bluuebunny/crossref_metadata_2025 huggingface dataset:
Large-Eddy Simulation of an Integrated High-Pressure Compressor and Combustion Chamber of a Typical Turbine Engine Architecture
Authors: Pérez Arroyo Carlos , Dombard Jérôme , Duchaine Florent , Gicquel Laurent , Odier Nicolas , Exilard Gorka , Richard Stéphane , Buffaz Nicolas , Démolis Jacques
Published: January 2021

The design optimization of aviation propulsion systems by means of computational fluid dynamics is key to increase their efficiency and reduce pollutant and noise emissions. The recurrent increase in available computing power allows nowadays to perform unsteady high-fidelity computations of the different components of a gas turbine. However, these simulations are often made independently of each other and they only share average quantities at interfaces. In this work, the methodology and first results for a sectoral large-eddy simulation of an integrated high-pressure compressor and combustion chamber of a typical turbine engine architecture is proposed. In the simulation, the compressor is composed of one main blade and one splitter blade, two radial diffuser vanes and six axial diffuser vanes. The combustion chamber is composed of the contouring casing, the flame-tube and a T-shaped vaporizer. This integrated computation considers a good trade-off between accuracy of the simulation and affordable CPU cost. Results are compared between the stand-alone combustion chamber simulation and the integrated one in terms of global, integral and average quantities. It is shown that pressure perturbations generated by the interaction of the impeller blades with the diffuser vanes are propagated through the axial diffuser and enter the combustion chamber through the dilution holes and the vaporizer. Due to the high amplitude of the pressure perturbations, several variables are perturbed at the blade-passing frequency and multiples. This is also reflected on combustion where two broadband peaks appear for the global heat release.
Influence of Probe Blockage Effect on Compressor Test Performance
Authors: Li Bowen , Wu Hu , Hou Chunke
Published: January 2021

In order to study the influence of probe blockage effect on the test performance of the compressor, a full-channel steady simulation method was used to establish a regression model of the influence of the probe on the compressor performance. Taking NASA Rotor67 compressor as research objects, different sizes and quantities of probes are arranged at different axial positions of the compressor inlet and outlet respectively, the flow-efficiency and flow-pressure ratio characteristic line are obtained under different probe blockage ratios, circumferential and axial layouts at the design speed. The calculation results show that due to the blockage effect of the probe, the flow rate of the blocking point is reduced, the flow rate of the stall point is increased, the efficiency and pressure ratio of the compressor are decreased. The separation of the rotor surface layer caused by the presence of the probe and the blending loss of the probe wake and the mainstream are the main reasons for the above changes. The response surface model was used to model the regression of the data, and the regression model of the compressor characteristics in the presence/absence of the probe was obtained, and the regression model was verified. The relative error was within 3%, indicating the established regression model of probe on the influence of compressor performance has good accuracy.
H2 in an Existing Natural Gas Pipeline
Authors: Huising O. J. C. , Krom A. H. M.
Published: January 2021

N.V. Nederlandse Gasunie (Gasunie) has converted an existing gas transmission line from transporting natural gas to transporting a mixture of gaseous hydrogen and 30% to 0% methane. To enable this, an assessment was carried out on technical safety, process safety, work safety and external safety.

The pipeline, with two valve stations, was constructed in 1996 according to applicable Dutch regulations and actively managed in accordance with Gasunie company standards.

The pipeline was evaluated for hydrogen transportation and, based on the following measures, this was seen as being feasible:

- The water dew point of the feed must not exceed −8° C;

- The pipeline must be separated from the natural gas transport system;

- Blowdown must be performed either at the site of the supplier or the user of the hydrogen;

- Gas measurement equipment, personal safety and leak detection must be suitable for hydrogen;

- Due to the assignment of hydrogen as a chemical agent, the safety contour was reduced by performing extra measures, such as additional communication to landowners, additional requirements for the pressure-regulating system and verification of additional settlement and stresses.

The operational changes consist of a number of maintenance and management issues:

• In-service welding and hot tapping are not allowed;

• Equipment suitable for use in gas group IIC (ATEX) must be used;

• Emergency and maintenance procedures must be updated to those applicable for pipeline and valve stations containing hydrogen.
Recommended Procedures for Evaluation and Synthesis of Pipelines Subject to Multiple IMU Tool Surveys
Authors: Hart James D. , Zulfiqar Nasir , McClarty Ed
Published: January 2021

This paper summarizes recommended procedures for evaluation and synthesis of geometry data from pipelines subjected to repeat in-line inspections (ILI) using strapdown Inertial Measurement Unit (IMU) tools. The paper provides an overview of IMU tool instrumentation (gyroscopes, accelerometers and odometers), a brief summary of IMU tool data processing and discusses IMU tool sensitivity and accuracy specifications. The paper also provides a review of the approaches that are used to identify ground movement signatures in IMU data profiles. Based on a single IMU survey, it can be difficult to determine with certainty if a given bending strain feature was induced during construction of the pipeline (e.g., by conforming the pipeline profile to an uneven trench profile) or was the result of post-construction movement of the pipeline (e.g., due to geohazards along the alignment such as landslides, karst, etc.). Because such a large percentage of vendor identified bending strain anomalies in IMU surveys are the result of construction, comparison of pipeline geometry changes between two (or more) inertial inspections is normally a more reliable method of identifying areas of actual post-construction movement of the pipeline. This is because a high degree of repeatability is observed in overlays of the pipeline geometry data signatures obtained from different IMU surveys at construction-induced bending features whereas the geometry signals associated with real pipeline movement frequently exhibit change patterns in out-of-straightness, pitch and heading and curvature/bending strain profiles that correspond to increasing pipe curvature and deformation. The primary focus of this paper is to summarize recommended data deliverables and plots of three-dimensional pipeline geometry profile data from different IMU tool surveys at vendor-identified bending strain anomalies including multi-panel overlay plot packages as well as survey-to-survey difference or change profiles that greatly assist in distinguishing if the feature is the result of construction or due to post-construction movement and to aid in the evaluation of pipeline deformation states.
Enhancing Flooding Monitoring and Response to Improve Geohazard Management
Authors: Song Peter , Tetteh-Wayoe Debra , Pierce Kimberly , Hill Mike , Maxwell Mark
Published: January 2021

In March 2019, snow melt and heavy rainfall resulted in major flooding at one of Enbridge’s (Company) pipeline river crossings. Based on an earlier hydrotechnical assessment, it was identified that the estimated scour in the river channel during a flood event of this magnitude could have the potential to create a pipe span of length where vortex induced vibration (VIV) may be initiated, potentially causing pipe failure and product release. As a precautionary measure, the Company shut down and isolated the pipeline; the two mainline block valves on either side of the river were closed for several days. This un-planned pipeline shut down impacted customers and resulted in revenue loss. An extended shutdown period would have also impacted downstream refineries. In order to promptly restart of the pipeline, bathymetric surveys (measuring the depth of a water body as well as mapping the river bottom profile and the underwater features of a water body) were performed in high flow conditions to verify the pipeline burial condition.

This crossing had been identified in the Company’s long range forecast with a planned remediation completion in 2020. However, the potential residual threat to the integrity of the pipeline due to high flow events existed until the remediation could be completed. Consequently, Company Pipeline Integrity group had been closely monitoring this crossing.

The Company’s Pipeline Integrity (PI) Department is on the journey to become a High Reliability Organization (HRO) where there is a strong preoccupation with failure and emphasis on determining the root cause of an incident, with the goal of striving for error free performance. As such, this incident was treated with as much emphasis as a pipeline failure, and several lessons learned from this incident were identified.

This paper will discuss the enhancements made to the Company’s flood monitoring program, including the incorporation of the flood forecast monitoring into the flood monitoring program, identification of high priority crossings, development of purge plan, utilization of new technology for surveying during flooding and the development of a flood response guideline.
Analysis of Hazardous Liquid Pipeline Spill Volumes
Authors: Paxman Tyler , Stephens Mark
Published: January 2021

For onshore pipelines transporting hydrocarbon products that remain in a liquid state after release, environmental damage and socioeconomic impact are the dominant concerns. It is reasonable to assume that the magnitude of impact from such a release event is, at least in part, a function of the volume of product released. Analytical models exist for estimating the release volume from pipelines as a function of the physical and operational parameters of the line, and the effective size of the opening at the point of line break. While the estimates of release volumes obtained from such models are an important component of risk assessments and serve to inform emergency response planning activities, it is also important to understand what historical data indicates in terms of actual release volumes and how they are affected by key pipeline attributes. This paper summarizes the findings of an analysis of product release events associated with the onshore United States (US) hazardous liquid pipeline network, as obtained from reportable incident data publicly available from the Pipeline and Hazardous Materials Safety Administration (PHMSA). The findings of the study suggest that, for major releases resulting from large pipeline openings, release volumes are correlated with line diameter; whereas, releases as the result of a leak are largely independent of line diameter. Based on this, simple models have been developed from which both the average release volume and the range of likely release volumes can be estimated as a function of the pipeline diameter and mode of failure. These simple release volume estimation models are useful for benchmarking exercises where the goal is to estimate expected or most likely release volumes for calibrating and/or validating more complex release volume estimation models, and for estimating worst-case release volumes for emergency response planning purposes.
Experimental Investigation of the Difference in Wax Deposition Aging Rate Between Polyethylene and Steel Pipes
Authors: Li Rongbin , Li Yaping , Cao Danfu , Wang Junfang , Liu Xin
Published: January 2021

Wax deposition is an intrinsic problem existing in the production and transportation of waxy crude oil. In the oilfield, non-metallic pipe especially high-density polyethylene pipe (HDPE) has been widely used to solve corrosion problems due to its excellent performance in intensity and corrosion. However, the wax deposition problem in polyethylene (PE) pipe has never been evaluated using dynamic and systemic apparatus. Only a few studies focus on the wax deposition on the coated polyethylene surface by using the cold finger apparatus in recent decades. In this study, the wax deposition experiments were performed using an in-door flow-loop with detachable PE and stainless steel (SS) test sections under the laminar flow regime at the same time to investigate the difference in wax deposition aging rate between the PE and SS pipes. The wax deposits under different operating conditions in both PE and SS pipes were sampled by three layers to study the aging rate at different radial locations during the wax deposition. The wax precipitation characteristics of the wax deposits were determined by using the differential scanning calorimetry (DSC) method. It was found that the wax contents of the wax deposits in PE pipe were lower than that in the SS pipe. And the difference of the wax content between PE pipe and SS pipe decreases with the depositing duration. Eventually, the wax contents of the wax deposits in PE pipe were almost the same as that in the SS pipe. The heat conduction and heat transfer processes in PE pipe and SS pipe were analyzed. The thermal gradient and the concentration gradient at wall were calculated and combined with the heat and mass transfer of wax during the wax deposition to illustrate the difference in wax content. It was found that the variations of the thermal and concentration gradients have significant effects on the diffusion process of wax molecules within the wax deposit layer and thus changing the aging rate. The comparisons and findings of wax deposition between the two kinds of pipes have provided a significant reference for the application of non-metallic pipe in the oilfield.
Advanced Eddy Current Array Tools for Stress Corrosion Cracking Direct Assessment on Pipelines
Authors: Sirois Michael , Bouchard Mathieu , Sweedy Ahmed
Published: January 2021

Magnetic Particle Inspection (MPI) has been the main reference for Stress Corrosion Cracking (SCC) detection in pipeline integrity for years. Although this technique is relatively economical and easy to deploy — thanks to a large pool of certified technicians — it remains time consuming and highly user dependent. Some of the factors impacting results during SCC Direct Assessment (SCCDA) include the total surface area requiring examination, hard-to-reach positions underneath pipes during inspection, improper surface preparation due to poor sandblast or contrast, condensation on pipes, and operator fatigue.

Recent trials have proved that Eddy Current Array (ECA) technology compares favorably against MPI on many aspects in the field, and that ECA has the potential to become the new standard for SCCDA on pipelines. Offering an impressive speed, combined with a particularly high Probability of Detection (PoD), ECA could transform the work of technicians in ditches and above all, offer greater control over the human factor.

Besides detection, ECA has also proven its reliability for SCC characterization on real SCC colonies in both lab and field environments. Comparisons to metallography sections, grinding measurements and X-Ray Computed Tomography (XCT) data have greatly contributed to optimized depth sizing algorithms for this new solution, providing accurate SCC depth readings. Although ECA and Phased Array Ultrasonic Testing (PAUT) are often complementary techniques in the field, the main advantage of ECA over PAUT resides in the short amount of time required to locate and size the deepest cracks among colonies containing sometimes thousands of cracks. Within a few minutes, technicians and engineers know where to concentrate and how critical SCC really is so that decisions can be made instantly. Combining ease of use and repeatability (ways to control the human factor) is another key benefit of ECA technology.

This paper provides information about a complete ECA solution for SCC detection and depth sizing on pipelines. It reveals results from the field, comparing ECA with MPI, covering several key points and demonstrating how ECA stands out as improving the overall screening process efficiency during examinations in digs. Furthermore, it also exposes and compares ECA data with both destructive and non-destructive testing performed on test pieces containing real SCC.
Hydrate Formation in Water-in-Oil Emulsions in the Presence of Resins
Authors: Zhang Dongxu , Huang Qiyu , Li Rongbin , Cao Danfu , Li Huiyuan
Published: January 2021

Gas hydrate is one of the main concerns in the flow assurance issues for under water multiphase pipelines. Hydrate nucleation and growth in the water-in-oil emulsions have not been completely understood due to the complex factors, such as the composition of crude oils. Resins, as a common component in crude oil, can pose great effects on hydrate formation, which is still lack of investigation. This paper aims to bridge this gap with a custom-designed high pressure autoclave. Different with other hydrate investigation apparatus, an online viscometer was equipped for the real time viscosity measurement. Resins were separated from the Venezuelan residue for the purpose, following the saturates, aromatics, resins, and asphaltenes fractionation method. A series of experiments of hydrate formation were carried out in the emulsions with the presence of different resin contents, under the condition of 2.7 °C, 2.6 MPa, and 40 vol. % water cut.

It was observed that resins hindered hydrate formation in water-in-oil emulsions. The induction time increased with the increasing of resin content. The induction time in the emulsion with the presence of 1.0 wt. % resin content was almost 200 min longer than that in the emulsion without resins. It was found that an increase in resin concentration led to the significant reduction in temperature peak. In addition, a time delay phenomenon of temperature and pressure in the growth onset was found in the system with 0.5 or 1.0 wt. % resin content, by virtue of the online viscometer. It demonstrated the impeding effect of resins on hydrate growth. Moreover, the microphotographs of water-in-oil emulsions were obtained. It was observed that the resins can be adsorbed on the water droplet surface, and hence occupied the hydrate nucleation sites and formed a barrier for the further penetration of gas molecules. The adsorption phenomenon can preliminarily account for the inhibiting effect of resins on hydrate formation. It provides a scientific understanding for the effect of resins on hydrate formation in water-in-oil emulsions, excluding the interference of wax and other components. It would be useful to an appropriate flow assurance strategy designing for the under-water multiphase pipelines.
Crack Driving Force Calculation in Arbitrarily Shaped Defects Based on 3D Non-Destructive Evaluation and Finite Element Analysis
Authors: Hertelé Stijn , Adriano Vitor , Chaudhuri Somsubhro , De Wilde Laurens , Huising Otto Jan
Published: January 2021

The actual shape of a real defect differs from the simplified shapes that are assumed within an engineering critical assessment. Additionally, the re-characterization of interacting defects into one simplified defect is known to introduce conservatism, which may be undesirably large. Ongoing and expected technological advances of 3D NDE techniques (such as full-matrix capture ultrasonics and X-ray CT) allow to assume that defect simplification will no longer be required in the future, thus bypassing the uncontrolled conservatism resulting from defect simplification. A recently finished EPRG project has shown the feasibility of integrating the information provided by 3D NDE systems into finite element models. Promising results are obtained which, with additional effort, will provide a solid basis for in-the-field application.

This paper first reports on the overall procedure of defect assessment by the adopted finite element analysis (both linearelastic and elastic-plastic). Next, the ability to couple FE model construction with non-destructive evaluation results is demonstrated for three scans obtained from different sources (one X-ray CT and two ultrasonic full matrix capture scans). Finally, concrete opportunities to improve the robustness, speed and accuracy of the methodology are addressed, which will be tackled in a follow-up project funded within PRCI.
Papua New Guinea Earthquake Proves the Value of Robust Pipeline Materials Selection and Construction
Authors: Macia Mario L. , Crapps Justin , Noecker Fredrick F. , Nissley Nathan E. , Cook Michael F.
Published: January 2021

In 2018, the PNG LNG project sustained a Mw7.5 earthquake, and ca. 300 aftershocks, epicentered directly under key facilities. Around 150 km of high-pressure gas and condensate pipelines were affected. In anticipation of such an earthquake event and due to the challenging terrain that the pipeline traverses, two design methodologies were used in specifying the pipe and welds for the onshore pipelines: strain-based design and allowable stress design with robust materials selection. The strain-based design approach was used for segments crossing faults and was the subject of IPC2014-33550 [1]. In this paper, the robust allowable stress design that was used for the remainder of the onshore pipeline route will be discussed along with the performance of the pipeline designed with this methodology when it was subjected to the earthquake. Robust allowable stress design involved the selection of line pipe and welding procedures that would reduce the risk of failure during unanticipated ground movements. Lower grade, thicker wall pipe was selected, and enhanced weld properties were specified to increase weld strength overmatch and toughness. Additionally, enhanced testing of pipe and weld properties was performed in order to enable prediction of pipeline strain capacity and assessment of fitness for service of any portion of the pipeline that experienced longitudinal plastic strains due to ground movement. These efforts enabled the pipeline to safely sustain the ground movement experienced during the earthquake and allowed safe project operations to be rapidly restored.

This paper provides details of the selection of pipe grade and wall thickness and the specification of material properties for pipe and girth welds. The property distributions achieved and the impact on strain capacity are presented along with estimates of the strain experienced by the pipeline due to the earthquake. The performance of the pipeline during the earthquake illustrate the benefits of the robust allowable stress design approach for pipelines in challenging environments.
Development of Soil Restraints for Buried Pipelines in Muskeg Soils Subjected to Lateral Ground Displacements
Authors: Wijewickreme Dharma , Jayasinghe Thushara
Published: January 2021

A systematic research program was undertaken with the objective of developing quantitative geotechnical parameters to support soil-pipe interaction assessment for buried pipelines in muskeg. For this purpose, a field geotechnical investigation program comprising cone penetration testing (SCPT) with shear wave velocity (Vs) measurements, electronic field vane shear testing (eVST), full-flow ball penetration testing (BPT), and pressuremeter testing (PMT), along with fixed-piston tube soil sampling was undertaken in a muskeg soil terrain. The data from field testing were initially interpreted to obtain typical stiffness and strength parameters for the subject soils. These parameters were then used to numerically simulate pressuremeter tests and the results were compared with those obtained from field pressuremeter testing; the intent was to calibrate a suitable constitutive model to represent the muskeg soil mass. These ascalibrated constitutive model was then applied on numerical models developed to simulate buried pipelines in muskeg soil subject to relative lateral ground movements. The work is aimed at developing a framework to generate soil restraint versus relative ground displacement relations (“soil springs”) to assess soil-pipe interaction of pipelines buried in muskeg soils. Initial results from the research are presented herein, with a comparison made between soil springs developed from numerical analyses and those generated from current practice guidelines.
Modeling Stress-Activated Creep at Axial Cracks in Pipelines
Authors: Leis Brian N. , Zhu Xian-Kui , Cosham Andrew
Published: January 2021

The failure of a pipeline that had just passed a proof-pressure test as it was being re-pressurized for its return to service (a so-called pressure reversal) reflects the stable growth due to stress-activated creep of a near-critical anomaly that had remained stable as the proof test ended. In the same way that stable growth of a near-critical anomaly can lead to a pressure reversal, stable tearing (cracking) can occur and remain stable at the pressure first imposed upon the pipeline’s return to service, and so pose concern for in-service failure. Ductile failures that are absent evidence of time-dependent degradation mechanisms, like corrosion, and show the traits of stable tearing have been termed time-delayed failures. As time passed, the reasons for time-delayed failures became clear, and criteria to prevent such failures through a pressure reduction were established.

The advent of much tougher steels opened to the potential for crack initiation and stable tearing at service pressures under circumstances that differed from that for the early line pipe steels. The 2004 incident at Ghislenghien involving a modern high-toughness X70 pipeline raised the need to better understand how to manage time-delayed failures in such steels.

This paper develops a model to quantify stable tearing and possible instability at axial part-through-wall defects as a function of the steel, the length and depth of the defect, and the operating pressure. The theoretical basis for this nonlinear fracture mechanics (NLFM) model is outlined first. Case-specific finite-element analysis were used to benchmark NLFM Handbook results, which extended the use of predictive technology developed previously for lower toughness steels. As before, this solution is recast for time-marching analysis that is coupled with isochronous stress-strain response and NLFM resistance curves. Finally, the model is used to make blind predictions of cracking and instability in step-load and hold testing, and found to be viable in that context. Companion papers at this conference present the details of related work.
An Onshore Pipeline Failure due to Hydrogen Assisted Cracking Induced by Cathodic Protection Operated at Near -1200 mV CSE: A Case Study
Authors: Cazenave Pablo , Gao Ming , Moneta Andrea , Cruzado Juan , Hryciuk Pedro
Published: January 2021

A 22-inch onshore natural gas transmission pipeline experienced an in-service rupture in January of 2018. The rupture was caused by an axial crack that occurred 150 Km (93 miles) downstream of the closest compression station.

While the root cause analysis of the rupture was in progress, excavations of indications reported by a Hard Spot In-Line Inspection (ILI) were undertaken starting approximately 42 km (26 miles) downstream of the rupture. These excavations discovered predominantly circumferential crack colonies, with a number of through-wall cracks being leak.

The root cause analysis concluded that both the axial and circumferential external surface cracks are consistent with hydrogen environment assisted cracking generated by the impressed-current cathodic protection system, operated near the pipe-to-soil recommended potential limit of −1200 mV as measured with respect to a saturated copper/copper sulfate reference electrode (CSE).

Transportadora de Gas del Norte (TGN) implemented a series of preventive and corrective measures that included pressure testing, cathodic protection improvement, coating rehabilitation programs and In-Line Inspection programs among others.

This paper presents the background and approach used in the root cause analysis, summarizes the methodology, results and findings, and discusses their implications in the management of the Pipeline Integrity of the pipeline system operated by TGN.
Effect of Cooling Process on Microstructure Especially Precipitation Behavior of High-Strength Pipeline Steel
Authors: Hesong Zheng , Tao Niu , Fei Li
Published: January 2021

The effect of different cooling processes on microstructure especially precipitation behavior and properties of high grade pipeline steel was investigated in this paper. The results showed that: By two stage controlled cooling process, ferrite-bainite phase was obtained in X80 pipeline steel with high deformability, the average size of Martensite and Austenitic islands (M/A) was approximately 1μm, the Uniform Elongation (UEl) was 10%. Whereas granular bainite was obtained after conventional laminar cooling process and fine M/A of 1∼2μm size dispersed in grains or along grain boundaries. Compared with conventional pipeline steel, high deformability pipeline steel through two stage controlled cooling process had higher Elongation (El), impact toughness and lower yield ratio, due to the existence of ferrie+bainite phase structure which reduced yield strength (YS) and enhanced deformation performance and fracture toughness. Additionally, the effect of precipitation strengthening of high grade pipeline steel produced by Ultra-fast cooling (UFC) process was superior to that produced by conventional laminar cooling process. A significant amount of nano particles precipitated with the size of 1nm to 5nm were obtained through the UFC process. The application of UFC made the precipitation process avoid the nose temperature of precipitation temperature time (PTT) curve, thus the size of nano particles were smaller and the distribution of precipitation was more dispersive.
Full-Scale Step-Load-Hold Tests on X65 and X70 Line Pipe Steels
Authors: Cosham Andrew , Leis Brian N. , Zarèa Mures , Orth Fabian , Linton Valerie
Published: January 2021

A time-delayed failure due to stress-activated creep (cold-creep) will occur if the applied load is held constant at a level above the threshold. The results of small and full-scale tests on line pipe steels conducted by the Battelle Memorial Institute and the British Gas Corporation in the 1960s and 70s indicated that the (empirical) threshold for a time-delayed failure was approximately 85–95% SAPF (straight-away-pressure-to-failure). The line pipe steels were Grades X52 or X60, and the full-size equivalent Charpy V-notch impact energy (where reported) did not exceed 35 J.

The strength and toughness of line pipe steels has significantly increased over the decades due to developments in steel-making and processing. The question then is whether an empirical threshold based on tests on lower strength and lower toughness steels is applicable to higher strength and higher toughness steels.

A Tripartite Project was established to answer this question. The Australian Pipelines and Gas Association (APGA), the European Pipeline Research Group (EPRG) and the Pipeline Research Council International (PRCI) collaborated in conducting six full-scale step-load-hold tests on higher strength and higher toughness steels. Companion papers present the other aspects of this multi-year project. The line pipe supplied for testing is summarised below.

• Identifier — Dimensions and Grade — f.s.e. Charpy V-notch impact energy at 0 C

• APGA [A] — 457.0 × 9.1 mm, Grade X70M, ERW — 263 J

• EPRG [E] — 1016.0 × 13.6 mm, Grade X70M, SAWL — 165 J

• PRCI [P] — 609.6 × 6.4 mm, Grade X65, SAWL — 160 J

Six step-load-hold tests, each with four part-through-wall defects, were conducted. Test Nos. APGA 1 and 2, and Nos. EPRG 1 and 2 were conducted at Engie, France. Test Nos. PRCI 1 and 2 were conducted at EWI, USA. The full-scale tests, and associated small-scale testing, are described and discussed.

A time-delayed failure due to stress-activated creep occurred in each of the step-load-hold tests. The failures occurred during a hold-period at 93.7–104.4% SAPF, after a hold of approximately 1.0–13.9 hours. The results of the six step-load-hold tests are consistent with a threshold for a time-delayed failure of approximately 90% SAPF.
Plausible Profile (Psqr) Corrosion Assessment Model: Refinement, Validation and Operationalization
Authors: Zhang Shenwei , Yan Jason , Kariyawasam Shahani , Huang Terry , Al-Amin Mohammad
Published: January 2021

This paper presents the refinement, validation, and operationalization of Plausible Profiles (Psqr) corrosion assessment model that TC Energy (TCE) published in IPC 2018.

Metal-loss corrosion continues to be a major integrity threat to oil and gas pipelines. Inline inspection (ILI) based corrosion management, where ILI measured anomalies are assessed and mitigated, has proven to be the best way to manage corrosion. The assessment model used to estimate the burst pressure of pipelines has the most significant impact on integrity decisions. These decisions include (1) which anomalies to excavate based on In-line inspection (ILI); (2) pressure reduction (i.e. derate) required to maintain safety until repairs are completed, and (3) repair decisions during the excavation. Consequently, TCE focused on improving the shape factor of the Modified B31G effective area technique and published an overview of the improvement in IPC 2018 paper titled “A More Accurate and Precise Method for Large Metal Loss Corrosion Assessment”. From 2018 TCE refined the model using further testing, validation, internal review, and external review.

In 2019, the model was reviewed by eight industry experts through Pipeline Research Council International (PRCI) project “EC-2-9 Peer Review of the Plausible Profile (Psqr) Corrosion Assessment Model”. The project outcome recommended Psqr as an improved corrosion assessment model. The comments and recommendations provided by the reviewers will be reported in IPC 2020 in a companion paper. Validation results show the Psqr model is safe, and more accurate and precise than RSTRENG. The resulting magnitude of reduction in unnecessary activities depends on the corrosion morphology.
Statistical Analysis of Dig Operations Leading to Productive Repairs
Authors: Petrov Yevgeniy , Dubuc Jordan , Murray Michael H. , Edward Tim
Published: January 2021

Inline inspection data from several runs spanning many years is available for individual pipeline segments, but compilation of this data into a comprehensive picture of pipeline integrity necessarily relies on computational tools. A critical advantage of modern data storage, analysis, and visualization techniques is the relative ease of performing statistical assessments of integrity operations. Data from a single user of OneBridge Solution’s software may comprise over 1,000 in-line inspections (ILI) runs, hundreds of pipe segments, several million aligned anomalies, and thousands of repair records. Automated alignment of ILI data allows a single physical anomaly to be reliably tracked through many years of growth and repeated measurement and then correlated to repair records.

We present a study of cases where ILI anomaly measurements warranted a dig operation in which repair actions were either performed or found to be unnecessary. The fraction of dig operations leading to a productive repair varies with the condition triggering the dig and discretionary choices about dig condition parameters. The analysis is done through the exploration of different methods of corrosion growth forecasting in use by operators and how they compare. The measures that have been taken into consideration for the purpose of this study include half-life vs. pit-to-pit where the effectiveness of identifying and mitigating fast-growing anomalies is compared across models. Further exploration of how forecasting and building a dig program based on pit-to-pit alignments and a comprehensive growth model through the advances in data science and machine learning can bring efficiency improvements and an overall reduction in risk.

We analyze the relationship between these parameters, ILI measurements, repair-to-dig ratios and the impact on operational spend. We examine whether a reduction in overall inspection frequency and expenses is possible through advanced growth modeling. Ultimately this would provide a more accurate view of long-term operating costs and allow for operators to consider scenarios relating to repair and replacement of assets.
Judge Me by My Size, Do You? How Reliable Are Dent Assessments Based on ILI Data?
Authors: Dotson Rhett , Sager Ryan , Curiel Fernando , Le Roy Marcus
Published: January 2021

Pipeline dents have historically been regulated and assessed using dent depth as the primary metric. Many of the earliest analytical models for dent remaining life are based upon depth. Current assessment guidelines from ASME and the Code of Federal Regulations utilize depth as a primary metric. Consequently, ILI geometry tool capabilities are stated in terms of dent depth. However, the best modern dent assessments, including both strain and fatigue assessments, are based on dent shape. At a minimum, these models require both axial and circumferential dent profiles, or the models may utilize the full three-dimensional shape of the dent. The utilization of advanced dent assessments is expected to grow in the future as the methods are incorporated into API Recommended Practices and US regulations. While operators may have confidence in the ability of an ILI tool to confidently capture the dent depth, the shape of a dent is a recent consideration that is not addressed by current tool specifications. Unlike depth alone, dent shape is often a function of sensor coverage, speed, and caliper technology. Unfortunately, there is virtually no information available on the reliability of these assessment methods when they are based on ILI data. To-date, there have been no published comparisons examining the variation in strain or fatigue life in identical dents between multiple inspections. The reliability of these dent assessment methods is critical when choosing safety factors or reinspection intervals. This study presents a first look at the repeatability of strain and remaining life assessments based on two separate geometry inspection using different technologies. The study examines dent strain according to ASME B31.8 and fatigue life calculated using shape factors and finite element methods for 257 dents. The paper examines the variation in each of the methods and provides guidance on how users should understand the results when they are based on a single geometry inspection.
Dense and Sparse Stress Corrosion Crack Initiation in an X65 Pipeline Steel With Mill Scale
Authors: Wang Shidong , Lamborn Lyndon , Chevil Karina , Gamboa Erwin , Chen Weixing
Published: January 2021

Near-neutral pH stress corrosion cracking (SCC) is a significant threat to the operational safety and reliability of gas and oil pipelines. The SCC cracks are typically formed in colonies with different crack density populations on the external surface of the pipe. The density of SCC cracks affect how pipeline integrity and remaining lifetime are assessed. Although sparse and dense crack colonies are commonly observed on pipelines, it has not been well established how these crack colonies with different crack populations were developed in the field.

This research was made in an attempt to replicate near-neutral pH SCC cracks with different crack densities in the laboratory with realistic loading conditions commonly found during field operation. An X65 pipeline steel with different surface preparations was used. The results showed that the dense near-neutral pH SCC cracks were successfully reproduced on the primer-coated samples, whereas sparse cracks were reproduced on the mill-scaled and polished samples. The densely spaced cracks could transform into sparsely spaced cracks when most of the primer layer and mill scale had been removed during the long period of corrosion under cyclic loading and further corrosion occurred thinning the crack density. The results of crack initiation obtained from this investigation have also been found to be quite consistent with crack initiation scenarios found during field operation.
Demonstration of Limit States Design Method for Assessment of Corrosion and Crack Features
Authors: Adianto Riski , Ibrahim Mahmoud , Nessim Maher , Hassanien Sherif , Bott Steven
Published: January 2021

A reliability-based limit states design (LSD) method for assessment of corrosion and crack features has been developed for onshore transmission pipelines as part of a joint industry project. The rule-based LSD approach is a simplified form of the reliability-based approach that reduces the latter to a set of deterministic checks. The LSD corrosion assessment method and a comparison of its performance against one operator’s reliability approach were published in previous IPC papers [1,3]. This paper compares the LSD corrosion and crack assessment methods to another simplified reliability-based approach, namely the Pipeline Integrity Reliability Analysis (PIRA) Level I, that was published in a previous IPC paper [2]. The PIRA model is staged into three levels, where Level I analysis is a simplified form of the reliability-based approach where the probability of failures of predefined features’ sizes are precalculated using conservative assumptions for a fast turnaround screening analysis of the entire pipeline system in order to identify areas requiring more in-depth full probabilistic Level II or III analyses. This paper describes the application of both LSD and Level I methods on two low vapour pressure (LVP) liquid pipelines and provides a comparison of the results.

The comparative analysis was based on the number of features not meeting reliability targets in both methods and, thus, are eligible for repair according to each method. Out of the two pipelines considered, one has corrosion and the other has cracks as the dominant threat. The results show that there are noticeable differences between the outputs of the two methods. The root cause of these differences was investigated by conducting a sensitivity analysis on the input parameters, including: reliability target, wall thickness distribution, feature depth and length distributions, pipeline sectioning procedure and the usage of model error (which is used in the LSD method but not in the PIRA Level I method). For cracks, differences between the Modified Ln-Secant model used in the LSD method and the CorLAS model used in PIRA Level I were also considered.

It was observed that the discrepancies in the required repairs resulting from the two methods can be mostly attributed to the feature depth distribution, wall thickness distribution and the reliability target. For cracks, the burst pressure model selection also had a significant impact on the results.
Numerical Simulation of Crude Oil Spreading in a Complex River Channel
Authors: Yu Dongliang , Wang Ji , Cao Quan , Zhang Xinglong , Liu Xueguang
Published: January 2021

Crude oil leaking in rivers may cause serious damages, such as environmental pollution and death of river animals. The crude oil spreading in rivers could be much faster than that on lands, as the leaking crude oil may flow rapidly downstream with the flowing water. Therefore, accurately estimating the transient crude oil spreading area in rivers is a vital task for emergency response and disaster rescue. However, the estimating methods in the literature mainly refer to spreading process in underwater, ocean and soil, which commonly happened in the history. The crude oil transportation pipelines in China pass through many rivers with very complex channel geometries, introducing the necessity of estimating of leaking crude oil spreading in actual river channels. In the current study, the crude oil spreading process along an actual river channel is numerically simulated. The river channel geometry is extracted from a map database, which is further treated using image binarization and edge extraction to obtain the discrete river channel data. The river channel data is then smoothed by picking less data representing main geometric characteristics. The smoothed data is used to reconstruct the river geometry and generate calculation mesh. The mesh is a two-dimensional structured grid with several possible leaking points along the actual crude oil transportation pipeline passing through the river. A multi-fluid MIXTURE model is used to simulate the crude oil spreading process on the water surface, meaning crude oil blending in the flowing water. Cases with a leaking mass flow rate of 240 kg/s and a river flow velocity of 1.58 m/s are simulated for 10 possible leaking sources on the traversing pipeline. The effect of leaking locations and river channel bending on crude oil spreading on river surface were significant according to the simulation results. Sudden widening river channel may result in vortexes and slightly delays the crude oil spreading. The simulated data could be used to make the rescue strategy of crude oil leaking in this specific river.
Subset Simulation for Structural Reliability Analysis of Pipeline Corrosion Defects
Authors: Bandstra Daryl , Fraser Alex M.
Published: January 2021

One of the leading threats to the integrity of oil and gas transmission pipeline systems is metal-loss corrosion. This threat is commonly managed by evaluating measurements obtained with in-line inspection tools, which locate and size individual metal-loss defects in order to plan maintenance and repair activities. Both deterministic and probabilistic methods are used in the pipeline industry to evaluate the severity of these defects. Probabilistic evaluations typically utilize structural reliability, which is an approach to designing and assessing structures that focuses on the calculation and prediction of the probability that a structure may fail. In the structural reliability approach, the probability of failure is obtained from a multidimensional integral. The solution to this integral is typically estimated numerically using Direct Monte Carlo (DMC) simulation as DMC is relatively simple and robust. The downside is that DMC requires a significant amount of computational effort to estimate small probabilities.

The objective of this paper is to explore the use of a more efficient approach, called Subset Simulation (SS), to estimate the probability of burst failure for a pipeline metal-loss defect. We present comparisons between the probability of failure estimates generated for a sample defect by Direct Monte Carlo simulation and Subset Simulation for differing numbers of simulations. These cases illustrate the decreased computational effort required by Subset Simulation to produce stable probability of failure estimates, particularly for small probabilities. For defects with a burst probability in the range of 10−4 to 10−7, SS is shown to reduce the computational effort (time or cost) by 10 to 1,000 times. By significantly reducing the computational effort required to obtain stable estimates of small failure probabilities, this methodology reduces one of the major barriers to the use of reliability methods for system-wide pipeline reliability assessment.