Buried Gas Pipeline Research Articles

A Buried Gas Pipeline Leakage Model

A Buried Gas Pipeline Leakage Model

Multi-physics coupled simulation and experimental investigation of alternating stray current corrosion of buried gas pipeline adjacent to rail transit system

As the gradual emergence of alternating current (AC) electrified rail transit system in urban areas, buried gas pipeline adjacent to the system will be seriously corroded by induced alternating stray current. These buried gas pipelines are at serious risk of electrochemical corrosion, which leads to safety and environmental threaten. In order to study the distribution of alternating stray current corrosion on pipeline surface on a larger spatial scale, this paper conducted numerical simulation and experimental validation of alternating stray current corrosion of buried gas pipeline. In the numerical simulation model, coupling between different physical fields are realized through the relationship between current density of pipe-to-soil interface, electrolyte, and electrodes. Proposed numerical method based on coupled multi-physics in this paper are in good agreement with experimental results under different influencing factors. A novel evaluation index was proposed to assess the corrosion risk within different zones on the pipeline surface. Results show that corrosion distribution is greatly influenced by spatial interaction between buried pipeline and rail transit system including crossing angle and parallel distance. Besides, alternating stray current corrosion on buried gas pipeline are proved to be both affected by dynamic characteristics due to AC fluctuation and operation mode of locomotive.

Experimental study on the leakage identification for the buried gas pipeline via vibration signals

It is difficult to detect and locate small leakages, especially for buried pipelines. Fortunately, a non-intrusive leakage identification method for buried gas pipelines is proposed in this study. Accelerometers were arranged in the soil at a certain distance from the leakage orifice to capture the acceleration signals caused by leakage. A 7-layer wavelet transform was applied to extract the leakage characteristic frequency band. Meanwhile, the attenuation characteristics of vibration signals were analyzed and the signal amplitude attenuation patterns in the axial, radial, and circumferential directions were analyzed. The results show that the leakage recognition rate is nearly 100% by selecting a P-SNR threshold of 7.26. Thus, the non-intrusive method based on accelerometers can be successfully applied for the leakage monitoring of buried gas pipelines.

Efficient finite element reliability analysis employing sequentially-updated surrogate model for fragility curve derivation

As the threat of natural disasters to structures intensifies, risk assessment of infrastructure has gained much importance. Fragility curves are essential tools in predicting disaster-related losses and making disaster mitigation decisions. In this paper, we propose a new method to efficiently derive accurate fragility curves for structures with high levels of nonlinearity or complexity, addressing the computational challenges of conventional finite element reliability analysis (FERA). To reduce the computational cost for calculating probability of failure in FERA, the proposed method utilizes the first-order reliability method (FORM). However, even with this approach, the computational cost of deriving the fragility curve may remain high; therefore, a surrogate model is used to further reduce costs. By training the surrogate model using the initial structural damage probabilities for a few hazard intensities, an optimal starting point can be calculated for the subsequent FORM analysis. During the fragility analysis, the surrogate model can be updated sequentially to increase the efficiency of FORM analysis continuously. In particular, the training process of the surrogate model requires no separate or additional finite element analysis because it is constructed using previous FERA results. The accuracy and efficiency of the proposed method are tested using conventional FERA and Monte Carlo simulations through a hypothetical short-column example. In addition, fragility curves are derived through a bridge flood fragility assessment considering the scour and seismic vulnerability assessment of a buried gas pipeline considering soil-structure interactions. The derived fragility curves closely match those derived using the conventional FERA, and the computational costs are reduced by 36.54 % and 52.38 %, respectively, compared with the conventional FERA, confirming its cost-effectiveness.

Proposing new correlations to improve the accuracy of hydrostatic tests for buried steel pipelines

This study proposes an efficient and effective method to estimate the water temperature inside buried gas pipelines during hydrostatic tests. The goal is to develop appropriate correlations that can easily calculate the pipeline’s water temperature, taking into account the adjacent soil temperature variations, pipeline size, thickness, and coating properties. The study first presents a mathematical model of the problem, introducing relevant non-dimensional parameters. Then, the unsteady problem is numerically analyzed, considering all significant variables, and next, the effects of each non-dimensional parameter on the water temperature are carefully examined and evaluated. The numerical simulations show that the difference between the pipeline water temperature and the adjacent soil temperature can be up to 80%, particularly for large-diameter pipelines. The proposed correlations are able to estimate the pipeline water temperature during the hydrostatic test with around 1% deviation from the direct numerical solutions. Additionally, the results indicate that for typical test cases, the pipeline size is the main influential parameter, while the pipeline thickness and material coating with conventional properties do not significantly affect the water temperature variations.

Gas Free Dissipation Characteristics Analysis and Safety Repair Time Determination of Buried Pipeline Leakage Based on CFD

Buried pipelines, as the most common method of natural gas transportation, are prone to pipeline leakage accidents and are difficult to detect due to their harsh and concealed environment. This paper focused on the problem regarding the free dissipation of residual gas in buried gas pipelines and soil after closing the gas supply end valve after a period of leakage by numerical simulation. A multiple non-linear regression model was established based on the least squares method and multiple regression theory, and MATLAB 2016b mathematical calculation software was used to solve the problem. The research results indicated that compared to the gas leakage diffusion stage, the pressure and velocity distribution during the free dissipation stage were significantly reduced. The increase in leakage time, pipeline pressure, leakage size, and pipeline burial depth led to a large accumulation of natural gas, which increased the concentration and distribution range of gas on the same free dissipation stage monitoring line. A prediction model for natural gas concentration in the free dissipation stage was established with an average error of 7.88%. A calculation model for the safety repair time of buried gas pipeline leakage accidents was further derived to determine the safety repair time of leakage accidents.

Active Acoustic Excitation Method for Leak Detection of Buried Gas Pipelines Based on Cavity Resonance Reflection

Active Acoustic Excitation Method for Leak Detection of Buried Gas Pipelines Based on Cavity Resonance Reflection

Research on the vibration response characteristics of PE gas pipeline aimed for third-party damage monitoring

Third-party damage (TPD) incidents account for over 73% in China, becoming the primary cause of urban buried gas pipeline disruption. Therefore, real-time monitoring of TPD holds significance. This passage introduces a novel method for third-party damage monitoring of urban gas pipeline networks without excavation. The approach involves installing acoustic sensors in the pipeline to detect abnormal signals caused by construction activities. While the effectiveness of this method has been confirmed for buried steel pipelines, the propagation patterns, frequency characteristics, and the impact of fluid flow within PE pipelines remain unclear. To this end, this study explores these issues through experiments and simulations. According to the research, sound waves are the primary mode of signal propagation. The impact of gas pressure can be disregarded, but if the flow is reversed, the signal will weaken by 26%. The signal energy is concentrated in the 0–2 kHz range, decreasing exponentially as the distance increases. Moreover, a positive linear correlation exists between the signal energy and the load size to the power of 0.1. This research provides theoretical support for studying third-party damage monitoring technology and identifying and localizing damage types.

Method for identifying the main factors controlling landslides based on a particle coupling algorithm simulating the ultimate state of a gas pipeline

To determine the ultimate load of buried gas pipelines under different working conditions under landslide action and provide a quick decision-making tool for landslide risk management, a pipe–soil coupling model is established based on smoothed particle hydrodynamics and the finite element method. The double elastic slope criterion and fault tree analysis method are used to perform limit and failure analyses on the pipelines. The research results indicate that pipeline stress and strain during oblique crossing are positively correlated with the crossing angle. The upper section of the pipeline exhibits tensile bending, whereas the lower section exhibits compressive bending. Local stress is concentrated at the elbows at both ends of the pipeline during longitudinal crossing, which is similar to the force applied during oblique crossing. The ultimate pipeline bearing capacity is negatively correlated with its burial depth and pressure. There is a positive correlation between the distance from the pipeline to the rear edge of the landslide and the width of the landslide. There is also an optimal value for the moisture content of landslides. Fault tree analysis reveals that, to prevent pipeline failure under the action of landslides, priority should be given to determining a reasonable pipeline laying method, reducing the moisture content of the sliding body, controlling the thickness and width of the landslide body, controlling the displacement and inclination angle of the sliding body, timely eliminating soil and soil pressure, and avoiding the failure of drainage systems and support facilities. Based on the research results, we propose a method that can preliminarily identify the main control factors affecting pipeline integrity. This method provides a reference for studying and developing engineering mitigation measures, identification procedures, and operation guidance documents for geological disaster risks for pipelines crossing landslide sections.

Analysis of external corrosion protection performance on buried gas pipeline using CIPS and DCVG methods

The present work investigates the effectiveness of external corrosion protection using Close Interval Potential Survey (CIPS) and Direct Current Voltage Gradient (DCVG) on a buried gas pipeline. These surveys were performed on 12” gas pipeline in East Kalimantan. Coating and cathodic protection were the primary corrosion protection on these pipelines. Soil resistivity measurement was conducted every km along the pipeline to obtain the resistivity profile combined with the pH profile. CIPS showed that the Cathodic Protection system protects 79.21 % of the pipeline area. There is no sign of telluric or stray current effect from the result of CIPS. DCVG showed 159 defects that can be divided into three different clusters. There is 6-point coating defects that should be repaired immediately due to the characteristics and category of the defect. The integrated data analysis of CIPS and DCVG showed a correlation which dips pattern on CIPS graph indicating coating defect on DCVG surveyed. Soil resistivity measurement showed that the soil resistivity profile is negligible from KP 0 – 5, while KP 5 – 14 is mildly corrosive. pH measurement showed the acidity level or the soil along the pipeline were neutral. Cathodic protection level could be improved with the increase of cathodic protection current and coating repair along the area with low-level protection.

Research on fluctuation characteristics of AC interference parameters and corrosion behavior of buried gas pipelines

With the large-scale construction of high-speed railways in China, pipelines are subject to increasingly severe alternating current (AC) interference. It's been found through detection that the AC interference parameters of pipelines near high-speed railways fluctuate greatly. Based on the field test data, this paper statistically analyses the fluctuation law of parameters on the pipeline. On this basis, an indoor simulation experiment was configured to explore the effect of AC current density and cathodic protection potential on dynamic AC corrosion. The results showed that for the same level of cathodic protection, a higher AC current density indicates a higher dynamic AC corrosion rate. When the AC current density increases to 100 A/m2 or higher, the corrosion rate tends to decrease first and then increase with the negative shift of cathodic protection potential. The corrosion risk assessment diagram under dynamic AC interference was drawn through the experiment of field buried coupon experiment and the laboratory simulation experiment. In addition, the mechanism of AC corrosion is discussed to provide a reference for assessing the corrosion risk under dynamic AC interference.

Enhancing the integrity of a buried gas pipelines: Investigating ruptures, explosions, and strengthening solutions

The present paper presents findings from a case study of a buried gas pipeline that ruptured, causing a gas cloud explosion and subsequent fire. The study aimed to identify the incident's cause and improve the pipeline's strength under specific conditions. The study measured the pipe's actual wall thickness and conducted stress analysis using analytical and finite element methods to assess its integrity under corrosion. It evaluated if the 20-inch pipeline near road crossings could withstand external forces.In conclusion, the research underscores the importance of accurately assessing the structural integrity of buried pipelines, especially under conditions of corrosion. It highlights the utility of finite element analysis in providing a more precise understanding of stress distribution and can aid in designing pipelines that are better equipped to withstand various external pressures.The investigation illustrates the importance of increasing the strength of buried natural gas pipelines, in the crossing road area and, for this purpose, it was proposed (in terms of novelty associated with the study) a solution consisting in introduction of the pipeline in protective sleeves fitted with spacer rings.

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.

Mechanical Properties of Buried Gas Pipeline under Traffic Loads

Dynamic loads generated by heavy vehicles are among the loads resisted by pipelines buried under road surfaces. Most recent analyses are based on static assumptions; however, in practice, vehicle loads change dynamically. In this study, the finite element model of the pipe–soil interaction of a buried pipeline was established using the ABAQUS 2020 finite element software, and dynamic loads were applied above the model soil to simulate the influence of vehicles above the highway on the buried X80 pipeline. The mechanical responses of different influencing factors to buried pipelines were analyzed. Increasing the pipe diameter and burial depth decreases the effect of vehicle rolling on the buried pipeline. The mass of the vehicle is the most significant factor that influences the stress and strain on the pipeline. The stress increase of the conventional vehicle load on the X80 gas pipeline does not exceed 10 MPa, and the maximum shape variable of the pipeline is within 13 mm. This study provides a data reference and a risk warning regarding the rolling of buried natural gas pipelines under a single vehicle load.

Dynamic predictive analysis of the consequences of gas pipeline failures using a Bayesian network

Modern natural gas pipeline failures constitute devastating disasters, as they can result in cascading secondary crises. Therefore, reduction of buried gas pipeline's reliability, has become a major concern among stakeholders and researchers in recent years. This study employs a dynamic Bayesian network to investigate the consequences of natural gas pipeline failures. We consider seven parent nodes—age, diameter, length, depth, population, time of occurrence, and land use—and twelve consequence factors to analyze the overall losses stemming from pipeline failure. The proposed model can handle both static and dynamic systems using quantitative and/or qualitative data. To demonstrate the applicability and effectiveness of our developed model, we analyze the gas pipeline network of Regina in Saskatchewan, Canada. The results show that age and diameter are the two most important and sensitive parameters. The developed Bayesian network model will aid decision-makers in effectively managing and improving the reliability of their assets.

Seismic evaluation of buried gas pipelines based on the fault slip tendency in South Korea

As numerous earthquakes occur worldwide, securing the seismic performance of infrastructure is important because the damage to buried gas pipelines during an earthquake can cause significant secondary damage. Buried gas pipelines are subject to damage owing to permanent ground movements, one of which is faulting. In this study, the expected displacement of faults caused by earthquakes is predicted by introducing the concept of slip tendency. Using approximately 14,000 fault segments obtained from fault surveys, we calculated the slip tendency based on the Korean Stereonet by region. Thus, the maximum displacement by region that could be triggered by fault reactivation was calculated. A finite-element model of a pipeline passing through a fault zone was developed by varying the actual pipeline used in Korea and various types of geotechnical information. Using this model, a structural analysis of the pipe during fault displacement was performed, and structural integrity evaluation results were derived. The strain value increased as the angle between the pipe and the fault plane increased and as the dense ground and compression-dominated movement increased, confirming this with an application example. Finally, a process capable of evaluating all regions of Korea was established using the displacement values of the predicted fault occurrence by region based on the slip tendency.

Simulation-based dynamic risk analysis of urban buried gas pipeline network

With the increasing scale and complex structure of urban buried gas pipeline network, traditional analysis techniques have become difficult to meet the risk cognitive needs of the system. The advantages of simulation technology in analyzing risks of such complex system thus become prominent. This study proposes a new simulation-based method to analyze the risk of urban buried gas pipeline network. First, the network structure and key factors of the risk system are determined according to the author's previous research. The dynamic mechanics of risk transfer in the risk system is characterized based on the Complex Dynamic Network Theory. Second, the simulation model is developed based on Arena software, which can quantitatively evaluate the effect of different risk control strategies. Third, a series of simulation experiments under four scenarios are conducted. The results show that when there is an additional risk disposal resource, the most efficient strategy for risk control is allocating it by importance of key risk factors. The correctness of the selection of key factors has thus been verified. Finally, this paper illustrates the applicability of the risk simulation model by taking an actual gas pipeline network as an example. The results show that only focusing on superficial direct risk factors cannot control risk to an acceptable level. Some suggestions to improve the risk control efficiency for the engineering example are also derived from the simulation results.

Evaluation of the reliability of buried gas pipelines exposed to ground movement in the perspective of their use for hydrogen transportation: A state-of-art review

Hydrogen (H2) has been recognized as having the potential to become the cornerstone of a low-carbon energy system. As a result, it has garnered much interest from policymakers and industry as a focus for future infrastructure.
 In its race towards climate neutrality by 2050, the European Union seems to be betting on green hydrogen as a high-potential energy source. Europe envisages to develop more than 11,000 km of pipelines transporting hydrogen in 2030 [2]. The French government seems to prioritize the reuse of gas networks for the transport and storage of H2 [4]. On the other hand, the substitution of gas by hydrogen leads to an evolution of the mechanical characteristics of steel pipelines, and consequently, increases their vulnerability vis-à-vis external stresses (loads, ground movements, natural hazards, etc.). It has been shown that pipeline steel could lose up to 40% of its ductility after exposure to 100 bar H2 [3]. Thus, the reuse of the existing gas networks for the hydrogen transport raises today a set of scientific and technical questions. The problematic of pipelines vulnerability is getting even more serious by both the climate change and the evolution of human activities associated with the ecological transition.
 In the framework of a thesis that we recently started (October 2022), we aim to understand the interaction between buried networks (gas networks reused for hydrogen transport) and ground movements, with a purpose to enhance risk prevention and to reduce the associated consequences. The aim is to establish a reliable analytical model enabling sensitivity studies to be performed and the influence of the uncertainties on the results to be assessed. The outcomes will be also valued by developing fragility curves that constitute operational approaches when assessing damages in an uncertain context.
 The aim of this study is to synthesize the existing research work available in the literature addressing the behaviour of buried pipelines subjected to various ground motion phenomena. This review covers the various modelling approaches and simulation techniques for the soil-pipe system found in the literature. The main limitations of the existing methods are also stated.These studies encompass a diversity of ground motion sources including, but not limited to: Fault movements (strike-slip, normal-slip), soil settlements due to tunnelling, differential ground settlements related to groundwater lowering, and soil liquefaction. The main research methodologies employed are analytical analysis, numerical simulation and experimental testing.
 One way to study the behaviour of the buried pipelines is the analytical modelling based on theoretical analysis [6, 7, 8]. For this approach, reasonable assumptions and simplification are necessary when simulating the pipe-soil system but also the ground movement. Soil-pipe interaction models found in previous study are mainly based on Winkler model, Pasternak model and others. The pipeline material behaviour was considered to have either elastic, bilinear or tri-linear stress-strain response. The adopted simplifying assumptions in the abovementioned studies can be prominent in certain cases of practical interest.
 Analytical models based upon empirical curve fits have also been employed in some studies. The fitted functions can be derived from a numerical parametric analysis, by performing regression analyses on data obtained from a large number of configurations covering different values of the input parameters, such as pipe diameter, burial depth, soil subgrade modulus, pipe elasticity, and maximum displacement of the soil [11]. The derived empirical expressions can be used to directly estimate pipe response induced by a soil settlement.
 Another major way to investigate this topic is the numerical simulation. Numerous studies were carried out using numerical finite element models [10, 12]. The results of these computational methods are becoming increasingly accurate as currently available numerical analysis techniques allow this problem to be solved in a rigorous manner, minimizing the number of required approximations. However, the non-linear behaviour of the pipeline steel, the soil-pipeline interaction and the second-order effects induced by large displacements make these analyses quite challenging.
 Apart from the above analytical and numerical methodologies, there have been a growing number of papers involving the experimental simulation of buried pipes under ground motion. These investigations were based on centrifuge tests [1, 5] and other designed testing apparatus [9].
 However, despite the advancement of modelling techniques, there are still some limitations when examining the behaviour of buried pipelines subjected to ground settlement such as the need for accurate soil and pipe parameters and the lack of consideration of external loads.

Dynamic risk assessment model for third-party damage to buried gas pipelines in urban location class upgrading areas

Buried gas pipeline leakage accidents caused by third-party interference in urban location class upgrading areas are time-varying and can cause serious consequences. This study proposed an integrated dynamic risk assessment model to address this issue. First, a bow-tie model combining a fault tree (FT) with an event tree (ET) was used to construct an overall evolutionary process from basic events to accidents and thus mapped into a Bayesian network (BN). The prior probabilities of basic events in FT and safety barriers in ET were determined by four types of methods, and the critical basic events were identified by sensitivity analysis. By integrating the Hierarchical Bayesian analysis method with time-varying precursor data, the dynamic probability updating of critical basic events and safety barriers was achieved, enabling adaptation of accident probabilities using BN. Then, a dynamic calculation method for accident consequences was proposed by integrating the appropriate leakage rates with a new time-varying method for calculating fatalities. Finally, a new risk matrix method was proposed to dynamically evaluate the risk level by integrating the accident probabilities with the consequences. A case study showed that the proposed model could dynamically evaluate the integrated accident risk, providing explicitly quantified support for risk management and emergency rescue of buried gas pipeline networks in urban location class upgrading areas.

Vibration Characteristics and Location of Buried Gas Pipeline under the Action of Pulse Excitation

In this paper, the attenuation of sound waves in underground gas pipelines and the vibration characteristics of pipelines are studied, and the feasibility and effectiveness of acoustic measurement of PE pipelines are verified. In this paper, the attenuation equation of sound waves in an underground gas transmission pipeline is derived based on the propagation characteristics of gas and the vibration characteristics of the pipeline itself. In order to verify the experimental results, we conducted an experimental test on the air pipeline model and verified the feasibility and effectiveness of the acoustic measurement of the PE pipeline through the test under the action of pulse excitation. Then, we detect the background noise, design the test scheme according to the characteristics of the buried pipeline, and select the test site for field test. In the test process, we collected the test data and obtained the spectrum diagram of the test data by fast Fourier transform (FFT). By analyzing the results of the spectrogram, we find that the pulse signal can penetrate the medium composed of the pipe formation, but the amplitude of the sound will be sharply attenuated. At the same time, according to the size of the peak in the spectrum, we can determine the location of the pipe. In summary, the feasibility and effectiveness of acoustic measurement of the PE pipeline are verified through experimental tests, and attenuation equations based on acoustic wave propagation characteristics and pipeline vibration characteristics are proposed. It has important practical application value for the safety monitoring and positioning of the buried gas pipeline.