bluuebunny/crossref_metadata_2025 huggingface dataset:
Field Validation of a Dynamic Model for an MFL ILI Tool in Gas Pipelines
Authors: Botros K. K. , Golshan H.
Published: April 2011

Movements of pigs in gas pipelines are subject to more stringent parameters than that in liquid pipelines, predominantly due to the compressibility of gas. This is accentuated when the pig has to negotiate an upward inclination in the section of the pipeline, where the gravity force due to its weight can compromise the driving pressure drop across it. On a downward slope, a pig can accelerate to a velocity higher than the maximum required for the proper operation the instrumentation (which is typically around 5 m/s). On the other hand, in-line inspection tools often face challenges at wall thickness transitions or bends. The ability to accurately predict the functional performance of pigs is vital in the design and operation of pipelines and their associated pigging programs. The present paper provides a general formulation for the motion of pigs in an inclined pipeline section, taking into account effects of gas properties, wall friction, by-pass flow for speed control, differential pressure across the pig, seal efficiency, and gap flows, among other parameters. Comparison between model prediction and actual data from pigging a 158 km NPS 18 gas pipeline on TransCanada’s pipeline system in Alberta, Canada is presented. The elevation profile along this pipeline contains both positive (upward) and negative (downward) slopes. This is a lateral line which features 28 gas receipt points along the line, all were feeding in gas during the pigging program. Good agreement between model prediction and field data is demonstrated within ± 8% of St. Deviation. Example of a problem occurring at wall thickness transition at a valve section is demonstrated by a sudden stop of an MFL tool followed by a shootout at a higher velocity once the pressure is built up behind it.
Pressure Influence in LPG Measurements by Uncertainty Evaluation
Authors: Cruz de Oliveira Elcio
Published: April 2011

In Brazil, National Metrology Institute, INMETRO, elaborated an N° 64 Ordinance, on April 11th 2003 [1], based on OIML [2]. This document approves the Metrological Technical Regulation, establishing the metrological and technical requirements applicable to measurement systems supplied with flow meters used in the measurement of oil, its derivatives liquid, alcohol anhydrous and hydrous alcohol fuel. For custody transfer purposes, liquefied petroleum gas (LPG) volumes are generally stated at a fixed base temperature and saturation pressure. As most volume transfers occur at temperatures and pressures other than standard conditions, these volumes are adjusted to standard conditions through the use of correction factors. The measurement uncertainty of these custody transfer systems must be controlled. Based in norms ASTM, IP, ISO and API – MPMS, the mathematical model for the calculation of the volume, it basically depends on quantities as: K factor, density, pulse number, turbine meter factor, temperature and pressure corrections. This work develops a methodology to calculate the LPG mass uncertainty that is completely different form the other liquid oil derivatives. This work details this calculation showing the complex temperature and pressure algorithms, including the equilibrium bubble point pressure. Based on this methodology, it is noticed that the pressure uncertainty contribution is not less than 43% overall the process and the expanded uncertainty is less than 1%, as required by INMETRO.
Evaluation of Double Jointing Girth Welds of High Grade Line Pipes
Authors: Duan Da-Ming , Lazor Robert , Taylor David
Published: April 2011

Double jointing is an effective approach for pipeline construction in terms of both welding productivity and consistent weld quality as a result of a controlled working environment. However, the high heat input associated with the submerged arc welding (SAW) process used for double jointing must be considered with respect to the material properties of both heat affected zone (HAZ) and the weld metal of double jointing welds. This is particularly important for strain-based design pipeline applications utilizing high grade pipe, such as X80 and X100. High grade pipe materials achieve their strength as a result of controlled rolling practices that produce a fine grained steel. High heat input welding results in an increased grain size in the heat-affected zone, and often results in softening and a detrimental effect on the properties of the welded joint. The softening effect in the HAZ will potentially cause highly localized deformation, which is undesirable in conditions where strain-based design is applicable. Understanding the material mechanical property in double jointing welds, and approaches for measuring mechanical behavior of such welds are required in order to meet the increasing demand for double jointing in the pipeline industry. This paper presents an approach that has been used in TransCanada for understanding and evaluating double joint welds of high grade pipes. The approach has been implemented into detailed testing protocols, data analysis procedures and requirements, and has been proven to be an effective and practical means for double jointing evaluations.
Effects of Inline Inspection Sizing Uncertainties on the Accuracy of the Largest Features and Corrosion Rate Statistics
Authors: Huyse Luc , van Roodselaar Albert
Published: April 2011

With the increased acceptance of the use of probabilistic fitness-for-service methods, considerable effort has been dedicated to the estimation of the corrosion rate distribution parameters. The corrosion rate is typically computed from the difference in anomaly size over a specific time interval. The anomaly sizes are measured through either in-line inspection or direct assessment. Sizing accuracies for inline inspection methods are reasonably well established and in many cases the sizing uncertainty is non-negligible. In many approaches that are proposed in the literature the time-averaged corrosion rates are computed without explicitly considering the effect of the sizing uncertainties and as a result considerable interpretation and engineering judgment is required when estimating corrosion rates. This paper highlights some of the effects of the sizing uncertainties and the resulting biases that occur in the subsequent reliability calculations. These assessments are used to determine the most appropriate course of action: repair, replacement, or time of next inspection. The cost for repair or replacement of subsea pipelines is much higher than for onshore pipelines. For subsea applications, it is therefore paramount that the risk calculations, and therefore the corrosion rate estimates, be as accurate as possible. In subsea applications, the opportunity to repair individual defects is often limited due to practical constraints and there is merit in an approach that focuses on entire spools or pipeline segments. The proposed statistical analysis method is ideally suited to this application although the principles behind the analysis apply equally well to onshore lines subject to either internal or external corrosion threats.
Measurement of CTOA of Pipe Steels Using MDCB and DWTT Specimens
Authors: Xu S. , Tyson W. R. , Eagleson R. , McCowan C. N. , Drexler E. S. , McColskey J. D. , Darcis Ph. P.
Published: April 2011

Two types of specimen for crack tip opening angle (CTOA) measurement have been investigated for pipeline applications, i.e., the modified double cantilever beam (MDCB) (at NIST) and the drop-weight tear test (DWTT) specimen (at CANMET). Results of effects of specimen types, thicknesses and loading rates on CTOA are summarized and discussed. The main observations include: (i) For both MDCB and DWTT specimens tested at quasi-static loading rate, crack front tunnelling (i.e., with a deep triangular crack-tip shape) was present in high-strength steels; (ii) For DWTT specimens, CTOA values measured optically at the surface were significantly higher than those from the simplified single-specimen method (S-SSM) and those measured at mid-thickness [on sections cut using electric discharge machining (EDM)]; and (iii) CTOA values from surface measurement of MDCB specimens were comparable to those derived from S-SSM of DWTT specimens, but the surface values of DWTT were higher than those of MDCB specimens.
Validation of Latest Generation EMAT In-Line Inspection Technology for SCC Management
Authors: Marr Jim , Tappert Stephan , San Juan Riverol Elvis , Mann Andy , Weislogel Jo¨rg , Jiangang Sun
Published: April 2011

TransCanada typically manages the integrity of sections of gas transmission pipelines that are susceptible to stress corrosion cracking (SCC) by periodically performing hydrostatic testing. Interest in an alternative approach to manage pipeline integrity in the presence of SCC and other forms of longitudinally oriented defects resulted in the endorsement of the latest generation of dry coupled in-line inspection tool. GE’s EMAT In-Line Inspection (ILI) tool uses the electromagnetic acoustic transducer technology to meet this requirement. This paper will summarize field experience results of the latest generation Emat In-Line inspection tool, which is commercial available since September 2008. It demonstrates, that the challenges have been overcome, the targets have been achieved, and the tool delivers the information of a distinguished ability of detection, sizing and discrimination performance, key parameters to conduct an effective pipeline integrity program.
Advanced Technologies for Manufacturing High Strength Sour Grade UOE Line Pipe
Authors: Kobayashi Kenji , Omura Tomohiko , Takahashi Nobuaki , Minato Izuru , Yamamoto Akio
Published: April 2011

X70 grade large diameter UOE linepipe steel for sour service has been manufactured stably by optimizing the continuous casting process, controlling the shape of inclusions and decreasing coarse precipitates. It is confirmed that the HIC and SSC resistance are good enough for severe sour conditions to apply. These higher strength linepipe steels for sour service are useful for the offshore and deep-sea pipelines. Additional improvements of HIC and SSC resistances are needed for manufacturing thicker and higher strength UOE linepipe steels for sour service. Optimizing alloying elements and ACC process are very important for the additional improvements of HIC and SSC resistance. In addition, the HIC evaluation method should be revised in order to match applied field conditions.
Initial Approach to Assess Lateral Buckling Behavior: Comparison Between Design and Operational Condition of Offshore Pipeline
Authors: Solano Rafael Familiar , Antunes Bruno Reis , Hansen Alexandre Santos
Published: April 2011

Recently Petrobras has been developing a production module of Roncador field through the P-52 platform in the Campos Basin, offshore Brazil. This platform is a floating production facility located in deep water and was tied back to the PRA-1 platform in shallow water by an 18-inch pipeline in order to export the oil production. This pipeline operates under high pressure and high temperature (HP/HT) conditions and was laid on the seabed. As a result of the extreme operating conditions, this pipeline is highly susceptible to lateral buckling and a buckle initiation strategy based on triggers to control the buckling behavior was designed. Thus sleepers and distributed buoyancies were designed and installed along the pipeline route. In addition to the buckles at the triggers, some additional, on-bottom, buckles were assessed in order not to compromise the design strategy. In recent geophysical data surveys carried out along the route length with the pipeline in operation, both engineered and on-bottom buckles were identified. This paper aims to present the thermo-mechanical design of the P-52 oil export pipeline, performing a comparison between some results obtained in design and observed during operation. Thus this paper intends to evaluate the pipeline as-built plus the operational pipeline configurations, and to assess the robustness of the design strategy applied regarding lateral buckling behavior.
The Analysis of Deviations on Measured Volumes Between OSBRA Pipeline Tank Farms and Its Customers
Authors: Kotchetkoff Neto Andre´ Paulo , Kawamoto Fabio Yoshikazu
Published: April 2011

The Sa˜o Paulo–Brasi´lia pipeline (OSBRA) is a collection of installations built to transport, store and deliver Diesel oil, gasoline and Liquefied Petroleum Gas (LPG), from the Refinaria do Planalto (REPLAN) to several distribution companies located in the Brazilian Midwestern region. The volumes of these fuels are usually measured before deliverance at two serial measurement points: at the OSBRA tank farm installations and at the customer tank farm installations. At the OSBRA tank farms, the volume of each delivered batch product is usually measured by turbine type custody Measurement Station, called EMED. On the other side, at the customer tank farm, the received volume is usually measured by tank gauge systems or, in a few cases, by the customer EMED. The procedure used by PETROBRAS in Brazil is to compute the differences between these measurements and to compare these differences each month with a pre-established data range. If the differences computed are lesser than that benchmark values, the measurement is considered good. Otherwise, inspections of the measurement installations must be done, looking for the causes which deviates the measurement differences out of the desired range. That pre-established data range was built over historical data and using statistical tools. In this paper it is proposed to use statistical tools to analyze the behavior of the already existing historical data differences, rather than see only the differences magnitudes. These tools can give more information about each pair of measurement system, like the existence of systematic errors, the variability of each individual system and even if an observed difference greater than the pre-established data has real significance. These tools can be used to analyze other measurement system, like to verify the accuracy of operational measurement devices and to check if the mass conservation among the entries and withdraws of a system is being achieved. Furthermore, a real data analyze between two tank-farms is presented.
Effects of M/A Islands Microstructure Characteristic on Mechanic Properties of High Grade Pipeline Steel
Authors: Tong Ke , Shao Xiaodong , Zhu Lixia , Liu Qiang , Li Jinfeng
Published: April 2011

The microstructure characteristic of martensite/austenite (M/A) islands of X80-1#, X80-2#, X100-3#, X100-4# steel pipelines come from different manufacturer were investigated by OM and SEM contrastively, and the influence of M/A islands microstructure characteristics of pipelines were studied combining with tests of mechanic properties. The result shows that the effect of the M/A islands volume fraction, average dimension, form and distribution on the material strength, yield ratio and toughness were distinct. When the M/A islands distribute uniformly with small size and spherical or crossed strip form, under the certain volume fraction, the pipeline steel exhibits excellent strength-toughness matching.
Microstructure Evolution in the HAZ of Girth Welds in Linepipe Steels for the Arctic
Authors: Poole W. J. , Militzer M. , Fazeli F. , Maalekian M. , Penniston C. , Taylor D.
Published: April 2011

A critical aspect of building pipelines to transport natural gas will be development of suitable high strength steels and new economic welding procedures, e.g. dual torch welding, without compromising the pipeline’s structural integrity during its in-service performance. The objective of this project is to predict the microstructure and mechanical properties of the weld heat affected zone (HAZ) of an X80 linepipe steel as a function of its temperature-time history. The approach taken involves a combination of experimental techniques and advanced modelling approaches. On the experimental side, dual-torch weld trials for assessment of spatial and temporal variations of temperature in the HAZ were conducted. To simulate and investigate the microstructure evolutions in the HAZ, i.e. precipitate dissolution, austenite formation, grain growth and decompositions, Gleeble thermo-mechanical simulations were performed. These simulations include rapid heating and cooling tests at rates of up to 1000 °C/s. Notably, real-time monitoring of austenite grain growth was possible by using a novel laser ultrasonic technique. Further, bulk samples were produced using the Gleeble adopting the experimentally determined temperature time history. These bulk specimens were subsequently subjected to tensile and fracture resistance tests. A concise overview of these novel experimental activities, highlighting new insights, is presented and challenges associated with the measurements are discussed.
Prediction of Pipe Wrinkling Using Artificial Neural Network
Authors: Chou Z. L. , Cheng J. J. R. , Zhou Joe
Published: April 2011

As the demand for oil and gas resources increases pipeline construction pushes further into the geologically unstable Arctic and sub-Arctic regions. Consequently, these buried pipelines suffer much harsh environmental and complex loading conditions. In addition, higher strength and larger size pipes with higher operation pressure are used gradually. These severe and unknown conditions increase the risk of pipeline failure, especially, local buckling (wrinkling) failure. The wrinkling failure and sequential pipe fracture can cause enormous cost loss as well as high risk in safety and environmental impact. In the past, to prevent the buried pipelines from buckling failure, the pipeline maintenance was processed by periodical inspections and excavations in the field. The whole procedure is expansive and time consuming, and has no active warning system for possible failures between the inspection periods. Therefore, to overcome these problems, an automatic warning system for monitoring pipeline buckling is developed. A damage detection model (DDM) with artificial neural network (ANN) is a kern of the warning system and discussed in this paper. The proposed DDM will allow engineers to diagnose the pipe condition reliably and continuously without interrupt the normal operation of buried pipelines. The proposed DDM successfully identifies the distributed strain patterns in local characteristics as well as global trend. Some significant findings in the ANN model working with distributed strain patterns of the pipes are discussed, and a guideline of applying the DDM to the field pipe is also presented in this paper.
Study on Tensile Property and Strain Ageing Behavior of X100 Linepipe
Authors: Li Yang , Zhang Weiwei , Gong Shaotao , Ji Lingkang , Huo Chunyong , Feng Yaorong
Published: April 2011

A series research programs and industrial trials of X100 linepipe have been launched by CNPC so as to build an X100 trial in China for long-distance gas pipeline in the coming years. In present paper, tests have been conducted on 20.6mm×1016mm diameter Grade X100 linepipe. The microstructures, tension properties will be presented. In order to investigate the influence of anti-corrosion coating process on the performance of pipe, strain aging tests in lab have been carried out as well. It is found that testing method, tensile specimen size and sampling location had a noticeable effect on the testing results. The difference is also observed between the flattened strap specimen and round bar. The influence of time, temperature and pre-strain amount of aging tests on the shape of S-S (stress-strain) curve, tension tests results, yield ratio of pipes are presented as well.
The Role of Electrochemical Conditions in Near-Neutral pH SCC Initiation Mechanism(s)
Authors: Eslami Abdoulmajid , Marvasti Mohammadhassan , Chen Weixing , Eadie Reg , Kania Richard , Worthingham Robert , Van Boven Greg
Published: April 2011

In order to improve our understanding of near-neutral pH SCC initiation mechanism(s), a comprehensive test setup was used to study the electrochemical conditions beneath the disbonded coatings in cracking environments. In this setup the synergistic effects of cyclic loading, coating disbondment, and cathodic protection were considered. Our previous results showed that there can be a significant variation in the pH of the localized environment under the disbonded coating of pipeline steel. The pH inside the disbondment can change significantly from near-neutral to high pH values, strongly depending on the level of cathodic protection and CO2 concentration. Both of these variables affected the electrochemical conditions on the steel surface and therefore the initiation mechanisms. This work highlights the role of electrochemical conditions in near-neutral pH SCC initiation mechanisms.
Modeling Approaches for Anisotropic Material Properties of High Strength Steel Pipelines and the Effect on Differential Settlement
Authors: Neupane Sunil , Adeeb Samer , Cheng Roger , Zhou Joe
Published: April 2011

High strength steel (HSS) pipelines exhibit anisotropic behavior; the yield stress in the circumferential direction is higher than the yield stress in the longitudinal direction. In addition, the shape of the stress vs. strain curve is distinctly different. The circumferential stress vs. strain curve has a sharp yield point, while there is no distinct yield point in the longitudinal direction. Most of the research done in the past on the behavior of high strength steel was based on the isotropy assumption. The material behavior of high strength steel pipelines cannot be satisfactorily modeled based on this assumption. Different material models are available which can take into account this plastic anisotropy of high strength steel. They can be grouped into two categories. First, there are models which treat material as intrinsically anisotropic [15]. And, there are other models which can take into account plastic anisotropy as being caused by the load history. In this paper, the plastic anisotropy is modeled using the second approach. Freezing and thawing of the discontinuous permafrost in the northern regions of Canada causes differential settlement of pipes. This induces significant longitudinal stress in addition to the circumferential stress due to internal pressure. It is very important to accurately model the differential settlement of the pipe and the stresses caused by it. In this paper the differential settlement is modeled using beam elements in Abaqus. The behavior of the pipeline under differential settlement loads is investigated using three different material models. The first two are assuming that the material behaves according to the traditional isotropic plasticity model, once with the longitudinal and another time using the circumferential stress strain curve as basis for the model. The third one is using an analytical virgin material stress strain curve based on the kinematic hardening plasticity model which predicts the appropriate behavior in each direction. The displacement versus the reaction force of the pipe is obtained for pipes without internal pressure and for pipes subjected to internal pressure causing a circumferential stress that is 80% of the specified minimum yield strength of the material. It is found that the response of the pipe is different for different material models. The response based on the analytical virgin material stress strain curve is closer to the response based on the longitudinal stress strain curve when the pipe is not subjected to internal pressure. But, when the pipe is subjected to internal pressure, the response using the analytical virgin material curve is closer to the circumferential stress strain curve.
Failure Assessment for Girth Weld Defects of Pipeline
Authors: Feng Qingshan , Lin Yi-han , Li Bin , Song Hanchen
Published: April 2011

This paper studies some key issues of fitness-for-service assessment for pipelines constructed in 1970s in Northeastern China, which were found to have large amount of weld defects resulting in leakage and rupture accidents. The mechanical behaviors of tensile strength, Charpy V-notch impact energy and fracture toughness are tested for the spiral weld metal and pipeline steel, showing that the state standards of steel for pressure vessel are still met after serving for more than 30 years. The safety limit line of the failure assessment diagram (FAD) is derived according to BS7910: level 2B assessment, based on the obtained stress-strain curve of weld metal. The chemical composition of pipeline steel analyzed by the energy spectrum method indicates the pipeline was made of 16Mn steel. The metallographic examination reveals that the metallurgical structure of weld metal was composed of ferrite and pearlite with five different zones. The morphology of tensile fractured surface shown by ductile dimples indicates the tensile fracture is of ductile type, which implies the weld metal and pipeline steel after long time service have not yet become brittle. The stress magnification factor for the bulge effect of through-wall girth defect is extracted from the stress intensity factor evaluated by the finite element simulation method, indicating the applicable ranges of Kastner solution and Schulze et al solution. The stress magnification factor caused by the bending stress of the misalignment imperfection of girth weld joint is calculated by FEM to review the applicability of relevant formulas given in BS7910 for engineering critical assessment. Finally, it is concluded by FE simulation that though the stress magnification effect of shallow cracks in weld toe zone is significant, it may be insignificant in its fracture failure assessments.
The Characteristics of Girth Welds for Strain-Based Design API-X100 Grade Plate and Pipe
Authors: Chae Hyunbyung , Song Woohyun , Lee Jinwoo , Seo Donghan
Published: April 2011

As the major oil wells run dry, many efforts on exploring a new one are under way especially in the northern area of the Earth. In this cold environment, the pipelines should have a distinctive ability of being able to endure the large longitudinal strain caused by the ground movements, such as seismic activity, slope instability, frost heave and so on. To overcome these difficulties strain-based design (SBD) of pipeline is getting spotlighted, and POSCO has developed SBD API-X80 including higher grades of line pipe steels. In this work noticing that the reliability of girth welds becomes more important in SBD compared with stress-based design, ways to improve the reliability of girth welds in a SBD API-X80 grade steel have been investigated. Mechanical and metallurgical properties were evaluated, and further CTOD tests in mechanized gas metal arc (GMA) girth welding with narrow gap grooves were conducted and the results were discussed.
Description of Pipeline Strength Degradation as a Pure Death Markov Process and Its Implementation in IMP
Authors: Bushinskaya A. V.
Published: April 2011

The paper describes a new comprehensive Markov model of deterioration of the pipeline residual strength as related to its ability to withstand the inner pressure due to defects growth, and its implementation when designing the pipeline integrity management program (IMP). This Markov model is designed for defects that will cause pipeline rupture (the model describing pipeline leak is given in [8]). The pipeline degradation is described by a non-homogeneous pure death Markov process of the continuous time, discrete states type. The initial data used to construct this model is the whole set of defects found during an ILI, and verification or DA. This set is then filtered to select defects which will actually contribute to the pipeline rupture type of failure. For each of such defects its residual strength is calculated, using one of the three internationally recognized pipeline design codes: B31Gmod, DNV, and Shell-92. The constructed model is checked by an independent method, which compares the Markov model with real life experimental data, combined with sound analytical corrosion growth models. The above model takes into account formation of new defects and elimination of dangerous defects via pipeline repair. This approach provides an assessment of the conditional probability of rupture of a pipeline segment, as it is derived using the data set from a specific pipeline length. On the basis of this model an algorithm is constructed for optimizing the time of the next inspection, using the two-level maintenance policy. Results of numerical analysis show that the expected number and volume of repairs largely depend on the value of the ultimate permissible pipeline failure probability. A brief description of the software which implements the described above methodology is given.
Determination of Full Range Stress-Strain Behavior of Pipeline Steels Using Tensile Characteristics
Authors: Hertele´ Stijn , De Waele Wim , Denys Rudi
Published: April 2011

It is standard practice to approximate the post-yield behavior of pipeline steels by means of the Ramberg-Osgood equation. However, the Ramberg-Osgood equation is often unable to accurately describe the stress-strain behavior of contemporary pipeline steels with a high Y/T ratio. This is due to the occurrence of two distinct, independent stages of strain hardening. To address this problem, the authors recently developed a new ‘UGent’ stress-strain model which provides a better description of those steels. This paper elaborates a methodology to estimate suited parameter values for the UGent model, starting from a set of tensile characteristics. Using the proposed methodology, good approximations have been obtained for a preliminary series of eight investigated stress-strain curves. Next to all common tensile characteristics, the 1% proof stress is needed. The authors therefore encourage the future acquisition of this stress level during tensile tests. Currently, the authors perform a further in-depth validation which will be reported in the near future.
Effect of Fracture Speed on Ductile Fracture Resistance: Part 1—Experimental
Authors: Shim Do-Jun , Wilkowski Gery , Duan Da-Ming , Zhou Joe
Published: April 2011

The effect of fracture speed on the ductile fracture resistance of line-pipe steels can have an important effect in the basic understanding of the toughness requirements for crack arrest. Over the last few decades, it has become recognized that the drop-weight tear test (DWTT) better represents the ductile fracture resistance than the Charpy test since it utilizes a specimen that has the full thickness of the pipe and has a fracture path long enough to reach steady-state fracture resistance. However, the fracture speed in the DWTT is typically 50 to 60 feet per second (15.2 to 18.3 m/s), whereas the fracture speed in the full-scale pipe test is 300 to 1,000 fps (91.4 to 305 m/s). Recently, the authors have extended the DWTT work and developed a modified back-slot DWTT specimen to obtain higher fracture speeds. One aspect of this modified specimen was to increase the width of DWTT sample from the standard 3-inch (76.2 mm) to 5-inch (127 mm). This was done to increase the ligament length in a relatively deep back-slotted specimen to capture more steady-state data. The initial experimental results demonstrated that this type of specimen can be used to obtain higher fracture speeds. Furthermore, the experimental results clearly showed the effect of fracture speed on the ductile fracture resistance. In this paper, to extend the work on modified back-slot DWTT specimens, the tup was instrumented to measure the load during dynamic impact. From this, the load-displacement curve, steady-state energy (or energy per area) was obtained for the modified back-slot DWTT specimens. These results were compared to those obtained from the standard 3-inch specimens. These results also clearly showed the effect of fracture speed on fracture resistance.
SE(T) Testing of Pipeline Welds
Authors: Drexler Elizabeth , Wang Yong-Yi , Sowards Jeffrey W. , Dvorak Marc D.
Published: April 2011

Single edge-notch tension (referred to as SE(T) or SENT) tests are increasingly being used in the pipeline community, as they are a laboratory-scale fracture toughness test, capable of being performed on linepipe steels and welds. The constraint and loading conditions of the SE(T) specimens more closely correspond with actual field flaws than those of the conventional three-point-bend CTOD (crack tip opening displacement) specimens. The test matrix covered in this paper consists of two nominally X65 pipes and one X80 pipe. Two welding procedures were applied to one of the X65 pipes, resulting in two different welds. Consequently four girth welds were in the test matrix. Notches were cut with electrical discharge machining (EDM) from the outer-diameter (OD) surface of the pipe with the target locations in the base metal, weld centerline, and heat-affected zone (HAZ). The EDM notches were grown by fatigue precracking in a three-point bend fixture to generate sharp flaws. The specimens were loaded in tension and periodically unloaded to generate J-integral resistance curves. The specimens with the weld and HAZ flaws were tested at room temperature and three to four lower temperatures. This paper covers the specimen preparation and the comparison of test results among specimens with different flaw locations at a wide range of temperatures. The specimen preparation and fatigue crack front straightness presented significant challenges. In general, at a given temperature, cracks propagated at lower energies in the weld material than in the HAZ or base material. Comparison of the J-integral curves for the even-matched and over-matched welds showed greater toughness in the over-matched weld at lower temperatures (but still on the upper-shelf of the curves of the ductile-to-brittle transition temperature (DBTT)). Testing at low temperatures appears to affect the HAZ differently than the weld material, as significant increases in toughness were observed between room temperature and −80°C in the HAZ.
Innovative Plugging Head Solution for a Nitrogen Gas Pipeline Provider in Latin America
Authors: Dum Frank , Drysdale Colin
Published: April 2011

A major nitrogen gas pipeline provider in Latin America was faced with an emergency situation when a local hot tapping contractor failed to perform what seemed to be a simple hot tapping job on an 8″ nitrogen gas line. The tapping machine became stuck and caused a gas leak. Faced with a leaking pipe and a hot tapping machine that was stuck to the pipeline, the pipeline provider called upon TDW to resolve the multiple issues and perform the hot tap as originally intended. A customized solution was required and a special plugging head was designed that included a plug holder with a urethane plugging head. A 6″ hot tap was made on the part of the pipeline that was direct opposite to the faulty hot tap, and the hole from the faulty hot tap was immediately plugged with the urethane plugging head. The tapping machine was subsequently removed and valve finally closed. The focus of this paper is intended to illustrate the importance of safety and introduce a unique back-up solution that can be put together in the event of an emergency.
Large Scale Experiments to Study Hydrogen Pipeline Fires
Authors: Acton Michael R. , Allason Daniel , Creitz Leonard W. , Lowesmith Barbara J.
Published: April 2011

To gain an understanding of the risks associated with a hydrogen pipeline failure, Air Products commissioned GL Industrial Services UK to perform two experiments where a buried 6″ diameter pipeline at an initial pressure of 60 bar was intentionally failed using an explosive charge to generate a full bore release of hydrogen gas from two open ends, simulating a pipeline rupture event in which a ground crater is formed naturally in the surrounding soil by the released gas. The first experiment was performed with the pipe buried 1m deep in a typical soil and the second experiment was performed with a 1m deep backfill of a mixture of sand and soil. The hydrogen released was ignited immediately following the pipeline failure. Following initiation of each experiment, the properties of the hydrogen gas release and resulting fire were measured. The two experiments were conducted under similar conditions, with the main differences being the nature of the soil used for the pipeline backfill and the wind speed (which was significantly higher in the first experiment). The initial pipeline pressure was very similar in the two experiments, with complete depressurisation of the gas pipeline and reservoir taking place over a period of approximately 80 seconds. Maximum flame lengths of up to approximately 100m were measured in each experiment. A number of previous experimental programmes have been carried out by GL in order to investigate the fire characteristics of natural gas releases from ruptured pipelines, conducted under nominally similar conditions. Recently, experiments of this type were also conducted to investigate releases of mixtures of hydrogen and natural gas. The paper will present a high level overview of the results including a discussion of the observed differences between the release and fire behaviour of the different gases.
Characterization of Weld Metal Deposited With a Self Shielded Flux Cored Electrode for Pipeline Girth Welds and Offshore Structures
Authors: Narayanan Badri K. , McFadden Lisa , Mills M. J. , Quintana Marie A.
Published: April 2011

Pipeline girth welds deposited with a self-shielded flux cored electrode process (FCAW-S) have been characterized to assess the effect of micro-alloying elements on microstructure and precipitate evolution and correlate it to strength and toughness. A 2.0 mm diameter electrode was used to deposit weld metal in a 12.7 mm thick API grade X-70 pipe joint. The weld metal properties were characterized and shown to overmatch the pipe. The DBTT of the weld metal has been determined through Charpy V-Notch toughness measurements. The effect of heat input and welding procedure has been assessed over a range of heat inputs (1–1.5 kJ/mm.). The effect of dilution from the base plate on toughness has been assessed by measuring the sensitivity of weld metal toughness to changes in carbon content. The as-welded region of the weld has been characterized using different characterization techniques. Ferritic weld metal deposited with a self-shielded arc welding process has intentional additions of aluminum, magnesium, titanium and zirconium. This results in a complex precipitation process that has been characterized with a combination of electron microscopy techniques. The effect of micro-alloying additions on the variant selection during the austenite to ferrite transformation and microstructure evolution has been studied with electron back scattered diffraction (EBSD) in conjunction with orientation imaging microscopy (OIM). Transmission electron microscopy (TEM) was used to characterize the precipitate evolution in these welds. The evidence shows that the formation of a spinel oxide is critical for the nucleation of nitrides of zirconium and titanium and prevents the agglomeration of aluminum rich oxides and the formation of large aluminum nitrides. The evolution of precipitate formation is critical to limit large inclusions and improve weld metal toughness. The presence of titanium and zirconium increases the fraction of high angle grain boundaries within the microstructure resulting in increased resistance to crack propagation. The characterization of the microstructures at two different carbon contents indicates the greater propensity to form twin related variants with increase in carbon content. This suggests a lower transformation temperature of austenite and may be the reason for poor toughness.
Mechanical Properties and Microstructure of Weld Metal and HAZ Regions in X100 Single and Dual Torch Girth Welds
Authors: Gianetto James , Tyson William , Wang Yong-Yi , Bowker John , Park Dong-Yeob , Shen Guowu
Published: April 2011

The main objectives of the current study were to further develop tensile and toughness testing protocols and to provide a better understanding of the factors that control both weld metal and HAZ microstructure and properties in pipeline girth welds. In this investigation, two series of rolled (1G) girth welds were made in X100 pipe of 36 in. diameter and 0.750 in. wall thickness using two pulsed-gas metal arc welding process variants: single and dual torch. The small-scale testing program included evaluations of all-weld-metal tensile strength, Charpy impact and standard fracture toughness measured by single-edge bend SE(B) tests, along with preliminary fracture toughness results using a single-edge tension SE(T) test developed at CANMET. Additional information was obtained from detailed microstructural characterizations of weld metal and HAZ regions along with microhardness testing. All-weld-metal tensile tests using round and strip tensile specimens showed variations with through-thickness location and in some case with clock position. Full stress-strain curves were generated, and 0.2% offset yield strength, flow stress, ultimate tensile strength, and uniform strain were measured and compared with pipe properties using calculated weld strength mismatch factors based on these properties. Charpy V-notch transition curves were generated for both weld metal and HAZ (notched within 0.5 mm of the fusion line). Fracture toughness of both weld metal and HAZ regions of single torch welds was assessed using standard SE(B) testing procedures with Bx2B preferred specimens notched through–thickness at the weld centerline and in the HAZ (within 0.5 mm of the fusion line). Full J-resistance curves were measured using SE(T) tests of surface-notched WM and HAZ specimens; the SE(T) test was designed to match the constraint of full-size pipeline girth welds.
Experimental Investigation of Spiral Seam Induction Bends
Authors: Chi Qiang , Wang Peng , Liu Yinglai , Ji Lingkang , Gong Shaotao
Published: April 2011

The three kinds of dimensions that is Φ325mm×8mm, Φ426mm×8mm and Φ711mm×10.3mm X52 spiral seam induction bends were manufactured via the induction bending process. Based on that, the property and structure of spiral seam induction bends were investigated. According to the processing technic and design feature of spiral seam bend, the destructive test sampling plan of spiral seam induction bend was proposed. Through the mechanical property tests and design proof test, the spiral seam induction bend was studied and evaluated. The tension and impact tests results show that the strength-toughness of spiral seam induction bend can approach the property of mother pipe when the suitable process was adopted. The transverse guided-weld bend tests results show that the root bend samples in several fixed location of Φ325mm×8mm bend pipes crack, which indicate that the smaller diameter spiral seam pipe is not fit for the hot bending. The observational check results show that the welding joint misalignment occurs at the inner arc of Φ711mm×10.3mm spiral seam induction bend, which indicate that the configuration of spiral seam induction bend is easy to be affected during bending process with the decrease of thickness-to-radius ration of pipe. The design proof test of Φ426mm×8mm bend pipe shows that the spiral seam induction bend does not rupture at the computed proof test pressure.
Pipe Bending Test With Girth Welding on X80 Grade SAW Pipes
Authors: Hamada Masahiko , Shitamoto Hidenori , Okaguchi Shuji , Takahashi Nobuaki , Takeuchi Izumi , Matsuhiro Yoshiyuki , Fujita Shusuke
Published: April 2011

This study was planned as a part of a test program to confirm the effect of girth welds on the strain capacity of pipes. In this study, full-scale pipe bending tests are performed by using X80 SAW pipe. This paper covers pipe manufacturing procedure, developed welding procedure to obtain even match weld metal and properties of welded joints. And this work demonstrated that the X80 pipes welded under the developed procedure fractured in base metal remote from girth welded portion by full scale pipe bending test conducted under the internal pressure of 72% SMYS of X80.
Pipeline Integrity Monitoring: What’s the Present Situation for Offshore Pipelines and the Future?
Authors: Purvis Brian
Published: April 2011

This paper will discuss both the present situation and future developments in Pipeline Integrity Monitoring. It will also highlight how integrity monitoring is a vital part of any Pipeline Integrity Management System (PIMS). To give the true picture of a pipeline’s condition, the integrity monitoring systems must identify those elements of the pipeline which are at most risk to any potential modes of failure. Pipeline integrity monitoring offshore tends to be the periodic monitoring of specified components above and below the water surface. This being in the form of long and short term monitoring programs, which are derived from threat identification, risk assessment and mitigation processes. These programs normally follow the relevant industry standards that define specific monitoring activities and frequencies, especially for the safety critical components. PIMS documentation review cycles can be long and complex, but should be undertaken on a regular basis. When these reviews are undertaken they don’t always use new data sources that could give us more information about potential failure modes. At present these processes tend to be more reactive or lagging in nature. The future monitoring of pipeline integrity should be more forward-looking and be proactive as well as being reactive. Where are the next major developments? We need to make better use of the data we have by studying trends, changes and impacts wherever possible. Also, have a better understanding of the in-service behaviour and how this can change over the life cycle of a pipeline system.
The Calculation Method of Mixing Volume in a Products Pipeline
Authors: Gong Jing , Wang Qin , Wang Weidong , Guo Yi
Published: April 2011

In order to improve the operational management of a products pipeline, we need to identify a suitable formula to calculate the volume of the contaminated product accurately when it arrives at the end point of the products pipeline. This paper presents a calculation method of mixing volume in a products pipeline. By combining the empirical formula of Austin-Palfrey with field data, we establish a new formula which meets the characteristics of the products pipeline. The flow characteristics and growth rules of mixed oil products are considered in the formula of Austin-Palfrey, but many influential factors are not taken into account, such as the structure and the terrain of the pipeline, the characteristics of mixed oil products in pumping stations and the distribution of the products along the pipeline. We obtain a group of coefficients from field data which are collected from a products pipeline. This new formula is proved by the validation of field data; it not only can improve the accuracy of the mixed oil products volume prediction, but also can be easily used for field application. This paper also discusses the relationship between mixing volume calculation and the terrain of products pipeline.