , Prattinger Gunther
Published: October 2016

Prior to the introduction of plastic pipe many gas utilities used cast iron to build their gas distribution network. Currently, there is approximately forty thousand kilometres of cast iron pipe in service in North America and a further two hundred thousand kilometres in Europe. Mostly found in dense urban locations, the cost of replacing these systems can be significantly high, such that extending the life of these systems is now a common strategy. The main problem has been leakage from bell and spigot joints caused by road vibration, freeze/thaw cycles of the ground, and the swelling and drying of clay soils.

Repair technologies have evolved from mechanical joint clamps, to elastomeric seals, to shrink sleeves, to encapsulants and finally to anaerobics. The most advanced of these technologies involve the use of anaerobic sealants which are injected into the jute packing by drilling into the pipe bells. These sealants have been studied at Cornell University for longevity, and are predicted to withstand many years of service.

The use of anaerobics has been adapted to work with robotics that allows the injection to take place from the inside of the pipeline while the gas main is in operation. This technology allows 24 joints to be sealed from a single excavation. The robot is a tethered electro-mechanical device that allows visual location of the joint, internal drilling into the jute packing, and injection of the sealant. A semi-rigid umbilical cable contains the electrical, hydraulic, and communication lines, and a unique drive mechanism that allows for remote operation and positioning.

The development of this prototype technology was conducted by Engineering Services Inc. (ESI) of Toronto at the request of Enbridge Consumers Gas and was co-funded by Consolidated Edison of New York. Over 2000 joints have been successfully sealed in the last two years and the system is expected to be commercially available within the next year. Internal robotic repair of live mains is an industry first and has the potential to significantly reduce both costs and disruption of road excavations in urban areas.
Highly Tensioned Suspended Pipelines
Authors: Smith Robert E. , Hart James D. , Powell Graham H. , Zulfiqar Nasir
Published: October 2016

In 1996, ARCO Technology and Operations Support (ARCO TOS) began considering Highly Tensioned Suspended Pipelines (HTSPs) as a promising concept for above ground, cross-country pipelines in Arctic regions. HTSPs resemble high voltage, cross-country power lines. Similar construction methods and support towers are used. The primary differences are that the pipelines are larger in diameter and are supported against out-of-plane wind loads. Three years of development work are summarized in this paper. This work includes analytical modeling, pipeline code compliance, conceptual design of components, and construction studies. Fatigue resistance under North Slope Alaska wind conditions is estimated. HTSPs are judged to be technically feasible and a cost effective alternative to traditional elevated pipelines.
Simulation of Transient Liquid Pipeline Flow Using the Deformable Characteristic Grid
Authors: Kossatz Helmut
Published: October 2016

This study describes the numerical solution and computational implementation of the isothermal transient flow of several different compressible liquids contained in a single elastic pipeline. The method of characteristics is used to integrate the equations of conservation of mass and momentum along the deforming Eulerian characteristic mesh. Integration along the deforming mesh, which is generated as integration proceeds in time, minimizes the need for interpolation so that problem variables are accurately determined at the computed mesh points. On the other hand, since calculated mesh points are not regularly spaced in the x-t plane, interpolations among the computed points become necessary to find the value of variables at a given fixed instant of time along the length of the pipeline. The computational implementation allows for the simulation of flow across locations where there may be changes in nominal pipe diameter, valves or pumps, as well as tracking the position of fluid interfaces as different batches of fluid move along the pipeline, and results are found to be numerically accurate and stable.
Transient Pig Motion Through Non-Isothermal Gas and Liquid Pipelines
Authors: Nieckele A. O. , Braga A. M. B. , Azevedo L. F. A.
Published: October 2016

Simulation of the dynamics of pigs moving through non-isothermal pipelines is presented. The differential mass, linear momentum and energy equations were numerically solved by a finite difference numerical scheme, for compressible flow through pipelines. The fluid flow equations were combined with an equation representing a force balance on the pig. Pressure forces developed due to flow through by-pass holes in the pig, pig acceleration and pig/pipe contact forces were considered. A stick/slip model was developed to account for the distinct friction regimes that prevail depending on whether the pig is stopped or in motion. An adaptive grid technique was employed to account for the moving pig. Heat losses to the ambient play an important role in the fluid temperature distribution. However, for the test cases conducted, the temperature variations caused virtually no effect on the pig dynamics.
New Technical and Economic Solutions for Gas Exploitation in the Amazon Region (Peru-Brazil Pipeline)
Authors: Carrera Guido Z. , dos Santos Edmilson M.
Published: October 2016

The Amazon region has been demonstrating a great oil and gas potential in Brazil and in the neighboring countries, specially the field of Camisea in Peru. However, the development of feasible and economically justifiable transport systems, that can allow the flow of those resources to their potential markets, continues to be the great challenge. In this work, we present some options that can be transformed into competitive and commercial projects. We describe different gas pipeline options, discussing their technical, economic and commercial aspects.
UV Degradation of Fusion Bonded Epoxy Coating in Stockpiled Pipes
Authors: Cetiner Matt , Singh P. , Abes J. , Gilroy-Scott A.
Published: October 2016

Sunlight exposure is known to cause degradation in polymer coatings. However, quantitative data relating exposure to mechanical and corrosion properties is missing. Thus, it is very difficult for pipeline operators to make fair assessment of the impact of stockpiling coated pipe on project economics and pipeline integrity. As a result, a study was undertaken to quantify the effects of sunlight exposure on Fusion Bonded Epoxy (FBE) coating on stockpiled pipe. Sections of production pipe stockpiled in the southern Alberta area for the Alliance Pipeline project was selected, and a plan to evaluate the coating properties at periodic exposure intervals, to a total duration of approximately 2 years was implemented. The coating was tested at both full sunlight exposure condition (12 o’clock position) and with minimal exposure condition (6 o’clock position). The properties evaluated include residual coating thickness, cathodic disbondment, adhesion, flexibility, and impact. These tests were carried out following procedures in CSA Z245.20–98 standard. Results after 15–21 months of aging indicate that the coating with full sunlight exposure, had a reduction in thickness, flexibility and loss of gloss with chalking due to degradation of the FBE coating by the UV radiation. However, there were no significant differences for cathodic disbondment, adhesion, and impact properties compared to the 6 o’clock position.
Detection and Verification of SCC in a Gas Transmission Pipeline
Authors: Ashworth B. , Uzelac Neb , Willems H. , Barbian O. A.
Published: October 2016

Two sections of a 914mm OD (36 in.) TransCanada (TCPL) gas transmission pipeline (predominantly with 9.14 mm wall thickness) were inspected using an ultrasonic liquid coupled crack detection In-Line Inspection (ILI) tool. One of the objectives of the inspection was to establish the condition of the pipeline sections with a known history of stress-corrosion cracking (SCC). Under test was the practicability of inspecting a gas line using a liquid coupled ILI tool, specifically its ability to detect and size defects deeper than 1 mm and distinguish cracks and crack-like defects from other types of anomalies, such as inclusions and laminations. In order to assess the confidence level of the tool, both sections were inspected in two independent runs and the repeatability of inspection was assessed. Cracks and crack-like defects with depths greater than 12.5% of the wall thickness from both runs were compared and correlation was established to assess repeatability. The accuracy of tool predictions was verified in excavations in both sections. 40 reported features, varying in depths up to over 40% were examined with respect to location, type, and size. Examples of defect patterns are shown to demonstrate the accuracy of the inspection method.
Influence of Line-Pipe Steel Metallurgy on Ductile Tearing of Stress-Corrosion Cracks During Simulated Hydrostatic Testing
Authors: Brongers Michiel P. H. , Beavers John A. , Jaske Carl E. , Delanty Burke S.
Published: October 2016

Hydrostatic testing is one method to confirm the integrity of pipelines containing colonies of stress-corrosion cracks. Although this technique is widely used, a concern of the pipeline industry is the potential for ductile tearing damage of subcritical flaws in pipes with cracks in the base metal and in the welds. The objectives of the current study were to determine the amount of ductile tearing and crack tip blunting that may occur at the crack tips of flaws that survive a hydrotest and to evaluate the influence of metallurgy on the extent of ductile tearing. In this research, stress-corrosion cracks (SCC) were grown in a near-neutral-pH environment in compact tension (CT) specimens made from two heats of X-65 line-pipe steel and one heat of X-52 line-pipe steel with an electric resistance weld (ERW). Simulated hydrostatic tests were performed on these specimens at loads that corresponded to hoop stresses at and above the specified minimum yield strength (SMYS) of the pipe steel, resulting in applied J-integral values near and above J(Q). Some specimens ruptured; some did not fail. Crack tip blunting and the extent of tearing were evaluated. Based on curve fits of the data collected from the CT specimens, the CorLAS™ software was utilized to predict the maximum amount of tearing for cracks of varying flaw dimensions and hydrostatic pressures.
Experimental Database for Corroded Pipe: Evaluation of RSTRENG and B31G
Authors: Cronin Duane S. , Pick Roy J.
Published: October 2016

The evaluation and development of the current corrosion defect assessment procedures for pipelines has been based on experimental burst tests of line pipe. In these tests, external corrosion has often been simulated with machined defects of simple geometry. As a result, assessment procedures which model the corrosion defect geometry with only a few parameters, such as ASME B31G, show reasonable agreement with the experiments. However, the degree of conservatism in these assessment methods is undefined when they are applied to complex corrosion defects. The authors have burst over 40 pipes removed from service due to corrosion defects. All corrosion defects on each pipe were measured in detail and the material properties were determined from tensile tests. The currently accepted assessment procedures for corroded line pipe (B31G and RSTRENG) have been applied to the database. The degree of conservatism in these procedures is quantified and a statistical model for the failure predictions is proposed.
Development of an Alternative Criterion for Residual Strength of Corrosion Defects in Moderate- to High-Toughness Pipe
Authors: Stephens Denny R. , Leis Brian N.
Published: October 2016

This paper presents the development of a new, simplified criterion, known as PCORRC, for prediction of the remaining strength of corrosion defects in moderate- to high-toughness pipeline steels that fail by plastic collapse. Comparisons against an experimental database indicate that, when toughness is sufficient, the PCORRC criterion reliably predicts the remaining strength of blunt defects using only the maximum depth and maximum length of the defects with less excess conservatism than existing criteria. The value of PCORRC is demonstrated in comparisons that show it capable of reducing excess conservatism significantly in the class of defects that fail by plastic collapse, potentially resulting in significant reductions in pipeline maintenance and repair costs. This new criterion was developed at Battelle under sponsorship of the Line Pipe Research Supervisory Committee of PRC international.

The new simplified criterion was developed from a finite-element software analysis model. The analysis software was applied in a parametric investigation to evaluate the influence of geometry and material characteristics on the remaining strength of corrosion defects in moderate- to high-toughness steels that fail by plastic collapse. The model development and parametric investigations demonstrated that:

• The failure of this class of defects is controlled by the ultimate tensile strength rather than yield strength or flow stress;

• Defect depth and length are the most critical defect geometry variables;

• Defect width and material strain hardening are of lesser importance.
Validation of an In-Line Inspection Metal Loss Tool
Authors: Morrison Tom , Mangat Naurang , Desjardins Guy , Bhatia Arti
Published: October 2016

Enbridge Pipelines Inc. (“Enbridge”), together with U.S. affiliate Lakehead Pipe Line, operates the world’s longest crude oil and petroleum products pipeline system. These companies transport liquid hydrocarbons from their point of supply to refining markets in the Midwestern United States and Eastern Canada.
The Conception, Design and Implementation of 36″ by 48″ Dual Diameter In-Line Cleaning and Inspection Tools in a Crude Oil Transmission System
Authors: Couchman Peter , Bhatia Arti , Ronsky Daryl
Published: October 2016

Enbridge operates the world’s longest hydrocarbon transmission system. The pipeline infrastructure has experienced additions over its 50 years of operation. The expansions were implemented as successively larger pipe sections upstream from pumping stations. After completing three lines (20″, 24″ and 34″) in parallel configuration, 48″ sections were installed upstream from pumping stations in 1972 and 1973. In order to accommodate future throughput requirements, part of the Enbridge’s 1998 Terrace Expansion Project was designed to connect the 48″ pipe sections into a continuous line with 36″ pipe sections.

The first Terrace Expansion design included sending and receiving traps for both the 36″ and the 48″ sections. An intricate network of crossover piping and mainline valves would allow in-line tools to be both launched and received at the diameter transition point without impacting flow. Since the transition points occur anywhere from 10 to 40 kilometers upstream from pumping stations, more aboveground facility locations would be added.

Enbridge approached vendors of the different in-line inspection technologies to conduct feasibility studies for building 36″ by 48″ dual diameter tools for pipeline cleaning, geometry and metal loss inspection applications in January 1998. Enduro Pipeline Services, Williamson Industries (TD Williamson) and Pipeline Integrity International (PII) were selected to assemble the working tools based on the viability of their technical presentations and cost estimates. The development of 36″ by 48″ dual diameter cleaning and inspection tools would save Enbridge time and money by eliminating the need to install traps and associated valving at the transition areas. As a result, the accelerated schedule and targeted project completion for inspection in Enbridge’s Terrace Expansion line within a twelve-month time frame was accepted by all parties.

This paper discusses the phases of the project from the technical feasibility studies, original and progression of design concepts, test loop execution and actual field use and validation of the tool performance and information.
Development of Robotic Inspection System for Small Pipelines
Authors: Qian Jinwu , Zhang Yanan , Cheng Weiming , Shen Linyong , Su Jianliang , Yang Jianhong , Li Jinsong
Published: October 2016

Automated probing and inspection inside small pipelines have become a hot topic among the micro-robot researchers in both universities and companies worldwide. The reason for that is the potential applications in nuclear power plants (PWR), civil engineering (gas and water) and in chemical plants and so on. This paper outlines the R & D activities on robotic inspection systems for 20mm-diameter pipelines conducted at Shanghai University in collaboration with NDT Center for Nuclear Industry. The locomotion mechanism comparison and synthesis are covered first. Several robotic inspection systems and different locomotion mechanisms are presented. Further development goals underway are briefly discussed.
Comparison of Estimates From a Growth Model 5 Years After the Previous Inspection
Authors: Worthingham Robert , Morrison Tom , Desjardins Guy
Published: October 2016

A corrosion growth modelling procedure using repeated inline inspection data has been employed as part of the maintenance program planning for a pipeline in the Alberta portion of the TransCanada system. The methodology of matching corrosion features between the different in-line inspections, and estimating their severity at a future date, is shown to be an excellent proactive cost saving methodology.

Throughout this paper estimated 80% confidence intervals for tool measurement error, total prediction error and growth methodology error are given. In this abstract the values have been rounded. For maximum penetration, for the features reported on three inspections, the confidence interval for total prediction error varies from ±12% to ±17%, and for the growth methodology from ±8% to ±10% of the wall thickness (for the 1998 and 1999 dig programs respectively). For features reported on two inspections the confidence interval varies from ±19% to ±22% for total prediction error (1998 and 1999 digs respectively), and is about ±17% for the growth methodology (for both dig programs).

The estimated confidence interval for prediction error in failure pressure is about ±560 kPa for the 1998 dig program. For the 1999 dig program a good estimate of the confidence interval for total prediction error could not be obtained. Assuming the failure pressure data obtained from field measurements were perfect, the estimate of the maximum confidence interval was ±850 kPa.

For the laser profile measurement field tool, compared to an ultrasonic pencil probe, the confidence interval for penetration is less than ±2% of the wall thickness.

The true confidence interval values in some cases are expected to be smaller than reported above for several reasons discussed in this paper.
Laboratory Study of Local Buckling, Wrinkle Development, and Strains for NPS12 Linepipe
Authors: Das Sreekanta , Cheng J. J. Roger , Murray David W. , Wilkie S. A. , Zhou Z. Joe
Published: October 2016

Buried pipelines are subjected to fluid pressure (oil/gas/water), axial loads, moments, and complex load combination histories. As a result, they may develop large compressive strains and curvatures leading to formation of localized buckles or wrinkles in the pipe shell. Recently, full-scale tests on 12.75″ diameter (NPS12) energy pipes have been carried out at the University of Alberta to study the behavior of wrinkle development and the ultimate limiting strains at the wrinkle locations. Different internal pressures, and axial loads were applied to produce a wrinkle, followed by load variations intended to produce fracture that could develop in buried pipelines in the field.

Three different axially loaded tests are reported. Two different internal pressures were applied, namely, (i) 0.8py and (ii) 0.4py, where py is the required internal pressure to cause the yield stress of the pipe material to be developed in the circumferential direction. Also, two different specimen lengths were adopted. They are: (i) 406 mm (16 inch) and (ii) 736 mm (29 inch). All specimens were loaded axially until the wrinkle formed. It was observed that the pipes are highly ductile and very large compressive strains can be developed without fracture or leakage in the pipe wall.

Because the pipe specimens of the first two tests did not fail (i.e. fracture) under monotonically increasing displacements and strains, the third wrinkled specimen was subjected to load histories involving strain reversals. This load history resulted in a low cycle failure after a very few cycles. The paper addresses test procedures, buckling and post-buckling behavior of NPS12 energy pipelines and relates them to three different types of strain measures, namely, material strain, wrinkle strain and overall strain as observed from these tests.
Analytical Simulation and Field Measurements for a Wrinkle on the Norman Wells Pipeline
Authors: Yoosef-Ghodsi Nader , Cheng J. J. Roger , Murray David W. , Doblanko Rick , Wilkie Scott
Published: October 2016

In laboratory testing of full-sized pipe subjected to combined axial load, internal pressure and bending, the normal failure mode consists of local buckling on the side of the maximum compressive fiber. If loading is continued beyond the initiation of buckling, and if the pipe is pressurized internally, the pipe retains its integrity while it develops a wrinkle in which very large deformations occur. Buried pipelines should behave in the same way. The paper presents the analyses carried out to assist in the interpretation of Geopig field evidence that, in September of 1997, a wrinkle existed on Slope 92 on the Norman-Wells Pipeline.

A finite element analysis of a shell model of a segment of the pipe confirmed that the wrinkle should exist. A subsequent pipe dig uncovered the wrinkle which had a configuration remarkably similar to those observed in the laboratory and to the form predicted by the analysis. Supplementary geotechnical investigations, a review of operational procedures on the line, and additional testing to determine strains within wrinkles, are presented in companion papers elsewhere in this conference. These combined papers provide a thorough documentation relative to this most interesting case history.
Effect of Microstructure on Near-Neutral-pH SCC
Authors: Bulger Jeffrey , Luo Jingli
Published: October 2016

Three components are required for stress corrosion cracking: stress, an environment and a susceptible alloy. The environment that causes near-neutral-pH SCC has been established as a dilute bicarbonate environment and the effect of stress on this type of SCC has received a considerable amount of research; however, the third component, the susceptible alloy, has received little research.

The effect of microstructure on near-neutral-pH SCC was investigated using the slow strain rate test. The effect of the microstructure on the corrosion properties is also investigated using polarization resistance tests, potentiodynamic scans and electrochemical impedance spectroscopy. The results indicate that the microstructure influences both the SCC and corrosion behaviour.
Mechanical Factors Affecting Stress Corrosion Crack Growth Rates in Buried Pipelines
Authors: Lambert S. B. , Beavers J. A. , Delanty B. , Sutherby R. , Plumtree A.
Published: October 2016

Over the past several years, investigations have been carried out into the rate of crack growth in pipeline steels in simulated, near-neutral pH, groundwater environment (NS4 solution). Pre-cracked specimens were subject to constant amplitude loading under various frequencies, maximum loads and R-ratios (minimum/maximum load). Test times varied from about 20 to 400 days. Transgranular crack features, similar to those found in service, have been observed. The extent of crack growth was monitored using either electrical potential drop or detailed metallographic examinations at two laboratories. The resulting crack growth rates from both labs are consistent with a superposition model based on a summation of fatigue (Paris Law) and static (SCC) crack growth rates. Differences between the results at the two laboratories are discussed.