bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Crack Tip Constraint Effects on the Assessment of Pipes Subjected to Combined Loading Conditions
Authors: Cravero Sebastian , Bravo Richard E. , Ernst Hugo A.
Published: July 2009

Under certain conditions, pipelines may be submitted to biaxial loading situations. In these cases, questions arise about how biaxial loading influence the driving force (i.e.: CTOD, J-integral) of possible presented cracks and how affects the material fracture toughness. For further understanding of biaxial loading effects on fracture mechanics behavior of cracked pipelines, this work presents a numerical analysis of crack-tip constraint of circumferentially surface cracked pipes and SENT specimens using full 3D nonlinear computations. The objective is to examine combined loading effects on the correlation of fracture behavior for the analyzed cracked configurations. The constraint study using the J-Q methodology and the h parameter gives information about the fracture specimen that best represents the crack-tip conditions on circumferentially flawed pipes under combined loads. Additionally, simulations of ductile tearing in a surface cracked plate under biaxial loading using the computational cell methodology demonstrate the negligible effect of biaxial loadings on resistance curves.
Modelling Magnetic Flux Leakage Signals From Dents
Authors: Clapham Lynann , Babbar Vijay , Marble Kris , Rubinshteyn Alex , Zarea Mures
Published: July 2009

The Magnetic Flux Leakage (MFL) technique is sensitive both to pipe wall geometry and pipe wall strain, therefore MFL inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, the combined influence of strain and geometry makes MFL signals from dents and gouges difficult to interpret for a number of reasons: 1) the MFL signal from mechanical damage is a superposition of geometrical and strain effects, 2) the strain distribution around a mechanically damaged region can be very complex, often consisting of plastic deformation and residual (elastic) strain, 3) the effect of strain on magnetic behaviour is not well understood. Accurate magnetic models that can incorporate both strain and geometry effects are essential in order to understand MFL signals from mechanical damage. This paper reviews work conducted over the past few years involving magnetic finite element analysis (FEA) modeling of MFL dent signals and comparison with experimental results obtained both from laboratory-dented samples and dented pipe sections.
Enhanced Valve Placement Decision Making Approach for Liquid Transmission Pipelines That Utilizes Risk Reduction Techniques
Authors: Weir David A. , Li Yanping
Published: July 2009

The Intelligent Valve Placement (IVP) approach that considers risk (defined as likelihood × consequence) reduction techniques to identify optimum locations for sectionalizing (block valves) for new liquid transmission pipelines has been enhanced to straightforwardly optimize valve placements based on the effectiveness and potential volume out reduction of valves. Valve effectiveness is a measure that quantifies the effectiveness of a valve in reducing volume out for pipe sections that can affect one or more identified sensitive areas. The valve effectiveness calculation does not adequately consider those situations where there is significant volume out reduction potential with few or no sensitive areas present, thus the potential volume out reduction for a given valve must also be considered. The enhanced IVP approach incorporates risk reduction by reducing consequence. This is achieved through potential reduction of impacts to sensitive areas and potential volume out reduction for pipeline ruptures. A method of establishing a decision making threshold for both the valve effectiveness and potential volume out calculations has been incorporated into the approach. The valve placement effectiveness and volume out calculations are applied in an iterative manner that facilitates quick and simplified interpretation and identification of optimum valve placement. The IVP approach meets and exceeds the requirements set forth in both the National Energy Board’s On-shore Pipeline Regulations and the U.S. Department of Transport’s Emergency Flow Restricting Device expectations set out in its HCA Rulemaking. This paper outlines the approach used to augment decision making within the enhanced IVP process and presents its application to new pipeline development. Limitations to the approach are also addressed.
Ductile Fracture Characterization of an X70 Steel: Re-Interpretation of Classical Tests Using the Finite Element Technique
Authors: Thibaux Philippe , Mu¨ller Se´bastien , Tanguy Benoit , Van Den Abeele Filip
Published: July 2009

The crack arrest capacity of a linepipe is one of the most important material parameter for such components. In current design codes, it is expressed as the energy absorbed by a CVN impact test. This prescribed impact energy for a given pipeline is typically between 50 and 120J, depending on the grade of the material, the pressure and the dimensions of the pipe. The continuous improvement of steel production has lead to the situation that the impact values achieved in standard pipeline steel production are much larger than 200J for the base material. The question of the significance of these high impact energies can be raised, particularly considering that no correlation has been found between CVN values and crack arrest properties of very high strength materials (X100–X120). In this investigation, instrumented Charpy tests and notched tensile tests were performed on an X70 material. The same tests were also simulated using the finite element method and the Gurson-Tvergaard-Needleman damage model. The combination of supplementary experimental information coming from the instrumentation of the Charpy test and finite element simulations delivers a different insight about the test. It is observed that the crack does not break the sample in 2 parts in ductile mode. After 6–7mm of propagation, the crack deviates and stops. The propagation stops when the crack meets the part of the sample becoming wider due to bending. Finite element simulations proved that it results in a quasi constant force during a displacement of the hammer of almost 10mm. The consequence is that more than 25% of the energy is dissipated in a different fracture mode at the end of the test. Finite element simulations proved also that damage is already occurring at the maximum of the load, but that damage has almost no influence on the load for two-thirds of the displacement at the maximum. In the case of the investigated steel, it means that more than 27J, as often mentioned in standards for avoidance of brittle failure, are dissipated by plastic bending before the initiation of the crack. From the findings of this study, one can conclude that the results of the Charpy test are very sensitive to crack initiation and that only a limited part of the test is meaningful to describe crack propagation. Therefore, it is questionable if the Charpy test is adapted to predict the crack arrest capacity of steels with high crack initiation energy.
Self Excited Eddy Currents for the Detection of SCC
Authors: Coleman Grant A.
Published: July 2009

Self Excited Eddy Currents (SEEC) present a unique and novel method for internal inspection of natural gas transmission pipelines for the presence of features aligned with the main pipe axis such as Stress Corrosion Cracking (SCC). This paper outlines the theory, methodology and basic design principles of building a SEEC based tool. Results from initial proof of concept testing are presented.
Predictive Assessment of External Corrosion on Transmission Pipelines
Authors: Pognonec Gae¨l , Gaschignard Vincent , Notarianni Philippe
Published: July 2009

Oil and Gas operators have to deal with the ageing process of their transmission pipeline grid. Some of these pipelines can be inspected using In Line Inspection (ILI) tools. In order to maintain an acceptable integrity level, re-inspection operations have to be performed. This process needs to be optimized in terms of resources and cost. Gaz de France R&D Division has developed a methodology which prioritizes rehabilitation operations on a pipeline after in-line inspections, and determines the optimal interval for re-inspection. A reliable help decision software tool which applies the methodology has also been developed. Dealing with defects assimilated to external electrochemical corrosion, the developed methodology is based on: • pigs information in order to assess a probable corrosion growth rate; • probabilistic distribution of input parameters (geometrical characteristics of defects, characteristics of the pipe and corrosion growth rate); • probabilistic methods of calculation : the probability of failure is calculated with the Monte-Carlo method. The convergence of the calculation is accelerated with the Cross Entropy method. The calculation results take the form of three probabilities of failure: • a punctual probability of failure for each defect; • an annual probability of failure for each defect; • an annual probability of failure per kilometer of pipe. To interpret the results, the annual probability of failure per kilometer of pipe is then compared with threshold values.
Geotechincal Assessment for Mitigation of a High-Pressure Pipeline Across Active Landslides: Design of a Directional Bore in Southern California
Authors: Hitchcock Christopher S. , Gailing Richard W. , Lindvall Scott C.
Published: July 2009

Landslides are often a hazard to high-pressure gas transmission pipelines operating in hilly and mountainous terrain. Typical mitigation options include pipeline rerouting or removing the landslide from the pipeline, if possible. When rerouting or hazard removal is not a viable option due to terrain conditions or the size of the landslide loading the pipeline, directional bores can be used to place the pipeline beneath the active portion of the slope failure. As part of our study of the geotechnical viability of mitigation options for a pipeline impacted by coastal landslides, rerouting and landslide mitigation alternatives were fully investigated. Geologic interpretation of high-resolution, publicly available IfSAR and privately-flown LiDAR data were used to evaluate alternative routes around active and potentially active landslides. Geotechnical borings through the landslides ultimately provided sufficient information supporting directional drilling beneath the active landslides as the most efficient alternative, returning the pipeline to full service.
Educational Program “To Practice Safety Is to Value Life”
Authors: Lopes Marcelo Garcez , Alves da Cunha Helena Lucia Sobral
Published: July 2009

Accidents which resulted in lost work time: using a different concept to deal with safety, focusing directly on the behavior of the worker, leading the worker to a sharper perception of the risks and thus enabling a change of behavior towards a safer attitude. “Sounds and Links” Project: the programmatic content was made through musical dynamics because music has the power to evoke feelings, stimulating the participants to live intrapersonal and interpersonal relationships in order to promote safe behaviors. The methodology used was: • “Andragogic (adult education) Model”; • multidiscipline language; • Methodology of “experiencing and living”; and • Focus on the day-by-day situations of work and life. The project was applied to four groups with 60 people, consisting of employees from TRANSPETRO and its contractors, other group with 60 people, composed by leaders, and one group with all participants of the five groups for the general closing session. Expected Results and consequences of the Project: • to turn the concept of safety as a real value to the worker; • to preserve the integrity and to value the life; pursuit a lasting and stable changing of behavior, based on a safety culture; and • to support the management safety system and reduction of the accidents.
Integrating Airborne Datasets Into the Design and Construction Planning Phases
Authors: Guerrero Hugo , Shankland Cameron
Published: July 2009

Today, obtaining field information in traditional pipeline design workflows rely on the use of conventional aerial photography, mapping and field visits. As a Designer, Engineer or Project Manager, a field visit can answer many questions and perhaps be the key to achieving a sound, successful design and installation. While conventional aerial orthophotography and mapping is invaluable during the design, it lacks a dimension that allows you to visualize the right-of-way the way you would if you were there. The use of Airborne Video and Oblique Imagery is not intended to replace conventional aerial orthophotography or mapping, but augment its use by providing a rich visualization that, in conjunction with the planimetric data sets, can aid the project team immensely during the design and permitting phase of a project. Currently, there are Airborne Data services available serving the pipeline industry that contain custom tools that either integrate into GIS platforms or operate as stand-alone proprietary software. These tools aid designers, engineers and constructors navigate through the video without having to sit and watch the whole video. In addition, video can be geocoded to specific pipeline or right-of-way features, such as a valve sites or stream crossings. Some tools even allow you to take rough measurements from visible features like fences or roads. Having such a dataset enables project team members to revisit any location along the right-of-way as many times as required to get information to finalize a design, permit application or to estimate the cost of construction. As Project Managers, we regularly face having new team members join the project at all stages of the project. Having a video to hand to new team members reduces the time they will take to get on board and familiarize themselves with the right-of-way. It also reduces the amount of field trips required just for this purpose. Another great use of Airborne Datasets is to use it during a pre-bid conference and provide it to the contractors bidding on the job. On large pipeline projects, it is unfeasible and impractical to have the project management team tour the entire right-of-way during a job walk, and there is likely areas along the right-of-way that are not very accessible thus requiring a flyover to review it with others.
Fracture Control in Pipelines Under High Plastic Strains: A Critique of DNV-RP-F108
Authors: Cosham Andrew , Macdonald Kenneth A.
Published: July 2009

Offshore pipelines experience strains greater than yield during pipelay and in service. Installation by reeling introduces high levels of plastic strain, typically on the order of 2 percent for a 12 in. flowline. Controlled lateral buckling in offshore pipelines, due to high operating pressures and/or temperatures, may also give rise to high strains and large cyclic loads. Similarly, frost heave or ground movement in onshore pipelines can cause high strains. To date, most of the cases involving high strains are to be found in offshore pipelines, in terms of both design and the assessment of accidental states. However, some of the experiences in the offshore industry have relevance to onshore pipelines. Fracture control in this context is designing pipelines to address the implications of these high static and cyclic strains during installation/construction and operation. Pipeline design codes such as DNV-OS-F101 and DNV-RP-F108 give guidance. Two issues to consider are: the degradation of the material properties, and the failure of the girth welds. High strains may cause failure or the growth — by stable ductile tearing — of preexisting flaws in the weld. Subsequent fatigue loading may cause pre-existing flaws to grow to failure. Engineering critical assessments (ECAs) are conducted during pipeline design to determine tolerable sizes for weld flaws. Standards such as BS 7910 and API 579 are primarily stress-based and it is not straightforward to apply them to strain-based situations. DNV-RP-F108 addresses this gap by providing additional guidance derived from UK and Norwegian research programmes. Assessing flaws subject to high strains is at the ‘cutting-edge’ of applied fracture mechanics. ECAs often have a reputation of being ‘over-conservative’. ECAs of pipelines subject to high strains may indicate that only very small flaws would be acceptable, whereas practical experience has shown that the girth welds are highly tolerant to the presence of flaws. It is therefore instructive to consider under what situations might ECAs be too conservative, and when they may be non-conservative. The available guidance for ensuring fracture control in pipelines under high plastic strains is discussed in this paper, and the wider issues are addressed.
Nearshore Geohazards in the Southern Beaufort Sea, Canada
Authors: Solomon Steven M. , Forbes Donald F. , Fraser Paul , Moorman Brian , Stevens Christopher W. , Whalen Dustin
Published: July 2009

Proposed development of a gas pipeline southward from the Mackenzie Delta and the presence of known accumulations of gas and oil in the southern Beaufort Sea suggest that construction of pipelines and associated infrastructure in the nearshore are likely to be proposed in the future. Recent surveys undertaken by Natural Resources Canada and its partners have focused on the shallow, poorly mapped nearshore region of the Mackenzie Delta (<6 m water depth) that extends ∼50 km offshore and lies largely within the landfast ice zone. Ice-keel scouring, strudel scour and nearsurface ice-bonding are being investigated. High resolution sidescan sonar and multibeam bathymetry systems were used to map the seabed over three consecutive years and show that ice keel scouring of the seabed is extensive. The maximum scour depth measured was 0.6 m in 6 m water depth with an average scour depth of 0.2 m. The same scours were visible in repeat surveys indicating that sedimentation was sufficiently low during the study, so that the scours were not infilled. Strudel drainage and associated seabed scour occurs when spring-melt river water overflows onto the surface of the landfast and bottomfast ice once discharge exceeds under-ice channel capacity, then drains back through the floating landfast ice via cracks and holes. Although common offshore of small deltas on the Alaska and Yukon coast, these features were first documented in the Mackenzie Delta area during field surveys in 2006 and 2007 that revealed strudel drainage (radial drainage patterns) features on the ice surface. A total of three strudel scours were later identified using swath-survey equipment in 1.2 m of water. The largest scour was 20 m wide with a maximum depth of 0.8 m below the surrounding seabed. Extensive surveys in Alaska have identified strudel scours exceeding 3 m below the seabed. Nearsurface ice-bonding and permafrost are known to occur in shallow water where sea ice freezes to the seabed. A combination of Synthetic Aperture Radar (SAR), ground penetrating radar (GPR) and multi-year ground temperature measurements have been used to map the horizontal and vertical extent of nearsurface ice bonding in extensive shoals found off the front of the Mackenzie Delta. In the shallowest water depths permafrost extends to 22 m below the seabed with an active layer of less than 1.2 m. In deeper water, permafrost disappears but seasonal frost can form in the upper 2–3 m of the seabed.
The Effect of Hoop Stress on the Burnthrough Susceptibility During In-Service Welding of Thin-Walled Pipelines
Authors: Boring Matthew A. , Bruce William A.
Published: July 2009

Most companies control the risk of burnthrough by prohibiting welding on pipelines with wall thicknesses below a specified thickness. This is a safe approach but the risk of burnthrough depends not only on the wall thickness, but also on the welding parameters and the operating parameters of the pipeline which include pressure. It is generally acknowledged that the hoop stress caused by pressurizing the pipeline has a relatively minor effect on the risk of burnthrough since the size of the area heated by the welding arc is small. While this has certainly been shown to be true for thicker materials, previous research has shown that the pressure can have a dramatic effect on burnthrough risk for thinner materials. The objective of this project was to further investigate the effects pressure and hoop stress has on the burnthrough risk of welding onto thin-walled pipelines in service. For circumferential welds, pressure and wall thickness determine the burnthrough risk and pipe diameter appears to have no effect. The failure mechanism for circumferential welds is consistently a burnthrough. For longitudinal welds, pipe diameter does appear to affect burnthrough risk even though the effect appears to be secondary to pressure and wall thickness. The pipe diameter is believed to be more influential for longitudinal welds because of the larger area of heated material that is exposed to the hoop stress. Also, the results indicate that the magnitude of the hoop stress has a direct effect on the failure mechanism for longitudinal welds (i.e., burnthrough or weld centerline cracks). For longitudinal welds, the failure mechanism is commonly burnthrough for welds made onto pipes with a hoop stress below 30% specified minimum yield stress (SMYS) which indicates that the internal pressure of the pipe is the main driving force for failure. Longitudinal welds made on pipes which are experiencing hoop stress above 30% SMYS commonly fail by weld cracking. It is important to note that even though pressure does have an effect on the burnthrough susceptibility of welds made on thin-walled pipelines, pressure only becomes a factor for welds made at heat input levels in excess of what is predicted safe by thermal analysis modeling.
Societal Risk as an Input to Risk Assessment
Authors: Harron Lorna
Published: July 2009

Societal risk has been investigated in the United Kingdom by the Health and Safety Executive (HSE) (2), the Netherlands (1), and most recently Canada (3). All methodologies focus on the high consequences of a significant event with a low probability of occurrence. Enbridge Pipelines Inc. uses various techniques to assess risk of mainline pipe and facilities. An index based risk model has been used for both mainline and facility risk assessment to provide relative risk values. These models have proven to be a useful means of risk evaluation. However, there are certain facilities or segments of pipe that have been identified by operating personnel as sensitive areas for reasons other than those defined for high consequence areas under 49CFR195 for liquid operations and 49CFR192 for gas operations regulated by the United States Department of Transportation. This paper proposes a method of identifying and quantifying these higher sensitive areas that could be applied to the any organization in the Oil and Gas Industry by incorporating societal risk into existing risk methodologies. For the purposes of this paper, societal risk is defined as the presence of a sensitive area from a social viewpoint with the potential for enhanced risk control or negative public reaction in the event of a significant incident at a specified location. Societal risk is approached in this paper as a multiplier to the total risk score obtained from existing risk assessment techniques. This multiplier can be applied to risk models, quantitative risk evaluations or other numerical based risk methodologies. This paper discusses the development of a societal risk factor, including a definition and scope for societal risk, and application of this risk multiplier to existing risk assessment techniques. Risk management strategies that may result from the use of a societal risk factor are also included.
A Methodology for the Prediction of Pipeline Failure Frequency Due to External Interference
Authors: Lyons C. , Haswell J. V. , Hopkins P. , Ellis R. , Jackson N.
Published: July 2009

The United Kingdom Onshore Pipeline Operators Association (UKOPA) is developing supplements to the UK pipeline codes BSI PD 8010 and IGE/TD/1. These supplements will provide a standardized approach for the application of quantified risk assessment to pipelines. UKOPA has evaluated and recommended a methodology: this paper covers the background to, and justification of, this methodology. The most relevant damage mechanism which results in pipeline failure is external interference. Interference produces a gouge, dent or a dent-gouge. This paper describes the fracture mechanics model used to predict the probability failure of pipelines containing dent and gouge damage and contains predictions of failure frequency obtained using the gas industry failure frequency prediction methodologies FFREQ and operational failure data from the UKOPA fault database. The failure model and prediction methodology are explained and typical results are presented and discussed.
Testing of a Dual Field Magnetic Flux Leakage (MFL) Inspection Tool for Detecting and Characterizing Mechanical Damage Features
Authors: Rubinshteyn Alex , Paeper Steffen , Nestleroth Bruce
Published: July 2009

Battelle has developed dual field magnetic flux leakage (MFL) technology for the detection and characterization of mechanical damage to pipelines. The basic principle involves the use of a high magnetic field between 140 and 180 Oersted (11.1 to 14.3 kA/m) and the use of a low magnetic field between 50 and 70 Oersted (4 to 5.6 kA/m). At high magnetic field levels, the flux leakage signal is primarily influenced by changes in the geometry of a pipe wall. At low magnetic field levels, the MFL signal is due to residual stresses and metallurgical changes as well as geometry changes to the pipe caused by mechanical damage and wall thinning. A decoupling signal processing method developed by Battelle is used to isolate the portion of the mechanical damage signals due to metallurgical damage and residual stresses, which allows the characteristics of a dent-gouge feature to be more clearly differentiated. The decoupling method involves first scaling down the high field signal to the level of the low field signal, and then subtracting it from the low field signal. This produces a decoupled signal that is primarily influenced by the residual stresses and metallurgical changes caused by mechanical damage. Rosen has developed a tool to test the dual field technology and is evaluating tool performance by running the tool in a 30 inch diameter pipeline segment. The tool itself is composed of three separate modules coupled together: a high field unit downstream of a low field unit which is downstream of a caliper arm unit that is used to detect and characterize reductions in the internal diameter. The general and magnetic design of the tool, along with the scaling algorithm is discussed. Results from a pull test in a pipe section with dents whose geometry has been independently characterized are also discussed. This work is partially funded by the U.S. Department of Transportation, Pipeline and Hazardous Materials Safety administration (DOT PHMSA) and the Pipeline Research Council International, Inc. (PRCI).
On the Mechanism of AC Assisted Corrosion of Buried Pipelines and Its CP Mitigation
Authors: Ibrahim I. , Meyer M. , Tribollet B. , Takenouti H. , Joiret S. , Fontaine S. , Scho¨neich H.-G.
Published: July 2009

Mechanisms of AC assisted corrosion of pipelines under cathodic protection (CP), and CP criteria for its mitigating remain still subjects of controversy. This paper presents a critical review of the fundamental understanding of the AC assisted corrosion phenomenon and also some laboratory investigation; such as the analysis of corrosion products obtained under carefully controlled AC corrosion tests using Raman spectroscopy, simultaneous recording of potential and current, and separation of this experimental overall current into its faradic and charging of the double layer capacitance contributions. For the latter, a simplified equivalent circuit model of the steel / solution interface, taking account of the interfacial and transport phenomenon was used. Results obtained are discussed: • to highlight the effect on corrosion rate and corrosion feature, of some critical parameters namely AC current density, AC voltage amplitude, CP level, soil resistance between the coating defect and remote earth, and development of iron oxide layers; • to devise some aspects on the mechanistic view of the phenomenon; and • to comment on the CP criteria currently in use, with a special focus on the dependency of CP protection level with AC current density and voltage amplitude.
On the Probabilistic Distribution of External Pitting Corrosion Rate in Buried Pipelines
Authors: Caleyo F. , Vela´zquez J. C. , Hallen J. M. , Araujo J. E. , Perez-Baruch E.
Published: July 2009

External pitting corrosion constitutes the degradation mechanism responsible for about 66% of the incidents reported in the last decade for oil and gas pipelines in Mexico. Thus, major efforts are underway to improve the characterization and modeling of pitting corrosion of buried pipelines. Special attention is devoted to estimate the average corrosion rate and corrosion rate variance because they are the key parameters in the estimation of the trend in pipeline reliability. This work presents the results of field and simulation studies in which soil and pipe data were gathered together with the maximum depth of external corrosion pits found at more than 250 excavation sites across southern Mexico. The distributions of parameters such as chloride, bicarbonate and sulfate levels, resistivity, pH, pipe/soil potential, humidity, redox potential, soil texture and coating type have been used to predict the distribution of pitting corrosion rate of pipelines in contact with clay, clay-loam and sandy-clay-loam soils. The time dependence of the pitting corrosion rate was fitted to a power law through a multivariate regression analysis with the maximum pit depth as the dependent variable and the pipeline age and the soil and coating properties as the independent variables. Monte Carlo simulations were conducted in which random values drawn from the distributions fitted to the field data were used to evaluate the power law model proposed for the corrosion rate. For each soil type, the distribution that best fitted the corrosion rate data was found. The results of this study will provide reliability analysts with a more accurate description of the growth rate of external corrosion pits. It is expected that this information will positively impact on integrity management plans addressing the threat posed by this damage mechanism.
Repair Technology for Single Deck Distortion of Floating Roof Tank
Authors: Pan Hongli , He Ping , Liu Guangzhong
Published: July 2009

The repair welding procedure and assembly method that is considered as the key of repair single deck distortion are pointed out in this paper. Also presented is the repair plan of single deck distortion which consists of four stages: stress release, distortion repair, stress adjusting, and sequential assembly. The steps and technical requirements of repair single deck distortion are as follows: Step 1: Installing repairing platform — The platform should have enough stiffness, or else it will influence the repair effect of single deck distortion. Step 2: Inspecting the stress and distortion of single deck plates — The intention of inspecting the stress and distortion of single deck plates is in order to select the welds which should be retained or removed, and to confirm the sequence of removing the welds. The method of lattice is applied in inspection. Step 3: Removing single deck plates — The principle of removing single deck plates is to remove longitudinal welds and adjust the longitudinal distortion of single deck plates first, then removing transverse welds and adjust the transverse distortion of single deck plates. Step 4: Eliminating the local stress of single deck — The key of eliminating local stress of single deck is to control the skill of releveling the single deck plates, assembly of shaped single deck plates, dot welding of single deck plates and inspecting the distortion of the single deck plates. Step 5: Eliminating the integral stress of single deck — The single deck is divided into nine parts. Small distortion of single deck is eliminated first, then the serious distortion. Step 6: Adjusting the distortion of assembled single deck plates — Adjusting the distortion of assembled single deck is a very important process for single deck repair. The adjusting method is from integral to local and then from local to integral of single deck repeatedly. Step 7: Welding single deck plates — The step is to weld short welds first, then long welds. From the center to all sides of single deck, the method of skip welding is applied. Step 8: Nondestructive examination — All welds should be examined in accordance with relevant standards. This technology can eliminate 98% of single deck distortion, which can eliminate the sinking risk of floating roof. The technical requirements of construction process developed in this paper can also be used to instruct the construction of the new floating roof tank’s single deck. The construction process helps to reduce the initial distortion of single deck.
Extending the In-Line Inspection Interval for a Gas Pipeline Using Direct Assessment
Authors: McCallum Marcus , Ford Graham , Francis Andrew
Published: July 2009

RWE npower own and operate a 12km long 8″ diameter natural gas pipeline that supplies natural gas from the National Transmission System (NTS) to a CHP unit. The pipeline has a nominal wall thickness of 6.35mm, is constructed from API 51 X42 grade steel and has a maximum operating pressure of 75barg. The pipeline was commissioned about 8 years ago and has been operating safely since that time. The pipeline was designed in accordance with BS 8010 Parts 1 and 2, with consideration given to the Institute of Gas Engineers Recommendations, IGE/TD/1, IGE/TD/9 and IGE/TD/12. One of the requirements of IGE/TD/1 is that the time interval between in-line inspections should not normally exceed 10 years. However, IGE/TD/1 Edition 4 allows the time interval to be exceeded if justification can be demonstrated using risk based techniques. For older pipelines it is often possible to determine the required time dependent failure probability based on the results of previous ILIs. This allows the time to next ILI to be determined. This time will depend on what has been found previously and values of other pipeline parameters. However, in the case of this pipeline there are no previous ILI data. In view of the above a probabilistic approach to External Corrosion Direct Assessment (ECDA) was adopted. The method makes use of the results from the above ground surveys rather than ILI data. However, in this instance, rather than being used to determine the time interval to the next above ground survey the method was used to determine the time interval to the next (first) ILI. The method is based on structural reliability analysis (SRA) which is used to determine the time dependent probability of failure based on available data. In view of the quantity and quality of the available above ground survey data it was possible to use the method to extend the time to the next ILL by several years.
Crack Geometry Effect on Stress-Strain Fields for Crack Under Biaxial Loading
Authors: Minami Fumiyoshi , Ohata Mitsuru , Watanabe Daisuke , Igi Satoshi , Kubo Takahiro , Suzuki Nobuhisa
Published: July 2009

With increasing demand of high strength and high pressure pipelines in gas transmission industries, the fracture control design of pipelines has been driven primarily. This paper addresses the stress and strain fields for a crack in a wide plate component under biaxial loading, which simulates a large diameter pipe subjected to inner pressure coupled with axial loading. Three-dimensional FE-analyses are conducted. It was found that biaxial loading has a significant effect on the stress fields of through-thickness crack; the near crack-tip stress is elevated to a large extent by biaxial loading. By contrast, the stress field for a surface crack is not sensitive to biaxial loading, while the near crack-tip stress at the crack corner is increased locally by biaxial loading. The Weibull stress criterion was applied to discuss the biaxial loading effect on the brittle fracture strength of the wide plate. Ductile crack initiation properties are also discussed with two-parameter (plastic strain and stress triaxiality) diagram. The ductile damage is increased by biaxial loading for a through-thickness crack, whereas a surface crack has little effect of biaxial loading on the ductile damage.
Comparison of Soil Properties From World-Wide Full-Scale Pipe Testing Facilities
Authors: Rudland D. , Mannucci G. , Andrews R. , Kawaguchi S.
Published: July 2009

The dynamic behavior of an axially propagating crack in buried line pipe is dependent not only on the pipe material, and the decompressing gas, but also the surrounding soil. The density and cohesiveness of the soil restrains the forming pipe flaps behind the crack tip and decreases the apparent crack driving force. Traditional fracture analyses, such as the Battelle Two-Curve (BTC) approach, lump the soil behavior into one empirical correction factor that does not differentiate between different soil types. In this effort, soils from the full-scale pipe test facilities in the United States, Italy, United Kingdom, and Denmark, were tested with standard procedures to characterize the soils by type, grain size, density and strength. A comparison of these properties is presented in this archival paper, which can be used in future fracture analysis development efforts.
Dealing With Knowledge Uncertainties in Pipeline Reliability Based Design and Assessment
Authors: Nessim Maher , Zhou Joe , Fuglem Mark
Published: July 2009

Knowledge uncertainties result from limitations of the data and other information required to define parameters that are used in estimating reliability with respect to a given failure threat. The parameters affected typically represent distribution parameters of input random variables used in the calculation; for example, the mean corrosion growth rate for a given pipeline segment. Knowledge uncertainties are distinct from randomness, which is typically manifested in variations in the basic input parameters affecting a given limit state; for example, variations in the excavator force applied to the pipeline in different impact events. Randomness is reflected in the probability distributions used to model the input variables affected and is automatically built into the reliability estimate. However, the reliability estimate is conditional on the values used for parameters affected by knowledge uncertainty. Since these parameters can take a range of values with different probabilities, knowledge uncertainty is best represented as a distribution or confidence interval on the calculated failure probability. Two approaches are proposed to deal with knowledge uncertainties in Reliability Based Design and Assessment (RBDA) applications in which design and operational choices are accepted if they meet a specified reliability target. The first is a formal approach in which reliability targets must be met with a specified level of confidence (e.g. meet the reliability targets with 90% confidence). The second approach is an informal one in which a single conservative value is used for each parameter affected by knowledge uncertainties. Although this approach relies on the judgment of the user, it has the advantage of being simple. In the context of standardizing RBDA, it is recommended that epistemic uncertainty be identified as an important issue that must be considered in demonstrating compliance. It is also recommended that both formal and informal approaches be permitted as viable means of accounting for epistemic uncertainty. The informal approach should be included as a minimum requirement, whereas the formal approach should be presented as an option. This recommended strategy addresses epistemic uncertainty without creating a significant obstacle to the application of RBDA.
First Chinese SCADA System for Long Distance Oil and Gas Pipelines
Authors: Yufei Xia , Tse Wai , Qin Xinyan , Liu Sheng , Zhang Sen
Published: July 2009

Up until 2007, China has been relying on foreign SCADA vendors to provide SCADA systems for the controlling and monitoring of long distance oil and gas pipelines. While foreign SCADA systems satisfy most requirements, there are still issues such as high cost, limited localization, lack of experienced local representatives, and slow to respond to system changes, etc., remain to be solved and improved in the future. In Jan 2006, Sinopec, one of the major oil and gas corporations in China, initiated a joint venture with a local IT company, Beijing East Mainstay Technology Company Ltd. (East MS), to develop a SCADA system for oil and gas pipelines. The first prototype was finished in Aug 2006. It then went through 4 months of rigorous system testing and refinement and finally it was applied to 5 refined products pipelines in China. This paper unfolds the architecture of the system and discusses the system features in detail to give the audience an insight into the first Chinese SCADA system for long distance oil and gas pipelines.
Property of X80 Grade SAW Pipes for Resistance to Ground Movement
Authors: Takeuchi Izumi , Matsumura Masakazu , Okaguchi Shuji , Shitamoto Hidenori , Fujita Shusuke , Yamamoto Akio
Published: July 2009

It is aware that the expansion of gas utilization is an important issue to restrict CO2 emission. The reduction of gas transportation cost is essential to increase gas supply to market. The high-pressure gas pipeline with high strength pipes has contributed for safe and economical transportation of natural gas and is expected more for the future demand of gas. The primary objective of high strength line pipe is to hold high pressure safely. The property in circumferential direction under hoop stress is the primary target of the line pipe. High strength and high toughness steel at low temperature has been developed for large diameter line pipes, which have been supplied to major gas pipelines. The increase of D/T of pipelines for transportation efficiency tends to decrease critical compressive strain. Since long distance pipelines come across various ground conditions, the pipeline might encounter some serious ground movement. It is pointed out that in this event the strain by the ground movement might be high enough to deform pipelines to leak or rupture. There are various forms of ground movement, but the Japanese guideline for earthquake resistance and liquefaction is considered as basic conditions for SBD and for FEA in this study. The relation between pipe deformation and property in axial direction is investigated to identify the effective parameter to design the steel property for gas pipelines. Metallurgical factors and microstructure can change the parameters not only on strength and toughness, but also on the critical strain of X80 line pipes. It is discussed that the effectiveness of those changes to improve the safe operation of high-pressure gas pipelines with X80 grade line pipe.
Research on Mechanics Monitoring System of Long Distance Oil and Gas Pipeline
Authors: Cui Tao , Wang Weibin , Liu Guangwen , Ma Tingxia , Tong Wenqiang
Published: July 2009

The paper establishes a comprehensive organizational framework and a mechanical Remote Monitoring System with SCM technology, electronic communicating technology, network technology, electronic measuring technology, which can be used for long-distance pipeline stress and strain, displacement and the pressure monitoring. The system complete data collection, amplification, conversion, transmission, storage and automatic measurement from acquisition in the pipeline surface resistance strain tablets with the pipeline deformation resistance changes with the contingency collection, data conversion processor, complete automatic control box, and use GPRS data transmission means to achieve the long-distance data transmission and control.
Effects of Millscale on Corrosion of ASTM A 36 Steel in 3% NaCl
Authors: Schwarz-Tonhauser Melissa
Published: July 2009

Millscale is an oxide layer formed during the manufacturing processes of the pipe. Standard corrosion specimen preparation as recommended by ASTM G1 includes the cleaning and removal of the millscale layer, often by abrasion or acid pickling. These cleaning techniques can act to change the mechanical surface properties and can result in hydrogen charging. These standard corrosion tests do not show the true nature of the corrosion. The effects of millscale generally have been ignored in the past first due to the large amount of scatter that can be introduced into the results and second due to the belief that the millscale has negligible effects on the overall corrosion rate. This paper explores the effects of millscale on the corrosion conditions of hot rolled ASTM A36 steel with and without mill scale in dearated 3% NaCl solution at various pH levels through polarization experiments.
Improving Pipeline Integrity Management Through Using Corrosion KPIs
Authors: Morshed Ali
Published: July 2009

To mitigate the threat of corrosion in any hydrocarbon pipeline a pipeline corrosion management strategy (CMS) is required. Once this Pipeline CMS is implemented its performance should be monitored and assessed on a regular basis to maintain and improve pipeline integrity. Corrosion key performance indicators (KPIs) are a powerful tool and should be used for this purpose. This article provides a detailed account on how corrosion KPIs are selected, expressed and what their main benefits are for hydrocarbon pipelines.
Effects of Density and Viscosity Measurements Errors at the Pipeline Batch Tracking System
Authors: Liebenberg Marais , Bueno David Eduardo G. P. , Magalha˜es Claudia C.
Published: July 2009

Batch Tracking System (BTS) is commonly found as pipeline operational real time functionality within operator companies’ control room. It tracks batches, offering amongst other information their volumes, positions and Estimated Time of Arrival (ETA). In order to reliably calculate those system outputs, BTS requires operational information like pressures, temperatures and flow rates, elevation profile, as well as some fluid physical properties, being the most important ones density and viscosity. This work aims to track the actual necessity of measuring those variables and to establish their impact on ETA in a 700km long South African multi-product pipeline network. Thus, the flow dynamic was analysed using a commercial pipeline flow simulator, where the network operational scenario was entirely reproduced and then variations of density and viscosity were introduced to track the effects on batches’ ETA, per pipeline segment. As a result of the study, which employed usual refined products such as petrol and Diesel, it was identified: (i) both variables played a relevant role on the ETA estimation requiring to be accurately determined, even though viscosity is the most relevant; (ii) viscosity showed a more predictable behaviour as flow resistance shall take place independently of the elevation profile; (iii) density was highly dependent of the elevation profile; and (iv) the biggest ETA accumulated variation verified was around 128 minutes (due to a variation of –20% in the viscosity value) and the lowest one around 4 minutes (due to a variation of –2% in the density value).