Pipeline Capacity Research Articles

Nonlinear structural responses of the buried oval steel pipelines crossing strike-slip faults

The permanent ground deformation may lead to bending failure or fractures of the buried steel pipelines. In practical applications, the buried pipelines may also exhibit ovality defects due to soil pressure, gravity of the pipeline, and misalignment of joints, which have the potential to diminish the load-bearing capacity of the buried pipelines. This paper introduces a comprehensive analytical methodology to examine the dynamic behavior of pipelines with different initial ovality defects subjected to strike-slip faults. A modified permissible lateral displacement function is introduced to determine the strain distribution of the deformed pipelines. One may predict the yield displacement of the oval pipelines accurately based on the yield theory of classical beams and the static equilibrium method. Then, the accuracy of the proposed method was validated by developing a finite element model and other results. Good agreement was reached characterized by the yield displacement and the yield strain, respectively. Finally, a parametric analysis was conducted on the effects of different ovality, steel grades, diameter-to-thickness ratios, fault inclination angles, and soil properties on the displacement and strain distributions of the deformed pipeline.

Machine Learning Modeling for Predicting Tensile Strain Capacity of Pipelines and Identifying Key Factors

Abstract Machine learning (ML) techniques have recently gained great attention across a multitude of engineering domains, including pipeline materials. However, their application to tensile strain capacity (TSC) modeling remains unexplored. To bridge this gap, this study developed and evaluated an ML model to predict the tensile strain capacity of girth-welded pipelines. The model was trained on over 20,000 data points derived from a TSC equation available in the literature. The ML model demonstrated robust performance in predicting tensile strain capacities. Evidence of this lies in the near-zero means, minimal standard deviations, and normal distribution of residuals for both the training and test datasets. These collectively suggest that the model provides a good fit for the data. Furthermore, the model's loss behavior indicates successful convergence and generalization, without signs of overfitting or underfitting. An analysis using the random forest method revealed that the geometry of the flaw, specifically the flaw depth, is the most influential variable in predicting the TSC. This could be attributed to its significant impact on the fracture toughness of materials. In contrast, material properties and fracture toughness exert less influence relatively, despite their contributions to the model. This finding underscores the importance of flaw geometry in TSC prediction models. Overall, the development of a data-driven TSC model has shown efficient TSC modeling. This model leverages ML techniques, allowing for continuous updates with new data via deep learning.

Study on fracture behaviour of pipeline girth welds based on curved wide plate specimens: Experimental and numerical analysis

Understanding the fracture characteristics and strain capacity of pipelines with girth welds under external loads is crucial for evaluating pipeline safety. The use of curved wide plate (CWP) specimens closely resembling full-scale (FS) pipelines in geometry provides a more realistic representation of crack tip constraint states compared to small-size fracture toughness test specimens in laboratory settings. This study aims to investigate the ductile fracture characteristics of center cracks on the outer surface of girth welds in high-grade steel pipelines under external loads through large-scale CWP tensile tests and advanced numerical simulations. Tensile tests were conducted on CWP specimens using a kiloton tensile testing machine, with double crack opening displacement (COD) gauge monitoring crack mouth opening displacement (CMOD), and high-precision displacement sensors and strain gauges tracking deformation and strains at various positions. The study yielded significant experimental results, and a finite element (FE) model of the CWP was developed using the nonlinear finite element method (FEM) to validate the experimental data against simulation results. The FE model was then used to investigate the influence of material properties on crack propagation resistance and driving force curves. A method for determining the ultimate tensile strain capacity (UTSC) of pipelines based on actual material fracture toughness was proposed. This research contributes valuable experimental data for further exploration of fracture behaviour in large-scale pipeline girth welds and offers insights for safety evaluations of such welds.

Levelized cost of long-distance large-scale transportation of hydrogen in China

Hydrogen plays a crucial role in supporting the transition to clean energy systems, and effective hydrogen transportation technologies are essential for the development of the hydrogen economy. However, long-distance, large-scale hydrogen transportation costs in China, particularly for liquid hydrogen trucks (LH2 tank trucks) and gaseous hydrogen pipelines (GH2 pipelines), remain unknown. Using the latest data from the ongoing hydrogen project in China and a techno-economic model, this study estimates the delivery costs of hydrogen over long distances for LH2 tank trucks and GH2 pipelines, and compares them with those of GH2 trucks. Specifically, we analyze the levelized cost of hydrogen transportation (LCOT) for these different technologies at varying distances and conduct sensitivity analyses on how these LCOT would change with factors such as vehicle travel speed, electricity prices, and pipeline capacity. Results show that for short distances (<150 km), GH2 trucks are most cost-effective, with costs around 28.96–34.26 CNY/ton-km. For long distances (>200 km), GH2 pipelines and LH2 tank trucks are more suitable, with pipelines being more cost-effective at higher capacity utilization rates. Lower electricity prices further reduce the LCOT for LH2 tank trucks. Policy recommendations on promoting the development and application of hydrogen transportation technologies are also provided.

Automatic topology and capacity generation framework for urban drainage systems with deep learning-based land use segmentation and hydrological characterization

This paper proposed a comprehensive and automated framework that integrates the entire urban drainage design process, from refined land use segmentation, to catchment subdivision and characterization, to network topology generation, and finally to hydraulic estimation of pipeline capacity, based on multiple open-source datasets. The method incorporated deep learning-based semantic segmentation, GIS-based hydrological characterization, topology generation and hydraulic calculation algorithms. The performance and applicability of the method were validated through case studies of two cities. The results showed that the deep learning model with prior knowledge could accurately segment urban land use to obtain the detailed shape and boundary description, and achieved higher detection accuracy for water bodies, buildings, and roads. The stormwater drainage topology and conveyance capacity were automatically generated based on subcatchment division and hydrological characterization under a set of topological parameter conditions. In the optimal Critical Success Index (CSI) scenario, only 8% and 21% of the generated pipelines were inconsistent with the expert-designed networks. Compared to the traditional manual design process, the automated approach can save significant time and resources and reduce the reliance on field surveys and empirical/expert work. At the same time, the tool can be employed for system layout and capacity optimization, providing important support for the automation, design, and rehabilitation of stormwater drainage systems.

A quantitative assessment of the rehabilitative impact of Kevlar liners on offshore pipelines

Offshore pipelines transport oil and natural gas that contain different corrosive contaminants, leading to internal corrosions. The presence of internal metal loss problems can significantly degrade the load-bearing capacity and reliability of pipelines over time. To address this issue, a Kevlar liner, offering a more accessible and cost-effective solution, is employed for repairing corroded pipelines. However, a quantitative assessment of the rehabilitating effect of Kevlar liner has been lacking. This study performed an investigation of the burst pressure of internal corroded pipelines reinforced with the Kevlar liner through a combination of experimental testing and finite element numerical simulations. While previous research primarily concentrated on single external defect, this study has investigated the burst pressure of pipelines in the presence of both single and dual internal corrosion defects. The results indicated that the presence of two corrosion defects further decreases the burst pressure of the pipelines. This study examined the reinforcement mechanism of Kevlar liner, revealing that it largely postpones the stress development in the corrosion zone and thereby enhances the ultimate internal pressure load-bearing capacity of the pipelines. Moreover, the contact stress resulting from the friction between the Kevlar liner and the steel pipeline contributes to the overall improvement in the load-bearing capacity of the corroded offshore pipelines.

Analyze of pipeline transport characteristics and optimization method of structural parameters in slurry shield circulation system with spiral structure

This study introduces the application of a spiral structure in pipeline transportation to enhance the pipeline capacity of a slurry shield circulation system. A numerical model of solid–fluid coupling in a pipeline with a double spiral structure was established based on computational fluid dynamics and the discrete element method (CFD–DEM) theory, and its validity was confirmed through comparison with experimental data. The characteristics of the spiral pipeline were evaluated by comparing them with those of a conventional smooth straight pipeline. A multi-objective optimization method for determining the structural parameters of a spiral pipeline in a slurry shield circulation system is proposed using the Kriging surrogate model. The optimized design of a spiral pipeline was demonstrated through a specific project, and the impact of the main structural parameters on the slurry transport characteristics of the pipeline was analyzed. The results indicated that the optimized structural parameters led to an 18.65% increase in the average flow rate of the slurry and a 19.13% reduction in the accumulation of stones in the pipeline.

Finite element analyses of burst capacities of corroded pipelines containing pinhole-in-corrosion defects

This study carries out extensive parametric three-dimensional elasto-plastic finite element analysis to evaluate the burst capacity of oil and gas pipelines containing pinhole-in-corrosion (PIC) defects. The analysis results reveal that the burst capacity of the PIC defect is insensitive to the pinhole diameter but largely affected by the depth of the pinhole and length of the general corrosion. A pinhole located at the centre of the general corrosion is found to have a larger impact on the burst capacity than the same pinhole located near the edge of the general corrosion. The observed size and location effects on the burst capacity are attributed to the bulging deformation of a corroded pipeline under internal pressure. The findings of this study provide the basis for developing a practical, accurate engineering burst capacity model for PIC defects.

Effect of chord-cut defects on the collapse response of thick-walled pipelines

Corrosion defects can significantly reduce the ultimate bearing capacity of thick-walled pipelines in deep water. Uneven depth defects pose a serious threat to the integrity of pipeline structures. However, in the study of uneven depth defects, the influence of chord-cut defects is often overlooked. To study the impact of chord-cut corrosion defect on pipeline collapse response, a dynamic model is established. Two sets of full-scale pipeline experiments are conducted to verify the model. The validated model is used to obtain the pipeline collapse responses under different defect parameters, which include defect length, defect depth, defects’ location, and pipeline ovality. The changes in pipeline collapse pressure and collapse mode under different defect parameters are analyzed. The research shows the increase in defect length and the decrease in diameter-to-thickness ratio (D/t) will enhance the influence of defect angle θ on pipeline collapse configuration. And the change of collapse mode will lead to abnormal changes in collapse pressure. With the increase of internal defect length, the collapse mode variation rule is “∞” - “∩” - “P” - “U”. A collapse pressure empirical formula for pipeline with chord-cut corrosion defects is obtained. The empirical formula fits well with the numerical simulation results.

The throughput capacity of the main gas pipeline when transporting gas-hydrogen mixtures

To determine the effect of hydrogen concentration in the gas-hydrogen mixture on the throughput capacity of the main gas pipeline and the volume of energy transported by it. The range of molar concentrations of hydrogen in the gas-hydrogen mixture up to and including 20%, which does not require significant technical modernisation of the system, was investigated.Performing theoretical studies and applying mathematical modelling methods to establish the regularities of thermo hydrodynamic processes in a gas pipeline, gas turbine and centrifugal blowers while transporting gas-hydrogen mixtures.In the example of a gas turbine unit widely used in the gas transmission system of Ukraine, it was found out that the molar content of hydrogen, if it does not exceed 20%, has a negligible effect on its rated power and other energy parameters. Adding hydrogen to natural gas with the above molar content will lead to a slight decrease in the pipeline system's capacity (up to 5%) and a significant reduction in the volume of energy transportation (up to 18%).The next stage of the study is to determine the impact of gas-hydrogen mixture properties on the pipeline capacity, taking into account changes in seasonal factors and the degree of system load.A method and software have been developed to predict the pipeline capacity and energy transfer volume for the transportation of gas-hydrogen mixtures, taking into account the influence of seasonal factors, gas-dynamic characteristics of blowers, and combinations of gas-pumping units at compressor stations.Modern international standards are used to calculate gas-hydrogen mixtures' physicochemical and thermodynamic properties under standard and operating conditions. The originality of the approach lies in the fact that the compressor station and the linear section of the gas pipeline are considered as a SLE gas-dynamic system.

A new set of explicit solutions for postbuckling behaviour of anisotropic shear deformable laminated cylindrical shells with general imperfection distribution and thermal loading

Thermal postbuckling analysis is presented for shear-deformable anisotropic laminated cylindrical shell with general imperfection distribution under several typical temperature fields are analyzed, including uniform temperature, tent-like linear distribution, axial and circumferential quadratic parabolic temperature fields over the shell surface and through the shell thickness. On this basis, the general temperature distribution can be obtained based on the three-dimensional steady-state heat transfer equation. At the same time, based on the high order shear deformation theory including anisotropic coupling effect, geometrically nonlinear large deflection displacement-strain relationship, the general initial geometric imperfections obtained by measurement and analytical means are introduced, and the thermal buckling equilibrium differential equation of anisotropic shear deformable laminated cylindrical shell with initial imperfections is established. A two-step perturbation-Galerkin integral method is used to obtain explicit solutions for the path development direction of post-thermal buckling equilibrium. The results of parameter analysis show that the material properties and temperature dependence, temperature distribution, lay-up and geometric parameters such as radius-to-thickness ratio have important effects on the thermal buckling load and postbuckling equilibrium path. The present method provides an effective theoretical prediction and analysis method for the design of the carrying capacity of submarine pipelines.

Influence analysis on the storage capacity of hydrogen-blended natural gas pipeline

Influence analysis on the storage capacity of hydrogen-blended natural gas pipeline

DETERMINATION OF THE CAPACITY OF PIPELINES TRANSPORTING LIQUID PRODUCTS, DEPENDING ON THE THERMOBARIC CONDITIONS

The article discusses the issues of calculating the capacity of pipelines through which liquid hydrocarbon products are transported, depending on thermobaric conditions. These calculations are important for such urgent tasks of pipeline transport practice as carrying out an inventory and establishing the fact of illegal withdrawal of oil/oil products from the pipeline. The work provides a fundamental equation of the state of the stopped pipeline, in consideration of which the focus of attention is on changing the geometric capacity of the pipeline depending on the change in temperature and pressure of the pumped medium. When considering the change in volume, from the classical equations of mechanics, refined dependencies were obtained for two cases: underground and above-ground laying. A comparison of the obtained relationships has been made, in which it has been found that a number of effects such as a change in gas volume and a temperature factor «mask» the effect of leakage/illegal sampling, preventing their identification from the pressure/temperature change data. An analytical explanation of the processes occurring in the shut down pipeline will allow further quantification of the uncertainties that arise, which will facilitate the decision and allow adjustments to be made to the software used.

Calculation model for bearing capacity of steel-CFRP composite pipeline under internal pressure

The Carbon Fiber Reinforced Polymer (CFRP)-wrapped steel pipeline system is emerging as an alternative for the repair and long-distance transportation of oil and gas. This system is recognized as a composite material. Under internal pressure, the pipe predominantly undergoes circumferential stretching. This study derives the tensile constitutive model of the steel-CFRP composite material using uniaxial tensile tests and the rule of mixtures. Subsequently, utilizing this newly calibrated constitutive model, a computational model to assess the internal pressure capacity of the steel-carbon fiber composite pipe was established. Finally, a comparison between the theoretical outcomes of the computational model and the actual internal pressure test results revealed a high degree of correlation. This holds substantial significance for the design and practical implementation of this novel composite pipeline system.

Hydrate formation due to moisture, occuring by mixing natural gas streams of dewatering different degrees

The key problem during transporting natural gas through gas pipelines is to ensure reliable, safe transportation and supply of gas to consumers. Reliable operation of the main gas pipeline depends on transported gas quality. Under production conditions, gas is saturated with moisture vapor to an equilibrium state, and when thermodynamic conditions (pressure, temperature) change, its condensation occurs. Due to the heterogeneity of the fields, the problem of gas quality control is the key reliability criterion, especially such as the moisture content in the gas. The main complication is the formation of hydrate plugs, which lead to an increase in hydraulic resistance and a decrease in pipeline capacity, which contributes to the occurrence of emergency situations. Therefore, before supplying natural gas to main gas pipelines, the gas is dried to its dew point, which prevents condensation of water from the gas.

Regional Planning for Just and Reasonable Rates

Natural gas—a fuel used for electricity generation, heating, and transportation—plays an outsized role in the U.S. economy. Under the Natural Gas Act, the Federal Energy Regulatory Commission (FERC or the Commission) is responsible for overseeing the orderly development of interstate natural gas pipelines, which facilitate the transmission of natural gas throughout the country. Before a developer can construct or expand an interstate pipeline, it must apply to FERC for authoriza-tion; FERC can approve the pipeline only if it finds that it is required by the “public convenience and necessity.” Although FERC should consid-er a range of factors to determine whether a pipeline will serve the public interest, in practice, it looks primarily to the existence of prece-dent agreements, i.e., contracts between a developer and its customers for the purchase of pipeline capacity. If a developer can demonstrate that there is a party willing to pay to use its pipeline, FERC rarely asks questions and almost always finds “public” need. In this way, the natu-ral gas transmission network has developed through a system of ad hoc decisionmaking organized around the needs of private companies that earn a hefty return on their capital investments.&#x0D; This pipeline-by-pipeline approach to natural gas transmission build-out leads to the construction of unnecessary, underused pipe-lines, which in turn increases ratepayer costs and decreases consumer welfare. Climate change further increases the risk that pipelines will become obsolete as cities and states move toward electrification. Fur-thermore, the gas transmission planning process—or lack thereof—stands in stark contrast to electric transmission planning, an activity that FERC also regulates but that is conducted by centralized entities on a regional scale. This contrast is especially confounding consider-ing that electric transmission is regulated under the Federal Power Act, a sister law to the Natural Gas Act with similar statutory require-ments.&#x0D; Relying on economic theory, legal history, and policy analysis, we make the case for FERC’s adoption of regional gas transmission plan-ning. We begin by describing the status quo and articulating why FERC’s current process is economically inefficient. In doing so, we draw parallels between gas and electric transmission planning and de-scribe how FERC treats the two activities inconsistently. We then ex-plain why, under two provisions of the Natural Gas Act, FERC possesses both the legal authority and obligation to require regional planning. Finally, we envision how FERC might conduct gas transmission plan-ning going forward, encouraging FERC to account for increasing elec-trification efforts and to plan for gas and electric transmission in tan-dem.

Allocation of transportation capacity for complex natural gas pipeline network under fair opening

China has formed a national natural gas pipeline network, and reasonable and accurate pipeline capacity allocation scheme has important significance for improving the utilization rate of pipeline network, improving the income of pipeline network operators and ensuring the gas consumption of downstream users, which poses greater challenges to the formulation of pipeline capacity allocation rules and mechanisms. This paper takes the natural gas pipeline network system as the research object, and studies the rules and mechanisms of pipeline capacity allocation. A capacity allocation model of natural gas pipeline network is proposed with the net present value of pipeline network operator's income as the goal, considering the gas consumption characteristics of downstream users, the dynamic change of gas source node capacity, pipeline hydraulic characteristics, pipeline flow direction, compressor and other constraints. Based on the simulation of the actual pipeline network by the proposed model, seven allocation rules and one mechanism are proposed. Specifically, the user priority of non-interruptible type, the pipeline path adjustable type and the gas source node adjustable type is higher than the corresponding comparison type. In the pipeline capacity allocation mechanism, the amount compensation mechanism for pipeline capacity transactions is as follows: When the pipeline capacity transaction occurs between users, the transaction information is submitted to the pipeline network operator. The pipeline network operator proposes the corresponding amount compensation according to the transaction information, and the transaction parties negotiate the proportion of the amount compensation and submit it to the pipeline network operator. In addition, it is recommended that pipeline network operators vigorously develop LNG receiving stations and downstream interruptible and compressible users in the future.

Modeling insights from the Austrian national gas grid under declining natural gas demand and increasing domestic renewable gas generation by 2040

This paper studies the development of the Austrian gas grid by 2040 under different decarbonization scenarios, ranging from electrifying most energy services to importing large amounts of renewable methane. The Austrian gas grid serves as a case study representative for those gas grids confronted with a drop in natural gas demand and an increase in domestic renewable gas generation in the future. A mixed-integer optimization model with a focus on the detailed representation of the existing grid (gas grid levels, pipeline capacity, route, and age) is used to determine the cost-optimal trade-off decision between expected low-utilized gas pipelines and an off-grid supply alternative (e.g., trucking and on-site gas storage) in a decarbonized Austrian and European energy system. Optimality determines whether to operate, decommission, or make replacement investments in the grid’s pipelines. Based on the required gas grid 2040 and its annual grid costs, estimates for tariffs of end customers are given. The paper’s main conclusion is that the domestic distributed renewable gas generation uptake will be associated with the need for an area-wide gas grid, but one that will be significantly less utilized. Future work could address, among other things, the exploration of the spatial interplay of local production and demand by forming regional clusters of renewable gas.

Increase of oil product pipeline throughput capacity by means of an anti-turbulent additive

The need to increase the capacity of the pipelines is increasing with the growth of oil and gas production in Russia. Russian and foreign scientists, who carry out numerous experiments and develop additives to oil and petroleum products that reduce hydraulic resistance and head loss from friction in the near-wall area of the pipeline, are working to solve the problem of oil pipeline capacity [1]. This paper considers the actual task of increasing the throughput capacity of oil product pipelines by the use of antiturbulent additive “CDR” and “M - FLOWTREAT” [2]. In the course of solving the task: an analytical review of methods to increase the throughput capacity of pipelines was carried out; a mathematical model of the additive effect on the conditions of oil flow in the pipeline was constructed; the effect of the additive on hydraulic resistance and oil flow velocity was investigated; a comparative assessment of the effectiveness of different additives on the throughput capacity of oil pipelines was given; the optimal concentration of the antiturbulent additive was selected [3]. The mathematical model proposed in this work, taking into account hydraulically smooth pipes and limitation, gives good results of capacity increase of up to 20%. Also, during the research it was found that the additive “M - FLOWTREAT” is more effective than “CDR” and from the point of view of capital investment is more favorable as to achieve the required performance, the amount of the additive is required less [4].

Finite element analysis of JCO-E fabrication process and its influence on the collapse capacity of offshore pipelines

In the present work, the JCO-E fabrication process is numerically simulated using advanced finite element tools for the case of a thick-walled 30-inch-diameter pipe, which is candidate for deep water installation. Subsequently, the structural performance of the line pipe under external pressure is investigated in a unified approach. Uniaxial tests are performed to obtain the material properties used in the finite element model, which are representative of the loading history that the plate is subjected during the process. The finite element model is validated with geometric measurements from the actual pipe fabricated in the pipe mill. The effect of the expansion level on the properties of the final product is investigated through extensive numerical studies. The results have shown that there exists an optimum expansion range for achieving the minimization of the geometric imperfections of the final product and the maximization of the collapse capacity of the pipe.