bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and Numerical Study on the Evolution of Mechanical Properties During Spiral Pipe Forming
Authors: Cooreman Steven , Van Hoecke Dennis , Liebeherr Martin , Thibaux Philippe , Yamaguti Enderlin Mary
Published: November 2016

Large diameter spiral welded pipes are produced from hot rolled coil. The forming of a spiral pipe out of a coil is a sequence of cold deformation steps which are: decoiling, levelling and 3-roll forming (followed by seam welding). Obviously the material experiences a quite complex deformation history since several strain reversals occur during the different steps. A further complexity is that the strain history will even vary along the thickness as it mainly concerns bending deformation. It is therefore not at all surprising that the mechanical properties on pipe and coil are different. The steel manufacturer is able to control the production of the steel within well-defined process limits. Consequently he can guarantee the properties of his product, i.e. the coil. However, the spiral pipe manufacturer only has limited possibilities to control the steel properties but eventually he is responsible for the properties of his product, i.e. the pipe. A detailed understanding of how spiral pipe forming affects the mechanical properties would definitely help steel mills to specify and target coil strength to ensure the final pipe strength. Therefore an experimental study was launched in which a 4-point bending setup was used to reproduce the different forming steps on lab scale. The mechanical properties were measured at intermediate process steps, i.e. on coil, after levelling, after pipe forming and after subsequent flattening. The last step was included because, in practice, the mechanical properties along the pipe transverse direction are typically measured using flattened tensile samples, i.e. after introduction of an additional cold deformation step with strain reversal. The advantages of this experimental approach are twofold: first, one has full control and knowledge on the deformations introduced during the different steps. Second, the typical statistical variation of mechanical properties from coil to coil or even within one coil is far less pronounced as all samples are taken within a relatively short distance from each other. For a more detailed understanding of the experimental study, an efficient Finite Element model to simulate spiral pipe forming was developed in Abaqus. A nonlinear kinematic-isotropic hardening law was applied to describe the material behavior. In this way it was possible to capture both yield point elongation and the well-known Bauschinger phenomenon. This paper summarizes numerical and experimental results for a 16mm thick X70 grade, where different production parameters (leveller settings, ratio of wall thickness to outer diameter) were considered.
Near Real-Time Automated Detection of Small Hazardous Liquid Pipeline Leaks Using Remote Optical Sensing and Machine Learning
Authors: Araujo Maria S. , Siebenaler Shane P. , Dupont Edmond M. , Blaisdell Samantha G. , Davila Daniel S.
Published: November 2016

The prevailing leak detection systems used today on hazardous liquid pipelines (computational pipeline monitoring) do not have the required sensitivities to detect small leaks smaller than 1% of the nominal flow rate. False alarms of any leak detection system are a major industry concern, as such events will eventually lead to alarms being ignored, rendering the leak detection system ineffective [1].

This paper discusses the recent work focused on the development of an innovative remote sensing technology that is capable of reliably and automatically detecting small hazardous liquid leaks in near real-time. The technology is suitable for airborne applications, including manned and unmanned aircraft, ground applications, as well as stationary applications, such as monitoring of pipeline pump stations. While the focus of the development was primarily for detecting liquid hydrocarbon leaks, the technology also shows promise for detecting gas leaks.

The technology fuses inputs from various types of optical sensors and applies machine learning techniques to reliably detect “fingerprints” of small hazardous liquid leaks. The optical sensors used include long-wave infrared, short-wave infrared, hyperspectral, and visual cameras. The utilization of these different imaging approaches raises the possibility for detecting spilled product from a past event even if the leak is not actively progressing.

In order to thoroughly characterize leaks, tests were performed by imaging a variety of different types of hazardous liquid constitutions (e.g. crude oil, refined products, crude oil mixed with a variety of common refined products, etc.) in several different environmental conditions (e.g., lighting, temperature, etc.) and on various surfaces (e.g., grass, pavement, gravel, etc.). Tests were also conducted to characterize non-leak events. Focus was given to highly reflective and highly absorbent materials/conditions that are typically found near pipelines.

Techniques were developed to extract a variety of features across the several spectral bands to identify unique attributes of different types of hazardous liquid constitutions and environmental conditions as well as non-leak events. The characterization of non-leak events is crucial in significantly reducing false alarm rates. Classifiers were then trained to detect small leaks and reject non-leak events (false alarms), followed by system performance testing. The trial results of this work are discussed in this paper.
Investigation of Crack Propagation Characteristics Using Instrumented Charpy and DWT Tests for Full-Scale Burst Tested 1219 mm OD Grade 550 (X80) Linepipe
Authors: Igi Satoshi , Guan Cindy , Rothwell Brian , Hiraide Takashi
Published: November 2016

TransCanada, on behalf of the Coastal GasLink (CGL) project, has carried out two full-scale burst tests [1, 2] at the Spadeadam test site of DNV GL, to validate the effectiveness of crack arrestors and refine the propagation control design for the large-diameter, X80 linepipe required for this project. The tests were supported by LNG Canada and TransCanada Technology Management Program. For these full-scale burst tests, Grade 550linepipe having Charpy energies from 125 to over 450 J were produced using thermomechanical controlled processing (TMCP) technology.

This paper describes propagation and arrest properties of the X80 linepipe materials having various Charpy energy values from the aspect of crack propagation energy and crack propagation speed relationships from instrumented Charpy and press-notched (PN) and static pre-cracked drop-weight tear (SPC-DWT) tests, together with in-situ observation of crack propagation by high-speed video camera. It was found that crack propagation speed is greatly affected by crack propagation energy measured by both Charpy and instrumented DWT tests. The crack propagation energy is lower in DWTT specimens with a higher separation index. It is not clear whether the crack propagation energy is only affected by the separations. However, the crack velocity is higher in DWTT specimens with a higher separation index. It is assumed that the crack propagation speed might be not only affected by separation but also low propagation energy. The testing data obtained from Charpy and instrumented DWT tests are compared with the fracture speed data measured from the full-scale burst test. The correlation between Charpy energy and crack propagation energy in DWTT is also compared with the predictions of an empirical equation.
Study of Uneven Distribution in Parallel Petroleum Processing Pipes
Authors: Liu Renwei , Zhu Haishan , Li Qingping , Wan Yufei , Fan Kaifeng
Published: November 2016

The aim of this article is to investigate uneven distribution of oil-gas two phase flow in parallel petroleum processing pipelines. On-site analysis on BZ35-2 central platform A and SZ36-1 central platform N/O (two typical platforms in China’s Bohai Bay) shows that uneven distribution is originated mainly by two sources: flow rate difference and dryness difference. A 3-dimensional numerical model of two-phase flow in T-junction before parallel processing units was built. Flow and dryness distribution under different operating conditions were simulated. It is demonstrated that unevenness of flow rate grows worse as the total flow rate increases or operating pressure difference between parallel units becomes larger. Moreover, unevenness of dryness is mainly caused by phase split in a tee. It can be concluded that the phase split will be more obvious when parallel units are located at different heights or gas volume fraction of feed stream and inlet flow rate is small. Besides, flow rate distribution has an effect on dryness distribution. There is a specific flow ratio that will cause the most serious phase split.

Finally, according to the conclusions, modification scheme for BZ35-2 central platform A piping layout was proposed. And this work may provide some guidance for process design and practical operation of parallel units.
Modified West Jefferson Burst Test for Assessment of Brittle Fracture Arrest in Thick-Wall TMCP Line-Pipe Steel With High Charpy Energy
Authors: Igi S. , Sakimoto T. , Kondo J. , Hioe Y. , Wilkowski G.
Published: November 2016

Three partial gas pipe burst tests were conducted to assess the brittle-to-ductile transition temperature and brittle fracture arrestability of a heavy-walled TMCP line-pipe steel. This steel had a very high Charpy energy (400 J) which is typical of many modern line-pipe steels. In standard pressed-notch DWTT specimen tests this material exhibited abnormal fracture appearance (ductile fracture from the pressed notch prior to brittle fracture starting) that occurs with many high Charpy energy steels. Such behavior gives an invalid test by API RP 5L3, which makes the transition temperature difficult to determine.

The first burst test was conducted in a manner that is typical of a traditional West Jefferson (partial gas vessel) burst tests. The crack was initiated in the center of the cooled vessel (with a partial air gap), but an unusual result occurred. In this test a ductile fracture just barely started from each crack tip, but one of the endcaps blew off. The pipe rocketed into the wall of a containment building. The opposite endcap impacted the wall of the building and brittle fractures started there with one coming back to the center of the vessel. The implication from this test was that perhaps initiation of the brittle fracture in the base metal gives different results than if the initial crack came from a brittle location.

The second burst test used a modified West-Jefferson Burst Test procedure. The modification involved cutting a short length of pipe at the center of the vessel and rotating the seam weld to the line of crack propagation. The HAZ of the axial seam weld had a higher dynamic transition temperature. The initiation flaw was across one of the center girth welds so that one side of the initial through-wall crack had the crack tip in the base metal while the other side initiated in the seam weld HAZ. On the base metal side, the crack had about 220 mm of crack growth before reaching steady-state shear area, i.e., the shear area gradually decreased as the fracture speed was increasing. On the other side, a brittle fracture was started in the HAZ as expected, and once it crossed the other central girth weld into the base metal, the fracture immediately transformed to a lower shear area percent. These results along with those from the first burst test suggest that the DWTT specimen should have a brittle weld metal in the starter notch region to ensure the arrestability of the material.

The final burst test was at a warmer temperature. There was a short length of crack propagation with higher shear area percent, which quickly turned to ductile fracture and arrested.

In addition various modified DWTTs were conducted and results were analyzed using an alternative brittle fracture arrest criterion to predict pipe brittle fracture arrestability.
Waveform Pattern Recognition Applied to Rapid Detection of Wall-Thinning in Pipes: A Simulation-Based Case Study
Authors: Alobaidi Wissam M. , Sandgren Eric , Al-Rizzo Hussain M.
Published: November 2016

Pattern recognition using correlation analysis (Cij) method is useful for non-destructive testing of physical objects, including pipes. An evaluation of the technique based on Computer Simulation Technology (CST) models has demonstrated the advantages of using the technique to detect and classify pipe wall thinning (PWT) in pipes. Given enough increments, the technique can be refined to detect any possible combination of PWT attributes. For this research 71 different simulations were modeled for purposes of calibration of the system, based on five varied properties of the modeled PWT instances. These properties include: location (29 simulations based on distance from origin and two lengths of PWT, for a total of 58 simulations), width (standardized at 25.4mm), depth (four simulations as radius of PWT at 78.74mm, 81.28mm, 83.82mm, and 86.36mm), length (four simulations as percentage of circumference: 25%, 50%, 75% and 100% circumferential PWT) and type of defect (five simulations based on five discrete profiles).

Microwaves were simulated from port 1 and port 2, with a sweeping frequency range (0.5 GHz bandwidth), analyzed as S11 and S21 for measuring and calibrating the response to the standards. The resulting waveforms became the standard patterns against which 11 unknown simulations were compared, sometimes using S11 waveforms for comparison, and at other times S21.

The correlation analysis technique was able to distinguish parameters for the unknown test cases. The technique is able to determine the correlation between the resonance frequency peak (RFP) and waveform for an unknown case, and those of nearby calibration models, via pattern recognition. For example, 0.847 and 0.872 correlations to two standard patterns for an unknown RFP which appears midway between two standard RFPs, produces a peak for the unknown that is equidistant from the RFPs for the standards.
Full-Bore Pipeline Rupture as ‘Transient Fanno’ Flow
Authors: Godbole Ajit , Michal Guillaume , Lu Cheng , Venton Philip , Colvin Philip
Published: November 2016

Full-bore decompression of an initially highly pressurized pipe has been studied extensively in recent years. The main aim of this effort has been to estimate the speed of the decompression wave and its relationship to the speed of a travelling fracture in the pipe wall. It has been demonstrated that the speed of the decompression wave is influenced by the friction at the gas-solid interface, and also by the pipe size (diameter). The numerical value of the friction factor has been traditionally estimated using known relationships such as the Haaland formula. However, it has also been noticed that the friction factor calculated in this way has to be increased many-fold to achieve agreement between theory and experiment. To date, there is no physical justification for this increase.

The present paper proposes an explanation by modelling the full-bore decompression as a ‘transient Fanno’ flow. The model development is based on the observation that the flow at the exit plane always tends to approach a ‘choked’ condition (sonic velocity).

It is shown that a re-interpretation of the Fanno flow formula allows an estimation of the irreversibility, and therefore the friction factor, in the evolving flow. When averaged over space and time, the friction factor attains a value that need not be artificially adjusted. This value of the friction factor can be used in one-dimensional models of the decompression process. Also, the role of the ‘second coefficient of viscosity’ during the initial instants of the highly transient flow is examined.
Mitigation of Infilling Around Pipelines With Cyclic Lateral Deflections
Authors: Phillips Ryan , McAffee Rodney , Dooley Sylvia , Martens Michael
Published: November 2016

The soil response around a high temperature pipeline proposed for construction was evaluated. Infilling of backfill around pipelines at side bends subjected to temperature changes may accumulate during cyclic displacements leading to ratcheting and possibly buckling of the pipeline. A medium-scale laboratory model testing program was used to gain a better understanding of how silty sand backfill migrates around a pipeline when subjected to cyclic lateral loading. Several mitigation techniques using geosynthetics and compressible materials were evaluated in order to both delay and reduce the net downward soil movement from pipe displacement cycles.
3-D Transient CFD Modeling of Pig Motion
Authors: Jaimes Parilli Diego , Loaiza Nelson , García Janneth , Blanco Armando
Published: November 2016

Pigging operations are common procedures for pipeline maintenance. However, questions still remain about pig dynamics due to the difficulties to accurately describe this complex phenomenon. Consequently, most predictions of pig dynamics are based on empirical knowledge deduced from experimental data and numerical models developed considering simplified physical models, without calculate transient pig-flow interaction and neglecting 3D aspect of flow dynamics. Therefore, to present an actual 3D transient model, this paper proposes a novel CFD methodology using a static mesh in a moving control volume. Forces acting on the pig are dynamically computed by a Fluid-Structure Interaction (FSI) approach; pig velocity is obtained for each time instant and it is set as a variable boundary condition. This method was validated with experimental results and it may be used to describe a wide range of rigid body motion immerse in a flow. This approach is then utilized to obtain the transient simulation of a pig launch in a straight water pipeline. Numerical predictions of the static grid method were compared with those obtained using moving mesh simulations. Results show that the pig reaches a terminal velocity higher than average flow velocity and a huge difference on predictions of maximum pressure drop (through the pig) between steady state based models and transient models. Additionally, it was simulated a 2D model to observe the differences between 2D and 3D simulations on the flow characteristics and pig motion features, which shows an important increase of the pressure drop on 3D model over 2D and high pig acceleration in the 3D simulation.
New FCAW Electrode for Producing Ultra-Clean High-Toughness Welds in X-80 and X-100 Steel
Authors: Fiore Susan
Published: November 2016

The challenges associated with the welding of high-strength pipeline steels, such as X-80 and X100, are well established. While there are many filler metals that provide either adequate strength or good impact toughness, it is difficult to find products that provide both. Add to that the need for all-position welding and high deposition rates, and the options become almost non-existent.

Several years ago, Hobart® Filler Metals began working on a line of flux-cored arc welding (FCAW) consumables that are unique in the welding industry. The products have a basic slag system, but do not operate like traditional EXXXT-5 electrodes. Traditional T-5 electrodes have a low-melting, fluid slag, which makes welding out-of-position especially difficult. They also have a high level of calcium fluoride, which affects the stability of the arc and causes weld spatter. While the weld metal mechanical properties and crack-resistance are excellent, the welder appeal and ease-of-use tend to be sorely lacking in most EXXXT-5 electrodes.

The new approach utilizes aluminum for deoxidation, which has the added benefit of very clean weld deposits. The composition has been carefully optimized with appropriate levels of carbon, silicon, nickel and manganese. Alternative fluorine sources are used in place of calcium fluoride, which results in very good welder appeal and all-positional capabilities, including vertical down. The novel use of aluminum in a gas shielded process results in very low oxygen, nitrogen and sulfur content, providing exceptionally clean, tough weld deposits.

Although the new products have been produced over a range of strength levels, the primary emphasis of this paper is on E691T5-GC (E101T5-GC) and E831T5-GC (E121T5-GC) electrodes. Testing shows that tensile strength levels ranging from 700–880 MPa (100–128 ksi) can be achieved, with toughness levels of 120 J at −60°C (90 ft-lbs at −76°F) or better. The highly basic slag, combined with low weld metal hydrogen (less than 4 ml/100 gm), provides excellent resistance to cracking. The product can be used in all positions, including vertically down, making it an especially appealing choice for welding high-strength pipe.
Am I Too Rich?: Determining Limits for Gas Composition to Ensure Crack Arrest in an Existing Pipeline
Authors: Andrews Robert M. , Smith Michael
Published: November 2016

Fracture control studies for new gas transmission pipelines usually produce a specified minimum Charpy energy, often including “correction factors”, which will ensure that a crack will arrest in the body of the pipe. The basic pipeline parameters such as pressure, pipe grade, diameter and wall thickness will be fixed early in design, and the reservoir and process engineering design will set limits on the extremes of the gas composition.

The inverse case, where the gas composition in an existing pipeline is to be changed from the original design basis, is more challenging. Changes in composition can arise from ageing of the reservoir supplying a pipeline, or opportunities for the operator to generate additional revenue from 3rd party access. Sales gas specification limits for general purpose natural gas transmission often have broad limits, which can be met by a wide range of compositions.

As a wide range of gas compositions can give the same crack driving force, determining the composition limits is a “many to one” problem without a unique solution. This paper describes the derivation of an envelope of richer gas compositions which gave an acceptable probability of crack arrest in an existing pipeline which had originally been designed for a very lean gas mixture. Hence it was necessary to limit the amount of rich third party gas to ensure that the crack driving force did not increase sufficiently to propagate a long running fracture.

Manufacturing test data for the linepipe were used with the EPRG probabilistic approach to derive a characteristic Charpy energy which would achieve a 95% probability of crack arrest in 5 joints or fewer. After “uncorrecting” the high Charpy energy, the value was used with the Battelle Two Curve model to analyse a range of gas compositions and derive an envelope of acceptable compositions. Sensitivity studies were carried out to assess the effects of increasing the temperature and of expanding the limits for nitrogen and carbon dioxide beyond the initial assumptions.

It is concluded that for a specific case it will be possible to solve the inverse problem and produce composition limits which will allow increased flexibility of operation whilst maintaining safety.
Identification of a 3D Anisotropic Yield Surface of X70 Pipeline Steel Using a Multi-DIC Setup
Authors: Denys Kristof , Coppieters Sam , Van Hecke Renaat , Cooreman Steven , Debruyne Dimitri
Published: November 2016

A new method is proposed combining multiple synchronized digital image correlation setups (multi-DIC) and finite element model updating to identify the hardening behaviour and anisotropy of 23.5 mm thick X70 line pipe steel. Curved tensile samples have been cut from a coil. While performing a tensile test on those samples, the force was obtained from the load cell and the back and front surface strain fields were measured by means of two synchronized stereo digital image correlation setups. The tests on the curved samples are reproduced with FE simulations, applying the same boundary conditions as the experimental setup to obtain the numerical force and strain fields. While simultaneously minimising the discrepancy between the experimentally and numerically obtained force and strain fields, the strain hardening behaviour is identified beyond the point of maximum uniform elongation.

A profound understanding of the anisotropy is also mandatory because the hot rolling operation develops substantial anisotropy which has an important influence on the line pipe performance. Due to the 23.5 mm thick steel that is used in this work, it is possible to measure the front and side surfaces with two synchronized stereo digital image correlation setups. Because full field information is available in all 3 material directions (lateral, longitudinal and through thickness direction), a 3D anisotropic yield criterion can be identified. A prerequisite for stable and accurate identification of the yield locus parameters is that the governing parameters are sufficiently sensitive to the experimentally measured response. For this purpose, a double perforated specimen has been designed which includes a side perforation. The latter guarantees the necessary through-thickness information to inversely identify the 3D anisotropic yield function through multi-DIC and finite element model updating.

The presented procedure could potentially be used by line pipe manufactures to verify whether the mechanical properties meet the specified requirements. The proposed approach has some advantages compared to conventional methods to determine mechanical properties of large diameter pipe. The curved specimen geometry is modelled in the FE simulation, hence the detrimental effects of flatting the tensile specimen can be avoided. Further, the new approach enables to consider the complete wall thickness as opposed to conventional testing with round bar samples of which a part of the wall thickness is removed during manufacturing.
Failure Pressure Ratios and Implied Reliability Levels for Corrosion Anomalies on Gas Transmission Pipelines
Authors: Zhou Wenxing , Gong Changqing , Kariyawasam Shahani
Published: November 2016

This study investigates the relationship between the failure pressure ratio (FPR) and implied reliability level for corrosion anomalies on natural gas transmission pipelines governed by the Canadian oil and gas pipeline standard CSA Z662-15 The model recommended in Annex O of CSA Z662-15 is adopted to evaluate the burst pressure capacity of a given corrosion anomaly on a pipeline, and the first-order reliability method (FORM) is used to evaluate the reliability index of the anomaly by considering uncertainties associated with the pipe geometric and material properties, ILI-reported anomaly sizes, operating pressure and accuracies of the burst pressure capacity models. The analysis results suggest that the FPR-reliability index relationship for pipelines with utilization factors greater than or equal to 0.72 is independent of the pipe attributes and geometry of the corrosion anomaly, if the measurement error associated with the ILI-reported anomaly depth is relatively small. Sensitivity analyses are carried out to examine the sensitivity of the FPR-reliability index relationship to the measurement error associated with the ILI-reported anomaly depth.
Pipeline Operator Perspective in Use of Hydrostatic Testing as an Integrity Management Tool
Authors: Hilger M. M. , Mittelstadt B. C. , Piazza M. , Vieth P. H.
Published: November 2016

Regulation in the United States mandating the use of pressure testing as an assessment tool for the construction and commissioning of pipelines was initiated in 1970. Prior to regulation, however, pressure testing was being applied within the pipeline industry to provide confidence in the operational integrity of pipeline systems. Additional assessment technologies and processes including high resolution in-line inspection continue to be developed and further enhanced; however pressure testing remains a valuable and acceptable tool in the management of pipeline integrity. Current applications include quality verification of original construction practices, integrity assessment of existing pipelines, and verification of material yield strength when key records may be missing or incomplete.

It is recognized that extensive hydrostatic testing knowledge exists today in the form of API Recommended Practices, ASME code documents, the body of work of industry consultants, regulatory language and other resources. A key element to implementing the current industry standards is a pipeline operator perspective in practical application on selection of hydrostatic testing as an assessment tool and the subsequent technical design of a hydrostatic test program in order to achieve integrity management goals. This paper discusses hydrostatic testing in the context of selection as an integrity management tool, development of risk-balanced objectives for a hydrostatic test program, and understanding the limitations and potential detrimental effects of hydrostatic testing.

This paper summarizes key considerations in guidelines published in 2016 that were developed through a Pipeline Research Council International (PRCI) project. While written to be applicable to all hydrostatic testing, this work is a key element of the multi-year PRCI Electric Resistance Welded (ERW) and Longitudinal Seam Pipe Program which began in 2011 and was formed to comprehensively study and develop strategies for management of factors that contribute to seam failures.
Graded EMAT Performance Specification Validated in Blind Test
Authors: Tomar Munendra , Fore Toby , Baumeister Marc , Yoxall Chris , Beuker Thomas
Published: November 2016

The management of Stress Corrosion Cracking (SCC) represents one of the challenges for pipeline operating companies with pipelines potentially susceptible to SCC. In order to help better support the management of SCC, a graded performance specification for the high-resolution Electro-Magnetic Acoustical Transducer (EMAT) In-Line Inspection (ILI) technology is derived which provides higher levels of confidence for detection of crack-field anomalies with critical dimensions. This paper presents the process used to derive the graded performance values for the EMAT ILI technology with regard to SCC. The process covers the Probability of Detection (POD) and Probability of Identification (POI).

A blind test was carried out to derive the graded performance specification. Test data set was compiled comprising EMAT data for several joints containing relevant anomalies and neighboring joints, some containing additional shallow SCC. These joints had been dug based on EMAT ILI data and all of the joints were evaluated with 360 degree Non-Destructive Examination (NDE) followed by destructive testing. For each target joint with relevant anomalies to be assessed, four additional joints were added in random order to generate a realistic density and distribution of anomalies. Furthermore, pipe joints with non-crack like anomalies, as well as pipe joints with mixed populations were included in the blind test data set to ensure a realistic feature population and to assess POI without side effects of a weighed feature population inside set of composed ILI data.

The data set was then evaluated by multiple analysts and result from each analyst were evaluated and utilized to derive the POD and POI values for the graded specification. In addition, the full process of data analysis including team lead review was carried out for one of the analysts for comparison to the individual analyst results. Anomaly dimensions were compared against the true population to derive the POD and POI values. Furthermore, length and depth sizing performance was assessed.
Evaluation of Fatigue in Gas Pipelines
Authors: Semiga Vlad , Tiku Sanjay , Dinovitzer Aaron , Wagster Wendy
Published: November 2016

There is a commonly held belief that internal operational pressure fluctuations of a gas pipeline is less likely to result in fatigue cracking than a liquid pipeline. A defensible engineering analysis process, demonstrating that this observation remains valid for all gas pipeline systems regardless of operation (i.e. transmission, bi-directional flow at storage facilities), existing features (i.e. dents or preexisting cracks), material properties (i.e. pipe vintage, grade) and pipeline geometry, needs to be developed. The work reported in this paper describes the work sponsored by the Interstate Natural Gas Association of America (INGAA) to support gas pipeline operators in completing Integrity Verification Programs (IVP) by defining which pipeline segments can reasonably be considered to be at risk of fatigue damage accumulation and which are not.

This paper presents an overview of the work completed to develop a defensible approach to demonstrate the conditions under which pipeline pressure fluctuation induced fatigue is not a concern. The development of this approach, presented in this paper, considers the results of a survey of the range of cyclic severities experienced by gas pipeline operators, typical feature types and sizes that could exist in a pipeline system (i.e. mechanical damage, cracking) and the role of material properties on these assessments. The paper includes the development of directions as to the collection and analysis of SCADA pressure data to produce a pressure spectrum severity indicator (SSI) characterizing the fatigue damage potential of an operational history. This SSI is used along with fatigue susceptibility tables indicating the conditions for which fatigue would not be a concern for a pipeline segment. The susceptibility criterion relates a pipelines operation, in terms of SSI to the maximum feature size that can exist in the system before fatigue is considered a threat to pipeline integrity.

The information presented in this paper would be of interest to pipeline operators, maintainers, consultants and regulators. The technical work presented in this paper was completed to support compliance with regulatory requirements and may also be used to influence the application of integrity management regulatory requirements on gas pipeline systems by providing information and processes to eliminate the need to consider fatigue as a damage accumulation process or integrity threat.
Evaluating Dents With Metal Loss Using Finite Element Analysis
Authors: Gossard Justin , Bratton Joseph , Kemp David , Finneran Shane , Polasik Steven J.
Published: November 2016

Dents created by third party mechanical damage are a severe integrity threat to onshore and offshore transmission pipelines. This type of damage is often associated with metal loss, which can be introduced during the initiation of a dent or develop as a result of the presence of a dent and associated coating damage. Once a dent has been found to be associated with metal loss through excavation, there is little guidance to determine the serviceability of the anomaly.

In this study, dents with associated metal loss due to corrosion examined in the field are evaluated to determine the contribution of the interacting dent and metal loss features to the associated burst pressure of the feature. Twenty dents with metal loss flaws were identified through an ILI survey while in service to capture dimensions of the dent and metal loss features. Each site was excavated and measured using a laser scanner. The laser scanner produced 3D imaging with sufficient resolution of both the dent and metal loss areas as a 3D surface mesh. The 3D surface mesh was transformed into a 3D solid mesh and analyzed using a finite element analysis software package in order to determine a predicted internal pressure that would cause failure. A subsequent statistical assessment was performed to analyze the relationship between the ILI measurements and the predicted burst pressure resulting from finite element analysis of each dent with metal loss feature. Statistical analyses were used to evaluate the prediction capabilities of burst pressures of dent with metal loss features identified through ILI, prior to excavation and direct examination.
The Effect of Niobium on Austenite Decomposition in Line Pipe Steels
Authors: Robinson I. D. G. , Garcin T. , Poole W. J. , Militzer M.
Published: November 2016

Niobium is a common micro-alloying addition in high-strength low-alloy (HSLA) steels primarily to add strength to the final product. Detailed quantification of the various effects of niobium is critical for understanding the microstructure evolution in the heat affected zone (HAZ) of welds. Laser ultrasonics for metallurgy (LUMet) was used to measure austenite grain growth kinetics in two experimental HSLA steels during continuous heating. For higher heating rates that are of relevance for the HAZ, grain growth during heating is negligible and grain size is determined during the brief time at the peak temperature. Thermal histories were designed based on these tests to produce a variety of microstructures relevant for various positions in the HAZ i.e. coarse and fine grain regions. It was found that the dissolution of niobium carbonitrides has a strong effect on austenite decomposition, particularily in the case of large austenite grain sizes. Nb in solution significantly depresses transformation temperatures in refinement of bainitic microstructures, significantly increasing the hardness in the coarse grained HAZ.
The Cheecham Landslide Event
Authors: Barlow J. Peter , Richmond John A.
Published: November 2016

Land disturbance associated with the progressive expansion of a major pipeline and power corridor, along with extensive timber harvesting, triggered the reactivation of an ancient, 100 million cubic meter deep-seated landslide in northern Alberta. The landslide threatened six major transmission pipelines, and caused a loss of containment in one of the pipelines. The level of landslide activity and associated pipeline damage was surprising given the relatively subtle disturbances in relation to the massive scale of the slide. Given the very shallow 4.5 degree slope inclination and the lack of any surface expression of distress over most of the slope area, this case history underscores the importance of considering regionally specific geological conditions within pipeline geohazard evaluations. An intensive, multi-pronged program was adopted to stabilize and manage the landslide, including a series of targeted surface and ground water control measures that produced an approximate 100-fold reduction in movement rates. This demonstrates that the sensitivity of slides in the region to subtle changes is a negative factor for triggering landslides, but can also be a positive factor for stabilizing them.
ILI to ILI Comparisons: Quantifying the Impact of Multiple Inspections
Authors: Moreno Pamela J. , Ellinger Matthew A. , Bubenik Thomas A.
Published: November 2016

Det Norske Veritas (U.S.A.), Inc. (DNV GL) prepared this paper in order to study the repeatability of inspection results between subsequent in-line inspections. DNV GL has access to a significant amount of data that spans many different pipeline operators, ILI vendors, inspection years, and inspection technologies. DNV GL is well suited to complete this study as a result of our access to these various data sets.

Over 55,000 one-to-one metal loss defect comparisons were assembled from ILI-to-ILI analyses. Reported metal loss defect depths, lengths, and widths spanning from 2003 through 2015 from 13 pipeline operators and 36 pipeline segments were compiled to meet the objectives of this paper. Inspection technologies include axial magnetic flux leakage (MFL), ultrasonic wall thickness (UTWT), spiral MFL, and circumferential MFL ILI.

From analyses of these data, the following conclusions were generated:

• Effect of ILI vendor: ILI repeatability is generally improved when the same ILI vendor is used (when compared to using two different ILI vendors in subsequent inspections), but this is not always true.

• Reported metal loss depths: ILI repeatability decreases with increasing metal loss depth.

• Pipe geometry and type: ILI repeatability is better in larger diameter pipelines and with increasing wall thickness.

• POF classification: ILI repeatability is better for pitting, general corrosion, and axial grooving defects as compared to the other POF classifications.

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

• Pipeline operators should consider using the same ILI vendor and tool if the goal is to identify change and/or corrosion growth in the pipeline segment. A raw signal review is encouraged in order to verify the presence, or lack thereof, changes in metal loss morphologies. The raw data review is especially important when comparing inspections from two different ILI vendors.

• If the goal is to identify corrosion growth, and a pipeline operator uses different ILI vendors, it is recommended that a statistical review of one-to-one matched metal loss features take place to identify candidate locations that are more likely to be growing. The candidate locations should have a raw signal review in order to verify whether or not growth is taking place.
Study of a Plastic Strain Limit Damage Criterion for Pipeline Mechanical Damage Using FEA and Full-Scale Denting Tests
Authors: Arumugam Udayasankar , Gao Ming , Krishnamurthy Ravi , Wang Rick , Kania Richard
Published: November 2016

Pipeline constructed in rocky terrain is vulnerable to damages such as denting, gouging and other mechanical damages. In-line inspection (ILI) of these pipelines often reported several hundreds or even thousands of dents. Although most of these reported dents are well below 6% outside diameter (OD) depth limit as per ASME B31.8, few dents (sharp rock dents) with high strain could pose threat to integrity of the pipeline. Recently, strain-based models have been proposed to assess mechanical damage severity in pipelines. Attempts have also been made to characterize cracking susceptibility in rock dents using the critical strain based ductile failure damage indicator (DFDI) model. The objective of this study is to validate this model using full-scale denting tests conducted at the laboratory. Additionally, validation also extends to against the simplified DFDI model without finite element analysis (FEA).

In this paper, the existing ASME strain limit and strain limit damage models are reviewed. The critical strain based strain damage model known as Ductile Failure Damage Indicator (DFDI) is then presented. The theoretical aspect of this model, including early work by Hancock and Mackenzie on strain limit (εf, reference failure strain) for ductile failure, is reviewed. The experimental aspect of material critical strain and its measurement using uni-axial tensile testing are then described. An elastic-plastic finite element analysis is employed to calculate DFDI, which is used to quantify the accumulated plastic strain damage and its susceptibility to cracking, and is validated using six full scale denting tests.

Finally, the simplified strain limits for plain dent is proposed and validated.
Implementation of CSA Z662-15 Annex K Option 2 on a 610mm Liquid Pipeline
Authors: Belanger Rory , Sarafinchan Derrick
Published: November 2016

For more than two decades, CSA Z662 Annex K has provided a method for developing alternative acceptance criteria for weld flaws in mechanized welded pipelines. Increasingly, over the years, fracture mechanics practitioners have found the method overly conservative and restrictive with respect to brittle fracture criteria when compared to other accepted fracture mechanics-based engineering critical assessment ECA codes and methods. These limitations rendered the CSA Annex K method difficult to implement on pipelines constructed with materials not possessing optimal toughness and in cases requiring consideration of fracture toughness at temperatures lower than the typical minimum design metal temperature (MDMT) of −5°C. This paper presents experiences implementing CSA Z662-15 Annex K Option 2 methodology on a 610 mm diameter liquids pipeline and compares and contrasts the utility and benefits of the code revision. This pipeline required consideration for installation during winter months, necessitating installation temperatures as low as −30°C. In addition to evaluation of actual ECA results, analytical evaluations of the Option 2 methodology were also conducted considering parameters outside those used on the project.

The new Annex K Option 2 method was found to be of considerable benefit in preparation of a practical ECA. Since fracture toughness testing was conducted at the anticipated lowest installation temperature, the flaw criteria were, as expected, principally controlled by elastic/plastic crack growth consideration. The failure assessment diagram implemented into the CSA Z662-15 Annex K Option 2 provided tolerance for both longer and deeper flaws than that afforded by Option 1 (which resorts to the former 2011 Annex K method). Furthermore, the reduced restriction to the surface interaction ligament (p distance) offers additional advantages including increased flexibility in weld profile design and weld pass sequencing.

Fracture toughness (CTOD) testing of TMP pipeline steels used in the project at −30°C often produced transitional fracture toughness results. It was found that the particular project materials were quite sensitive to the level of test specimen pre-compression (an acceptable plastic straining method to reduce residual stress gradients) applied to the CTOD specimens to enhance fatigue crack-front straightness. It was found that optimizing the level of pre-compression (to achieve acceptable pre-crack straightness while minimizing plastic pre-strain) achieved a balance between fully satisfying testing requirements, providing a conservative assessment of CTOD, and facilitating a functional Annex K ECA.
Hydrostatic Pressure Testing as Part of an Integrity Management Program: A Case Study
Authors: Keane Sean , Rosenfeld Michael , Heise Larry
Published: November 2016

Integrity management tools must be fit for their intended purpose and a hydrostatic pressure test is no exception to this. A hydrotest can be designed to demonstrate an industry recognized safety factor, or an alternate safety factor that aligns with a target reliability. Hydrostatic pressure tests are a destructive test, but they can be designed and executed to minimize likelihood of unnecessary damage to otherwise benign manufacturing anomalies. In order to determine a risk balanced design, a hydrostatic pressure test must be engineered to achieve fitness-for-service goals, risk goals, as well as asset goals.

This paper presents a risk balanced design to a hydrostatic pressure test. Key technical aspects related to the science of hydrostatic pressure testing are summarized as to the affect on fitness-for service goals, risk goals and asset goals. The approach to designing a hydrostatic pressure test is demonstrated through a case study on a 326 mile (525 km) NPS 26 (DN 650 mm) pipeline manufactured using 1950’s vintage flashweld longseam.