High-pressure Gas Pipeline Research Articles

Effects of hydrogen blending ratios and CO2 on hydrogen embrittlement of X65 steel in high-pressure offshore hydrogen-blended natural gas pipelines

In this study, the effects of hydrogen blending ratios and high CO2 content on hydrogen embrittlement (HE) of offshore natural gas X65 pipeline steel were investigated. In high-pressure hydrogen gas, the impact of hydrogen content on yield strength and tensile strength was minimal. However, the effect on elongation was more significant, with the area decreasing and the HE index increasing until the hydrogen-blended ratio approached 30%, at which point the HE index reached 8.94%. Introducing CO2 into high-pressure hydrogen-rich gas further increased the HE index with high CO2 content. At 40% CO2, the HE index was 2.42 times higher than in high-pressure hydrogen-blended mixtures (30% H2). Additionally, the local fracture morphology transitions from ductile to quasi-cleavage fracture with the addition of CO2 and H2.

Coupling Analysis of Safety Influencing Factors in Subway Station Operation under a High-Pressure Gas Pipeline

A subway station’s operation is susceptible to accidents when there is a high-pressure gas pipeline overlaying it, and analyzing the correlations between the safety influencing factors (SIFs) in this operating situation can provide paths to reduce safety accidents. Thus, this paper investigated the coupling correlations between the SIFs. We firstly identified the SIFs during subway station operation under a high-pressure pipeline (SSOUHP) based on a literature review and discussion with experts. Then, the analytic hierarchy process (AHP) and coupling degree analysis (CDA) were combined to assess the coupling correlations between the SIFs, and Y subway station was selected to test the proposed hybrid coupling analysis approach. Research results show that (a) 23 second-level SIFs were identified and these SIFs can be summed up into five first-level SIFs, namely, human-related SIFs, pipeline-related SIFs, station-related SIFs, environment-related SIFs, and management-related SIFs; (b) the proposed hybrid approach can be used to evaluate the coupling correlations between SIFs; (c) of the coupling situations during Y subway station’s operation, the internal coupling correlations among environment-related SIFs, the coupling correlations between pipe-related SIFs and environment-related SIFs, and the coupling correlations among human-related SIFs, pipe-related SIFs, and environment-related SIFs are all greater than 1, and the coordination degree is 0.778, 0.781, and 0.783, respectively, which is a high security risk; (d) the overall coupling degree among all SIFs during Y subway station’s operation is 0.995 and the coordination degree is 0.809, which is a low safety risk. The research can enrich knowledge in the safety evaluation area, and provide a reference for onsite safety management. The results are basically consistent with the conclusion of the enterprise report, which verifies the scientificity and validity of the evaluation method.

Failure of a high-pressure flash gas pipeline from coal coke gasification to the cleaning section due to hydrogen-induced cracking

ABSTRACT The high-pressure flash pipeline of coal coke gasification leaked within one week after the operation. Further macroscopic observation showed that cracks appeared in the base material area near the weld. The medium transported by the pipe was low-concentration acid gas. Visual inspection, tensile testing, impact testing, chemical composition analysis, metallographic analysis, energy dispersive spectroscopy, X-ray diffraction analysis, and electron backscattering diffraction analysis were used to reveal the sources of cracks in the pipeline. It was found that the cracks were intergranular and filled with corrosion products. The chemical composition of the corrosion products is rich in Cr, S, and O. After the crack was opened, fracture features of ‘rock candy’ were observed, exhibiting brittle fracture characteristics. The cracks were caused by hydrogen-induced cracking along the grain boundary. On this basis, suggestions and countermeasures were put forward for the failure of the high-pressure flash gas pipeline.

Vibration Characteristics and Structural Optimization of Pipeline Intelligent Plugging Robot under Turbulent Flow Field Excitation

Pipeline maintenance technology based on pipeline intelligent plugging robot (PIPR) has become an effective method for failure accident prevention of high-pressure subsea oil and gas pipelines. However, during the plugging operation, the vortexes and pressure fluctuation are presented under turbulent flow field excitation, which may lead to vortex-induced vibration and failure of the plugging operation. Therefore, in order to ensure the reliability of pipeline plugging, the vibration characteristics are analyzed using numerical simulation, providing guidance on the structural optimization of PIPR’s end face. Firstly, the flow field characteristics under different PIPR’s end faces are investigated. Secondly, an experimental scheme is designed based on Latin Hypercube Sampling Design (LHSD) optimized by greedy strategy. A mathematical model of the end face’s parameters and pressure gradient is established using a back propagation (BP) neural network. Then, an improved whale optimization algorithm (IWOA) is proposed to optimize the end face’s parameters to minimize the pressure gradient of the flow field. Finally, the experimental study is performed to observe the turbulent flow field and pressure fluctuation to validate the optimization results. The results demonstrate that the PIPR’s end face has a great influence on the vortex-induced vibration response. After structural optimization, the average pressure gradient of the optimal PIPR’s end face has decreased by 84.69% and 54.55% before and after the plugging process, compared to the original end face. This study can provide a reference for pipeline plugging operations, which is significant for preventing pipeline failure accidents.

Research on the application of interferometric optical fiber sensors in high-pressure gas pipelines

The advantages of fiber optic sensors based on fiber optic interferometers with explosion-proof safety in gas pipeline monitoring has gradually emerged. A monitoring system for natural gas pipelines was designed and implemented using a Michelson interferometer as the core structure of the fiber optic sensor and processed the collected data using phase carrier generation demodulation algorithms. Addressing practical issues such as phase wrapping and arm length difference losses, an improved phase carrier demodulation algorithm based on tangent transformation and arctangent-differential self-cross-multiplication was proposed. Field experiments were conducted in gas valve chambers, to analyze the characteristics of leak signals in the pipeline. This study lays the foundation for the application of fiber optic interferometer sensors in gas pipeline monitoring, promising enhanced safety and efficiency.

Leakage Simulation and Prediction for High-Pressure Natural Gas Pipeline in a Confined Space

Leakage Simulation and Prediction for High-Pressure Natural Gas Pipeline in a Confined Space

Characterization of the evolution of leakage and variation of in-pipe parameters in a full-size ethane high-pressure pipeline

There is a risk of leakage of ethane during high-pressure pipeline transportation. In order to investigate the effects of leakage conditions on the free-field ethane concentration distribution, temperature and pressure evolution, a full-size ethane high-pressure gas pipeline experimental platform was constructed, and high-pressure ethane leakage experiments were carried out with different diameters and leakage directions to investigate the effects of different leakage directions and diameters on the free-field ethane diffusion, temperature and pressure inside the pipeline. The experiment results show that in the free field, when the leakage direction is ≥45° to the horizontal plane, the near-surface ethane concentration is close to 0. When the horizontal leakage occurs, compared with the 15 mm leak diameters, the peak concentration of the 25 mm leak diameters rises by 17.7%, and the explosion danger range rises by 75%, and the explosion danger time is extended by 78.6%. It is worth mentioning that the initial pressure drop rate and the overall temperature drop in the pipeline increase and then decrease with the increase of leak diameters during the high-pressure ethane leakage process, and there is a critical diameter, which is 15 mm in this experiment. The results of the study provide a reference for the safe operation of the high-pressure ethane gas pipeline.

Research on physical explosion crater model of high-pressure natural gas pipeline

In this study, Hypermesh and LS-DYNA numerical simulation software are used to build a multi domain coupling model of natural gas pipeline, including soil, pipeline, TNT explosive and air domain, and the non-reflection boundary conditions are set for the model. The TNT equivalent method is used to convert the physical explosion amount of natural gas pipeline into 1387.38 kg TNT explosive amount. The simulation results show that the physical explosion of pipeline forms an approximate elliptical crater with a width of 12.68 m and a depth of 4.12 m; the TNT equivalent of the model is corrected by comparing the crater simulation value and the size value of the crater calculated by the PRCI empirical formula under the same laying condition, and the correction coefficient is selected as 0.9, and the corrected TNT equivalent is 1248.64 kg; the modified model crater size is 3.72 m deep and 12.66 m wide, compared with the crater size obtained from the field test, the error of crater depth and width calculated by the modified model simulation is 5.7% and 15.5% respectively.

Vortex of a Symmetric Jet Structure in a Natural Gas Pipeline via Proper Orthogonal Decomposition

The impact of particle addition jets on the flow field in natural gas pipelines was investigated, and the structural information of the flow field at different flow velocities in a symmetric jet flow was analyzed via numerical simulation. The results of coherent structures in the high-pressure natural gas pipeline reveal vortex structures of varying sizes both upstream and downstream of the jet flow. To determine the spatial distribution of the main vortex structures in the flow field, proper orthogonal decomposition (POD) mode analysis was performed on the unsteady numerical results. Moreover, the detailed spatial characteristics of the coherent vortex structures represented by each mode were obtained. The results indicate that the large-scale vortex structures within the pipeline are balanced and stable, with their energy increasing as the jet flow velocity increases. Additionally, higher-order modes exhibit significant shedding of small-scale vortex structures downstream of the jet flow. In this research, coherent structures present in symmetric particle addition jets are provided, offering theoretical support for future investigations on the distribution of particle image velocimetry (PIV) flowmeters.

Study on physical explosion equivalent of large diameter and high pressure natural gas pipeline

High pressure natural gas pipelines are prone to material failure and explosion due to various reasons. Over the years, scholars have done in-depth research on the process of chemical explosion. In this paper, the energy components of high-pressure trunk natural gas pipeline under normal operation state were derived. Based on the assumption of adiabatic non isentropic, the pressure distribution in the pipeline within a period of time after the pipeline cracks was derived, and the energy released by the physical explosion of the pipeline was further derived. To verify the theoretical results, an original size pipe explosion experiment was organized, and the pressure distribution obtained from the experiment was found to be in good agreement with the theoretical calculation results. Through the crack propagation time and the duration of ground motion obtained from the experiment, the range of the duration of the pipeline burst crack impact was obtained, and the equivalent range of the pipeline explosion was further calculated. At the same time, through the regression analysis of ground motion, the equivalent of the pipe explosion in this experiment was about 177 kg TNT, which was consistent with the theoretical results. Further, the theoretical model and experimental results were verified by numerical simulation, and deeply studied the influence factors of buried depth on the explosion equivalent, as well as the relationship between the environment of the pipeline and the explosion damage mode and hazard range of the pipeline. The research results of this paper give the calculation method and magnitude range of physical explosion equivalent of high-pressure trunk natural gas pipeline. It provides a reference for the formulation of safety standards for high-pressure trunk natural gas pipelines and inert gas pressure vessels.

Research Progress and Prospects on Hydrogen Damage in Welds of Hydrogen-Blended Natural Gas Pipelines

Hydrogen energy represents a crucial pathway towards achieving carbon neutrality and is a pivotal facet of future strategic emerging industries. The safe and efficient transportation of hydrogen is a key link in the entire chain development of the hydrogen energy industry’s “production, storage, and transportation”. Mixing hydrogen into natural gas pipelines for transportation is the potential best way to achieve large-scale, long-distance, safe, and efficient hydrogen transportation. Welds are identified as the vulnerable points in natural gas pipelines, and compatibility between hydrogen-doped natural gas and existing pipeline welds is a critical technical challenge that affects the global-scale transportation of hydrogen energy. Therefore, this article systematically discusses the construction and weld characteristics of hydrogen-doped natural gas pipelines, the research status of hydrogen damage mechanism, and mechanical property strengthening methods of hydrogen-doped natural gas pipeline welds, and points out the future development direction of hydrogen damage mechanism research in hydrogen-doped natural gas pipeline welds. The research results show that: ① Currently, there is a need for comprehensive research on the degradation of mechanical properties in welds made from typical pipe materials on a global scale. It is imperative to systematically elucidate the mechanism of mechanical property degradation due to conventional and hydrogen-induced damage in welds of high-pressure hydrogen-doped natural gas pipelines worldwide. ② The deterioration of mechanical properties in welds of hydrogen-doped natural gas pipelines is influenced by various components, including hydrogen, carbon dioxide, and nitrogen. It is necessary to reveal the mechanism of mechanical property deterioration of pipeline welds under the joint participation of multiple damage mechanisms under multi-component gas conditions. ③ Establishing a fundamental database of mechanical properties for typical pipeline steel materials under hydrogen-doped natural gas conditions globally is imperative, to form a method for strengthening the mechanical properties of typical high-pressure hydrogen-doped natural gas pipeline welds. ④ It is essential to promptly develop relevant standards for hydrogen blending transportation, welding technology, as well as weld evaluation, testing, and repair procedures for natural gas pipelines.

Leakage analysis and prediction model of underground high-pressure natural gas pipeline considering box culvert protection

Buried gas pipelines frequently experience failures as a consequence of adverse factors. The studies of gas leakage diffusion behavior and prediction of hazardous areas following pipeline failure hold profound significance in mitigating the risk of accidents. This paper exemplifies a specific segment of long-distance transportation gas pipeline in the "West-to-East Gas Transmission" project, employing the Soave-Redlich-Kwong (SRK) equation of state (EOS) to develop a numerical model for high-pressure gas leakage and diffusion, while considering box culvert protection. The characteristics of gas leakage diffusion and the effects of pressure, leakage diameter, and soil type on gas diffusion are presented. Furthermore, the prediction models for leakage rate, fastest hazardous time (FHT), fastest hazardous distance (FHD), and lateral hazardous distance (LHD) are introduced. The results show that the pressure and velocity at the beginning of the leakage manifest an annular diffusion centered on the leakage hole, stabilizing within 300 s. The gas primarily diffuses along the horizontal direction within the box culvert, and the peaks of gas concentration at the surface are situated at a distance of 2.35 m on either side of the pipeline. Variations in pressure and leakage diameter influence the gas concentration but do not alter the locations of the concentration peaks observed at the surface. The greater the viscous and inertial resistance of the soil, the shorter the overall diffusion distance becomes. However, backfilling the loam within the box culvert significantly elevates the concentration of gas that leaks to the surface. The leakage rate, FHT, FHD, and LHD can be well calculated by the prediction models proposed in this study.

Coupling effect of multiple factors on the crater size of physical explosion in high-pressure natural pipelines

he physical explosion of high-pressure natural gas pipelines causes craters and shock waves, which pose a serious threat to the people and buildings in the surrounding area. This study utilized HyperMesh and LS-DYNA software to establish a physical explosion model for high-pressure natural gas pipelines. The physical explosion processes for pipe diameters of 813, 1016, 1219, and 1422 mm under six burial depths and three soil conditions were calculated. Based on the simulation results, the equations for the variation in crater size were fitted, and the curves of the relationships between crater size and influencing factors were fitted to analyze the coupling effect of multiple factors on the crater size variation. The results showed that the crater size was positively correlated with the pipe diameter. As the diameter of the pipe increased, the length, width, and depth of the crater increased by 64.2, 53.8, and 32.1 %, respectively. The larger the burial depth was, the smaller the crater length and width were. However, the crater depth first increased and then decreased as the burial depth increased. The crater depth was the highest at a burial depth of 3 m. These findings can provide a reference for the design and safety evaluation of high-pressure natural-gas pipelines in high-consequence areas.

Leakage and diffusion of high-pressure gas pipeline in soil and atmosphere: experimental and numerical study

ABSTRACT Personal safety and environmental issues, such as fires and explosions, have climbed to the top of the list of concerns due to the rupture of a high-pressure gas pipeline. Analysis of the diffusion characteristics of methane leaks in soil and air is essential for engineering maintenance and the prevention of secondary mishaps. The primary contribution of this paper is the design and establishment of a full-scale experimental system to simulate small-hole leakage of high-pressure gas pipeline in order to observe the leakage and diffusion behavior of methane in soil and atmosphere under various leakage pore sizes and pressures. The results show that, near the leakage hole, the high-pressure jet dominates the action, whereas near the surface, lateral diffusion and accumulation dominate for an extended period of time. When the diffusion reaches a stable state, the vertical and horizontal diffusion distances are 0.76 m and 1.05 m, respectively, and the maximum temperature difference at the leakage hole is 8.7°C; Under the conditions of leakage holes of 0.5 mm, 1.0 mm, and 1.5 mm, the surface leakage radii are 0.4 m, 0.8 m, and 1.4 m, respectively. The leakage aperture is the main factor affecting the diffusion of methane in soil; A small hole leakage rate model for high-pressure gas pipelines was established based on experimental data, with an average error of 9%; The response time and steady time in the process of methane concentration growth have an exponential relationship with horizontal distance from the leakage hole and a power function relationship with vertical distance and leakage rate. The average relative errors of the calculation formula are 16% and 12%, respectively. This work can provide a basis for the hazard assessment of small hole leakage and diffusion in buried gas pipelines, and also provide data support for the theoretical and numerical models of high-pressure gas flow in soil and atmosphere.

Do soft soil layers reduce the seismic kinematic distress of onshore high-pressure gas pipelines?

AbstractOnshore high - pressure gas pipelines constitute critical infrastructure that usually cross seismic - prone regions and are vulnerable to Permanent Ground Deformations (PGDs) due to active seismic faults. In design, it may not be feasible to avoid fault rupture areas due to various technical, economical and topographic reasons. Moreover, the presence of soil layers affects the PGDs resulting from a tectonic fault, which in turn may alter the seismic demand on the pipeline. The current study investigates numerically the impact of soft soil layers on the seismic kinematic distress of onshore gas pipelines. For this purpose, a decoupled numerical modeling approach is adopted, consisting of two separate finite - element models for the simulation of soil response and pipeline distress, respectively. Soil non - linearities are taken into account utilizing the Mohr - Coulomb constitutive model with isotropic strain softening. An extensive parametric analysis is performed considering different faulting mechanisms and fault dip angles, as well as soil geometry and mechanical properties. Consequently, the maximum absolute values of both tensile and compressive pipeline strains are correlated with the seismic intensity level (i.e., in terms of bedrock offset which is associated with earthquake magnitude via simple relationships). The paper concludes with a set of design charts and tables for the preliminary seismic design of onshore high - pressure gas pipelines. These charts and tables predict with reasonable accuracy pipeline deformations, in terms of strains, for different magnitude, fault type, dip angle, sand type, and varying overlying soil layer thickness.

Preliminary evaluation of hydrogen blending into high-pressure natural gas pipelines through hydraulic analysis

Preliminary evaluation of hydrogen blending into high-pressure natural gas pipelines through hydraulic analysis

Study of the Thermal Radiation Hazard from a Combustible Gas Fireball Resulting from a High-Pressure Gas Pipeline Accident

With the rapid development of high-pressure combustible gas pipelines, it brings convenience and also buries potential safety hazards. This paper presents an in-depth exploration of the thermal radiation hazards of fireball accidents caused by leakage and provides a reference for the prevention and control of this type of accident and on-site rescue. Based on the basic principle of fluid mechanics and the calculation model of the leakage rate, a three-dimensional pipeline model was constructed by FDS software to simulate the fireballs with different positions of low, middle and high. The simulation shows that the ground temperature field of the low and middle fireballs is quite different from that of the high fireball, and the temperature level is: low position > middle position > high position. On this basis, the observation elevation angle is introduced to improve the classical fireball thermal radiation model formula, the model calculation value is compared with the numerical simulation value and the optimal threshold is determined by combining the thermal radiation flux criterion. The results show that the numerical simulation is basically consistent with the calculation results of the improved model. The smaller the observation elevation angle, the closer the target receives the thermal radiation flux to the optimal threshold and the calculated hazard range is more reliable.

Study on the leakage dispersion law of exposed high-pressure natural gas pipelines in the mountainous environment

The pipelines in mountainous areas have complex terrain conditions and pass through many densely populated areas. Once a pipeline leakage accident occurs, it will cause serious damage to the surrounding people and the environment. In this article, a leakage diffusion model of a bare natural gas pipeline is established for the exposed leakage scenario, and a simulation scheme is established according to the characteristics of pipeline-laying processes and environmental characteristics in mountainous areas. Research has been carried out on the diffusion pattern and the influence range of exposed gas transmission pipeline leaks under four types of factors: different leak apertures, ambient wind speed, mountainous obstacle conditions, and mountainous laying environment. The dangerous range formed by the gas diffusing along the ground and high altitude under different scenarios and the influence law of different influencing factors on the dangerous range are obtained, and suggestions for emergency rescue focus areas and emergency response strategies have been given. The research conclusions can provide a theoretical basis for emergency response strategies for exposed leakage accidents of high-pressure natural gas pipelines in mountainous environments and are of great significance to the quantitative analysis of the risk consequences of natural gas pipelines.

Gas production in the Czech Republic yesterday, today and tomorrow

The Czech Republic is one of the most advanced countries in the world in the field of gas industry. The production of gas from coal started here as early as 1847 and has been developing intensively since then. Initially, the gas was used to light the streets, which is why it was referred to as town gas. Soon its use also spread to other areas, e.g. for heating water and housing heating, but also for washing clothes and almonds and a number of other activities. A significant change occurred in the middle of the 20th century, when the process of coal gasification was developed, which began to replace the less effective methods of gas production with carbonization. The first pressurized gas plant in Bohemia was put into operation during the 2nd world war in Záluží near Litvínov and supplied gas not only to local chemical plants, but also to large cities in its vicinity via a high-pressure gas pipeline. Other pressurized gas plants were located in the 1950s in Úžín and in the early 1970s in Vřesová. The production of town gas in the Czech Republic at that time reached a volume of almost 4 billion m3/a. The construction of the transit gas system from the Soviet Union to mainland Central and Western Europe and its commissioning in the first half of the 1970s meant a gradual decline in the production of town gas and its replacement by natural gas. Therefore, the pressurized gas plants were gradually taken out of operation. The last gas plant in Vřesová ceased operation in the summer of 2020. However, gas production technologies are still being developed in the Czech Republic. Several devices for gasification of bio-mass and devices intended for gasification of various al-ternative fuels have been implemented. The interruption of natural gas supplies from Russia in the summer of 2022 has again revived interest in these technologies, especially in industrial enterprises with high gas consumption in technological processes.

Optimal Route Selection of Offshore Pipelines Subjected to Submarine Landslides

Background: Offshore lifelines (i.e., pipelines and cables) are usually vulnerable to seabed deformations induced by earthquake-triggered geohazards, such as submarine landslides, soil liquefaction, and tectonic faulting. Since the complete avoidance of all areas characterized by offshore geohazards is not always techno-economically feasible, optimal lifeline route selection is deemed necessary for the safety and serviceability of every such infrastructure, in order to minimize the risk of severe environmental and economic consequences. Objective: The current study presents a decision-support tool for the design of offshore high-pressure gas pipelines, capable of performing: (a) the assessment of submarine landslides along a possible pipeline route (i.e., impact force and landslide width), (b) the assessment of their potential impact on the pipeline (i.e., pipeline strains), and (c) the optimal pipeline route selection. Methods: The advanced capabilities of GIS in lifeline optimal route selection are successfully combined with efficient (semi-)analytical models that realistically assess the response of offshore pipelines when subjected to axial or oblique loading conditions due to a submarine landslide. Results: The efficiency of the smart tool is presented through a case study of an offshore pipeline that is crossing potentially unstable slopes -under static and seismic conditions- in the Adriatic Sea. Five alternative routings are proposed based on the adopted design criteria when crossing the seismically unstable slopes and zones characterized by steep inclination. Conclusion: Provided that sufficient and reliable data are available, the developed decision-support tool can be efficiently used for deriving the potentially optimal route of an offshore pipeline.