bluuebunny/crossref_metadata_2025 huggingface dataset:
Guidance for Selecting SCC Direct Assessment Locations and Estimation of Re-Inspection Intervals
Authors: King Fraser , Piazza Mark , Worthingham Robert
Published: April 2011

A significant amount of research and development has been carried out on the mechanism of the stress corrosion cracking of underground pipelines. This paper describes the results of a study, co-funded by PRCI, the US DOT, and pipelines companies, to bring together the results of these various studies in the form of a set of guidelines that will assist companies in identifying the most likely SCC locations on their systems and in predicting how frequently inspection or other mitigation is required. The guidelines have been developed along mechanistic lines, and are divided into four “steps” representing: susceptibility to SCC, crack initiation, early-stage growth and dormancy, and crack growth to failure. For each step, a series of Research Guidelines has been derived from the results of individual research papers or studies. These Research Guidelines may or may not be easily validated against field data. The SCC Guidelines were then developed based on one or more Research Guidelines. Wherever possible, the SCC Guidelines have been validated against field data, but in some cases currently un-testable SCC Guidelines were defined because they offer a potentially unique opportunity to identify where and when SCC might occur.
Assessment of Corrosion Rates for Developing RBIs and IMPs for Production Pipelines
Authors: Poluyan Lyudmila V. , Timashev Sviatoslav A.
Published: April 2011

Corrosion rates (CRs) for defect parameters are playing a crucial role in creating an optimal integrity management plan (IMP) for production pipelines (well piping, inter-field pipes, cross country flow lines, and facility piping) with a thinning web and/or growing defects. CRs are indispensible when assessing the remaining strength, probability of failure (POF) and reliability of a production piping/pipeline with defect(s), and permit assessing the time to reaching an ultimate permissible POF, a limit state, or time to actual failure of the leak/rupture type. The CRs are also needed when creating a risk based pipeline inspection (RBI) plan, which is at the core of a sound IMP. The paper briefly describes the state of the art and current problems in consistent assessing CR parameters using different mathematical models of corrosion growth currently introduced to pipeline industry. The possible sources and the needed quality of direct assessment (DA) and in-line inspection (ILI) to construct comprehensive CR models are listed and formulated. Since corrosion or, in general, deterioration of pipelines is a stochastic time dependent process, the best way to assess pipeline state is to monitor the growth of its defects and/or thinning of its web. Currently the pipeline industry is using such methods as electric resistivity probes (ERP), corrosion samples (CS) and weight loss coupons (WLC) to define the CR for pipelines which transport extremely corrosive substances, or are located in a corrosive environment. Additionally, inhibitors are used to bring the CR to an acceptable level. In this setting the most reliable methods which permit assessment of CRs with needed accuracy and consistency, are probabilistic methods. The paper describes a practical method of predicting the probabilistic growth of the defect parameters using the readings of separated in time different DA or ILI measurements, using the two-level control policy [1]. The procedure of constructing the probability density functions (PDFs) of the defect parameters as functions of time, linear/nonlinear CR growth, and the initial size of the defects is presented. Their use when creating an RBI plan and IMP based on time dependent reliability of pipelines with defects is demonstrated in two illustrative cases — a production pipeline carrying crude oil, and a pipeline subject to internal CO2 corrosion.
Application of B-Added Low Carbon Bainite Steels to X80 UOE Line Pipe for Ultra Low Temperature Usage
Authors: Fujishiro Taishi , Hara Takuya , Terada Yoshio , Sakamoto Shinya , Asahi Hitoshi
Published: April 2011

Demand for high strength line pipes is increasing because of the reduction in natural gas transportation costs of pipelines. Low temperature toughness is required for high strength line pipes. Reduction in manufacturing cost of high strength linepipes is also required in an environment where alloying cost is increasing. To meet these requirements, boron (B) addition is extremely useful because the addition of very small amounts of B remarkably improves the strength and low temperature toughness. B-added low carbon bainite (LCB) line pipes with American Petroleum Institute (API) grade X60 to X80 have been developed for several decades [1–2]. B-added LCB steels have excellent low temperature toughness, however, it is challenging to achieve excellent crack initiation resistance and crack arrestability for ultra low temperatures such as −60°C. In particular, it is very difficult to achieve both excellent Drop Weight Tear Test (DWTT) properties of base metal, and excellent Charpy V-Notched (CVN) properties of seam welds in heavier wall thickness of X80 UOE linepipe. Metallurgical concepts such as the optimum chemical compositions, Thermo Mechanical Control Process (TMCP) conditions and seam weld conditions of B-added LCB steels with API grade X80 for ultra low temperature have been proposed in order to achieve the excellent mechanical properties even in a low manufacturing cost. Based on this concept, excellent DWTT properties of base metal and CVN properties of the seam welds of API grade X80 line pipe with 25mm thickness down to –60°C were obtained.
A Study on the Residual Stress and Fracture Behavior of Pipeline Girth Welds Joining Pipes of Different Strength
Authors: Kim Woo-sik , Baek Jong-hyun , Kim Choel-man , Kim Young-pyo
Published: April 2011

The following cases of girth welded region between pipelines having different base strength were considered. The pipeline shows different fracture behavior from girth welded pipeline between similar materials due to strength mismatch and residual stress distribution. Investigation about the residual stress distribution and fracture behavior of pipeline having girth welds of the differnet base metals (X70/X65 and X70/X42) with different material property has performed using finite element analysis. The effect of mismatched material property on girth weld region is negligible when shape of pipeline is similar. The assessment for occurance of crack on girth weld region with pipes with material property mismatched can be replaced by that of the similar pipes with low strength on the point view of conservation.
Stress-Corrosion Crack Initiation in X-52 Pipeline Steel in Near-Neutral pH Solution
Authors: Fang B. , Eadie R. , Elboujdaini M.
Published: April 2011

Specimens from a failed X-52 pipeline that had been inservice for 34 years were pitted using the passivation/immersion method developed by the authors to simulate pitted pipelines observed in service. The resulting pitted samples were then cyclically loaded in an aqueous near-neutral pH environment sparged with 5% CO2 / balance N2 gas mixture at high stress ratios (minimum stress/maximum stress), low strain rates and low frequencies which were close to those experienced in service. It was found that the majority of cracks initiated from the corrosion pits and were less than 0.5 to 0.6 mm deep and were generally quite blunt. These cracks were transgranular in nature and designated as Stage I cracks and were typical of cracks found in most crack colonies. However, the further growth of these short, blunt cracks was significantly influenced by the distribution of the nearby non-metallic inclusions. Inclusions enhanced the stress-facilitated dissolution crack growth, which is the crack growth method proposed by the authors in a related paper. When the orientation of the inclusions was at a small acute angle to the orientation of the pits or cracks, and the inclusions were in the same plane as crack initiation or advance, these inclusions would enhance crack growth, or even trap hydrogen which further resulted in the formation of clusters of tiny cracks, which appeared to be caused by hydrogen. The hydrogen-produced cracks could be eaten away later by the stress-facilitated further dissolution of the blunt cracks. If these cracks can grow sufficiently however they pose an integrity risk, as they can initiate long cracks (near-neutral pH SCC). These hydrogen-caused cracks in Stage I were rare. It was nevertheless suggested that cracks deeper than 0.5 to 0.6 mm in the field should be removed to reduce or avoid the threat of rupture. If active corrosion and hydrogen generation can be prevented then smaller cracks are innocuous.
Microstructure–Property Relationship in 22mm Thick X80 Coil Skelp
Authors: Liebeherr M. , Bernier N. , Le`bre D. , Ilic´ N. , Quidort D.
Published: April 2011

The progress in the development of heavy gauge X80 linepipe steel on coil at ArcelorMittal was recently rewarded with a 6000 ton commercial order for the production of 21.6mm wall thickness spiral welded pipe. The further product development is concentrating on the improvement of the impact toughness at low temperatures. Research is currently focussing on the relationship between the mechanical properties and the microstructure of the steels. In the present study, two industrially hot rolled X80 steels with thickness 21.6mm were investigated. The steels had the same chemical composition but were processed with different parameter sets in the hot strip mill. The two resulting low-carbon bainitic microstructures were composed predominantly of quasi-polygonal ferrite and globular bainitic ferrite / bainitic ferrite, respectively. Emphasis of the microstructure and property characterisation was laid on through-thickness gradients of grain size, hardness, texture, impact toughness and tensile properties. Accordingly, the materials were characterised at different positions in the thickness. Grain size and texture were determined by means of Electron Backscatter Diffraction (EBSD). Sub-size Charpy as well as sub-thickness tensile test specimens were taken at different positions in the cross section. The results show that the link between microstructure and properties is not at all obvious. The influence of mean grain size, grain size distribution and texture is discussed in detail.
Influence of Residual Stress on the HIC Resistance of High Frequency Induction Welded Pipes With Regard to Process-Specific Influencing Factors
Authors: Kra¨geloh Joachim , Brauer Holger , Bosch Christoph
Published: April 2011

Over the last decades an increase in the exploration and exploitation of impure oil and gas resources in remote environments under aggravated conditions has become necessary. This led to a growing demand for pipes with resistance to sour service conditions. Salzgitter Mannesmann Line Pipe has enhanced its product range of High-Frequency-Induction (HFI) welded pipes in recent years accordingly. In the process of HFI welding of pipes, forming roles bend steel coil into a pipe which is then welded together without any filler metal. This cold forming results in residual stress, depending on the diameter and wall thickness of the pipe. The current state of technology is based on the perception that this residual stress has an adverse effect on the resistance of line pipes to HIC, because it amplifies — or if it is sufficiently high — even triggers the onset of HIC. Aim of this paper is to study the influence of residual stress on the resistance in HFI welded pipes to HIC with regard to process-specific influencing factors. Four material strengths are selected for the tests. The first three material strengths (API 5L Grade from Grade B up to X65) are intentionally produced from non sour service material in order to obtain sufficient HIC damage. The highest material strength examined is a sour service material alternative to ascertain whether under optimal material conditions HIC indications can result solely from high residual stress. Plate and pipe segments are examined by means of the cross-sectioning method for longitudinal and circumferential residual stress at the process steps that influence the residual stress. A series of experiments under simulated residual stress to determine the HIC resistance of these pipe materials in NACE TM0284 test solution A is carried out using the four-point-bend test according to ASTM G 39, usually applied in sulphide stress cracking tests of line pipe steels. A characteristic HIC value, the crack area ratio CAR, is determined as a function of C and Mn content and residual stresses. To verify the results, FEM was used to model a test bar with the same geometry and to re-calculate the above-mentioned case. The results of these experiments combined with the supporting theoretical considerations and modelling prove that in the case of HFI welded line pipes, the residual stress induced by the process has no negative impact on the resistance of HFI welded pipes to HIC.
Skelp End Welding in Helical Pipe Production
Authors: Collins Laurie E. , Bian Yankui , Penniston Chris , Weber Paul
Published: April 2011

The production of large diameter pipe by the helical welding process requires that consecutive coils be welded together to facilitate the advance of each subsequent coil through the forming section of the pipe mill. Traditionally, the skelp ends have been joined by a single-pass submerged arc weld simply designed to join the skelp ends together and provide sufficient strength and ductility to survive the pipe forming operation. Subsequent to pipe forming, the length of pipe containing the skelp end weld (SEW) has been cut off and discarded. This process results in both a substantial yield loss as well as additional processing costs as the shortened pipes are later double jointed to produce full size lengths. To overcome these inefficiencies, a process has been developed for making high quality skelp end welds which meet API and CSA requirements. In this paper, the welding process will be described and evaluation of the integrity of the skelp end weld is discussed. Of particular interest are the properties of both the weld and associated heat affected zone in the vicinity of the “T” where the skelp end weld merges with the helical weld. This paper demonstrates that skelp end welds meeting rigorous integrity specifications can be successfully produced. Incorporation of suitable skelp end welding and inspection procedures in the pipe production process significantly enhances the efficiency of helical pipe production.
A Summary of Biofuel Pipeline Activities and Progress in the U.S.
Authors: Smith Robert
Published: April 2011

The US Government has mandated the production and usage of biofuels to help reduce dependence on foreign petroleum and to help improve air quality. Partnerships between the Pipeline and Hazardous Materials Safety Administration, the pipeline industry, other Federal and State agencies and the emergency first responder community are rapidly addressing infrastructure challenges and removing the technical and regulatory barriers for transporting biofuels. These initiatives are critical for enabling biofuel usage to grow nationwide and reach government production targets. This paper will summarize recent biofuel activities and discuss the progress seen in removing challenges for safely moving biofuels in the pipeline infrastructure.
Surface, Sub-Surface Mapping, Geohazard Identification and Associated Risk Mitigation for Pipelines
Authors: Mitchell Todd , Hitchcock Chris , Amine Dima
Published: April 2011

Capture and analysis of remote sensing data of surface and sub-surface conditions can provide significant logistical information for improved efficiencies and cost savings in pipeline construction, upgrade, and maintenance programs. Cutting-edge LiDAR topographical mapping as well as subsurface electromagnetic and magnetic sensing datasets are practical tools for evaluation of surface and subsurface geologic-related hazards (‘geohazards’), landslide and fault avoidance, alternate routing options, salinity/corrosion detection, determining construction feasibility and constraints including bedrock and overburden detection, and encroachment discovery. Resulting datasets can be placed into a GIS database as well as a three-dimensional visualization environment for complete design planning, asset management and future health modeling.
Innovative Method to Double Block and Bleed
Authors: Dum Frank , Drysdale Colin
Published: April 2011

Double Block and Bleed (DBB) is the preferred approach used to maximize safety while performing piping maintenance. The aim of the paper is to outline an innovative method of achieving DBB on pressurized piping or pipelines. DBB is traditionally achieved by several methods, for example, through using Two Valves, a Valve & a STOPPLE® plugging head, a STOPPLE plugging head & an Isolation Plug or Tandem STOPPLE plugging heads. There are also several DBB methods which utilize inflatable bags or bladders. The STOPPLE Train is a patent pending tool that uses 2 STOPPLE® plugging heads. Only one hot tap is required in the piping for which the STOPPLE Train is inserted. The first STOPPLE plugging head is the trailing plugging head and forms a primary seal. The second STOPPLE plugging head is the leading plugging head and forms a secondary seal. Once sealed, the bleed is accomplished through a relief port allowing downstream maintenance to commence.
Reliability Based Facility Risk Assessment
Authors: Harper William V. , Stucki David J. , Shie Taylor M. , Davies Ray J.
Published: April 2011

Pipeline facilities are ageing and will likely soon come under closer scrutiny from federal regulation. It is imperative that sound reliability based inspection procedures be established that meet the goals of an organization while controlling time and cost. DNV Columbus has developed a statistically based sequential inspection decision support system for this purpose. This system was implemented for an international petroleum company and quickened the inspection process by making a “stop inspections” or a “continue inspections” decision after each inspection at a facility. This system allows inspections to be stopped because the desired reliability metrics have been met. This means that the point of diminishing returns has been met based on inspections that did not reveal a significant amount of corrosion. At this point, further sampling would provide minimal additional value to the reliability assessment. Inspections can also be stopped because the estimated reliability metrics have not been met. Stopping for this reason indicates the facility may need more significant repair or replacement. Engineers and managers can then make a decision that includes a variety of factors including safety and the economic feasibility of alternates. In contrast, when using this method, inspections continue because insufficient data have been collected to determine whether the reliability metrics have been met. This system will be illustrated with actual data. It will also describe the use of four key safety factors in developing site specific reliability goals. These factors are consequence, off site migration probability, product type, and facility size. This work can result in a major savings in time and financial expenditures for an inspection cycle. This reliability based inspection methodology leads to the following improvements: 1) Quicker decisions to save time and money, and allows more sites to be inspected in a timelier manner, 2) The reliability of a group of inspections performed is quantified after each inspection, 3) Results at a facility are broken down by database driven categories into a scorecard, 4) Methodology kept generic to be easily adapted to a wide variety of situations.
Eddy Current Sensor Arrays for Pipeline Inspection With and Without Coatings
Authors: Washabaugh Andrew , Haque Shayan , Jablonski David , Goldfine Neil J.
Published: April 2011

Coatings are used on pipelines throughout the oil and gas industry for a variety of applications including corrosion protection, temperature maintenance, and weight control. These coatings also present a barrier to inspections for damage and typically need to be removed prior to inspection with nondestructive evaluation (NDE) methods. This has led to the development of improved NDE methods for detection and characterization of damage without removing the coatings or insulation. This paper describes adaptations of JENTEK’s Meandering Winding Magnetometer (MWM®)-Array technology for improved NDE in pipelines, including rapid and reliable imaging of damage, such as external corrosion, external mechanical damage, and stress corrosion cracking (SCC). The MWM-Array technology uses magnetic field-based sensor arrays and model-based inverse methods to determine electromagnetic and geometric properties of the pipeline material, which are then related to specific damage conditions of interest. This technology has been successfully applied in the aerospace and manufacturing industries and provides substantially improved performance for imaging surface and buried damage through coatings and for curved surfaces compared to conventional NDE methods. Several representative applications are described. These include: 1) imaging of near surface material loss through moderate thickness coatings (less than 1.5-in. (38 mm)); 2) imaging of mechanical damage through thin (less than 0.25-in. (6.35 mm)) coatings; 3) imaging of SCC through very thin (less than 0.030-in. (0.76 mm)) and thin (less than 0.25-in. (6.35 mm)) coatings. For SCC, digital imaging of damage regions and automated analysis tools for assessing individual cracks has the potential to be a replacement for magnetic particle inspection (MPI). Initial work has demonstrated these capabilities in a laboratory environment with some field testing and ongoing work is transitioning this technology into field environments.
Assessing the Full Costs and Benefits of Pipeline Options
Authors: Buckley Michael , Kirvan Ash
Published: April 2011

Decision-making on modern pipeline projects is subject to a broader and more complex range of influences and risk drivers than ever before. Issues such as new and tightening regulations, public health and safety, construction constraints, water constraints, arctic geotechnical issues, carbon management, Aboriginal interests and increased stakeholder participation all impact the lifecycle costs and benefits of pipeline project options. These are in addition to the more traditional issues that need to be addressed, which include point of origin, terminus location, routing, volumetric sizing and expansion scenarios. Superior decisions may be achieved on pipeline projects by the application of a structured triple-bottom line risk assessment at the front end of project planning. By adopting a broader view of the impacts of project operations, optimized solutions can be identified and proven, ultimately leading to a more profitable and lower risk commercial operation.
Pressure Cycling Monitoring Helps Ensure the Integrity of Energy Pipelines
Authors: Song Peter , Lawrence Doug , Keane Sean , Ironside Scott , Sutton Aaron
Published: April 2011

Liquids pipelines undergo pressure cycling as part of normal operations. The source of these fluctuations can be complex, but can include line start-stop during normal pipeline operations, batch pigs by-passing pump stations, product injection or delivery, and unexpected line shut-down events. One of the factors that govern potential growth of flaws by pressure cycle induced fatigue is operational pressure cycles. The severity of these pressure cycles can affect both the need and timing for an integrity assessment. A Pressure Cycling Monitoring (PCM) program was initiated at Enbridge Pipelines Inc. (Enbridge) to monitor the Pressure Cycling Severity (PCS) change with time during line operations. The PCM program has many purposes, but primary focus is to ensure the continued validity of the integrity assessment interval and for early identification of notable changes in operations resulting in fatigue damage. In conducting the PCM program, an estimated fatigue life based on one month or one quarter period of operations is plotted on the PCM graph. The estimated fatigue life is obtained by conducting fatigue analysis using Paris Law equation, a flaw with dimensions proportional to the pipe wall thickness and the outer diameter, and the operating pressure data queried from Enbridge SCADA system. This standardized estimated fatigue life calculation is a measure of the PCS. Trends in PCS overtime can potentially indicate the crack threat susceptibility the integrity assessment interval should be updated. Two examples observed on pipeline segments within Enbridge pipeline system are provided that show the PCS change over time. Conclusions are drawn for the PCM program thereafter.
Finite Element Analysis of Flaw Growth History
Authors: Yoosef-Ghodsi Nader , Duan Da-Ming , Chen Qishi , Petersen Randy , Fan Chengye
Published: April 2011

Finite element models of curved wide plate (CWP) samples were used to generate a family of load-deformation curves, where each curve corresponds to a flaw with a constant depth. This family of curves was then compared to the test results to find the flaw depth corresponding to each load step using two techniques. One technique is based on mapping the crack mouth opening displacement (CMOD) response obtained from finite element analysis (FEA) and tests, while the other one is based on FEA and experimental unloading compliance data. Both the CMOD mapping and unloading compliance techniques were applied to six CWP specimens and the results from the two techniques were compared. The CWP specimens included flaws either at the centreline of the girth weld or at the heat affected zone (HAZ). Nominal flaw sizes were 3 or 5 mm deep by 25, 50 or 75 mm long. For all specimens, testing continued until either maximum load was reached or specimen rupture occurred. Failure strain, defined as the remote strain at peak load, ranged from 1.1% to 4.1%. The flaw growth history curves from the CMOD mapping and unloading compliance techniques for a given specimen were generally found to be in close agreement. The prediction of flaw growth at failure for the specimens with flaw in the weld was closer to the experimental flaw growth at failure than for the specimens with flaw in the HAZ. The average FEA to test ratio of the flaw growth at failure for these two groups of specimens was 0.95 and 0.6, respectively. Additional analyses were carried out to study the effect of HAZ softening and the shape of the input stress strain curves beyond the onset of necking.
The Importance of Pre-Planning for Large Hydrostatic Test Programs
Authors: Bennett Andrew Keith , Wong Everett Clementi
Published: April 2011

Large hydrostatic test programs require extensive pre-planning to avoid increased costs and delayed schedules. Recently, Enbridge Pipelines Inc. completed construction and testing of more than 1,200 km of an NPS 36 oil pipeline for the Line 4 Extension Project and the Canadian portion of the Alberta Clipper Expansion Project over three construction seasons. A total of 57 mainline hydrostatic tests were successfully completed and approved by the National Energy Board. Following the first construction and hydrostatic testing season, many lessons were learned that were implemented for hydrostatic testing during the second construction season. The most important aspect of large pipeline hydrostatic test programs is locating and securing water sources. Extensive ground truthing must be preformed to adequately determine locations, volumes and access to water sources. Once potential sources are identified, water quality and environmental issues must be assessed, which leads to applying for and obtaining the necessary permits for water withdrawal and discharge. Leaving an important item such as water sources to be “field-determined” can lead to unanticipated complications, schedule delay and increased construction costs. Water sources are just one of the many important pre-planning activities that must be given adequate attention before the start of pipeline construction to successfully and efficiently manage a large pipeline hydrostatic test program. Many projects only complete high-level desktop-based hydrostatic test planning during the detailed design phase of a project. However, the potential cost and schedule impacts far outweigh the extra costs required to complete proper pre-planning during the detailed engineering phase of a project.
Design of Pipeline Damage for the BP X100 Operational Trial
Authors: Andrews Robert M. , Johnson James , Crossley Julie
Published: April 2011

As part of an ongoing pipeline technology program for BP Alaska, a 1 km, 48-inch diameter, X100 demonstration pipeline was constructed and operated for a period of two years. Artificial defects were introduced into one of the two test sections. These defects were intended to demonstrate that current assessment methods could be used to predict the behaviour of pipeline defects in a very high strength steel under realistic conditions including accelerated pressure cycling and a range of cathodic protection levels. The defects included in the trial were volumetric corrosion, mechanical damage, arc strikes and girth weld defects. The volumetric corrosion defects included both isolated defects and pairs of interacting defects. All the defects and details such as the girth welds were assessed for fatigue failure in addition to failure at the Maximum Operating Pressure. This paper describes the design of the defects for the trial. The defects were designed to be close to failure, so as to provide a realistic test of the predictive methods. Current methods were used including the Pipeline Defect Assessment Manual (PDAM) and ongoing work sponsored by PRCI.
Trends in Time-Delayed Failure Under Constant Pressure
Authors: Leis Brian , Cosham Andrew , Zhu Xian-Kui , Roovers Paul
Published: April 2011

It has long been recognized that a defect in a pipeline, such as a crack, or a gouge, or a dent and gouge, can fail at a constant pressure after some period of time has elapsed, which is commonly referred to as a time-delayed failure. Modern line-pipe steels are more defect tolerant than the earlier vintages, but can be more susceptible to time-delayed failures by virtue of their higher toughness and tolerance for larger defects. Nowadays many pipelines are subjected to in-line inspection such that many more defects that previously went undetected are now found. However, because metal-loss due to external interference could be inferred as external corrosion, whereas a feature associated with a dent could lead to more immediate response, it is not clear that ILI will expose this threat. Thus, the defects prone to time-delayed failures could remain in the pipeline even where ILI is used. To prevent time-delayed failures and minimize the risk to first-responders, it is important that the operator quantify the potential response defects relative to the line-pipe steel, the pressure history since detection or presumed date of contact, and the damage size, while initially making the conservative assumption that the metal-loss is a gouge. This paper describes work undertaken to develop these guidelines to direct first-responders, and highlights the remaining work to complete their validation.
Production of Grade X80 High Strain Linepipes for Seismic Region Application
Authors: Muraoka Ryuji , Kondo Joe , Ji Lingkang , Chen Hongyuan , Feng Yaorong , Ishikawa Nobuyuki , Okatsu Mitsuhiro , Igi Satoshi , Suzuki Nobuhisa , Masamura Katsumi
Published: April 2011

In order to achieve safety and reliability of long-distance gas transmission pipeline installed in seismic region while obtaining economical benefit by reducing material and construction cost, it is essential to apply the high-strength linepipes with sufficient strain capacity against buckling and weld fracture by seismic ground movement. At the same time, it is quite important to develop appropriate material requirement for strain capacity depending on the pipe dimension and strain demand of the region where the pipeline is installed. Grade X80 heavy gauge linepipes with excellent deformability were mass produced by applying advanced plate manufacturing technologies. These linepipes exhibit low Y/T and high uniform elongation in the longitudinal direction even after pipe coating. Strain capacity of the pipe against bending deformation with internal pressure was verified by conducting full scale pipe bending testing. In this paper, production results of high strain X80 linepipes for the application in long-distance pipelines in seismic region and full scale pipe bending and hydraulic burst test results were introduced.
Effect of Local Imperfections on the Collapse of Tubes Under Bending and Internal Pressure
Authors: Limam Ali , Lee Liang-Hai , Kyriakides Stelios
Published: April 2011

Previous work by the authors investigated the inelastic response and stability of pipes bent in the presence of internal pressure [1,2]. It was shown that internal pressure tends to stabilize the pipe by reducing initial geometric imperfections and reducing the induced ovalization. Consequently pressurized pipe can sustain significantly higher bending strains before collapse than pipe bent in the absence of pressure. Pipelines have girth welds and other local imperfections such as dents. The present phase of this work uses experiment and analysis to investigate the effect of local dents on the collapse capacity of pressurized pipes under pure bending. A series of experiments was conducted on stainless steel 321 seamless tubes with diameters of 1.5 inches and D/t of 52. Small imperfections in the form of transverse dents were introduced to the specimens using a custom technique that limits the axial and circumferential spans of the dents. The dented tubes were loaded by pure bending at a fixed internal pressure (approximately one half the yield pressure) to collapse. Tubes with dent depths ranging from very small to about 1.7 times the pipe wall thickness were tested. It was found that such local imperfections tend to reduce the bending strain capacity of the pipe quite significantly. Smaller depth dents tend to cause relatively larger reduction in the bending strain at collapse whereas at larger depths the bending strain at collapse tends to level off. The inelastic response and the eventual localized collapse are being simulated using FE models. The material is represented as an anisotropic elastic-plastic solid using the flow theory of plasticity. The modeling includes simulation of the denting process followed by pressurization and bending. It will be shown that all aspects of the observed behavior including the sensitivity of collapse strain to the local imperfection are reproduced well by the models.
Why Conduct SEN(T) Tests and Considerations in Conducting/Analyzing SEN(T) Testing
Authors: Kalyanam S. , Wilkowski G. M. , Shim D.-J. , Brust F. W. , Hioe Y. , Wall G. , Mincer P.
Published: April 2011

This paper outlines a methodology used to conduct a SEN(T) fracture test and discusses the analysis procedure used to obtain J-R and CTOD-R resistance curves from the experimental data. The CTOD-R curve depicts the change in toughness with crack growth, in a manner similar to the J-R curve methodology. Significant crack growth can arise from the start of ductile tearing to maximum load in the case of surface-cracked pipes with heavier-wall piping used in recent designs of natural gas pipelines that are required to handle greater pressures and much lower temperatures. CTOD-R curves provide toughness values that are a factor of 2 to 3 times higher at maximum load when compared to the toughness at crack initiation. The impacts of this on stress and strain-based design of pipelines are highlighted. Further, the differences between the traditional approach that uses the crack-tip-opening-displacement at the initial crack tip (CTOD′) versus the more recent developments that employ the crack-tip-opening-displacement at the growing crack tip (CTOD) are examined. The CTOD-R curve for the growing crack tip is more consistent with J-R curve analyses. Single-edge-notched bend [SEN(B)] or popularly called bend-bar specimens are used for crack-tip-opening-displacement (CTOD) as well as J-integral toughness testing. This paper discusses the advantages of using the fracture toughness data determined from a single-edge-notched tension [SEN(T)] specimen from considerations of the constraints faced by surface cracks in pipelines and the differences in fracture toughness values seen between the SEN(T) and SEN(B) specimens in the transition temperature region.
Statistical Predictive Modelling: A Methodology to Prioritize Site Selection for Near-Neutral pH Stress Corrosion Cracking
Authors: Cote Edgar I. , Ferguson James , Tehsin Nauman
Published: April 2011

Pipelines are subjected to both residual and applied tensile stresses, and can form near-neutral pH SCC (transgranular stress corrosion cracking) if the pipeline is exposed to a conducive environment and is made from a material that is susceptible to SCC. This transgranular SCC is an ongoing integrity concern for pipeline operators. As part of an SCC Integrity Management Program (IMP), it is necessary to perform integrity assessments and prioritize segments of the pipelines to manage the SCC threat. Ultrasonic crack detection in-line inspection tools have proven capable of locating SCC, but reliability of these tools is not absolute and the reduced probability of detection of subcritical flaws limits options for proactive management. Hydrostatic retesting is a very effective program for removing near-critical axial defects, such as SCC, but does not provide useful information as to the location of SCC along the pipeline. NACE Standard RP0204-2004 (SCC Direct Assessment Methodology or SCCDA) outlines factors to consider and methodologies to employ to predict where the SCC is likely to occur, but the standard acknowledges that there are no well-established methods for predicting the presence of SCC with a high degree of certainty. The trend in probabilistic modelling has been to focus on establishing deterministic relationships between environmental factors, tensile stress and SCC formation, and growth; these models have achieved varying degrees of success. The Statistical Predictive Model (SPM) was previously developed to predict the likelihood of occurrence of near-neutral pH Stress Corrosion Cracking (SCC) for the NPS 10 Alberta Products Pipeline (APPL). SPM Phase 5 uses selected predictor variables representing tensile stress, environmental, pipe-related, corrosion control and operational relevant factors to determine the Probability of Occurrence of SCC. Regression techniques were used to create multi-variable logistic regression models. The results for each model are checked at locations where SCC is known to be present or absent to assess predictive accuracy, then used to prioritize susceptible segments for field excavation. The relative strength of individual predictor variables provides insight into the mechanism of near-neutral pH SCC crack initiation.
Numerical Modeling of Plastic Deformations in UOE Line Pipe
Authors: Hilgert Oliver , Ho¨hler Susanne , Zimmermann Steffen , Kalwa Christoph
Published: April 2011

In this contribution a model to investigate the structural response of pipelines in view of strain based design is developed. The approach is based on analytical modeling and verified with finite element solutions. The model is derived at first for isotropic structural behavior. Several load cases, namely pressure containment and combined loads are then evaluated with specific strain based requirements and their corresponding stress states. As a result the influence of Y/T ratio and hardening exponent on the structural behavior can be confirmed numerically. Finally, the model is extended to anisotropic structural behavior. With this extension pressure-strain diagrams from numerical and experimental hydro tests show an enhanced correlation to each other.
Analysis of Pipe Expansion Associated With Field Hydrostatic Testing
Authors: Rapp Stephen C. , Dimopoulos Dimitris , Gotsis Vassilis , Lamberth William , Rosenfeld M. J.
Published: April 2011

Pipeline construction projects built in the United States to the recent requirements for operation at 80% SMYS are subjected to high stress pre-service hydrostatic tests. At very high stress levels, pipe diameter expansion, as measured by an ILI caliper tool, should not be a surprising result. In some cases, however, excessive pipe expansion has occurred and been reported by PHMSA in an industry advisory bulletin regarding potentially low yield strength results for X-70 and X-80 grade pipes. In response to this advisory notice, a detailed review was made of pipe expansion conditions for the 270 mile Southeast Supply Header (SESH) pipeline which was built in 2008. This review included a statistical analysis of the pipe yield strength and dimensional characteristics prior to installation, a review of hydrostatic test levels during the pre-service field hydrotest, and the corresponding diameter results measured by the multi-channel in-line inspection caliper tool. The results demonstrate that the pipe yield strength property distribution was well within good X-70 and X-80 process capability. The purpose of this paper is to demonstrate that explanations other than low yield strength pipe may be responsible for pipe expansion.
Actuation Requirements of a Warp Induced Variable Twist Rotor Blade
Authors: Mistry Mihir , Gandhi Farhan , Nagelsmit Martin , Gurdal Zafer
Published: April 2011

This paper examines a warp induced twist concept to obtain quasi-static large amplitude twist changes of helicopter or tiltrotor blades for performance benefits over diverse operating conditions. The concept presented in this paper has a cylindrical spar with rotating ribs, with the ribs attached to the skin which is slit along the trailing-edge. Warping the skin then produces twisting of the blade section, while bending loads are still transferred to the main spar. Warp actuation is implemented by rotating a threaded rod passing through alternating unthreaded and threaded blocks connected to the interior of the upper skin near the trailing edge. During warp actuation the torsion stiffness is reduced and the blade twists easily, but in “power off” condition, the threaded rod effectively converts it to a closed section with correspondingly higher torsion stiffness. A prototype based on this concept was built and tested for both the warp-twist relationship and the actuation torque requirements for producing the twist of the blade. The prototype has a NACA 0012 airfoil profile, a 10.75 in chord and a 42 in span, and was capable of variations of up to ±18 deg of tip twist. The finite element model developed in the paper correlated very well with the experimental measurements made on the prototype. The validated finite element model is further used to conduct parametric studies to understand the effect of the beam span length, skin thickness, rib spacing and actuation block spacing variation on the system characteristics.
Modelling of Wire-on-Drum Shape Memory Actuators for Linear and Rotary Motion
Authors: Scire` Mammano Giovanni , Dragoni Eugenio
Published: April 2011

The paper presents the analytical model of a linear/rotary solid-state actuator formed by a shape memory wire wound over a cylindrical drum. The model assumes a bilinear stress-strain behaviour of the wire in the martensitic state (low temperature) and a linear elastic response in the austenitic state (high temperature). Based on simple equilibrium conditions, the model calculates the stress and strain distributions in the wire subjected to a constant backup force and to frictional sliding forces at the contact with the drum. Closed-form expressions are supplied for the stroke produced by whatever actuator geometry. The model shows that large strokes (up to one half of the drum diameter) are achieved if the frictional coefficient is kept below 0.01. Rolling-contact architectures or sonic-pulse excitation of the drum are discussed as technical solutions to obtain such low friction values.
Applications and Mechanics of Pressure Adaptive Honeycomb
Authors: Vos Roelof , Barrett Ron
Published: April 2011

One of the most compliant structures in aerospace applications that does not suffer from certification constraints is plain honeycomb. It is widely used in primary and secondary structure of FAR 23/25 certified aircraft. In this research, the compliant nature of this material is being exploited by inserting pouches in each of the honeycomb cells. Pressurizing these pouches results in a stiffening of the overall structure. By having an external (spring) force act on the honeycomb structure, this variable stiffness results in an overall deformation of the honeycomb. Strains in excess of 50% can be achieved through this mechanism without encountering the material (yield) limits. It can be shown that based on the maximum pressure that can be extracted from the High-Pressure Compressor in a typical jet engine, the energy density of pressure adaptive honeycomb is on the par with that of shape memory alloy, while exhibiting strains that are an order of magnitude larger at a transfer efficiency that is close to 1. The paper discusses the mechanics of pressure adaptive honeycomb and describes a simple reduced order model that can be used to simplify the geometric model in a finite element environment. The theory that underpins this reduced order model is shown to correlate well to experimental tests. In addition, a proof-of-concept application is presented where pressure-adaptive honeycomb is integrated over the aft 35% of a wing section. It is demonstrated that camber variations in excess of 5% can be generated by a pressure differential of 40kPa. Results of subsequent wind tunnel test show an increase in lift coefficient of 0.3 at a wind speed of 45kts across an angle of attack ranging from −6° to +20°.
The Challenges of Modeling Magnetic Shape Memory Alloys Under Complex Load Paths
Authors: Waldauer Alex B. , Feigenbaum Heidi P. , Ciocanel Constantin
Published: April 2011

Kiefer and Lagoudas proposed a thermodynamic model for predicting the magneto-mechanical behavior of magnetic shape memory alloys (MSMAs) and then confirmed their model experimentally [1]. The model was calibrated by placing the test specimen under a constant magnetic field and a varying compressive stress. Later, Feigenbaum and Ciocanel [2] used the model to predict behavior under a constant compressive stress and a varying magnetic field. Because the two experiments were done by different researchers on different specimens, the calibration gave different values for material paremeters. In this work, through experimental results from tests performed on the same specimen by the same researchers, the Kiefer and Lagoudas model, with any hardening function, will be shown to be unable to be calibrated so as to accurately predict the magneto-mechanical behavior of a specimen under both types of loading conditions.
Multifunctional Composite Structures With Integrated Damping Treatments: A Parametric Study
Authors: Lepoittevin Gre´goire , Zogg Markus , Ermanni Paolo
Published: April 2011

A parametric study on composite laminate plates with integrated damping treatment is realized. The goal is to assess the impact of a viscoelastic core on the mechanical performances as well as on the vibration damping efficiency. This work considers as design parameters the damping layer thickness and its position in the laminate lay-up. The obtained results enable to propose a guideline for multifunctional composite structure with intergrated damping treatment.