High-pressure Gas Pipeline Research Articles

Risk-targeted safety distance of reinforced concrete buildings from natural-gas transmission pipelines

Natural-gas pipeline accidents mostly result in major damage even to buildings located far away. Therefore, proper safety distances should be observed in land use planning to ensure target safety levels for both existing and new buildings.In this paper, a quantitative risk assessment procedure is presented for the estimation of the annual probability of direct structural damage to reinforced concrete buildings associated with high-pressure natural-gas pipeline explosions. The procedure is based on Monte Carlo simulation and takes into account physical features of blast generation and propagation, as well as damage to reinforced concrete columns. The natural-gas jet release process and the flammable cloud size are estimated through SLAB one-dimensional integral model incorporating a release rate model. The explosion effects are evaluated by a Multi-Energy Method. Damage to reinforced concrete columns is predicted by means of pressure–impulse diagrams. The conditional probability of damage was estimated at multiple pressure–impulse levels, allowing blast fragility surfaces to be derived at different performance limit states. Finally, blast risk was evaluated and allowed the estimation of minimum pipeline-to-building safety distances for risk-informed urban planning. The probabilistic procedure presented herein may be used for performance-based design/assessment of buildings and to define the path of new natural-gas pipeline networks.

Measurements of the Stack Metal Temperature During a Natural Gas Blowdown Event Through a Full-Bore Blowdown Valve

Experiments were used in conjunction with a compressible flow model to investigate the temperature recovery phenomenon along a blowdown stack during a high-pressure natural gas pipeline blowdown. The test rig involved instrumented 2 in. blowdown stacks mounted on a full-bore valve. Stacks with two wall thicknesses and stagnation pressures of approximately 3000 kPa-a and 5600 kPa-g were tested, giving a total of four test cases. Using the compressible flow model, which was calibrated using static pressure measurements, the stack-gas temperature was calculated to range from −38 °C to −18 °C for the four test cases. The respective stack wall temperatures were measured to range between −13 °C and 0 °C; thus, the temperature recovery ranged between 18 °C and 26 °C. Empirical correlations available in the literature, which were developed for aeronautical applications, were tested against the experimental results. Poor agreement was found between the measured temperature recovery factor and that predicted by five empirical correlations: the coefficient of determination (R2) between the measured and correlation-calculated recovery factor was found to be negative for all five correlations.

A review of modelling high pH stress corrosion cracking of high pressure gas pipelines

Modelling of intergranular stress corrosion cracking (SCC) in pipelines is an important field of study as predictive techniques are integral to pipeline integrity and management. An inclination of the SCC propagation direction has been observed for some pipelines, which is not predictable using existing models as they assume perpendicular crack growth. A review has been conducted to identify the applicable techniques from existing models, as well as the gaps in current knowledge. Existing work in crack growth rates, stress formulations and microstructural representations are reviewed. Mechanical dependency of the electrochemical response is identified as a gap and proposed for inclusion in a model alongside the other areas reviewed.

Numerical analysis of quasi-steady flow characteristics in large diameter pipes with low liquid loading under high pressure

Computational fluid dynamics (CFD) modeling was carried out to study wavy thin film flow and droplet transport in high-pressure natural gas pipelines with low liquid loading. The interactions between droplets and thin film were considered. The results of the CFD analysis showed periodic fluctuation in the axial film distribution in the straight pipe. In the bend, gas streamlines originated from the inside of the bend. As the gas velocity was increased, more droplets were stripped, while the stripped droplets were deposited further away. Liquid film peak formation and droplet motion were attributed to the actions of centrifugal force and gravity in the bend. Secondary flow enhanced the transport of droplets to the upper side of the pipe and supplemented the upper film. The droplet fraction distribution changed periodically with time. The accumulation of droplets on the film has a periodic characteristic. Dense droplets tended to accumulate in regions of low vortices. The results of the CFD simulation were in good agreement with previous experimental data and theoretical analyses reported in the literature.

Determination of the economical optimum insulation thickness for VRF (variable refrigerant flow) systems

This study deals with the investigation into optimum insulation thickness of installed inside building pipe network of VRF (variable refrigerant flow) systems. Optimum insulation thickness, energy savings over a lifetime of 10 years and payback periods are determined for high pressure gas pipelines, low pressure gas pipelines and low pressure liquid pipelines under the heating-only and cooling-only modes of the three-pipe VRF system using R-410A as refrigerant. By using the P1–P2 method, the value of the amount of the net energy savings is calculated. Under heating mode of VRF system, while the optimum insulation thickness varies between 16 and 20 mm depending on the pipe sections of high pressure gas pipeline, it varies from 11 to 13 mm for the pipe sections of low pressure liquid pipeline. Under cooling mode of VRF system, the optimum insulation thickness varies between 7 and 8 mm for pipe sections of low pressure gas pipeline and low pressure liquid pipeline.

Modeling, Simulation, and Optimization of a High-Pressure Cross-Country Natural Gas Pipeline: Application of an Ant Colony Optimization Technique

AbstractThe process of natural gas transportation through cross-country pipelines, with intermittent repressurization with the help of compressors that use part of the same gas for energy source, is a very interesting optimization problem that has attracted researchers. In the present work, an 18-node network connecting a single source to a single delivery point has been selected for analysis. A steady-state model, incorporating gas flow dynamics, compressor characteristics, and mass balance equations, has been developed. Ant colony optimization, a comparatively new evolutionary technique in pipeline optimization, has been used for minimizing fuel consumption for a fixed throughput. A comparison with a similar optimization tool, a solver of a general algebraic modeling system that extracts the principle of generalized reduced gradient algorithm, indicates an improved solution in terms of fuel consumption minimization.

An analysis of the changes of the composition of natural gas transported in high-pressure gas pipelines

An analysis of the changes of the composition of natural gas transported in high-pressure gas pipelines

273 高圧ガスパイプラインにおける高速延性破壊の連成数値計算モデル

273 高圧ガスパイプラインにおける高速延性破壊の連成数値計算モデル

Metal Magnetic Memory method used for analyzing high-pressure gas pipelines

Metal Magnetic Memory method used for analyzing high-pressure gas pipelines

Origin and Development of the Stress-Corrosion Defects in Large Diameter Steel Pipes of High-Pressure Gas Pipelines

This study presents the results of research of the stress corrosion defects detected at the compressor station gas pipeline. The effect of high-cycle fatigue on the development of such defects was found between the linear dimensions of the stress corrosion crack.

국외 천연가스 배관 사고 빈도 비교 및 분석 모형에 관한 연구

본 연구에서는 국내 매설 고압가스배관의 사고빈도 데이터 구축 시 활용할 수 있도록 국외에서 발표하고 있는 고압가스배관 사고빈도 데이터에 대해 고찰 하였다. 고압가스배관 사고빈도 데이터의 대표적인 것으로는 미국의 DOT, 유럽의 EGIG 및 영국의 UKOPA가 있다. 국외 사고빈도 데이터의 국내 적용 가능성을 확인하기 위하여 이들을 비교 분석한 결과 EGIG 데이터가 국내 실정에 더 적합하였다. EGIG 8차 보고서의 사고빈도 데이터를 사용하여 비선형회귀분석을 수행한 결과 배관 설치 연도에 따른 지수형의 곡선을 얻었다. 향후 전체 사고빈도의 약 50%를 차지하고 있는 타공사 부분과 국내 데이터와 국외 데이터의 합성에 대한 집중적인 연구가 필요하다. In this study, the overseas failure frequency data of the high-pressure gas pipeline were investigated to apply QRA of high-pressure gas pipeline. The typical overseas failure frequency data of high-pressure gas pipeline are DOT of United States, EGIG of Europe, and UKOPA of United Kingdom (UK). Comparative analysis of these data was shown that EGIG data was suitable for the situation in Korea. In order to apply QRA of high-pressure gas pipeline, non-linear regression analysis using the failure frequency data in the report of EGIG 8th was performed. In the future, intensive researches are required for the external interference because about 50% of the failure frequency of all incidents is the external interference, and for combining of domestic and overseas data.

Transient Flow in Natural Gas Pipelines Using Implicit Finite Difference Schemes

Transmission of natural gas through high pressure pipelines has been modeled by numerically solving the governing equations for one-dimensional compressible flow using implicit finite difference methods. In the first case the backward Euler method is considered using both standard first-order upwind and second-order centered differences for the spatial derivatives. The first-order upwind approximation, which is a one-sided approximation, is found to be unstable for CFL numbers less than 1, while the centered difference approximation is stable for any CFL number. In the second case a cell centered method is considered where flow values are calculated at the midpoint between grid points. This method is also stable for any CFL number. However, for a discontinuous change in inlet temperature, the method is observed to introduce unphysical oscillations in the temperature profile along the pipeline. A solution strategy where the hydraulic and thermal models are solved separately using different discretization techniques is suggested. Such a solution strategy does not introduce unphysical oscillations for discontinuous changes in inlet boundary conditions and is found to be stable for any CFL number. The one-dimensional flow model is validated using operational data from a high pressure natural gas pipeline.

Unconventional natural gas development: economic salvation or looming public health disaster?

The unconventional fossil fuel extraction industry has seen unprecedented growth in recent years. Unlike natural gas extraction from conventional reservoirs, unconventional natural gas development (UNGD) requires that rock in the source formation must be ‘stimulated’ in order to release the targeted methane. This may involve hydraulic fracturing, depressurising the coal seam aquifer or burning coal underground. With the alluring promise of economic salvation, job creation and clean energy, coal seam gas (CSG) has been strongly promoted by State and Federal governments. A network of wells, high pressure gas pipelines, processing plants, compressor stations, pumping stations, flow back ponds, vents and flares have already been permitted in agricultural areas and close to family homes. However, the extraction of unconventional gas may have adverse impacts on the environment and consequently on human health. Emerging evidence from Australia and overseas indicates that when fugitive emissions are taken into account, UNGD may be no cleaner than coal...

A CFD Analysis of Flow through a High-Pressure Natural Gas Pipeline with an Undeformed and Deformed Orifice Plate

A CFD Analysis of Flow through a High-Pressure Natural Gas Pipeline with an Undeformed and Deformed Orifice Plate

Risk and uncertainty analysis of gas pipeline failure and gas combustion consequence

Taking into account a general concept of risk parameters and knowing that natural gas provides very significant portion of energy, firstly, it is important to insure that the infrastructure remains as robust and reliable as possible. For this purpose, authors present available statistical information and probabilistic analysis related to failures of natural gas pipelines. Presented historical failure data is used to model age-dependent reliability of pipelines in terms of Bayesian methods, which have advantages of being capable to manage scarcity and rareness of data and of being easily interpretable for engineers. The performed probabilistic analysis enables to investigate uncertainty and failure rates of pipelines when age-dependence is significant and when it is not relevant. The results of age-dependent modeling and analysis of gas pipeline reliability and uncertainty are applied to estimate frequency of combustions due to natural gas release when pipeline failure occurs. Estimated age-dependent combustion frequency is compared and proposed to be used instead of conservative and age-independent estimate. The rupture of a high-pressure natural gas pipeline can lead to consequences that can pose a significant threat to people and property in the close vicinity to the pipeline fault location. The dominant hazard is combustion and thermal radiation from a sustained fire. The second purpose of the paper is to present the combustion consequence assessment and application of probabilistic uncertainty analysis for modeling of gas pipeline combustion effects. The related work includes performance of the following tasks: to study gas pipeline combustion model, to identify uncertainty of model inputs noting their variation range, and to apply uncertainty and sensitivity analysis for results of this model. The performed uncertainty analysis is the part of safety assessment that focuses on the combustion consequence analysis. Important components of such uncertainty analysis are qualitative and quantitative analysis that identifies the most uncertain parameters of combustion model, assessment of uncertainty, analysis of the impact of uncertain parameters on the modeling results, and communication of the results’ uncertainty. As outcome of uncertainty analysis the tolerance limits and distribution function of thermal radiation intensity are given. The measures of uncertainty and sensitivity analysis were estimated and outcomes presented applying software system for uncertainty and sensitivity analysis. Conclusions on the importance of the parameters and sensitivity of the results are obtained using a linear approximation of the model under analysis. The outcome of sensitivity analysis confirms that distance from the fire center has the greatest influence on the heat flux caused by gas pipeline combustion.

Stress Analysis and Strength Checking for High Pressure Gas Pipeline in the Earthquake Rupture Area

Based on the actual project example of high pressure gas pipeline crossing earthquake rupture area, the paper shows and explains the way to make stress analysis and strength checking calculation for the high pressure gas pipeline in the earthquake rupture area by the method of finite element.

Research and Application on the Dynamic Simulation of Natural Gas Pipeline

Based on the fundamental flow equations of high-pressure gas pipeline, the numerical solution for unsteady-state flow was studied with the Central difference scheme. Considered the energy equation and urban gas regular, the problem of low calculation precision caused by ignorance of the energy equation was solved. During the variation of gas consumption with time, the dynamic simulation program was generated. Finally, a numerical example of engineering application was presented .

Experimental study on dynamics of rotatable bypass-valve in speed control pig in gas pipeline

Periodically pigging of oil and gas pipelines for dewatering, cleaning and inspecting becomes a standard industry procedure. Speed control unit is needed to control the speed of the pig and keep it work at a moderate constant speed, especially in the large diameter and high pressure gas pipelines. Rotatable bypass-valve is a necessary part in speed regulating unit, which is used to control the speed of pig by changing the amounts of the bypass flow across the pig body. However, the dynamics of the bypass-valve is complexity and indeterminacy during bypassing. As a result, in this paper, an experiment facility is set up to simulate the real working condition and get the dynamic characteristics of bypass-valve. The relationship among the torque, the opening of bypass-valve and the differential pressure over bypass-valve can be obtained in this experiment, which can provide the references to make control algorithm for speed control pig.

Simulation and Optimization of NGE-MR Natural Gas Liquefaction Process

With the increased utilization of natural gas, there has been an increase in the research on peak-shaving natural gas liquefaction technologies. The NGE-MR natural gas liquefaction process, which precools natural gas with the cold energy generated by high pressure natural gas pipeline pressure energy recovery, is a promising technical candidate for peak-shaving LNG facilities. In this study, the effect of high pressure of the mixed refrigerant cycle (MRC) on the performance of the NGE-MR liquefaction process is analyzed under a fixed MRC pressure ratio. The result shows that for a certain mixed refrigerant composition, there is a corresponding optimal high pressure of the MRC, under which the minimum specific power of the liquefaction process could be obtained. The minimum specific power should be regarded as the evaluating indicator to represent the performance of the mixed refrigerant composition. Finally, the effect of mixed refrigerant composition on the performance of the NGE-MR liquefaction process is analyzed and the optimal operating conditions for the NGE-MR liquefaction process are obtained. As a result, the required specific power at the optimal operating conditions is less than 0.23 kW·h·kg-1 and is decreased by about 24% compared with the specific power of C3-MR natural gas liquefaction process.

Simulation Experiment for Gas Pipeline Leakage Detection

Because of the complex process of pipeline operation, there is not an authoritative and reliable way to detect the gas pipeline leakage. Simulation for the southern half ring of Tianjin high-pressure gas pipeline network which depends on the real-time data collected by the SCADA system can provide a reference to detecting and locating the leakage by the method of pressure gradient. It is a very useful way to ensure safe operation of the pipeline network daily.