bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Local Mechanical Properties of X80 Pipeline Girth Welds Using Advanced Techniques
Authors: Midawi Abdelbaset R. H. , Kisaka Y. , Santos E. B. F. , Gerlich A. P.
Published: November 2016

An instrumented indentation technique is proposed as a method to directly measure the local yield strength distribution in each zone of gas metal arc welds produced in X80 linepipe. The joints were produced with different microstructures and mechanical properties by applying shielding gases with varying Ar/CO2 ratios of 50 to 15% CO2 and the addition of a pure titanium wire into the weld pool was used to achieve in-situ alloying. The local yield strength distribution for each weld zone was then measured with instrumented indentation. The mapped yield strength distributions measured by instrumented indentation was compared to the hardness distribution. In addition, the yield strength of each zone obtained by instrumented indentation were then compared to tensile test results from Digital Image Correlation (DIC), in order to obtain stress-strain curves for each microstructural zone of the weld. The yield strength results obtained from both techniques are in good agreement, suggesting that instrumented indentation can be useful method to measure the local yield strengths of specific regions in a welded joint.
Microstructure and Mechanical Properties of Girth Weld HAZ in X80 Line Pipe With High Deformability for Strain Based Design Applications
Authors: Liu Yu , Li Yezheng , Li Shuo , You Zongbin , Yin Zhanghua
Published: November 2016

X80 line pipe with high longitudinal deformability (X80HD) has been developed and applied in the Strain Based Design (SBD) of pipelines in harsh environment such as seismic areas, permafrost areas, fault zones, etc. For SBD pipelines it is critical that the pipeline girth welds overmatch the tensile properties of the pipe material to avoid local strain accumulation in the girth weld during a strain event. Also, it is important that pipeline girth welds that may experience high strains in operation have sufficient toughness to ensure adequate resistance to failure by fracture.

The objective of this research was to gain a better understanding of the influence of chemical composition and essential welding variables on microstructure and properties of the HAZ regions formed in X80HD pipeline girth welds. In this study, by using the weld thermal simulation approach, the peak temperatures (Tp, representative of the distance to the fusion boundary) and the cooling times, particularly between 800 °C and 500 °C (t8/5, representative of the weld heat input), identical to those occurring in the girth weld HAZ of three different X80HD pipe steels, were artificially reproduced. It should be noted that t8/5 is influenced by both heat input and preheat temperature. The weld peak temperatures, Tp, from 500 °C to 1300 °C, in 100 °C increment, whereas the cooling times t8/5 from 5 to 30 seconds were in 5, 15, and 30 seconds, associated with the heat input range of self-shielded flux cored arc welding (FCAW-S). The thermal simulation specimens on tensile properties, Charpy impact toughness, and Vickers hardness were tested and analyzed. Microstructures of these simulated HAZ were characterized by optical microscopy (OM) and scanning electron microscopy (SEM). Finally, the actual FCAW-S girth welding experiments were carried out. These girth welds were subjected to different testing for evaluation of microstructure and mechanical properties of X80HD girth welded joints. These included transverse weld tensile testing, microhardness map of the weld joint, Charpy V-notch impact testing of weld metal and HAZ, and microstructure analysis. The results demonstrated that softening occurs in the fine grained HAZ (FGHAZ) and the inter-critical HAZ (ICHAZ) of X80HD line pipe girth welds. The severity of HAZ softening depends on the steel chemistry and the heat input applied during girth welding. The metallurgical design of the X80HD pipeline steel and the optimization of the girth welding procedures were proposed.
Development of Contemporary Welding Procedures for Heavy Wall Hot Tap Split Tee Longitudinal Seam Welds
Authors: Atkinson Mark , Slater Simon
Published: November 2016

Historically, the manual metal arc welding (MMA) process has been used for welding of full encirclement split tees on hot tap connections for gas transmission pipelines. The National Grid high pressure gas transmission network currently consists of pipelines up to and including 1219 mm outside diameter. The large diameter pipes require split tee assemblies up to 80 mm thick. The arc time to complete welding can be considerable and requires multiple welders to complete welding in one continuous operation.

The qualification of a mechanised gas shielded flux cored arc welding (GSFCAW) procedure for welding the longitudinal seams on large diameter tee connections would realise significant operational and cost benefits over the MMA method. The equipment for mechanised field welding is readily available for a large number of applications across many industries. Recent advances in the technology suggest that a suitable mechanised procedure can be developed for the longitudinal weld seams of split tee assemblies.

The primary aim of this project was to qualify a mechanised GSFCAW process and set of procedures in line with the National Grid specification for welding longitudinal seams of split tee assemblies. A comprehensive welding and test schedule was performed using 50 mm tee material. Welding was performed using the Firefly welding system in three positions, flat, overhead and horizontal to cover the full range of welding positions required for tee connections with either horizontal or vertical off-take branches.

Based on the mechanical testing and non-destructive examination (NDE) results, the combination of process and consumables used in this project have been qualified in accordance with the National Grid specification.

A number of quality issues were observed during welding and recommendations to address these have been identified. The travel speeds achieved using the GSFCAW process are up to twice those recorded when welding a similar size fitting using MMA. Even after considering the remedial work required to rectify quality issues, the overall welding times recorded using the GSFCAW process were lower than those recorded on a similar size fitting welded on site using the MMA process.
Material Properties and Flaw Characteristics of Vintage Girth Welds
Authors: Kotian Kunal , Wang Yong-Yi
Published: November 2016

Integrity assessment of girth welds in in-service vintage pipelines is sometimes necessary, including regulatory requirements, changes in service or pipe support conditions which may cause additional stress on the girth welds, or “indications” being reported in in-line inspection (ILI). Material properties and flaw characteristics are essential in such assessment, but very little data are available in most cases.

In a PRCI-funded effort, material properties and flaw characteristics of vintage girth welds are generated and analyzed to fill the critical gaps. The output of this effort is being used as the inputs to a vintage girth weld assessment procedure being developed in a separate and parallel effort. The outcome of these efforts collectively allows for the assessment of vintage girth welds, which is a part of an overall integrity management program.

The basic material property data being generated include (i) pipe tensile properties in both hoop and longitudinal directions, (ii) weld metal tensile properties, (iii) macrohardness traverse, and (iv) Charpy impact transition curves with notches in the heat affected zone (HAZ) and deposited weld metal. These data provide essential information on tensile strength, weld strength mismatch, and toughness. In addition, tensile tests were conducted on cross-weld specimens with natural flaws and artificially machined planar flaws. These cross-weld tests provide an indication of the welds’ stress capacity in the presence of flaws. They also provide the apparent toughness which is essential in assessing welds’ tensile strain capacity. All tested girth welds were inspected using radiography and phased array UT. Thus, this work provides a coherent picture of the material properties, flaw characteristics, and stress and strain capacities of the tested vintage girth welds.
Corrosion Growth and Remnant Life Assessment: How to Pick the Right Approach for Your Pipeline
Authors: Smith Michael , Argent Cheryl , Wilde Andrew
Published: November 2016

Accurate modelling of future corrosion growth is critical to long term pipeline integrity. A lot has been published within the industry regarding how to accurately determine corrosion growth rates (CGRs) from repeat in-line inspection data but there is limited guidance to support pipeline operators in deciding how to apply CGRs in order to support the development of repair plans and investigate pipeline remnant life. The consequences of significantly under- or overestimating CGRs are high and getting the balance right between the two is not straightforward.

Future integrity decisions can be made using maximum, upper bound, or average corrosion rates, and these rates may be calculated for and applied to individual features, pipe joints, or segments. All of the commonly used methods have advantages and disadvantages.

In this paper 10 CGR application methods have been applied to 3 onshore pipelines in which 3 inspections were conducted. The methods were compared against each other by reviewing the corrosion growth predictions from the 1st and 2nd inspections with the actual results of the 3rd inspection.

The aims of the study were:

i. to identify the methods that limit underestimation of corrosion growth but also do not severely overestimate corrosion growth, and

ii. to identify which methods are most appropriate for the different future integrity decisions, e.g. repair & re-inspection planning and remnant life estimation.

A scoring methodology was developed in order to compare and rank the CGR application methods. The methodology was based on an underestimation score (to identify which methods minimize underestimation) and an overestimation score (to identify which methods limit unnecessary repair work). The scoring method allowed for weightings to be applied to the under- and overestimation scores to take account of how the priorities vary when making different future integrity decisions.
Double Jointing Technology for Strain-Based Design (SBD) Pipelines
Authors: Verma Neerav , Fairchild Doug P. , Wasson Andrew J. , Anderson Timothy D. , Noecker Fredrick F.
Published: November 2016

Pipelines may experience significant longitudinal strains when subjected to large ground motions, such as seismic activity, landslides, etc. For these conditions, a strain-based design (SBD) approach can be used. The use of higher strength steels (like X80) for SBD approach can enable significant construction cost savings. Costs can be further reduced through the use of a double jointing process in order to reduce the amount of field welding. However, it is challenging to achieve adequate girth weld properties for SBD scenarios involving higher strength steels by using conventional double jointing processes such as submerged arc welding (SAW).

Acicular ferrite interspersed in martensite (AFIM) has been previously identified as an advantageous high strength weld metal microstructure that can be applied in field pipeline construction. In this paper, a double jointing technology for X70+ SBD applications will be discussed. Excellent strength and toughness properties were achieved in double joint welds by using an optimized AFIM welding technology that included a tailored welding consumable wire and a high productivity GMAW-P weld process. Welding procedures are discussed along with mechanical properties achieved. Productivity comparisons suggest that a fully optimized GMAW-P welding process in the 1G-rolled welding position can have productivity comparable to a conventional SAW double jointing process.
Non-Linear Corrosion Growth: A More Appropriate and Accurate Model for Predicting Corrosion Growth Rate
Authors: Al-Amin M. , Kariyawasam S. , Zhang S. , Zhou W.
Published: November 2016

External metal-loss corrosion is one of the major contributing factors for pipeline failures in North America. Corrosion growth rate plays a crucial role in managing corrosion hazard for gas and liquid pipelines. Quantifying the growth of corrosion over time is critically important for the risk and reliability analysis of pipelines, planning for corrosion mitigation and repair, and determination of time intervals for corrosion inspections. Conservatism in predicting the growth rate has significant engineering implication as non-conservatism can lead to critical anomalies being missed by mitigation actions and may cause pipeline failure; whereas, over conservatism can lead to unnecessary inspections and anomaly mitigations that may result in significant unnecessary cost to pipeline operators.

As more and more pipelines are now being inspected by in-line inspection (ILI) tools on a regular basis, the ILI data from multiple inspections provide valuable information about the growth of corrosion anomalies on the pipeline. Although the application of linear growth rate calculated by comparing depths from two successive ILI is a common practice in the pipeline industry, research has shown that the growth of corrosion anomaly is non-linear and anomaly-specific. The authors of this paper have previously developed anomaly-specific non-linear corrosion growth model based on multiple ILI data. The objectives of this paper are to demonstrate the appropriateness of anomaly-specific non-linear corrosion growth model, and to illustrate the advantages of using non-linear corrosion growth model in the integrity management program. Two case studies were performed to illustrate the application of non-linear growth model by incorporating the measurement errors associated with the ILI tools, which include both the bias (constant and non-constant) and random scattering error. The findings of these case studies are presented in this paper.
An Operator’s Perspective on Fracture Control in Dense Phase CO2 Pipelines
Authors: Barnett Julian , Cooper Russell
Published: November 2016

Carbon Capture and Storage (CCS) is an approach to mitigate global warming by capturing and storing carbon dioxide (CO2) from large industrial emitters. Pipelines will play a significant role in the transportation of CO2 in CCS projects. National Grid has an interest in this, and has carried out research to investigate the requirements for the safe design and operation of CO2 pipelines.

CO2 pipelines are susceptible to long running fractures which are prevented by specifying an adequate pipe body toughness to arrest the fracture. There is no existing, validated methodology for setting pipe body toughness for pipelines transporting dense phase CO2 with impurities. The methods for estimating the pipe body toughness are semi-empirical so full scale fracture propagation tests are required to validate and extend these methods.

As part of a major research programme into pipeline transportation of dense phase CO2, National Grid conducted two full scale fracture propagation tests using 900 mm diameter pipe in 2012. The tests demonstrated that the current natural gas practices for setting pipe body toughness was incorrect and non-conservative for dense phase CO2 pipelines. National Grid recognises the importance of understanding fracture arrest as it required to ensure design code compliance, impacts on pipeline design and provides reassurance to stakeholders.

As the results of the two tests cannot be used directly to set the toughness requirements for a specific project pipeline, a third full scale test was necessary to confirm the fracture arrest capability of the pipe for the proposed pipelines.

A third full scale fracture propagation test was conducted in July 2015. A propagating ductile fracture was initiated and successfully arrested in linepipe representative of that to be used on the proposed project.
Improved Pipeline Integrity Management by Using Multiple ILI Technologies
Authors: Chan Peter , Liu Kaiwen
Published: November 2016

The most common methods currently available for detecting cracks and linear features in pipelines are Ultrasonic Crack Detection (USCD) ILI and Electromagnetic Acoustical Transducer (EMAT) ILI. A third ILI technology using Spiral MFL with hard spot detection capability has also showed capability for detecting linear features within deformations that are not readily detectable by USCD or EMAT tools.

Any measurement technology, including ILI and field NDE tools, has a range of accuracy and detection capability. This paper analyzes and compares the performance of these ILI tools against the measurements obtained from field investigations. It will be shown that each technology has its own limitations, and features detected by one tool could be missed by the other tool.

Consequently, until one existing or new ILI technology has demonstrated its ability to catch all the features within its stated specification, employing multiple ILI technologies is an effective method to compensate for the weaknesses of any one particular ILI tool and ensure a higher level of safety for pipelines. An additional benefit of running multiple ILI tools is the opportunity for providing feedback of dig results to the different ILI vendors which could help them improve their own tool detection and sizing capabilities.
Development of Pipeline Sleeve End Fillet Weld Stress Intensity Factor and Reference Stress Solutions for Fatigue and Failure Assessment
Authors: Semiga Vlad , Dinovitzer Aaron , Eshraghi Amin , Lazor Robert
Published: November 2016

Pipeline defects such as cracks, dents and corrosion often require permanent pressure retaining repairs. Full encirclement metallic repair sleeves with fillet-welded end connections to the pipeline are often used for this purpose. In-service failures have occurred at pressure retaining sleeves as a result of defects associated with the sleeve welds, such as hydrogen-induced cracks, undercut at the fillet welds and inadequate weld size. At present, accurate quantitative fitness for service assessments for circumferential defects in a sleeve fillet welds are difficult to carry out due to a lack of detailed stress intensity factor (SIF) solutions for finite length cracks.

The primary objective of the project presented in this paper [1] was to develop flaw acceptance criteria which will fill gaps in the available Engineering Critical Assessment procedures for metallic sleeve repairs on all grades of pipelines. SIF solutions for finite length sleeve-end fillet weld toe and root cracks were generated and used to develop parametric equations suitable for carrying out defect assessments. These equations can be used in the assessment of fatigue crack growth and/or fracture using failure assessment diagram (FAD) methods at sleeve end fillets alongside the results developed for other structural geometries in national standards. The equations were developed based on detailed finite element (FE) analyses of a wide range of sleeve end fillet weld cracking scenarios to estimate the SIFs at both the deepest point and the surface breaking point along the crack front.
Integrity of Buried Gas Pipeline Subjected to an Adjacent Pipe Rupture Event
Authors: Krishna Shree , Krishnamurthy Ravi M. , Gao Ming
Published: November 2016

This paper discusses the integrity of 30” OD pipeline subjected to burst of 24” pipeline located 24’ away. Study discusses the detailed finite element analyses (FEA) of pipeline subjected to the stress waves emanating from the rupture event. Dynamic response of a 30” gas pipe buried approximately 6.5’ deep was studied using ABAQUS, to determine how it may have been affected by the rupture of an adjacent 24” gas pipe. The pressure at the 24” OD pipe was dropped from flow pressure to zero psi in a very short interval to simulate a rupture. Sensitivity analyses were conducted by varying the soil modulus and rupture time duration using 2-D and 3-D approaches to arrive at a consensus. In-addition, nonlinear Mohr-Coulomb based advanced soil constitutive models were also used to establish the effect of the soil behavior with the rupture event. Integrity of the pipeline was established based on the stresses/strains and strain based damage factors. Based on the FEA analyses compared with analytical results, the integrity of the 30” OD pipeline can be established and also qualified as either fit or unfit for the operations. The weight equivalent of TNT required to produce this shock loading was obtained by converting internal energy from finite element model using analytical approaches. Analytical solutions and the results from earlier conducted PRCI work were used to verify the simulation approaches. Amplification of stresses on the buried pipeline by using TNT explosives on the surface was obtained through FEA and correlated using experiments conducted and listed in PRCI work. Coupled Eulerian-Lagrangian analyses were further carried out to simulate the crater formation related to the burst event of the buried pipeline.
ILI-to-Field Data Comparisons: What Accuracy Can You Expect?
Authors: Ellinger Matthew A. , Bubenik Thomas A. , Moreno Pamela J.
Published: November 2016

Det Norske Veritas (U.S.A.), Inc. (DNV GL) prepared this paper in order to study the expected accuracy of in-line inspections (ILI) as a function of year, depth (both reported and field measured), and length, amongst other factors. DNV GL has access to a significant amount of data that span many different pipeline operators, ILI vendors, inspection years, and inspection technologies. DNV GL is well suited to complete this study as a result of our access to these various data sets.

Over 3,000 individual comparisons of ILI and field depths and lengths spanning from 2010 through 2015 from 11 operators and 68 line segments were compiled to meet the objectives of this paper. Inspection technologies include axial magnetic flux leakage (MFL), ultrasonic wall thickness (UTWT), spiral MFL, and circumferential MFL.

Based on the analyses conducted in this paper, the following conclusions were generated.

• Axial MFL and UTWT inspections show significant improvements over the last several years.

• Axial MFL inspection systems are capable of meeting a depth accuracy of +/−10% of the wall thickness with 80% certainty, but this has not always been the case. UTWT inspection systems are capable of meeting a higher depth accuracy.

• Axial MFL inspection systems report more pits and circumferential grooves than UTWT systems. This could suggest UTWT systems are less sensitive to pits and circumferential grooves than axial MFL systems.

• Both axial MFL and UTWT inspection systems routinely under call defects with field measured depths greater than 50 to 80% of the wall thickness. This is contrary to a widely held notion that ILI is conservative for deep defects.

• ILI reported defect lengths do not correlate well to field measured defect lengths. In general, field measured defect lengths are greater than ILI reported defect lengths.

• Depth accuracy tends to decrease slightly for very short defects (less than 1-inch) and for very long defects (greater than 40-inches).

Based on these conclusions, the authors make the following recommendations:

• Pipeline operators should dig more than the deepest reported defects to better understand the accuracy of the inspection tools being used and to determine whether deeper anomalies are being under called.

• Pipeline operators should consider methods for evaluating change in corrosion depth from ILI survey to ILI survey to lessen the dependence on the accuracy of the ILI tools. This should include a raw data signal analysis in order to determine whether the general morphology (metal loss length and width) are changing between ILI surveys.

• ILI reported defect lengths should be used in conjunction with field measured defect depths (if available) when performing failure pressure calculations.

• Additional accuracy, especially for deeper defects, may only come with new tool developments. Industry support of such developments will be required to bring them to fruition.
Improved Pipeline Dent Integrity Management
Authors: Tiku Sanjay , Eshraghi Amin , Semiga Vlad , Torres Luis , Piazza Mark
Published: November 2016

Pipeline dents can be developed from the pipe resting on rock, a third party machinery strike, rock strikes during backfilling, amongst other causes. The long-term integrity of a dented pipeline segment depends upon parameters including pipe geometry, indenter shape, dent depth, indenter support, secondary features, and pipeline operating pressure history at and following indentation. US DoT and other standards include dent repair and remediation criteria broadly based upon dent depth, dent location (top or bottom side), pressure cycling (liquid or gas), and dent interaction with secondary features (weld, corrosion, cracks). These criteria are simple and easily applied, however, they may not direct maintenance appropriately and be overly conservative or, in some cases, unconservative.

Previous IPC papers have discussed the full-scale dent fatigue testing and dent modelling efforts to support integrity management criteria development by collecting material and structural response during dent formation and pressure loading. The present paper will present the results of this extensive dent structural and fatigue life numerical simulation program using a validated finite element (FE) analysis process. The paper describes the numerical simulation technique, as well as, the development of the novel engineering tool for integrity management, eliminating the need for numerical simulation of individual dent features to assess the relative integrity threat they pose.

The development of the engineering tool presented in this paper considers the dent formation, re-rounding and through life response to pressure fluctuations to evaluate the fatigue life of dent features. The results of these analyses are used to develop fatigue life trends based on dent shape, restraint condition and operating pressure. These trends were used to develop models to predict dent relative severity and life based upon ILI inspection dent shape data for single peak dents. Dent shape has also been used to determine the restraint condition of a dent and its influence on the dent feature fatigue life. The tools were developed to address many of the uncertainties inherent in existing regulatory repair and remediation criteria. Current and future applications of the integrity assessment model are described along with recommendations for further development and testing to support pipeline integrity management, industry guidelines and standards.

The results of this research will be of use in improving integrity management decisions and support further development of industry guides and standards. As such the information presented in this paper will be of interest to pipeline operators, integrity management specialists, in-line inspection (ILI) organizations and regulators. The recommendations presented in this paper may be used to influence the direction of pipeline standards in their direction in the disposition of dent features.
Evolution of Linepipe Manufacturing and its Implications on Weld Properties and Pipeline Service
Authors: Wang Yong-Yi , Horsley David , Rapp Steve
Published: November 2016

Pipe grade is a dominant parameter in a pipeline’s service life. Critical decisions on the design, construction, and maintenance of pipelines are made on the basis of pipe grade. The implied assumptions or expectations are that pipes of the same grade would behave similarly and the experiences with a particular grade can be applied to all pipelines of the same grade. This simplification does not adequately take into account the other characteristics that are not represented by pipe grade, but can play a critical role in the safe and economical operation of pipelines. For instance, the evolution of steel-making processes and advancements in field welding practice can lead to significant differences in weld behavior among pipes of the same nominal grade.

Most of the design, construction, and maintenance practices in the pipeline industry were established before the extensive use of modern control-rolled and microalloyed steels. With the exception of a few isolated research projects, the impacts of the fundamental changes in the steel metallurgy in modern microalloyed steels have not been systematically examined and understood. For instance, these steels may have very low strain-hardening capacity as a result of the TMCP process and may be subject to high levels of heat-affected zone (HAZ) softening due to their ultra-low carbon low-hardenability steel chemistry. HAZ softening reduces the longitudinal pipe strain capacity of girth welds, and low strain-hardening can potentially have a negative impact on tolerance to anomalies such as corrosion or mechanical damage.

This paper starts with a brief review of linepipe manufacturing history with a focus on the chemical composition and rolling practices that directly affect the mechanical properties and the response to welding thermal cycles. The characteristics of linepipes made from modern microalloyed steels are contrasted with those made from vintage hot-rolled and normalized steels. The resulting mechanical properties of these two types of materials in the presence of welding thermal cycles are presented, and compared in terms of their behavior.

The consequence of the weld characteristics is shown using examples of girth welds subjected to longitudinal strains. The implications of the pipe and weld characteristics on the design, field girth welding, and maintenance of pipelines are highlighted. Future directions and best practices in linepipe alloying and manufacturing strategies, linepipe specifications, field girth welding, and building strain-resistance girth welds are briefly described. It is emphasized that assessing the performance of pipelines based on their grades has fundamental shortfalls, and that gaps in codes and standards can lead to unexpected outcomes in pipeline integrity. In the long-run, revising relevant codes and standards is necessary to ensure consistent and reliable applications of new materials in the entire industry.
AIV and FIV in Pipelines, Plants, and Facilities
Authors: Harper Chris B.
Published: November 2016

Acoustic-induced vibration (AIV) and flow-induced vibration (FIV) are two common phenomena that can lead to vibration-induced fatigue failures in piping systems. Pipeline facility managers, operators, designers, and engineers are faced with identifying and mitigating the risks of AIV and FIV to avoid catastrophic instances of vibration-induced fatigue failures in their facilities. This paper identifies common challenges to conventional AIV/FIV analyses methods, and discusses advanced techniques available to address these challenges.

Acoustic-induced vibrations are caused by the sound energy created by flow through pressure reducing devices like valves or restrictive orifice plates. This sound energy can cause the piping wall to vibrate, thus exciting, and possibly damaging, any nearby small-bore branch connections. Flow-induced vibrations are caused by pulsations induced by flow past dead legs in piping systems. These pulsations can create shaking forces that cause vibrations of piping, vessels, and equipment. The two phenomena will be compared and contrasted, while offering simple tips and best practices in identifying, evaluating, and solving these two common flow-induced issues.

A field case study utilizing pulsation and vibration measurements between a line heater and inlet separator for a gas plant will be presented and discussed. The case presents an opportunity to investigate mainline and small-bore piping AIV/FIV risks in plants, provides example data of clear AIV and FIV phenomena, and identifies complex situations that require more rigorous analysis. Advanced techniques for analyzing and solving complex issues that are commonly found in piping systems will be explored. Further, the case highlights the benefits of early screening and preventive considerations of upset conditions when dealing with flow-induced pulsation and vibration issues.

In this paper, the reader will gain an increased understanding of the importance of AIV/FIV in maintaining integrity of their facilities, and be provided with tools and knowledge to mitigate any risks that may be encountered.
Rational Stress Limits and Load Factors for Finite Element Analyses in Pipeline Applications: Part III — Elastic-Plastic Load Factor Development
Authors: Dotson Rhett , Alexander Chris , Iyer Ashwin , Gourlie Al , Kania Richard
Published: November 2016

In this paper, a methodology is presented to develop load factors for use in elastic-plastic assessments of pipelines and their components. The load factors are based on the pipe material properties and the ASME pipeline code’s design margin for the service and location of the pipeline installation [1, 2]. These codes are recognized by 49 CFR 192 and 195 [3, 4].

Minimum required load factors for internal pressure loads can be derived analytically based on design equations from the ASME B31 piping codes and minimum material requirements for API 5L line pipe [6]. Once the load factor is established for a particular case, the elastic-plastic methodology may be used in the Finite Element Analysis (FEA) of pipelines and related components. This methodology is particularly useful in the assessment of existing systems when linear elastic numerical analysis shows that local stresses may exceed the elastic design limits.

Two case studies are presented showing analyses performed with Abaqus [5], a commercial, general purpose FEA software package. The first case study provides an assessment of a large diameter elbow where the stress on the outer fibers of the intrados exceeded the longitudinal stress limits from B31.8. The second case study examines an assessment of a tee connection where the stresses on the ID exceeded the yield strength of the component. In addition to the case studies, the paper also presents the results of a full-scale test that demonstrated what margin was present when the numerical calculations were based on specified minimum properties.

This paper is not intended to revise or replace any provision of B31.4 and/or B31.8 [1, 2]. Instead, it provides the means for calculating load factors that can be used with an elastic-plastic analysis approach in a manner that provides the same design margins as the ASME B31 codes. The approach described in this paper is intended for use in the detailed FEA of pipelines and their associated components.
Finite Element Modeling and Quantification of Mechanical Damage Severity in Pipelines
Authors: Zhu Xian-Kui , Leis Brian N.
Published: November 2016

Mechanical damage is one of the major threats to oil and gas transmission pipeline integrity, which has been the case now for decades. Although much work has been done in that context, due to the complexity of its effects mechanical damage severity remains difficult to quantify. Thus, work continues to better understand the failure mechanism and develop the means to screen damage severity.

The present paper adopts a validated elastic-plastic finite element analysis (FEA) model to simulate mechanical dents in pipelines and to quantify the effects of damage through a broad parametric study. This considers the need for three-dimensional FEA models and the effects of FEA element type, soil constraint condition, indenter type, pipeline grade and initial pipe pressure on dent response. The FEA model is also used to assess the minimum wall thickness for which a dent has the minimal effect on pipeline integrity. Finally, application of the proposed FEA model is illustrated by successfully predicting the failure behavior of a dent in a full-scale fatigue test involving a modern pipeline steel.
A Novel Approach to Leak Sensitivity Testing of Computational Pipeline Monitoring Systems for Hydrocarbon Liquid Pipelines With Hydraulic Simulators
Authors: Hung Daniel , Mokamati Satya
Published: November 2016

In the operation of hydrocarbon liquid pipelines, Computational Pipeline Monitoring (CPM) systems are used for software based leak detection. When installed, CPM systems must meet the regulatory requirements such as API 1130 in the USA and CSA Z662 in Canada. API RP 1130 provides several methods that can be used to test a CPM system: forced parameter testing, simulated leak test (SLT), and fluid withdrawal testing (FWT).

Leak tests are performed to establish and verify the leak detection capabilities of the installed CPM system and in some cases test the response of the personnel. One of the primary interests in leak testing is the realism or hydraulic accuracy of the leak signature, in order that the reported leak sensitivity results of the test are reflective of the real performance of the CPM system.

Simulated leak tests (SLT’s) use an offline pipeline model to generate hydraulically accurate data which can be fed into the CPM model. SLT’s provide the most flexible and hydraulically accurate solution to simulating leaks, compared to some of the other API RP 1130 compliant test methods. SLT’s do not have leak location restrictions and also correctly models the flow and pressure hydraulic signature of a leak.

The paper outlines a novel approach and method to leak simulation, based on its size and shape of the leak hole. This method can be used to represent various sizes of a leak, ranging from a pin hole to a large rupture along the seam. Implementation of the method in a simulator developed with commercial software is discussed. The results of the simulation, namely the hydraulic signatures from the simulated leak and the CPM response, are compared with the widely used leak simulation method using a constant leak rate. Finally, possible applications of this method are considered.
Organic electronics for high-resolution electrocorticography of the human brain
Authors: Khodagholy Dion , Gelinas Jennifer N. , Zhao Zifang , Yeh Malcolm , Long Michael , Greenlee Jeremy D. , Doyle Werner , Devinsky Orrin , Buzsáki György
Published: November 2016

Conducting polymer–based electrodes can acquire population and individual neural activity from the surface of the human brain.
Local and transient gene expression primes the liver to resist cancer metastasis
Authors: Goodwin Tyler J. , Zhou Yingqiu , Musetti Sara N. , Liu Rihe , Huang Leaf
Published: November 2016

Targeted nanoparticles induce expression of a CXCL12/SDF-1 trap in a transient and liver-specific manner to inhibit colorectal cancer liver metastasis.
Macrophages build a wall and the host pays for it
Authors: Bhattacharya Mallar
Published: November 2016

Epithelioid-like macrophages suppress immunity during mycobacterial infection.
Comparisons of the Humoral and Cellular Immune Responses Induced by Live Attenuated Influenza Vaccine and Inactivated Influenza Vaccine in Adults
Authors: Hoft Daniel F. , Lottenbach Kathleen R. , Blazevic Azra , Turan Aldin , Blevins Tamara P. , Pacatte Thomas P. , Yu Yinyi , Mitchell Michelle C. , Hoft Stella G. , Belshe Robert B.
Published: November 2016

Both live attenuated influenza vaccines (LAIV) and inactivated influenza vaccines (IIV) induce protective immunity against influenza. There is evidence that LAIV induces superior protection in children, whereas IIV may induce superior protection in adults. The immune mechanisms responsible for these differences have not been identified. We previously compared LAIV and IIV in young children of 6 to 36 months of age, and we demonstrated that while both induced similar hemagglutination inhibition (HAI) antibody responses, only LAIV induced significant increases in T cell responses. In the present study, 37 healthy adult subjects of 18 to 49 years of age were randomized to receive seasonal influenza vaccination with LAIV or IIV. Influenza virus-specific HAI, T cell, and secretory IgA (sIgA) responses were studied pre- and postvaccination. In contrast to the responses seen in young children, LAIV induced only minimal increases in serum HAI responses in adults, which were significantly lower than the responses induced by IIV. Both LAIV and IIV similarly induced only transient T cell responses to replication-competent whole virus in adults. In contrast, influenza virus-specific sIgA responses were induced more strongly by LAIV than by IIV. Our previous studies suggest that LAIV may be more protective than IIV in young children not previously exposed to influenza virus or influenza vaccines due to increased vaccine-induced T cell and/or sIgA responses. Our current work suggests that in adults with extensive and partially cross-reactive preexisting influenza immunity, LAIV boosting of sIgA responses to hemagglutinin (HA) and non-HA antigenic targets expressed by circulating influenza virus strains may be an important additional mechanism of vaccine-induced immunity.
delta psi-mediated signalling in the bacteriorhodopsin-dependent photoresponse
Authors: Grishanin R N , Bibikov S I , Altschuler I M , Kaulen A D , Kazimirchuk S B , Armitage J P , Skulachev V P
Published: November 2016

It has been shown previously that the proton-pumping activity of bacteriorhodopsin from Halobacterium salinarium can transmit an attractant signal to the bacterial flagella upon an increase in light intensity over a wide range of wavelengths. Here, we studied the effect of blue light on phototactic responses by the mutant strain Pho8l-B4, which lacks both sensory rhodopsins but has the ability to synthesize bacteriorhodopsin. Under conditions in which bacteriorhodopsin was largely accumulated as the M412 bacteriorhodopsin photocycle intermediate, halobacterial cells responded to blue light as a repellent. This response was pronounced when the membrane electric potential level was high in the presence of arginine, active oxygen consumption, or high-background long-wavelength light intensity but was inhibited by an uncoupler of oxidative phosphorylation (carbonyl cyanide 3-chlorophenylhydrazone) and was inverted in a background of low long-wavelength light intensity. The response to changes in the intensity of blue light under high background light was asymmetric, since removal of blue light did not produce an expected suppression of reversals. Addition of ammonium acetate, which is known to reduce the pH gradient changes across the membrane, did not inhibit the repellent effect of blue light, while the discharge of the membrane electric potential by tetraphenylphosphonium ions inhibited this sensory reaction. We conclude that the primary signal from bacteriorhodopsin to the sensory pathway involves changes in membrane potential.
Cloning, sequencing, and expression of clustered genes encoding beta-hydroxybutyryl-coenzyme A (CoA) dehydrogenase, crotonase, and butyryl-CoA dehydrogenase from Clostridium acetobutylicum ATCC 824
Authors: Boynton Z L , Bennet G N , Rudolph F B
Published: November 2016

The enzymes beta-hydroxybutyryl-coenzyme A (CoA) dehydrogenase (BHBD), crotonase, and butyryl-CoA dehydrogenase (BCD) from Clostridium acetobutylicum are responsible for the formation of butyryl-CoA from acetoacetyl-CoA. These enzymes are essential to both acid formation and solvent formation by clostridia. Clustered genes encoding BHBD, crotonase, BCD, and putative electron transfer flavoprotein alpha and beta subunits have been cloned and sequenced. The nucleotide sequence of the crt gene indicates that it encodes crotonase, a protein with 261 amino acid residues and a calculated molecular mass of 28.2 kDa; the hbd gene encodes BHBD, with 282 residues and a molecular mass of 30.5 kDa. Three open reading frames (bcd, etfB, and etfA) are located between crt and hbd. The nucleotide sequence of bcd indicates that it encodes BCD, which consists of 379 amino acid residues and has high levels of homology with various acyl-CoA dehydrogenases. Open reading frames etfB and etfA, located downstream of bcd, encode 27.2- and 36.1-kDa proteins, respectively, and show homology with the fixAB genes and the alpha and beta subunits of the electron transfer flavoprotein. These findings suggest that BCD in clostridia might interact with the electron transfer flavoprotein in its redox function. Primer extension analysis identified a promoter consensus sequence upstream of the crt gene, suggesting that the clustered genes are transcribed as a transcriptional unit and form a BCS (butyryl-CoA synthesis) operon. A DNA fragment containing the entire BCS operon was subcloned into an Escherichia coli-C. acetobutylicum shuttle vector. Enzyme activity assays showed that crotonase and BHBD were highly overproduced in cell extracts from E. coli harboring the subclone. In C. acetobutylicum harboring the subclone, the activities of the enzymes crotonase, BHBD, and BCD were elevated.
Dihydrolipoamide dehydrogenase from the halophilic archaeon Haloferax volcanii: homologous overexpression of the cloned gene
Authors: Jolley K A , Rapaport E , Hough D W , Danson M J , Woods W G , Dyall-Smith M L
Published: November 2016

The gene encoding dihydrolipoamide dehydrogenase from the halophilic archaeon, Haloferax volcanii, has been subcloned and overexpressed in the parent organism by using the halophilic archaeal rRNA promoter. The recombinant protein has been purified to homogeneity and characterized with respect to its kinetic, molecular, and salt-dependent properties. A dihydrolipoamide dehydrogenase-minus mutant of H. volcanii has been created by homologous recombination with the subcloned gene after insertion of the mevinolin resistance determinant into the protein-coding region. To explore the physiological function of the dihydrolipoamide dehydrogenase, the growth properties of the mutant halophile have been examined.
Efficient homologous recombination in fast-growing and slow-growing mycobacteria
Authors: Baulard A , Kremer L , Locht C
Published: November 2016

Although homologous recombination is a major mechanism for DNA rearrangement in most living organisms, it has been difficult to detect in slowly growing mycobacteria by a classical suicide vector approach. Among the possible reasons for this are the low levels of transformation efficiency, the relatively high levels of illegitimate recombination, and the peculiar nature of the recA gene in slowly growing mycobacteria. In this report, we present an efficient homologous recombination system for these organisms based on the use of replicative plasmids which facilitates the detection of rare recombination events, because the proportions of recombined molecules increase over time. Intraplasmid homologous recombination in Mycobacterium smegmatis and Mycobacterium bovis BCG was easily selected by the reconstitution of an interrupted kanamycin resistance gene. Chromosomal integration via homologous recombination was selected by the expression of the kanamycin resistance gene under the control of a chromosomal promoter that was not present in the plasmid before recombination. This technique was termed STORE (for selection technique of recombination events). All the clones selected by STORE had undergone homologous recombination, as evidenced by PCR analyses of the kanamycin-resistant clones. This technique should be applicable to all organisms for which homologous recombination has been difficult to achieve, provided the gene of interest is expressed.