Underground Gas Pipelines Research Articles

A Study of the Stress State of Underground Gas Pipelines in Mine Working Zones Using the Method of Internal Response Function

The stress state of pipelines in mine working zones, where the main loading factor is longitudinal soil displacements caused by the gradual filling of mine voids, has been calculated. Differential equations of pipe deformation have been formulated, for the solution of which the method of internal response function is proposed, which takes into account the mutual displacement of the pipe and soil in each iteration using a classical three-part nonlinear model of pipe–soil interaction. The type of interaction is determined on the basis of the concept of the basic displacement of the pipe, which is refined using displacements calculated in the previous iteration. The procedure of refining the basic solution is an important component of the method, where the basic solution in the next iteration is found as the sum of the previous solution and the difference between the calculated and previous solutions, multiplied by the convergence-control factor of the iterative procedure. To check the convergence accuracy and rate of the proposed iterative procedure, a comparative analysis with other existing procedures and results, obtained with the aid of commercial finite element programs, has been performed. To diagnose the stress state of pipelines during the working of longwall faces, a system for their continuous monitoring has been created. The correctness of the results of the performed numerical modeling of the stress state of a gas pipeline and the effectiveness of the measures that are developed to reduce the high stress level in its individual zones have been confirmed by relevant monitoring data, which are important both for refining the physical characteristics of pipe–soil interaction and for further taking into account the relaxation of these relations in time.

UNDERGROUND PIPELINE CORROSION MONITORING SYSTEM

One of the pressing issues of underground gas and oil pipelines protection against corrosion is the reliability of the cathodic protection efficiency assessment. This work is devoted to the problem of insulation coating transient resistance control and the effectiveness of underground structure protection by its potential. The assessment of the decrease in the protected structure potential due to the inclusion of potential sensors that are part of the stationary copper-sulfate comparison electrodes in the cathodic protection scheme in the absence of measurements is performed. Recommendations on documentary standard correction are presented. It is necessary to reconsider the approach to measuring potentials, abandon the excessive use of sensors due to their inefficiency, optimize the placement of diagnostic points using remote monitoring methods based on the introduction of world experience in applying the electrochemical impedance spectroscopy method and technical and economic feasibility.

Обнаружение утечек в подземных нефте- и газопроводах

Обнаружение утечек в подземных нефте- и газопроводах

Evaluation of the reliability of the underground oil and gas pipeline on stability criterion

Evaluation of the reliability of the underground oil and gas pipeline on stability criterion

Determination Scheme for Accurate Defect Depth in Underground Pipeline Inspection by Using Magnetic Flux Leakage Sensors

The magnetic flux leakage-type nondestructive testing has been applied for the highly efficient inspection of defects in ferromagnetic materials such as underground gas pipelines. In the system, the magnetic field is applied to magnetize a steel pipe so as to induce the leakage signal in the vicinity of defects on the pipe. From the measured sensor signals, decomposing or estimating sizes and shapes of defects are necessary. For the maintenance, the depth estimation is the most important procedure for the management of a safety accident. However, the previous depth estimation contains high error rate inevitably because the depth signal implies the width and length error simultaneously. This paper focused on the enhanced algorithm for the depth sizing in various defects by using the decoupling algorithm to enhance the accuracy of defect depth. Estimated results show good agreements with measured ones.

Research of main gas pipeline (steels X65, X60, 17G1S) susceptibility to stress corrosion cracking, hydrogen uptake and ST 37-2 steel fatigue testing

According to the data from the slow strain rate stress corrosion cracking test, two histograms were constructed that shows an increase in the susceptibility of metals to stress corrosion and hydrogen charging due to the rise in temperature (+ 25°C to +50°C). Consequently, susceptibility to stress corrosion increased from 0.85 to 0.87 for steel X65 and rose to 0.9 for steel X60, respectively. The same trend was observed for hydrogen charging (from + 25°C to + 50°C, the hydrogen charging increased from 1 to 2 (mol · H)/(n) for steel X65 and from 1.2 to 3.5 (mol · H)/(n) – for steel X60). In the second study, for the low-cycle fatigue under varying strain conditions, V-shaped shear specimens of ST 37-2 steel were used. It shows that grain-boundary steel has a crack width of 1.3 µm, whereas steel with an initial and cellular structure - 0.34 and 0.42 µm. Comparing the data obtained from Severgazprom, a histogram of the dependence of corrosion-stressed defects in the pipeline segments in front of the compressor station was constructed. The sections of the 115 km of the underground gas pipeline infrastructure were surveyed. In case of steel grade 17G1S, the diameter of the pipes ranged from 1020 mm to 1420 mm. Graphs were constructed for the dependence of the density of corrosive destruction in winter or summer seasons. The range of temperatures during operation of main gas pipelines was from 60°C to 25°C in summer and from 30°C to −30°C -in winter.

Robust Network Hardening Strategy for Enhancing Resilience of Integrated Electricity and Natural Gas Distribution Systems Against Natural Disasters

Recent revolution of the electricity distribution sector, especially a deeper penetration of gas-fired distributed generations (DGs), intensifies the interdependence of electricity on natural gas distribution systems. Such integrated electricity and natural gas distribution systems (IENDS) are facing with significant threats from frequent natural disasters that cause enormous economic losses. Network hardening is regarded as an effective technique for enhancing resilience of IENDSs against natural disasters. This paper presents a trilevel robust optimization-based network hardening model for minimizing worst-case total weighted electricity and gas load shedding of IENDSs with respect to hardening budget limits and random damages caused by disasters of different severity levels. Specifically, distinct failure probabilities of overhead power lines and underground gas pipelines are considered, while DGs and gas storages are modeled as effective emergency response resources for supplying high-priority electricity/gas loads during disasters. The proposed model is solved by a column-and-constraint generation approach, in which nonlinear gas network constraints are linearized via Taylor series expansion. Numerical case studies evaluate the proposed robust hardening strategy against natural disasters.

Efficiency and Cost Analysis of Power Sources in Impressed Current Cathodic Protection System for Corrosion Prevention in Buried Pipelines of Balochistan, Pakistan

Corrosion is the physical deterioration of metals, including buried metal structures and gas pipelines, resulting from chemical reactions between metals and the surrounding environment. Cathodic protection of these underground metal structures & pipelines can be achieved either by the Impressed Current method or by the sacrificial anodes method. This research paper focuses on the corrosion prevention of buried metal structures in general and gas pipelines in particular, by the novel method of Impressed Current Cathodic Protection (ICCP) which uses electrical current from an external DC power source for its operation. Three major DC power sources i.e. Transformer Rectifier, Thermoelectric Generator and the Solar System are selected for this purpose and are projected over a period of time in a pre-designed ICCP for high transmission underground gas pipeline in Balochistan province of Pakistan. The efficiencies of these three power sources are then analysed and compared according to the climate effects, the versatility effects, the intensity of power output, their operational limitations and their initial, running and maintenance costs. The measured results will aid the selection of efficient and robust DC power source for ICCP design and will contribute to mitigating and controlling the corrosion rate in underground pipelines. Based on analysis of the measured results for the three available DC sources, the Solar System was found as the most efficient DC power source for Impressed Current Cathodic Protection of buried gas pipelines. The selection of efficient corrosion protection system will result in a smooth flow of oil and gas products through these buried pipelines which may otherwise lead to huge monetary and accidental losses when get corroded.

KKR will acquire embattled Taiwanese firm LCY

The private equity firm KKR will pay $1.5 billion to acquire LCY Chemical, a Taiwanese producer of thermoplastic elastomers, specialty polymers, fibers, and industrial chemicals. An underground gas pipeline owned by LCY blew up in 2014 in a residential neighborhood in Kaohsiung, Taiwan, killing 32 and injuring 300. The firm denies responsibility for the accident. In May, a Kaohsiung court sentenced the former chairman of LCY, Bowei Lee, to four years in jail, but he is appealing the sentence. KKR is buying LCY’s shares at a 17% premium to their value on July 20, their last day of trading before the deal was announced. LCY’s shares lost over half their value after the 2014 explosion but gradually recovered to exceed their preblast price. LCY says the stable financing provided by KKR will enable it to implement a long-term expansion strategy. In 2014, before the Kaohsiung tragedy, the U.S. firm Kraton

CFD analysis of natural gas emission from damaged pipelines: Correlation development for leakage estimation

Natural Gas (NG) leak may occur from either an above- or an under-ground pipeline, resulting in environmental and financial consequences. Although there are some relations for estimating the gas leak from an above-ground pipeline, there is no equation for the calculation of a buried pipeline leakage. The main objective of this work is to develop precise gas leak calculator equations for low- and medium-pressure buried pipelines. For this, an under-ground gas pipeline is numerically modeled considering the surrounding soil as a porous medium. Two- and three-dimensional models are used to investigate the gas leak through a hole intentionally made on the pipe. Pure methane, with a steady state, compressible and turbulent flow, is assumed through the pipe. The developed correlations are functions of the pipe diameter, the hole diameter, and the gas flow pressure. Comparison of the results with previous works in the field demonstrates that considering a one-dimensional model for the pipe and neglecting the length of the pipe after the hole causes up to 20% error. The results indicate that a two-dimensional model is not precise enough for estimating the gas leak from an under-ground pipeline (due to the soil resistance in three directions in a real situation). In addition, linear, second order and fourth order relations are observed between the amount of gas leak and the three effective parameters of the pipe entry pressure, the hole diameter, and the ratio of the hole diameter to the pipe diameter, respectively. Analysis of the results indicates that the relative difference between the results of the simulation and the results given by the developed correlations is within the range of ±7% for all cases.

Reliability-based lifecycle management for corroding pipelines

Corrosion-induced damage is a major source of deterioration in infrastructure and industrial systems such as bridges, offshore and onshore structures, and underground oil and gas pipelines. The uncertainty is pervasive in the parameters affecting the evolution of corrosion process. Risk assessment and management of these systems require a suitable dynamic description of the corrosion process that sufficiently accounts for the underlying uncertainty and subsequently propagates it into the lifecycle reliability assessment of these systems. In this paper, we present a novel approach for reliability-based life cycle management of buried pipelines subjected to corrosion damage. We view our main contributions as twofold. First, a probabilistic model for time evolution of corrosion growth is constructed from available data using polynomial chaos formalism. The model is used to systematically propagate the underlying uncertainty into the limit state functions and the lifecycle reliability analysis. Second, we propose a computationally efficient and accurate optimization strategy using polynomial surrogate in order to solve the stochastic optimization associated with the lifecycle management of buried pipelines. The proposed method facilitates the optimization of maintenance scheduling to achieve minimum expected lifecycle cost by allowing implementation of a gradient-based optimization scheme. This is generally a challenging task due to the discontinuous nature of the objective function with respect to design variables. We examine the sensitivity of the optimum maintenance scheduling with respect to the different measures related to failure probability representing different risk strategies. The proposed development provides an uncertainty-aware decision support tool for making more informed decision regarding the lifecycle management of corroding pipelines. This formalism can also be adapted to other deterioration mechanisms that result in damage-induced structural failure over the lifetime.

Bayesian analysis of small probability incidents for corroding energy pipelines

This paper presents a new methodology for estimation of small posterior failure probabilities for underground energy pipelines, based on external corrosion inspection data. The analysis of the data is based on the BUS (Bayesian Updating with Structural reliability methods) that sets an analogy between Bayesian updating and a reliability problem. The structural reliability method adopted herein is Subset Simulation (SuS) and the whole analysis is referred to as BUS-SuS. Corrosion data obtained from multiple in-line inspections (ILI) of an underground natural gas pipeline are used to illustrate and validate the proposed methodology. The growth of the corrosion defects is modelled through an hierarchical Bayesian framework and the ILI associated measurement errors are comprehensively considered. Through this efficient method, it is ensured that the final samples have reached the posterior distribution. It is also more advantageous over other methods typically employed for Bayesian analysis of corroding pipelines, because it allows the estimation of small posterior failure probabilities directly within the same framework. The proposed methodology can be incorporated in a reliability-based pipeline integrity management program to assist engineers in selecting suitable maintenance strategies.

Crater formation by the rupture of underground natural gas pipelines: A probabilistic-based model

Parallel and crossing pipelines are frequently implemented due to land-use restrictions and their ease of operation and maintenance. Given the proximity of these pipelines and the hazardousness of the substances they transport, an eventual Loss of Containment (LOC) in a parallel/crossing corridor can lead to a domino effect that should be considered in Quantitative Risk Analysis (QRA). For underground pipelines, this LOC is accompanied by a formation of a crater, which can uncover adjacent pipelines triggering a domino effect scenario to take place. This paper aims to develop a model to predict feasible crater dimensions (i.e., width and depth) from a LOC in underground natural gas pipelines using operational and structural parameters. For this purpose, a recent review of 57 underground natural gas pipeline accidents were considered in a probability-based approach once data was processed. This approach initially predicts the Width-to-Depth crater ratio (WD) using a multivariate regression. Then feasible crater dimensions were determined using the regression prediction interval and the width-depth joint probability function, which is approximated with a Gaussian copula. This approach proposes a worst, mean and less severe scenarios to support decision-making processes regarding parallel or crossing underground natural gas pipelines with a LOC. Besides the identification of domino effect scenarios, this information can be used to support pipeline segmentation for risk analysis or even to support Right-of-Way (ROW) definition during pipeline installation.

ПЛАНУВАННЯ БАГАТОФАКТОРНОГО ЕКСПЕРИМЕНТУ ПРИ ДОСЛІДЖЕННІ ВПЛИВУ ПАРАМЕТРІВ АНОДНОГО ЗАЗЕМЛЕННЯ НА ОПІР РОЗТІКАННЮ СТРУМУ

In order to ensure and increase the reliability of distribution medium steel underground gas networks, it is necessary to provide for the development of the project of the gas supply system or during the period of their putting into operation of the application of organizational, technological and technological measures to protect steel pipelines against the negative effects of electrochemical ground corrosion. The widespread method of electrochemical protection on extended sections of steel underground gas pipelines is the installation of high-power cathodic protection plants using deep anode earthing systems made of metal-coated concrete. The paper presents the study of the influence of parameters of anode earthing from metal-bearing concrete at the station of cathodic protection of underground steel gas pipelines on its resistance to current deformation. The mathematical planning of the experiment is carried out in relation to the establishment and research of factors influencing the conditions for the protection of pipelines from soil corrosion. The regression equation for the target function is obtained – current propagation resistance, which can be used for technical grounding simulation, as well as during the development of a methodology for engineering calculations of its parameters. The surface of the response of the target function – the resistance of the current spreading and its two-dimensional cross sections in the planes of the influence parameters: the length of the anode ground, the distance from the surface of the earth to its center and the specific electrical resistance of the ground, where the earthing switch will be placed, is constructed. The expediency of using anode earthing from metal-saturated concrete has been established to increase the reliability of electrochemical protection of gas pipelines. The priority of parameters of the anode earthing was determined in relation to the current propagation resistance: the most influential specific electrical resistance of the soil, and the least – the distance from the surface of the earth to the middle of the anode earthing.

WORN-OUT GAS DISTRIBUTION PIPELINES RECONSTRUCTION BY MEANS OF TRENCHLESS TECHNOLOGY AS THE WAY TO INCREASE GAS DISTRIBUTION SYSTEMS SAFETY

Background Today the main part of gas distribution pipelines consists of worn-out steel pipes with the expired effective life that adds to the problem of gas distribution networks safe operation as the condition of these objects industrial safety is substantially defined by physical wear of the gas pipelines, constructions and the equipment which have exhausted the useful operating life. Such prospect threatens a possibility of gas sale, and decrease in reliability and safety of gas distribution objects will increase risks of accidents on them. Therefore the salvation of problem of efficient reconstruction execution remains at the moment a relevant task. Aims and Objectives To consider modern technologies of reconstruction of gas distribution pipelines and to offer a method of safe functioning of the underground gas pipeline. Methods For selection of the safest method of reconstruction there has been carried out the analysis of scientific and technical literature and normative documents on building, repair, reconstruction of gas distribution networks, there have been studied modern technologies of reconstruction promoting gas pipeline safe operation and permitting to carry out repair works the most safe and economical. Results The research work resulted in developing of the decision-making algorithm at the choice of the gas distribution pipeline reconstruction technology and offering the optimum and safest reconstruction method for the considered section of the distributive underground gas pipeline according to the worked out algorithm on the basis of the comprehensive analysis of shortcomings and advantages of various reconstruction technologies for specific conditions. Thus, introduction of modern technologies of gas distribution pipelines reconstruction will lead to long, trouble-free and, the principal point, safe operation of one of the most important links of gas distribution system and will allow to improve safety and efficiency of gas distribution qualitatively, thereby providing high level of industrial safety on objects of the gas complex.

РАЗРАБОТКА МАТЕМАТИЧЕСКОЙ МОДЕЛИ МАССОПЕРЕНОСА КОМПОНЕНТ ВОДНО-СОЛЕВОГО РАСТВОРА В ПУЧИНИСТЫХ ГРУНТАХ НА ОСНОВАНИИ КИНЕТИЧЕСКОЙ ТЕОРИИ ЖИДКОСТЕЙ

The reliability of engineering structures mostly depends on the possibility to resist adverse environmental factors. One of the most dangerous geological processes is frost heaving of soils, which is capable to develop a huge pressure and significant irregular vertical deformations. This processes is especially dangerous for non-rigid structures with a negative average annual temperature (–6...–0,5 ° С ), for example, for underground gas and condensate pipelines. Pipelines has a strong bends in short sections under the influence of frost heaving pressure, that often leads to emergency incidents. To predict the frost heaving it is necessary to solve the problem of mass transfer of water-salt solution from thawed to frozen soil. Using the kinetic theory of fluid, the authors of the article developed a mathematical model of the mass transfer of water and salt in thawed, freezing and frozen soils. The model allow to determine in an explicit form the contribution of different mechanisms of mass transfer: thermal diffusion, concentration diffusion, and filtration. The equations of diffusion transport allow to take into account the unequal mobility of molecules in an adsorbed film. In addition, it was shown that the classical expression for the diffusion flux density is valid only in the particular case of equality of the diffusion coefficients of each com-ponent in accordance with the kinetic theory of the liquid.

A New Sensitive Excitation Technique in Nondestructive Inspection for Underground Pipelines by Using Differential Coils

In general, a magnetic flux leakage (MFL) pipeline inspection gauge (PIG) has been applied to nondestructive testing for investigating ferromagnetic materials, such as underground gas pipelines. Although MFL PIG is efficient to the inter-city large-scale pipelines, it is hard to apply to small-size pipelines that are usually installed in the city, because the permanent magnet for MFL PIG is too big and heavy to operate inside the small pipe. The strong adhesive magnetic force of permanent magnet to the pipe wall also prevents the usage of MFL PIG in small pipelines. In this paper, we propose a new technology of nondestructive inspection by using a differential coil, which is easy to be manufactured with lightweight, low cost, and simple structure for operating inside the underground pipelines. Comparing with the conventional permanent-magnet MFL PIG, the results of the proposed system could also maximize the detection sensitivity of defect signals and minimize the magnetic adhesive force on the pipe wall simultaneously.

Integrated Planning of Electricity and Natural Gas Transportation Systems for Enhancing the Power Grid Resilience

Power systems are exceedingly faced with extreme events such as natural disasters and deliberate attacks. In comparison, the underground natural gas system is considered less vulnerable to such extreme events. We consider that the overhead power grid can be hardened by replacing segments of electric power grid with underground natural gas pipelines as an energy transportation system to countereffect extreme events which can damage interdependent infrastructures severely. In this paper, an integrated electricity and natural gas transportation system planning algorithm is proposed for enhancing the power grid resilience in extreme conditions. A variable uncertainty set is developed to describe the interactions among power grid expansion states and extreme events. The proposed planning problem is formulated as a two-stage robust optimization problem. First, the influence of extreme events representing natural disasters is described by the proposed variable uncertainty set and the proposed robust model for the integrated planning is solved with the grid resilience represented by a set of constraints. Second, the investment decisions are evaluated iteratively using the conditional events. The integrated electricity and natural gas planning options are analyzed using the modified IEEE-RTS 1979 for enhancing the power grid resilience. The numerical results point out that the proposed integrated planning is an effective approach to improving the power grid resilience.

Improvement of Regulatory Requirements for Ensuring the Quality of Underground Gas Pipelines in Conditions of Corrosion Fatigue

The article develops recommendations for improvement of normative documents concerning the quality of underground pipelines (gas pipelines) under conditions of fatigue and the impact of an aggressive environment, taking into account cathodic (electrochemical) protection. It is established that the basis of information provision of normative documents is the method which includes the following main criteria: the value of the minimum current density of cathode protection; minimum security potential; maximum protective potential, minimal displacement of protective potential; strength criteria of pipe material; criteria of strength of phase layer between the and the coating; the strength of the in the defect of the insulation coating. It has been found out that the system metal pipe - insulating dielectric coating is characterized by such basic procedures as: identification of hazards; various variants of load asymmetry; evaluation of the boundary and optimal values of potentials and currents for the system of cathodic protection of the pipeline. The prospect of further research in this area is determination of the complex indicator of quality and reliability of the linear part of underground main gas pipelines on the basis of research results (submitted information support).

Pitting corrosion failure analysis of a wet gas pipeline

Abstract This paper presents corrosion failure analysis of an underground natural gas pipeline. The pipeline material grade is API 5L X65 with 10-in ID. The pipeline transfers multiphase fluid (gas, condensate, and water) from a gas well to a gas gathering plant, located 4200 m away from the well site. A portion of the line failed due to pitting corrosion under unknown circumstances. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) are employed to characterize the scales and/or corrosion products near the failed portion. Based on visual and microscopic analyses and reviewing the background information, the following pitting corrosion sequences were identified: the oversized pipeline changed the dominant flow regime to “stratified”. In the stratified flow regime, the accompanying water phase accumulated in the pipelines' low points. Considerable concentration of calcium ions along with high pH in CO 2 media favored precipitation of calcium carbonate. The relatively thick scales adhered to the pipe surface were partially loosened and removed by the regional turbulent flow. This exposed the fresh steel surface to the corrosive media. The uncovered areas acted as the preferential anodic sites coupled with nearby large cathodic sites which were covered by scales and/or corrosion products. Under such conditions, pits emerged on the steel surface until one of them grew faster and failed the gas pipeline.