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Pipelines are crucial for transporting energy sources, yet corrosion especially stress corrosion cracking (SCC) poses a complex and potentially catastrophic form of material degradation. Traditional techniques like finite element analysis (FEA) have been utilized for SCC prediction, but it suffers from high computational cost and limited scalability. Deep learning (DL) with integration of FEA leverages large-scale data and learn complex nonlinear patterns for SCC prediction. Currently, literature on deep learning-enabled finite element analysis for pipelines SCC prediction is scarce, offering limited insights into this emerging approach and lack of comprehensive review. This paper reviews and investigates the current research directions and applications of DL-enabled FEA methodologies for simulation of SCC prediction. The importance of DL, technique type and network are also outlined in this review paper. This paper delves into integration of DL algorithms with FEA and their ability to grab complex interactions between mechanical stress, material properties, and environmental factors. Based on this comprehensive review, it was found that DL and FEA have proven to be strong prediction tools with high accuracy and lower training cost. DL-enabled FEA techniques are also being utilized to replace time-consuming methods and conventional codes. Furthermore, article discusses potential of this integrated approach for enhancing accuracy and efficiency of SCC prediction, leading to improved pipeline integrity management practices. [ABSTRACT FROM AUTHOR]

Pipelines are crucial for transporting energy sources, yet corrosion especially stress corrosion cracking (SCC) poses a complex and potentially catastrophic form of material degradation. Traditional techniques like finite element analysis (FEA) have been utilized for SCC prediction, but it suffers from high computational cost and limited scalability. Deep learning (DL) with integration of FEA leverages large-scale data and learn complex nonlinear patterns for SCC prediction. Currently, literature on deep learning-enabled finite element analysis for pipelines SCC prediction is scarce, offering limited insights into this emerging approach and lack of comprehensive review. This paper reviews and investigates the current research directions and applications of DL-enabled FEA methodologies for simulation of SCC prediction. The importance of DL, technique type and network are also outlined in this review paper. This paper delves into integration of DL algorithms with FEA and their ability to grab complex interactions between mechanical stress, material properties, and environmental factors. Based on this comprehensive review, it was found that DL and FEA have proven to be strong prediction tools with high accuracy and lower training cost. DL-enabled FEA techniques are also being utilized to replace time-consuming methods and conventional codes. Furthermore, article discusses potential of this integrated approach for enhancing accuracy and efficiency of SCC prediction, leading to improved pipeline integrity management practices.Abbreviations: SCC: Stress corrosion cracking; FE: Finite element; FEA: Finite element analysis; FEM: Finite element method; ML: Machine learning; DL: Deep learning; EGIG: European gas pipeline incident data group; PHMSA: Pipeline and hazardous materials safety administration; DNNs: Deep neural networks; HpHSCC: High pH stress corrosion cracking; SMYS: Specified minimum yield strength; HE: Hydrogen embrittlement; NNpHSCC: Near-neutral pH stress corrosion cracking; ASME: American society of mechanical engineers; DNV: Det norske veritas; AI-FEM: Advanced iterative finite element method; CGR: Crack growth rate; ME: Mechanoelectrochemical; XGB: XGBoost; CAT: Catboost; CP: Cathodic Protection; AI: Artificial intelligence; ANNs: Artificial neural networks; CNNs: Convolutional neural networks; RNNs: Recurrent neural networks; ReLU: Rectified linear unit

The dynamic stress–strain state and fracture of a steel main gas pipe section between supports with a straight-through crack was analyzed with consideration of the temperature effect on changes in the mechanical properties of the pipe material. The numerical solution of the problem was implemented in the ANSYS-19.2/Explicit Dynamics software package. The process of fracture in a section of the gas pipeline "Beineu–Bozoy–Shymkent" with a linear crack in the temperature range of −40 °C to +50 °C at the operating pressure of 7.5 MPa and critical pressure equal to 9.8 MPa was considered. As a result, it was found that at the initial growth of the internal pressure from working pressure to critical pressure, the length of the crack doubled. At the same time, the process had a local characteristic. Further development of the crack had the nature of avalanche fracture and depended on the temperature of the steel pipeline. With increasing temperature, there was also an increase in the length of the crack at the avalanche fracture. Thus, at a temperature of 40 °C, the crack lengthened 67.75-fold; at a temperature of −10 °C, the crack lengthened 68-fold; at a temperature of +20 °C, the crack lengthened 68.25-fold; and at a temperature of +50 °C, the crack lengthened 68.5-fold. In this work, this difference was 75% of the initial crack length. This fact will be used for further development of the technique of strengthening damaged pipe sections using bandages. [ABSTRACT FROM AUTHOR]

Pitting corrosion defect is a common defect in pipelines employed in the oil and gas industry. This paper explores the mechanical behavior and failure pressure (Pf) of the pipelines, and compares the traditional empirical methods used in oil and gas pipelines with pit arrangements including an isolated pit and pitting colony (three and five pits aligned in the longitudinal direction). This study is based on nonlinear finite element method (FEM) and 3-D pipeline models. Pf was predicted by FEM and traditional methods considering the interaction of pitting corrosion defects. The pipeline Pf values obtained by FEM and methods were compared to determine similarities in applications.

Abstract In-line inspection (ILI) is important to pipeline integrity management since it can detect pipeline defects and identify potential failure locations through periodical examinations. However, effectively evaluating defects based on ILI data is challenging. Measurements of ILI are easily influenced by instrument performance and maintenance activities, leading to unmatched and imbalanced data. Poor ILI data make it difficult to establish defect growth models based on multiple inspections. This study conducted comprehensive analysis of ILI data for evaluating corrosion defects of a steel pipeline. First, statistical analysis was performed on raw data to visualize distributions of corrosion depths and number of corrosions. Second, hierarchical clustering method was used to classify corrosion severity levels based on features of corrosion depth and estimated repair factor. The interaction effect between adjacent corrosions was considered. Machine learning methods, including k-nearest neighbor, support vector machine, random forest, and light gradient boosting machine were used to explore the relationship between the location parameters of adjacent corrosions and severity levels. Then, maximum corrosion depths and corrosion density were filtered from raw ILI data of multiple inspections, which were critical for pipeline failure prediction. Finally, distribution parameters were fitted to establish stochastic growth models on maximum corrosion depth and corrosion number density. This study presents data analytics based approach to obtain valid information from ILI data in practice.

This paper proposes a semi-analytical method for the time-dependent reliability assessment of steel pipelines exposed to localized corrosion. The failure modes considered in this paper include corrosion perforation and local burst due to the growth of defect depth and length. For a short pipeline, a spatial-temporal Poisson model is used to describe the occurrence of corrosion defects. The method is further generalized for the reliability assessment of a long pipeline, which is treated as a series system consisting of different segments. The spatial correlation of the behaviour of adjacent segments is taken into account, and is modeled by the Nataf transformation method. An example is presented to demonstrate the applicability of the proposed method. Analytical results show that the reliability of a short pipeline can be significantly underestimated if the assessment method for a single corrosion defect is used instead. For a long pipeline, the failure probability is smaller in the presence of a stronger spatial correlation between different segments, suggesting that the manufacturing procedure and assembling practice of different segments should be synchronized with each other in order to improve pipeline reliability. [ABSTRACT FROM AUTHOR]

This paper considers the deformation process of a typical section of a steel trunk pipeline with a defective zone, strengthened with a carbon fiber composite lining, under the influence of stationary internal pressure. Defects in the form of thinning of the pipe thickness and cracks were investigated. The stressed-strained state of the structure at critical pressure was analyzed. The thickness of the composite lining was determined, at which the bandage compensates for the effect of internal pressure on the damaged section of the pipeline. Research was carried out numerically based on finite element modeling in the ANSYS software package. When studying the stressed-strained state of a pipe with a defect of an arbitrary complex shape under the influence of critical pressure, a compensating value was obtained. The result showed that a carbon fiber lining with a thickness of 17 % of the rated thickness of the pipe could completely compensate for the effects of internal pressure in the defect area. In this case, the stresses in the carbon fiber lining were close to minimal. When studying the stressedstrained state of a pipe with a large crack of arbitrary shape at critical pressure, a compensating value was also obtained. It has been established that to compensate for the concentration of internal pressure in the crack zone, the thickness of the composite lining should be at the level of 34 % of the rated thickness of the pipe. In this case, the deformation of the steel pipe in the area of the crack occurs in the elastic region. The exception is the crack tips, where plastic deformations are observed, and stresses arise up to 93 % of the ultimate strength of the pipe steel. At the same time, the stresses in the carbon fiber lining remain close to minimal. Thus, it is recommended to use carbon fiber linings with a thickness of 17 % or more of the rated pipe thickness to bandage damage constituting up to 75 % of the thickness of a steel pipe. To bandage cracks, it is recommended to use carbon fiber linings with a thickness of at least 34 % of the rated pipe thickness [ABSTRACT FROM AUTHOR]

The dynamic stress–strain state and fracture of a steel main gas pipe section between supports with a straight-through crack was analyzed with consideration of the temperature effect on changes in the mechanical properties of the pipe material. The numerical solution of the problem was implemented in the ANSYS-19.2/Explicit Dynamics software package. The process of fracture in a section of the gas pipeline “Beineu–Bozoy–Shymkent” with a linear crack in the temperature range of −40 °C to +50 °C at the operating pressure of 7.5 MPa and critical pressure equal to 9.8 MPa was considered. As a result, it was found that at the initial growth of the internal pressure from working pressure to critical pressure, the length of the crack doubled. At the same time, the process had a local characteristic. Further development of the crack had the nature of avalanche fracture and depended on the temperature of the steel pipeline. With increasing temperature, there was also an increase in the length of the crack at the avalanche fracture. Thus, at a temperature of 40 °C, the crack lengthened 67.75-fold; at a temperature of −10 °C, the crack lengthened 68-fold; at a temperature of +20 °C, the crack lengthened 68.25-fold; and at a temperature of +50 °C, the crack lengthened 68.5-fold. In this work, this difference was 75% of the initial crack length. This fact will be used for further development of the technique of strengthening damaged pipe sections using bandages.

The interaction between axially adjacent defects is more significant than that between circumferentially aligned defects. However, the existing failure pressure assessment methods cannot accurately predict the failure pressure of axial adjacent defects. In the paper, the finite element model is adopted to analyze the influence of defect size, distribution mode and spacing between adjacent defects on failure pressure. A new failure pressure evaluation method is proposed by establishing the effective depth calculation model of corrosion colony with different distribution model. The burst test of X52 pipeline is carried out to verify the applicability of the method. It shows that the results of new method are consistent with the test results of pipeline with various defects and steel grades. [ABSTRACT FROM AUTHOR]

In this study, a pulse Cathodic Protection (CP) rectifier was designed and made. The performance of the pulse rectifier was monitored and compared with a conventional system. In this regard, different values of duty cycle (73% and 50%) and frequency (50 kHz and 60 kHz) were analyzed. Results showed that the AC voltage and current consumption dramatically dropped compared to the conventional rectifier. Also, the pulse CP protection potential was distributed more uniformly as a function of pulse parameters in the optimum combination of 50 kHz and 73% for frequency and duty cycle, respectively. This was explained by the changes in the electrochemical polarization resistance of the environment when utilizing the pulse CP. [ABSTRACT FROM AUTHOR]

In-line inspection (ILI) is important to pipeline integrity management since it can detect pipeline defects and identify potential failure locations through periodical examinations. However, effectively evaluating defects based on ILI data is challenging. Measurements of ILI are easily influenced by instrument performance and maintenance activities, leading to unmatched and imbalanced data. Poor ILI data make it difficult to establish defect growth models based on multiple inspections. This study conducted comprehensive analysis of ILI data for evaluating corrosion defects of a steel pipeline. First, statistical analysis was performed on raw data to visualize distributions of corrosion depths and number of corrosions. Second, hierarchical clustering method was used to classify corrosion severity levels based on features of corrosion depth and estimated repair factor. The interaction effect between adjacent corrosions was considered. Machine learning methods, including k-nearest neighbor, support vector machine, random forest, and light gradient boosting machine were used to explore the relationship between the location parameters of adjacent corrosions and severity levels. Then, maximum corrosion depths and corrosion density were filtered from raw ILI data of multiple inspections, which were critical for pipeline failure prediction. Finally, distribution parameters were fitted to establish stochastic growth models on maximum corrosion depth and corrosion number density. This study presents data analytics based approach to obtain valid information from ILI data in practice. [ABSTRACT FROM AUTHOR]

Steel pipelines that are used for the transportation of natural gas and petroleum usually pass through different places with different soil characteristics. Due to distinct soil structures and other corrosive factors, pipelines tend to corrode at different rates. In this study, the effects of moisture content, salt concentration, pH, AC potential and cathodic protection levels on the corrosion rate were investigated as factors affecting corrosion in steel structures originating from the ground and external sources. The number of experiments to be carried out was decided as a result of experimental design with the Taguchi statistical method. L16 orthogonal array was used for 4 different levels of 5 corrosion rate affecting factors and 16 different experimental studies were conducted to obtain corrosion rate values for each experiment. Based on the statistical analysis results, the effect of changes in moisture content of the soil on corrosion rate was higher compared to other factors. Considering that underground pipelines usually pass through neutral environments (pH levels between 6-8), the effect of changes in pH value on corrosion rate is less than the other factors studied. In addition, with the regression analysis performed through the Minitab software, a linear regression model and an equation was created to calculate the corrosion rates. Corrosion rate results obtained with the regression equation were compared with the test results performed in different test environments. By calculating the corrosion rate for different factors, selection of or changing the pipeline route, selection of material wall thickness, planning of pipeline control and maintenance periods can be made in the most ideal way. Also, a comparison of corrosion rates against existing literature shows that corrosion rates of steel materials change between outstanding classification ranges according to corrosion resistance classification of steel materials. [ABSTRACT FROM AUTHOR]

In this study, a pulse Cathodic Protection (CP) rectifier was designed and made. The performance of the pulse rectifier was monitored and compared with a conventional system. In this regard, different values of duty cycle (73% and 50%) and frequency (50 kHz and 60 kHz) were analyzed. Results showed that the AC voltage and current consumption dramatically dropped compared to the conventional rectifier. Also, the pulse CP protection potential was distributed more uniformly as a function of pulse parameters in the optimum combination of 50 kHz and 73% for frequency and duty cycle, respectively. This was explained by the changes in the electrochemical polarization resistance of the environment when utilizing the pulse CP.

The pipeline in service may be subjected to complicated loads (including lateral, axial, vertical loads and hydrostatic pressure in addition to internal pressure) when crossing complex geohazard regions. In this study, two kind of loads that cloud be more fundamental are numerically investigated using finite element method. The loads imposed on pipelines depend on the pipe content and the environment that the pipeline is passing through. Axial compression can arise within pipelines from thermal loads arising from hot hydrocarbon passage from offshore oil wells to an onshore station or can arise from anchor forces acting on pipelines and External pressure can arise within pipelines from hydrostatic pressure, sudden valve closures, and pump failures. It is very important to select suitable geometric imperfection form to exact investigation behavior of pipelines and mechanism of failures. In order to verification response of numerical analyses, one of the experimental results is compared with numerical result and concluded that there is a good agreement between results. Meanwhile, the effect of the eccentric axial compression, pipe diameter to wall thickness ratio (D/t) on the buckling external pressure are studied. The interaction between the axial load and external pressure was graphically demonstrated and compared for different geometrical ratios through numerical analysis. During analysis, the eccentric axial compression load in the pipe was primarily induced and maintained constant less than its capacity. Subsequently, the uniform peripheral pressure was gradually increased until failure, and, besides, the response of some specimens was separately investigated under pure external pressure and axial compression load. It was found that the D/t ratio is the decisive parameter to specify the buckling behavior of steel pipelines and type of created failure mode subjected to axial compression. Some significant conclusions were drawn based on extensive parametric studies. The buckling external pressure reduces with the increase of pre-axial compression and diameter to thickness ratio.

Steel pipeline has been widely used in oil and gas transportation industry because of its unique advantages. However, while providing services, the steel pipeline is easy to be corroded, resulting in volumetric defects, which makes the pipeline thinner and the bearing capacity weaker, further causes the pipeline leakage, and even serious safety accidents. Based on the simplified form of volumetric defects, this paper compares and summarizes the evaluation criteria and evaluation methods, and gives suggestions on the simplified form of defects. The critical factors of single defect and multiple defects on pipeline safety evaluation are sorted out, and the interaction rules of adjacent defects are summarized. Finally, the research direction of multiple defects and the application of machine learning in pipeline safety evaluation are prospected.

In the process of contemporary industrial pipeline installation, most pipelines must be cleaned before being put into use due to production and operation process requirements. This paper takes the offline trough cleaning of pipelines as the research object, and explores the evolution process of the metal microstructure under this cleaning method and the best cleaning conditions under the influence of the three factors of concentration, temperature and time.

This work develops a theoretical analysis of the coating permeability necessary for use as internal coatings of transmission pipelines to prevent hydrogen embrittlement. Internal coating materials suitable to be applied in situ on existing steel pipelines are also evaluated. Twelve different commercially available coatings; crosslinked poly (vinyl alcohol) (PVA), poly (vinyl chloride) and bisphenol A diglycidyl ether (DGEBA)/polyetheramine (D-400) epoxy coatings prepared in-house were tested. Films fabricated from two commercial epoxies had hydrogen permeability of 0.40 Barrer and 0.35 Barrer respectively, which show potential as coating materials. A hydrogen permeability of 0.0084 Barrer was achieved with a crosslinked poly (vinyl alcohol) coating, indicating that this material shows the highest potential of all coatings tested. Unsteady-state hydrogen diffusion through coated steel was then modeled to evaluate the effect of the coating film in reducing hydrogen embrittlement. The result shows that with a 2 mm PVA coating, hydrogen permeation inside the coating will take seven years to reach equilibrium and the final hydrogen concentration on the steel surface will be 44% lower than that without a coating. Greater protection can be provided if coatings can be developed with lower hydrogen permeability. • Hydrogen permeability, solubility and diffusivity of 16 potential pipeline coatings were tested. • All commercial coatings were too permeable to prevent hydrogen ingress. • Crosslinked PVA films offered significantly lower hydrogen permeability. • A 2 mm PVA coating could reduce the equilibrium hydrogen concentration on the steel surface by 44% after seven years. [ABSTRACT FROM AUTHOR]

Copyright of Journal of China University of Petroleum is the property of China University of Petroleum and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the process of contemporary industrial pipeline installation, most pipelines must be cleaned before being put into use due to production and operation process requirements. This paper takes the offline trough cleaning of pipelines as the research object, and explores the evolution process of the metal microstructure under this cleaning method and the best cleaning conditions under the influence of the three factors of concentration, temperature and time. [ABSTRACT FROM AUTHOR]

Purpose. To develop methods for calculating of the expediency to use mine degassing system, made of the current composites, to improve safety in heavily loaded longwalls. Methodology. Solving the problems involved analysis of the current studies concerning the methane-air mixture removal from stopes while mining gaseous coal seams. Standard schemes of gas transmission systems have been considered as well as peculiarities of the methane-air mixture transportation using underground vacuum pipelines made from steel and composites. Findings. Expert evaluation concerning economic expediency to replace the traditional steel pipelines by the modern composite gas lines for the available mine degassing systems, has helped develop methods calculating the operational indices of degassing networks made from the recent polymeric materials. Originality. Methods have been developed to calculate technical and economic parameters of degassing network, made from the modern composites, and upgrade the current degassing systems to reduce expenditures connected with the captured methaneair mixture transportation from wells to vacuum pump stations. Practical value. Implementation of the fi ndings as for the evaluation of the technical and economic parameters and introduction of the innovative engineering solutions to replace the traditional steel degassing pipelines by the recent gas lines made of long composite chains, involving minimum joints, has been scheduled by Ukrainian gaseous coal mines. [ABSTRACT FROM AUTHOR]

The quality of the girth welds on pipelines is a critical point regarding the safe operation. Non-contact pipeline magnetic detection (NPMD) is a non-destructive detection technology based on the metal magnetic memory (MMM) method. However, present studies mostly focus on the qualitative analysis of girth welds instead of accurate quantitative analysis of the stress status. Here, many hydraulic tests in sealed pipelines are performed to investigate the magnetic signal under different internal pressures and detection heights. A numerical model of magnetic signal is established and verified by the experimental results. The results show the characteristics of the signal that the y component has sinusoidal fluctuations when the x and z component reach the extreme values. A new parameter K v s is proposed to comprehensively reflect the stress status of the girth welds. It is founded that the residual strength ratio (RSR) reduces from 0.97 to 0.83 when the K vs max increases from 7500 to 13500 nT/m The magnetic signals decay exponentially in the second order when the detection height varies within 0.1–1.0 m. This study provides a theoretical and experimental basis for identifying the stress status of the girth welds on pipelines. • Numerical field of non-contact magnetic signal is established and verified. • Magnetic signal is influenced by stress at welds and detection height. • The z component reaches the extreme valuesat girth welds. • A parameter is proposed to reflect the stress status of the girth welds. [ABSTRACT FROM AUTHOR]

Steel pipelines that are used for the transportation of natural gas and petroleum usually pass through different places with different soil characteristics. Due to distinct soil structures and other corrosive factors, pipelines tend to corrode at different rates. In this study, the effects of moisture content, salt concentration, pH, AC potential and cathodic protection levels on the corrosion rate were investigated as factors affecting corrosion in steel structures originating from the ground and external sources. The number of experiments to be carried out was decided as a result of experimental design with the Taguchi statistical method. L16 orthogonal array was used for 4 different levels of 5 corrosion rate affecting factors and 16 different experimental studies were conducted to obtain corrosion rate values for each experiment. Based on the statistical analysis results, the effect of changes in moisture content of the soil on corrosion rate was higher compared to other factors. Considering that underground pipelines usually pass through neutral environments (pH levels between 6-8), the effect of changes in pH value on corrosion rate is less than the other factors studied. In addition, with the regression analysis performed through the Minitab software, a linear regression model and an equation was created to calculate the corrosion rates. Corrosion rate results obtained with the regression equation were compared with the test results performed in different test environments. By calculating the corrosion rate for different factors, selection of or changing the pipeline route, selection of material wall thickness, planning of pipeline control and maintenance periods can be made in the most ideal way. Also, a comparison of corrosion rates against existing literature shows that corrosion rates of steel materials change between outstanding classification ranges according to corrosion resistance classification of steel materials.

This paper introduces a novel framework for developing reliable probabilistic predictive corrosion growth models for buried steel pipelines using pipeline inspection data. The framework adopts a power-law function of time model formulation, accounting for nonconstant damage growth rates, and considers the correlation between defect depth and length growth models. The proposed framework explicitly incorporates local influential soil properties in the model formulation; thus, it requires no segmentation and homogenous defect growth assumption and provides defect-specific growth models. The framework is applicable regardless of the availability of matched or non-matched defect data. For corrosion initiation time estimation, two different approaches are proposed: one is to use a Poisson process to account for defect occurrence, which can also predict newly generated defects since the last inspection, and the other is to use multivariate linear regression of soil and pipe properties. The statistics of unknown model parameters are assessed using a Bayesian updating framework in which the model error can be incorporated. The proposed framework is applied using two different sets of data: one set of inline inspection (ILI) data and one set of field excavation data. A case study is conducted, where time-dependent system reliability of an in-service pipeline is assessed considering small leak and burst failure modes using the developed defect growth models. The impact of the growth model accuracy on the probability of failure is investigated, and the importance analysis is performed to identify the most influential random variables to the probability of failure. • Local soil properties are used in the model formulation so that the model is defect specific. • The methodology is applicable to matched or non-matched defect data. • Two different approaches are proposed for modeling corrosion initiation time. • The correlation between defect depth and length models is considered. • The methodology is capable of incorporating measurement error. [ABSTRACT FROM AUTHOR]

During the service life of the offshore pipelines, different failure mechanisms like external/internal sheath damage, fatigue damage, or corrosion may arise. Therefore, high operating costs need to be consumed to confirm the fitness of the pipeline system. This research deals with an enhanced Risk-Based Inspection (RBI) methodology to certify the integrity management of the pipeline system, a radical new way of RBI practice is introduced for analysing steel pipeline and flexible pipeline. Case studies are executed to designate and give knowledge of how the technique works in exercise with what outcomes can be discovered. The discoveries present features of uncertainties which may not have been measured when implementing the traditional RBI scheme. The scope of this research is to display that with an efficient technique of execution the RBI practice, the failures of pipeline systems can be monitored and control system to ensures the integrity of the pipeline's system. [ABSTRACT FROM AUTHOR]

Affected by a complex environment, corrosion is a common defect in steel pipelines. Moreover, steel pipelines are subjected to large axial forces during their installation and operation. Corroded deep-sea steel pipelines are prone to local buckling under complex loads. Therefore, in view of this problem, the collapse response of corroded steel pipelines under the combined axial force and external pressure is analyzed in detail. First, a formula for evaluating the collapse pressure of corroded steel pipelines under external pressure and axial force is proposed. Then, the factors affecting the collapse pressure of the steel pipeline are parameterized by using the finite element method. The accuracy of the finite element model is proved by collapse tests of the corroded steel pipeline. As shown in finite element results, the diameter-to-thickness ratio, initial ovality and corrosion defect size have significant effects on the buckling response of a steel pipeline. The collapse pressure of the steel pipeline decreases as the axial force increases. Finally, based on the finite element simulation results, the parameter variables in the evaluation formula are obtained.

Deposits prevention and removal in pipeline has great importance to ensure pipeline operation. Selecting a suitable removal time based on the composition and mass of the deposits not only reduces cost but also improves efficiency. In this article, we develop a new non-destructive approach using the percussion method and voice recognition with support vector machine to detect the sandy deposits in the steel pipeline. Particularly, as the mass of sandy deposits in the pipeline changes, the impact-induced sound signals will be different. A commonly used voice recognition feature, Mel-Frequency Cepstrum Coefficients, which represent the result of a cosine transform of the real logarithm of the short-term energy spectrum on a Mel-frequency scale, is adopted in this research and Mel-Frequency Cepstrum Coefficients are extracted from the obtained sound signals. A support vector machine model was employed to identify the sandy deposits with different mass values by classifying energy summation and Mel-Frequency Cepstrum Coefficients. In addition, the classification accuracies of energy summation and Mel-Frequency Cepstrum Coefficients are compared. The experimental results demonstrated that Mel-Frequency Cepstrum Coefficients perform better in pipeline deposits detection and have great potential in acoustic recognition for structural health monitoring. In addition, the proposed Mel-Frequency Cepstrum Coefficients–based pipeline deposits monitoring model can estimate the deposits in the pipeline with high accuracy. Moreover, compared with current non-destructive deposits detection approaches, the percussion method is easy to implement. With the rapid development of artificial intelligence and acoustic recognition, the proposed method can realize higher accuracy and higher speed in the detection of pipeline deposits, and has great application potential in the future. In addition, the proposed percussion method can enable robotic-based inspection for large-scale implementation. [ABSTRACT FROM AUTHOR]

Fluctuated loadings from currents, waves and sea ground motions are observed on offshore steel pipelines, and they will result in small cracks to propagate continuously and cause unexpected damage to offshore/geotechnical infrastructures. In spite of the availability of efficient techniques and high-power computers for solving crack problems, investigations on the fatigue life of offshore pipelines with 3D interacting cracks are still rarely found in open literature. In the current study, systematic numerical investigations are performed on fatigue crack growth behaviours of offshore pipelines containing coplanar and non-coplanar cracks. Extended finite element method (XFEM) is adopted to simulate the fatigue crack growth. The qualitative validations of numerical results are made for certain cases with available experimental results. Parametric studies are conducted to investigate the influences of various important parameters on fatigue crack growth. The results will be helpful to assess the fatigue behaviours of steel pipeline with 3D interacting cracks. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highlights • A modelling technique is presented for coupling of an outflow and crack propagation. • A full-scale burst test is successfully simulated using the proposed coupled model. • The results show the importance of the fluid-structure interaction modeling. Abstract Long running fractures in high-pressure pipelines transporting hazardous fluid are catastrophic events resulting in pipeline damage and posing safety and environmental risks. Therefore, the ductile fracture propagation control is an essential element of the pipeline design. In this study, a coupled fluid-structure interaction modelling is used to simulate the dynamic ductile fractures in steel pipelines. The proposed model couples a fluid dynamics model describing the pipeline decompression and the fracture mechanics of the deforming pipeline exposed to internal and back-fill pressures. To simulate the state of the flow in a rupturing pipeline, a compressible one-dimensional computational fluid dynamics model is applied, where the fluid properties are evaluated using a rigorous thermodynamic model. The ductile failure of the steel pipeline is described as an extension of the modified Bai-Wierzbicki model implemented in a finite element code. The proposed methodology has successfully been applied to simulate a full-scale pipeline burst test performed by British Gas Company, which involved rupture of a buried X70 steel pipeline, initially filled with rich natural gas at 11.6 MPa and −5 °C. [ABSTRACT FROM AUTHOR]

Abstract In this research, we investigated microstructural aspects of intergranular and transgranular fatigue crack propagation in an API X65 steel pipelines. For this purpose, the fatigue testing, based on ASTM E647 Standard, was carried out on CT specimens. The micro-texture measurement results showed that fatigue micro-cracks propagates dominantly in transgranular manner through differently oriented grains. It was also observed that most of the grains involved in crack propagation are broken during the crack growth. Coincidence site lattice (CSL) boundaries are considered as crack resistant paths; however, there was an accumulation of Σ3 boundaries around the fatigue micro-cracks showing that such boundaries acts as high energy boundaries during crack propagation. Elongated manganese sulphide inclusion was determined as the most detrimental inclusion for crack propagation due to the highly disordered boundaries between metal matrix and this inclusion. In other words, this type of inclusion may initiate the fatigue crack due to a high stress concentration factor that can provide in some sharp edges. Moreover, it can facilitate fatigue crack growth by reducing the local fracture toughness. Many manganese sulphide inclusions were found on fatigue fracture surfaces. Highlights • Microstructural aspects of inter and transgranular fatigue crack propagation was studied in pipeline steels. • Fatigue micro-cracks propagates dominantly in transgranular manner through differently oriented grains. • Most of the grains involved in crack propagation are broken during the crack growth. • MnS inclusion was determined as the most detrimental inclusion for crack propagation. • There was an accumulation of Σ3 boundaries around the fatigue micro-cracks. [ABSTRACT FROM AUTHOR]

The main goal of this paper is to evaluate the burst pressure and structural integrity of a steel pipeline based on in-line inspection results, in respect to the grouping criteria of closely spaced volumetric surface features. In the study, special attention is paid to evaluation of data provided from the diagnostics using an axial excitation magnetic flux leakage technology in respect to multiple defects grouping. Standardized clustering rules were applied to the corrosion pits taken from an in-line inspection of the gas transmission pipeline. Basic rules of interaction of pipe wall metal losses are expressed in terms of longitudinal and circumferential spacing of the features in the colony. The effect of interactions of the detected anomalies on the tube residual strength evaluated according to the Det Norske Veritas Recommended practice was investigated in the current study. In the presented case, groups of closely-spaced defects behaved similarly as individual flaws with regard to their influence on burst pressure and pipeline failure probability.

The steel/soil interface on cathodically protected pipeline steel has been investigated using electrochemical polarisation measurements and electrochemical impedance spectroscopy, to add more insights into the electrochemical processes occurring at the interface. A critical electrode potential (CEP) was found that divides the steel corrosion reaction kinetics into two regions. When the electrode potential is below this critical value, the steel surface has a large impedance value, indicating much slower corrosion kinetics than when the electrode potential is more positive than the CEP value. This critical value is found to be related to pitting potential determined by potentiodynamic polarisation measurements. The CEP could be affected by the CP condition and environmental, including the CP potential and the soil moisture content. At a more negative CP potential, the CEP was found to be nobler; while at the same CP potential but in the soil with a higher moisture content, the CEP became more negative. The impact of the CP potential and soil moisture level on the CEP value is explained by local soil pH effects on steel passivity. [ABSTRACT FROM AUTHOR]

Cathodic protection (CP) may lose its effectiveness for protecting buried steel pipeline from soil corrosion due to the effects of potential excursions caused by stray currents. In this work, dynamic localised corrosion processes of buried steel due to the effects of cyclic potential transients have been visualised using an electrochemically integrated multi-electrode array, often referred to as the wire beam electrode (WBE). The focus has been on the understanding of the effect of cathodic transients. The WBE maps suggest that the amplitude of cathodic transient, as well as the ratio of anodic cyclic to cathodic cyclic, can significantly affect the corrosion rates and patterns. In particular, if the cathodic transient leads to a very negative potential, e.g. −1350 mVvs.CSE, rapid corrosion would occur on buried steel surface. These results have implications for CP parameter selection for preventing stray current-affected buried steel pipelines. [ABSTRACT FROM AUTHOR]

Anodic transients are known to affect buried pipeline cathodic protection (CP) systems; however, their actual effects on pipeline corrosion have not been sufficiently quantified due to the lack of direct experimental evidences. In this work, a novel methodology developed based on an electrochemically integrated multi-electrode array has been used to visualise the dynamic effects of anodic transients on localised corrosion processes occurring on buried steel surfaces. It is shown that anodic transients do not necessarily cause steel corrosion, as long as their amplitude and duration are below critical values. The electrode array is able to determine these critical values accurately due to its ability to detect localised corrosion initiation, while the conventional coupon electrode is only able to estimate these values. The critical anodic transient duration has been explained as the incubation period for the breakdown of passivity formed on the steel surface exposed to CP-generated high pH conditions. [ABSTRACT FROM AUTHOR]

• The test involves seamless steel tubes with D / t = 31 and different sizes of interacting defects. • The strains within and between the defects were measured and the data were analyzed. • The failure location for colony corrosion defects was obtained. • The conclusion is helpful to improve the efficiency of failure pressure evaluation for colony corrosion. The interaction between adjacent defects significantly influences the internal pressure loading capacity of corroded pipelines, and the failure pressure of the interacting defects is lower than that the defects would attain when they were isolated. Therefore, it is necessary to study the interaction mechanism between different defects. The experimental program described in the paper involves seamless steel tubes with D / t = 31 and different sizes of interacting defects. The fluid is passed inside the sealed pipeline and the failure pressure of such locally corroded pipeline was obtained experimentally. The strains within and between the defects were measured using strain gauges and the measured data were analyzed. The results of full-scale corroded pipeline tests showed that the strain of failure defect will rise first and then decrease, and the interaction between this defect and adjacent defects is the most obvious. Through the analysis of the failure location of interacting defects with internal pressure, it can be seen that the failure location was the defect with the lowest internal pressure bearing capacity for adjacent defects with significantly different failure pressures. In contrast, the failure location was the defect in the middle of the corrosion region for adjacent defects with no significant difference in failure pressure. [ABSTRACT FROM AUTHOR]