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Abstract By introducing the effects of the failure data and corrective maintenance, a novel methodology has been established to update the reliability of the corroding natural gas pipeline. Firstly, the methodology is able to calculate the failure probabilities for the small leak and burst based on the inspection data. The rank regression method is then applied to determine the fittest failure distribution function. Moreover, the failure distribution functions are updated by considering the failure data and the corrective maintenance. The Bayesian method and Markov Chain Monte Carlo (MCMC) simulation techniques are employed in the update process. Furthermore, the actual data from a natural gas pipeline located in China is used to illustrate this methodology, and the assessment indicates that the failure data and the corresponding corrective maintenance exert great impact on failure probability. [ABSTRACT FROM AUTHOR]

The main challenge in the maintenance planing lies in the realistic modeling of the maintenance policy. However, the complexity of the industrial systems makes difficult the achievement of this prospect. To face the realistic constraints, the present paper provides an approach for the maintenance planning of utility systems on the basis of opportunistic maintenance policy and Bayesian theory. The reliability assessment, which can be updated according to the evolution of the environmental conditions using the Bayesian theory, is integrated in the maintenance model, in order to evaluate the optimal preventive maintenance times and to update them when new degradation data become available. The opportunistic replacement is used to take benefit from the non-operating state of some components, caused by the maintenance action on other components, in order to replace them opportunistically. The effectiveness of the proposed approach is illustrated through a numerical application on operating gas supply system. [ABSTRACT FROM AUTHOR]

Pipelines used to transport oil and gas products are often subjected to external forces during its construction or operation, which can result in the formation of dents in the pipe. Various pipeline codes have stipulations on how a dent's severity can be ascertained in order to prioritize repairs. The most prominent being the depth-based criterion, which determines the severity of a dent by its depth. The depth-based criterion fails to consider the fact that the geometry of the dent can result in high strain concentration and eventually lead to integrity issues at the dented region. Alternatively, the strains associated with the dent can be an indicator of the dent's severity. Nonmandatory codified equations are available for evaluating the strains at the dented region of the pipe. The current implementation of these equations might fail to capture the strains that are not aligned with the most severe deformation profile of the dent and as such a global view of the strain distribution of the dented profile would be more informative as per the localized strain distribution. The study presented herein is the implementation of ASME B31.8 formulations together with the suggested modifications to evaluate the three-dimensional (3D) strain state of the dented pipe. The strain distributions obtained are compared against the strains predicted by finite element analysis (FEA) model. The correlation in the predicted strains indicates the possibility of the rapid and concise strain based characterization of dented pipes with the proposed technique. 0 [ABSTRACT FROM AUTHOR]

Copyright of Eastern-European Journal of Enterprise Technologies is the property of PC TECHNOLOGY CENTER and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Squeeze-off is widely used within the gas industry for temporary interruptions to supply, both when extending and repairing the polyethylene (PE) pipe network. Over the years a number of pipe failures, have been attributed to damage caused at the squeeze-off location, often linked to non-standard squeeze-off practices. The purpose of this paper is to examine PE pipes that have been squeezed in the laboratory under ASTM and non-ASTM standard conditions to determine if any changes to the PE structure can be measured. Changes in the PE due to squeeze-off was measured by FTIR at the squeeze-off ear. The carbonyl index (CI), a measure of polymer degradation, was calculated for the various squeeze-off conditions and it was found that over-compression of the PE pipe caused the greatest amount of damage to the pipe and that is directly linked to the integrity of the pipe prior to being squeezed-off. [ABSTRACT FROM AUTHOR]

Finite element (FE) method is employed to simulate the temperature field of the in-service welding on a single bead-on-pipeline. The methane gas was introduced as a cooling media to investigate the temperature field of the heat affected zone (HAZ) based on the validation of the numerical models. The heat transfer coefficient is significantly influenced by the pressure and flow rate of the gas and wall thickness of pipeline, which leads to the magnitude of cooling time, horizontal and vertical sizes of HAZ and peak temperature at inner wall were reduced. While, the t8/1 increases first and then decreases with the variable wall thickness and it get the maximum value about 208.42 s at wall thickness of 8 mm. It indicates that the effect of the gas and wall thickness on the temperature field of in-service welding need to be concerned. [ABSTRACT FROM AUTHOR]

The paper presents the risk management methodology, which uses geoinformation systems that include functions and instruments indispensable for the input, analysis and visualization of spatial information. A structure of the risk management system for the safe pipeline maintenance under geodynamic influences was formed. It is found that the insulation coating of the pipeline, as an indicator of the technical condition of the pipeline that shows the effect of land sliding processes on the pipeline, is damaged in the area, which is marked as landslide-prone, as evidenced by the results of examination of the adjacent rock mass by the NPEMFE method. So, the section between meters 15–50 of the surveyed pipeline can be defined as having a high degree of geodynamic risk (the risk of active sliding processes). It is established that a complex application of express-methods for the inspection of the pipeline and the adjacent rock mass allows obtaining the data to determine the actual level of geodynamic hazards on the route of the pipeline. A methodology approbated on Pasichna-Dolyna gas pipeline area, which is situated in a highly landslide-prone zone, was described. As evaluation, the express method of natural impulse electromagnetic field of the Earth (NPEMFE) registration was chosen. Measurement system RIDGID SR-60 from the surface has been applied with the purpose to conduct noncontact survey of pipeline insulation in the Pasichna-Dolyna area. [ABSTRACT FROM AUTHOR]

Multidimensional risk analysis in pipelines has been addressed in the literature in recent years which has led to a greater understanding of risk in the decision context. A risk assessment model based on different perspectives becomes attractive to decision-makers (DMs) who are responsible for the maintenance of pipelines, and can help to prioritize maintenance efforts, and therefore optimize the use of human financial and other resources. As to the transportation of gas by pipeline, efforts at risk analysis must consider the physical and operational characteristics of the product, failure modes and their consequences, based on each accidental scenario considered. Different parameters are collected and/or estimated in order to produce a recommendation for the DM. Therefore, this paper enhances previous suggestions for a multicriteria decision model that evaluates multidimensional risk by using visualization tools and statistical tests as part of global sensitivity analysis. Simulations are made considering patterns which provide the DM with information about the uncertainty of different groups of parameters for the model. Furthermore, the output of the disturbance can be checked based on Kendall's correlation coefficient. Finally an evaluation can be made graphically of the different rankings of sections, thereby making a more assertive recommendation to the DM. [ABSTRACT FROM AUTHOR]

The ‘Test, Analyze and Fix’ process is widely applied to improve the reliability of a repairable system. In this process, dynamic reliability assessment for the system has been paid a great deal of attention. Due to instrument malfunctions, staff omissions and imperfect inspection strategies, field reliability data are often subject to interval censoring, making dynamic reliability assessment become a difficult task. Most traditional methods assume this kind of data as multiple normal distributed variables or the missing mechanism as missing at random, which may cause a large bias in parameter estimation. This paper proposes a novel method to evaluate and predict the dynamic reliability of a repairable system subject to interval-censored problem. First, a multiple imputation strategy based on the assumption that the reliability growth trend follows a nonhomogeneous Poisson process is developed to derive the distributions of missing data. Second, a new order statistic model that can transfer the dependent variables into independent variables is developed to simplify the imputation procedure. The unknown parameters of the model are iteratively inferred by the Monte Carlo expectation maximization (MCEM) algorithm. Finally, to verify the effectiveness of the proposed method, a simulation and a real case study for gas pipeline compressor system are implemented. [ABSTRACT FROM AUTHOR]

Degradation of an underground pipeline during its service life leads to reduction of the pipe wall thickness. Periodic in-line inspections are performed by onshore pipelines operators to detect corrosion anomalies and size their depth and width. In the paper, a simple analytical method of burst pressure calculation for a straight pipeline repaired with a composite sleeve was investigated. Repair activities after an in-line inspection of a gas transmission pipeline were considered in this research to assess the pressure of a pipe with a flaw reinforced with a different number of layers of a fiber-based polymer sleeve. Det Norske Veritas criteria and formulation of a limit state function were applied to determine the burst pressure and corresponding failure probability of a pipeline with a large number of single and non-interacting part-wall defects. The Monte Carlo method was selected for estimation of pipeline failure probability and cumulative failure probability due to the external corrosion considering fluid pressure fluctuations in dynamic flow effects with respect to statistical distribution of input parameters were examined in this research. The proposed novel 3-step approach was validated on the real data collected from an onshore high pressure gas pipeline DN 700, MOP 5.5 MPa provided by two magnetic flux leakage inspections repeated at an interval of twelve years. A probabilistic methodology was applied to evaluate the part-wall external corrosion defects and their deterministic linear growth with time and repair activities on gas transmission pipelines were analyzed. The results of this study shall help maintenance engineers solve the problems of an optimal strategy in reliability-based high pressure gas pipelines management. [ABSTRACT FROM AUTHOR]

Gas transmission pipeline network is of great importance to any country using natural gases in its various technological processes. However, the usefulness cannot overshadow the threat posed to people and property by the grid failures. In order to quantify the reliability of the grid, se veral widely recognized pipeline incident databases have been established. However, each database contains data about pipelines operated in remote geographical regions with varying soil types, under different incident registration criterion. For a longer time period even in single database, there is variation of these incident registration criteria. Therefore, analysis of an entire sample without regard to the incident criteria change raises suspicions about the validity of resulting inferences. Authors move beyond the qualitative pipeline incident database comparison and provide a methodology for quantitative integration of all available statistical information to improve gas pipeline network reliability evaluation. We develop a new model called Criteria-dependent Poisson model, which takes into account various incident data collection criteria and extend it to the hierarchical (Bayesian) case when different databases with differing incident registration criteria can be joined in the same analysis. With the real data examples, we demonstrate the applicability of our method, which unfolds itself to be of great usefulness in reliability prediction. The Lithuanian pipeline network failure rate assessment shows the advantages of hierarchical structuring of Criteria-dependent Poisson model in small sample problems. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Prediction of the duration of a repair and maintenance project of a gas transport system is an important part of planning activities. There exist numerous sources of uncertainties that may result in time overruns possibly leading to multiple negative consequences. Our experience in planning this work suggests that accepting the stochastic nature of the project duration is a constructive step towards the preparedness to contingencies and defining penalties for repair companies. To support this approach, one needs to construct probability distributions of the durations of the projects. To address the issue of the scarcity of observed data, we suggest using a bootstrap resampling procedure. Gram-Charlier functions and order statistics are employed to approximate the distributions. It is demonstrated how to derive them for a separate repair project and a larger project consisting of a number of concurrently running subprojects. Following this, guidance is provided on how to decide about what duration should define the deadline for completion of the whole work. A simple example is provided. [ABSTRACT FROM AUTHOR]

The 2013 report card of America's infrastructure has scored the condition of oil and gas pipelines as D+ which means that such pipelines are in a relatively poor condition. More than 10,000 failures have been recorded in the US. These failures have resulted in environmental, health and property damages. Therefore, there is a definite need to give more attention to the maintenance of oil and gas pipelines. This paper develops a comprehensive model for the maintenance planning of oil and gas pipelines. The model selects rehabilitation/repair alternatives for oil and gas pipelines based on their condition during their service life. These alternatives are then used to calculate the cash flow throughout the service life of these infrastructures. The model, which uses Monte Carlo simulation and fuzzy approach to address the uncertainties in the estimation of the maintenance operation costs and the economic parameters, calculates the Equivalent Uniform Annual Worth of the identified alternatives. The optimum maintenance programmes consist of the alternatives that have the lowest life cycle cost of oil and gas pipelines. The model is expected to support pipeline operators in the maintenance decision-making process of oil and gas pipelines. [ABSTRACT FROM PUBLISHER]

The article offers information on the history, regulatory regimes, and challenges to the infrastructure development for transportation of the oil and natural gas in the U.S. Topics discussed include the role of the Federal Energy Regulatory Commission (FERC) in the maintenance of the interstate natural gas pipelines, the effects of the hydraulic fracturing on the domestic energy transportation infrastructure, and the significance of the Keystone XL Pipeline in oil supplies.

The effect of the in-service scattered damage in the pipe wall metal is evaluated, and the effect of hydrogen absorbed by metal on the variation of the structure and mechanical properties of the main gas pipeline after a long-term operation is found. The main regularities in the graded nature of the static deformation process and the effect of hydrogenation on the scattered damage and fracture accumulation are found. [ABSTRACT FROM AUTHOR]

In this paper, we describe both applied and analytical work in collaboration with a large multistate gas utility. The project addressed a major operational resource allocation challenge that is typical to the industry. We study the resource allocation problem in which some of the tasks are scheduled and known in advance, and some are unpredictable and have to be addressed as they appear. The utility has maintenance crews that perform both standard jobs (each must be done before a specified deadline) as well as respond to emergency gas leaks (that occur randomly throughout the day and could disrupt the schedule and lead to significant overtime). The goal is to perform all the standard jobs by their respective deadlines, to address all emergency jobs in a timely manner, and to minimize maintenance crew overtime. We employ a novel decomposition approach that solves the problem in two phases. The first is a job scheduling phase, where standard jobs are scheduled over a time horizon. The second is a crew assignment phase, which solves a stochastic mixed integer program to assign jobs to maintenance crews under a stochastic number of future emergencies. For the first phase, we propose a heuristic based on the rounding of a linear programming relaxation formulation and prove an analytical worst-case performance guarantee. For the second phase, we propose an algorithm for assigning crews that is motivated by the structure of an optimal solution. We used our models and heuristics to develop a decision support tool that is being piloted in one of the utility’s sites. Using the utility’s data, we project that the tool will result in a 55% reduction in overtime hours. [ABSTRACT FROM AUTHOR]

Abstract: Risk zone forecast is of great importance in natural gas pipeline route choice, safe separation distances determination and disaster assistance. In this article, the risk zone after the natural gas release in urban areas was predicted under the condition of different wind directions or different release rates, with the method of computational fluid dynamics (CFD). In addition, the change tendency of the risk zone with the increase of release rate under the environment of strong winds and breeze was studied respectively. [Copyright &y& Elsevier]

We propose a numerical-experimental procedure for the evaluation of the possibility of safe operation and the risk of failures oil and gas pipelines after long-term operation with regard for the influence of the potential development of in-service defects and degradation of the properties of the pipe metal. [ABSTRACT FROM AUTHOR]

Natural gas is the largest source of anthropogenic emissions of methane (CH4) in the United States. To assess pipeline emissions across a major city, we mapped CH4 leaks across all 785 road miles in the city of Boston using a cavity-ring-down mobile CH4 analyzer. We identified 3356 CH4 leaks with concentrations exceeding up to 15 times the global background level. Separately, we measured δ 13CH4 isotopic signatures from a subset of these leaks. The δ 13CH4 signatures (mean = −42.8‰ ± 1.3‰ s.e.; n = 32) strongly indicate a fossil fuel source rather than a biogenic source for most of the leaks; natural gas sampled across the city had average δ 13CH4 values of −36.8‰ (±0.7‰ s.e., n = 10), whereas CH4 collected from landfill sites, wetlands, and sewer systems had δ 13CH4 signatures ∼20‰ lighter (μ = −57.8‰, ±1.6‰ s.e., n = 8). Repairing leaky natural gas distribution systems will reduce greenhouse gas emissions, increase consumer health and safety, and save money. [Copyright &y& Elsevier]

To improve connectivity-reliability of gas pipeline network the possibility of gas pipe network with intermediate state before failure is expounded. Based on the improved two states with safety and failure of pipe unit, a three-stage connectivity reliability work mode of safety-intermediate-failure is established. Through adopting hierarchical exploded mode of full probability, multi-loop gas pipe network with bridge circuit can be broken down into several simple compound pipe systems for reliability vector solving. The influence of correlation parameter among pipe units to connectivity reliability of gas pipe network is considered and the trust in connectivity reliability calculation is increased in this paper. [ABSTRACT FROM AUTHOR]

The article discusses the pressure model tests of welded joints conducted on high-pressure gas pipelines to determine transmission pipeline destruction in Slovakia. It says the test was performed at the Welding Research Institute of the Slovak Republic in Bratislava. Authors mention the most common causes of pipeline destruction includes accidental mechanical damage of pipes, damage caused by additional bending load and corrosion as a result of insulation damage.

The article focuses on the factors that should be considered to prevent hazards and catastrophes when repairing natural gas pipes. It says that planning with people involved, skills, and resources required should be made before the repair. It says that lubricated plug valves of the piping must be applied with sealant annually to prevent leaks. It adds that pressure tests that are consistent or stringent than the National Fire Protection Association (NFPA) 54 code must be made after the repair.

The work of the corrosion protection system used at OOO Gazprom Transgas Yekaterinburg is considered, mainly for the period of 2008. It is noted that the passive corrosion protection component, which consists of different pipeline wrappings, requires repair and replacement. The active (electrochemical) corrosion protection component achieves a high level of corrosion protection of gas pipelines via the application of different technical processes. Their work is exemplified by the main gas pipelines of the Nev'yansk Regional Gas Pipeline Operation Center. [ABSTRACT FROM AUTHOR]

Copyright of Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil is the property of University of Puerto Rico and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: In an efficient and effective pipe integrity management programme, maintenance engineers often use the risk-based inspection (RBI) and maintenance strategy. Unfortunately, the calculation of risk is a daunting task because in order to calculate the risk of failure, a maintenance engineer needs to predict the rate of growth of a defect, the effect of the defect on the integrity of the structure and the consequence of failure. Unfortunately precise calculation for either of these parts is quite difficult. Fuzzy logic is a mathematical tool suitable for handling imprecise information in the real world. The benefit of this approach lies in its ability to include personal experiences along with acceptable deterministic models in the calculation. The structure of the model also allows easy calibration of the model to suit a particular plant condition. This approach can thus help to reduce the dependence upon the precise data, allow modelling even when a phenomenon is incompletely understood, and reduce the difficulties arising due to the complex computation required by more traditional methods. This paper presents a proposed methodology, based on fuzzy logic framework, for the establishment of an RBI programme for pipes. The paper also presents in detail a section of the methodology that can be used for calculating the estimated rate of CO2 corrosion in carbon steel pipes. In this technique the plant operating parameters (temperature, gas and liquid flow rates, total pressure, CO2 partial pressure and pH) are taken as fuzzy variables and used to calculate the Predicted Rate of Corrosion. The inspected rate of corrosion and the efficiency of inspection are also considered as fuzzy variables and are used to calculate Trust in Inspection Results and Trust in Predicted Results. By combining all the modules an estimated rate of corrosion is calculated. This estimated rate of corrosion can then be used for developing the risk-based inspection programme. [Copyright &y& Elsevier]

Abstract: Oil and gas pipelines covered with a mixture of sandy gravel and square-edged stones are subjected to abrasive shear loading steming from temperature-induced displacements of the pipeline in longitudinal direction. This requires wear protection of the outer anti-corrosion film of such pipes. In order to assess appropriate means for protection, adverse settlements on both sides of the soil-covered pipeline are assumed as relevant loading scenario. A nonlinear, elastoplastic, cap model-based Finite Element model delivers the radial stresses exerted onto the pipeline, due to settlement-induced load re-arrangement within the cohesionless soil body. Given a cover height of 1.5m, the aforementioned load re-arrangement leads to an increase of force action onto the pipe by up to 200%. Based on the grain size of the filling material, radial stresses are integrated as to estimate the maximum normal forces exerted by single stone corners onto the pipe’s anti-corrosion film. These forces, when analyzed through Archard’s law, allow for calculation of the service life of the protection layer enveloping the pipe, once the wear resistance of that layer is determined from experiments, as is done for geosynthetics. Since the service life of a geosynthetic protection layer of the anti-corrosion film turns out to be distinctively smaller than the standard service life of a soil-covered steel pipeline, protection through geosynthetic layers is insufficient. Hence, more effective means for protection are suggested. [Copyright &y& Elsevier]

This paper presents a new solution for inspecting and repairing defects in live gas pipelines. The proposed approach is the development of a modular and semi-autonomous vehicle system. The robotic system has a drive mechanism, capable of navigating and adjusting its orientation in various configurations of pipelines. Other features of the system are cable-free communications, semi-autonomous motion control as well as integration of sensory devices. The robotic system is designed to traverse in 150-300 mm diameter pipes through straight and curved sections, junctions and reducers. The vehicle control and navigation technique is implemented using a two-mode controller consisting of a proportional-integral-derivative (PID) and fuzzy logic control. Unlike other available systems, the vehicle employs proprioceptive sensors to monitor its own states. The fuzzy logic controller is used to evaluate the sensor outputs such as speed, climbing angle and rate of change of climbing angle. This control technique allows the vehicle to drive and adapt in a partially observable gas pipe system. Laboratory experiment results are presented. The paper also describes a cable-free communication method for the system. A brief account of typical pipe environments and currently available inspection tools is presented as background information. [ABSTRACT FROM AUTHOR]

Effectiveness of main pipeline repair in service is largely determined by contact pressure, created at sleeve mounting on pipe defective section. At correct selection of contact pressure value, long-term performance of the repaired section is ensured through partial unloading of the pipe wall. Such a result is achieved due to lowering of pressure in the main line before repair, and tight pressing of the sleeve around the pipe with a special device. Arc welding of sleeve reinforcing elements also is of considerable importance, resulting in formation of contact pressure, caused by shrinkage of multilayer longitudinal butt welds. In the work computational method was used to study the influence of sleeve wall thickness and pipeline diameter on the magnitude of contact pressure caused by deposited metal shrinkage. It is shown that contact pressure caused by metal shrinkage during welding performance has the strongest influence on unloading of a defective pipe wall in pipelines of 1020 mm and smaller outer diameter. Further increase of contact pressure magnitude caused by metal shrinkage can be achieved by increasing sleeve wall thickness. Such a technique is not effective for pipes of 1220 mm and greater diameter. [ABSTRACT FROM AUTHOR]

Analytical decisions supported by experimental data were used to determine the dependences for calculating the size of the heat-affected zone (HAZ) in multilayer welding of circumferential joints in transmission gas pipelines. Data on the dimensions of this zone are essential for evaluating the possibility of applying cold cutting in the rejection of elements of gas pipelines because of defects in circumferential welded joints or welded joints in transition rings in the vicinity of circumferential welded joints. [ABSTRACT FROM AUTHOR]

The article focuses on the prevention of magnetic arc blow in the repair of transmission gas pipelines at Tomsktransgaz Co. by using permanent magnets. This method is based on the superposition principle. The magnetic arc blow can be prevented most efficiently using two MKS-S1 magnets or four MKS-S magnet and a magnetometer.