The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Akram Alfantazi - One of the best experts on this subject based on the ideXlab platform.
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numerical simulations of soil physicochemistry and aeration influences on the External Corrosion and cathodic protection design of buried pipeline steels
Materials & Design, 2016Co-Authors: Ibrahim M Gadala, Magd Abdel Wahab, Akram AlfantaziAbstract:Abstract Corrosion of oil and gas transmission pipelines is a serious industrial problem with potentially catastrophic environmental and financial consequences. A finite element model of the External Corrosion of buried steel pipelines at coating failures is developed here to better predict degradation in different soil and cathodic protection (CP) environments. Synergistic interactions between steady-state temperature, potential, and oxygen concentration profiles in the soil surrounding the pipeline structure are quantified and discussed. Conductivity and oxygen diffusivity of soil conditions are represented as functions of soil matter, air porosity, and volumetric wetness. Theoretical formulations are uniquely merged with Corrosion experiments conducted on actual pipeline steel samples, greatly improving simulation results. Overall, drier sand and clay soil structures cause the most Corrosion, whereas wetter conditions impede oxygen diffusion and significantly augment hydrogen evolution. Geometric location of the coating breakdown site relative to the ground surface and the CP anode has a particular influence on oxygen concentration profiles and pipeline Corrosion. Model convergence is tested with a mesh sensitivity study, and the model’s ability in evaluating practical design changes in the CP system is demonstrated.
J.m. Hallen - One of the best experts on this subject based on the ideXlab platform.
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Bayesian analysis of External Corrosion data of non-piggable underground pipelines
Corrosion Science, 2015Co-Authors: Francisco Caleyo, A. Valor, L. Alfonso, Julio Vidal, E. Perez-baruch, J.m. HallenAbstract:A new Bayesian methodology for the analysis of External Corrosion data of non-piggable underground pipelines has been developed. It allows for the estimation of the statistical distributions of the density and size of External Corrosion defects from Corrosion data samples taken at excavation sites along the inspected pipeline and can incorporate the detection and measurement errors associated with field inspections. Corrosion data obtained from field inspections of an upstream pipeline and from an in-line inspection of a transportation pipeline are used to illustrate and validate the proposed methodology.
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The negative binomial distribution as a model for External Corrosion defect counts in buried pipelines
Corrosion Science, 2015Co-Authors: A. Valor, Francisco Caleyo, L. Alfonso, Julio Vidal, Eloy Perez-baruch, J.m. HallenAbstract:Abstract The spatial distribution of External Corrosion defects in buried pipelines is usually described as a Poisson process, which leads to Corrosion defects being randomly distributed along the pipeline. However, in real operating conditions, the spatial distribution of defects considerably departs from Poisson statistics due to the aggregation of defects in groups or clusters. In this work, the statistical analysis of real Corrosion data from underground pipelines operating in southern Mexico leads to conclude that the negative binomial distribution provides a better description for defect counts. The origin of this distribution from several processes is discussed. The analysed processes are: mixed Gamma-Poisson, compound Poisson and Roger’s processes. The physical reasons behind them are discussed for the specific case of soil Corrosion.
Francisco Caleyo - One of the best experts on this subject based on the ideXlab platform.
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Bayesian analysis of External Corrosion data of non-piggable underground pipelines
Corrosion Science, 2015Co-Authors: Francisco Caleyo, A. Valor, L. Alfonso, Julio Vidal, E. Perez-baruch, J.m. HallenAbstract:A new Bayesian methodology for the analysis of External Corrosion data of non-piggable underground pipelines has been developed. It allows for the estimation of the statistical distributions of the density and size of External Corrosion defects from Corrosion data samples taken at excavation sites along the inspected pipeline and can incorporate the detection and measurement errors associated with field inspections. Corrosion data obtained from field inspections of an upstream pipeline and from an in-line inspection of a transportation pipeline are used to illustrate and validate the proposed methodology.
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The negative binomial distribution as a model for External Corrosion defect counts in buried pipelines
Corrosion Science, 2015Co-Authors: A. Valor, Francisco Caleyo, L. Alfonso, Julio Vidal, Eloy Perez-baruch, J.m. HallenAbstract:Abstract The spatial distribution of External Corrosion defects in buried pipelines is usually described as a Poisson process, which leads to Corrosion defects being randomly distributed along the pipeline. However, in real operating conditions, the spatial distribution of defects considerably departs from Poisson statistics due to the aggregation of defects in groups or clusters. In this work, the statistical analysis of real Corrosion data from underground pipelines operating in southern Mexico leads to conclude that the negative binomial distribution provides a better description for defect counts. The origin of this distribution from several processes is discussed. The analysed processes are: mixed Gamma-Poisson, compound Poisson and Roger’s processes. The physical reasons behind them are discussed for the specific case of soil Corrosion.
Richard L Schmoyer - One of the best experts on this subject based on the ideXlab platform.
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Prediction of External Corrosion for Steel Cylinders--2007 Report
2008Co-Authors: Richard L SchmoyerAbstract:Depleted uranium hexafluoride (DUF{sub 6}) is stored in over 62,000 containment cylinders at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky, and at the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio. Over 4,800 of the cylinders at Portsmouth were recently moved there from the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee. The cylinders range in age up to 56 years and come in various models, but most are 48-inch diameter 'thin-wall'(312.5 mil) and 'thick-wall' (625 mil) cylinders and 30-inch diameter '30A' (including '30B') cylinders with 1/2-inch (500 mil) walls. Most of the cylinders are carbon steel, and they are subject to Corrosion. The United States Department of Energy (DOE) manages the cylinders to maintain them and the DUF{sub 6} they contain. Cylinder management requirements are specified in the System Requirements Document (LMES 1997a), and the activities to fulfill them are specified in the System Engineering Management Plan (LMES 1997b). This report documents activities that address DUF{sub 6} cylinder management requirements involving measuring and forecasting cylinder wall thicknesses. As part of these activities, ultrasonic thickness (UT) measurements are made on samples of cylinders. For each sampled cylinder, multiple measurements are made in an attempt to find, approximately,more » the minimum wall thickness. Some cylinders have a skirt, which is an extension of the cylinder wall to protect the head (end) and valve. The head/skirt interface crevice is thought to be particularly vulnerable to Corrosion, and for some skirted cylinders, in addition to the main body UT measurements, a separate suite of measurements is also made at the head/skirt interface. The main-body and head/skirt minimum thickness data are used to fit models relating minimum thickness to cylinder age, nominal thicknesses, and cylinder functional groups defined in terms of plant site, storage yard, top or bottom row storage positions, etc. These models are then used to compute projections of numbers of cylinders expected to fail various minimum wall thickness criteria. The minimum wall thickness criteria are as follows. For thin-wall cylinders: 0 (breach), 62.5, and 250 mils. For thick-wall cylinders: 0, 62.5, and 500 mils. For 30A cylinders: 0, 62.5, and 100 mils. Each of these criteria triplets are based respectively on (1) loss of DUF{sub 6} (breaching), (2) safe handling and stacking operations, and (3) ANSI N14.1 standards for off-site transport and contents transfer. This report complements and extends previous editions of the cylinder Corrosion report by Lyon (1995, 1996, 1997, 1998, 2000), by Schmoyer and Lyon (2001, 2002, 2003), and by Schmoyer (2004). These reports are based on UT data collected in FY03 and before. In this report UT data collected after FY03 but before FY07 is combined with the earlier data, and all of the UT data is inventoried chronologically and by the various functional groups. The UT data is then used to fit models of maximum pit depth and minimum wall thickness, statistical outliers are investigated, and the fitted models are used to extrapolate minimum thickness estimates into the future and in turn to compute projections of numbers of cylinders expected to fail various thickness criteria. A model evaluation is performed comparing UT measurements made after FY05 with model-fitted projections based only on data collected in FY05 and before. As in previous reports, the projections depend on the treatment of outliers.« less
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Prediction of External Corrosion for Steel Cylinders--2004 Report
2004Co-Authors: Richard L SchmoyerAbstract:Depleted uranium hexafluoride (UF{sub 6}) is stored in over 60,000 steel cylinders at the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee, at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky, and at the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio. The cylinders range in age from 4 to 53 years. Although when new the cylinders had wall thicknesses specified to within manufacturing tolerances, over the years Corrosion has reduced their actual wall thicknesses. The UF{sub 6} Cylinder Project is managed by the United States Department of Energy (DOE) to safely maintain the UF{sub 6} and the cylinders containing it. This report documents activities that address UF{sub 6} Cylinder Project requirements and actions involving forecasting cylinder wall thicknesses. These requirements are delineated in the System Requirements Document (LMES 1997a), and the actions needed to fulfill them are specified in the System Engineering Management Plan (LMES 1997b). The report documents cylinder wall thickness projections based on models fit to ultrasonic thickness (UT) measurement data. UT data is collected at various locations on randomly sampled cylinders. For each cylinder sampled, the minimum UT measurement approximates the actual minimum thickness of the cylinder. Projections of numbers of cylinders expected to fail various thickness criteria are computed from Corrosion models relating minimum wall thickness to cylinder age, initial thickness estimates, and cylinder subpopulations defined in terms of plant site, yard, top or bottom storage positions, nominal thickness, etc. In this report, UT data collected during FY03 is combined with UT data collected in earlier years (FY94-FY02), and all of the data is inventoried chronologically and by various subpopulations. The UT data is used to fit models of maximum pit depth and minimum thickness, and the fitted models are used to extrapolate minimum thickness estimates into the future and in turn to compute estimates of numbers of cylinders expected to fail various thickness criteria. A model evaluation is performed comparing UT measurements made in FY03 with model-fitted projections based only on data collected before FY03.
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Prediction of External Corrosion for Steel Cylinders 2003 Report
2003Co-Authors: Richard L SchmoyerAbstract:Depleted uranium hexafluoride (UF{sub 6}) is stored in over 60,000 steel cylinders at the East Tennessee Technology Park (ETTP) in Oak Ridge, Tennessee, at the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky, and at the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio. The cylinders range in age from six to 52 years. Although when new the cylinders had wall thicknesses specified to within manufacturing tolerances, over the years Corrosion has reduced their actual wall thicknesses. The UF{sub 6} Cylinder Project is managed by the United States Department of Energy (DOE) to safely maintain the UF{sub 6} and the cylinders containing it. The requirements of the Project are delineated in the System Requirements Document (LMES 1997a), and the actions needed to fulfill those requirements are specified in the System Engineering Management Plan (LMES 1997b). This report documents activities that address requirements and actions involving forecasting cylinder wall thicknesses. Wall thickness forecasts are based on models fit to ultrasonic thickness (UT) measurement data. First, UT data collected during FY02 is combined with UT data collected in earlier years (FY92-FY01), and all of the data is inventoried chronologically and by various subpopulations. Next, the data is used to model either maximummore » pit depth or minimum thickness as a function of cylinder age, subpopulation (e.g., PGDP G-yard, bottom-row cylinders), and initial thickness estimates. The fitted models are then used to extrapolate minimum thickness estimates into the future and to compute estimates of numbers of cylinders expected to fail various thickness criteria. A model evaluation is performed comparing UT measurements made in FY02 with model-fitted projections based only on data collected before FY02. The FY02 UT data, entered into the Corrosion model database and not available for the previous edition of this report (Schmoyer and Lyon 2002), consists of thickness measurements of 48'' thin-wall cylinders: 102 cylinders at Paducah, 104 at ETTP, and 117 at Portsmouth; and 72 thick-wall cylinders at Portsmouth. However, because of missing values, repeated measures on the same cylinders, outliers, and other data problems, not all of these measurements are necessarily used in the Corrosion analysis, and some previous measurements may simply be replaced with the new ones. In this edition of the report, cylinder subpopulation definitions and counts are updated using the latest (as of June 2003) information from the Cylinder Inventory Database (CID). Cylinders identified in the CID as painted during the last ten years are excluded from subpopulations considered at-risk of failing minimum thickness criteria, because it is assumed that painting fully arrests Corrosion for ten years. As in the previous edition of the report, two different approaches to Corrosion modeling are pursued: (1) a direct approach in which minimum thickness is modeled directly as a function of age, subpopulation, and initial thickness estimates; and (2) an indirect approach, in which maximum pit depth is modeled, and the pit-depth model is then combined with a model of initial thickness to compute estimates of minimum thickness.« less
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Prediction of External Corrosion for Steel Cylinders—2002 Report
2002Co-Authors: Richard L SchmoyerAbstract:The United States Department of Energy (DOE) manages the UF{sub 6} Cylinder Project. The project was formed to maintain and safely manage the depleted uranium hexafluoride (UF{sub 6}) stored in approximately 50,000 carbon steel cylinders. The cylinders are located at three DOE sites: the East Tennessee Technology Park (ETTP) site in Oak Ridge, Tennessee; the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky, and the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio. The System Requirements Document (SRD) (LMES 1997a) delineates the requirements of the project, and the actions needed to fulfill these requirements are specified in the System Engineering Management Plan (SEMP) (LMES 1997b). This report documents activities that in whole or part satisfy specific requirements and actions stated in the UF{sub 6} Cylinder Project SRD and SEMP with respect to forecasting cylinder conditions. The results presented here supercede those presented by Lyon (1995, 1996, 1997, 1998, 2000), and Schmoyer and Lyon (2001). Many of the wall thickness projections made in this report are conservative, because they are based on the assumption that Corrosion trends will continue, despite activities such as improved monitoring, relocations to better storage, painting, and other improvements in storage conditions relative to the conditions at the times most of the wall thickness measurements were made. For thin-wall cylinders (design nominal wall thickness 312.5 mils), the critical minimum wall thicknesses criteria used in this report are 0 (breach), 62.5 mils, and 250 mils (1 mil = 0.001 in.). For thick-wall cylinders (design nominal wall thickness 625 mils), the thickness criteria used in this report are 0, 62.5 mils, and 500 mils. The criteria triples are preliminary boundaries identified within the project that indicate (1) loss of material (UF{sub 6}), (2) safe handling and stacking operations, and (3) standards for off-site transport and contents transfer criteria, respectively. In general, these criteria are based on an area of wall thinning. However, the minimum thickness predicted in this report is essentially for a point--an area of about 0.01 square inches--because the thickness measurements on which the predictions are based are essentially for points. For thicknesses criteria greater than zero, conclusions based on minimum point thicknesses are conservative. Because of the interaction of UF{sub 6}, with atmospheric moisture and steel, a point breach would deteriorate in a year to one-inch diameter hole (DNFSB 1995), however, and so small area approximations should be close for the breach criteria. The most recently collected data, entered into the Corrosion model database and not available for the previous report (Schmoyer and Lyon 2001), consists of evaluations of wall loss of 48 inch thin-wall cylinders: 301 cylinders at Paducah, 101 at ETTP, and 139 at Portsmouth; 14 thick-wall cylinders at Portsmouth; and 99 model 30A cylinders at Paducah. However, because of missing values, repeated measures on the same cylinders, outliers, and other data problems, however, not all of these measurements are necessarily used in the Corrosion analysis. In several cases, difficulty with the data is also due to a mathematical approach to cylinder Corrosion modeling that is used in this report, in Schmoyer and Lyon (2001), and in earlier reports by Lyon. Therefore, an alternative approach is also considered in this report. In previous reports, minimum wall thicknesses have been modeled indirectly through separate models of initial thickness and maximum pit depth. In order to estimate minimum wall thicknesses, the initial thickness and maximum pit depth models are combined using mathematics that assumes independence of the statistical distributions of the initial thicknesses and maximum pit depths. Initial thicknesses are modeled from wall thickness maxima measured at relatively uncorroded wall areas of each cylinder. Maximum pit depths for each cylinder are estimated as differences between the initial thickness estimates and measured minimum wall thicknesses. The pit depth maxima estimates are modeled as a function of age and a cylinder grouping based on location
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Prediction of External Corrosion for Steel Cylinders 2001 Report
2001Co-Authors: Richard L SchmoyerAbstract:The United States Department of Energy (DOE) currently manages the UF{sub 6} Cylinder Project. The project was formed to maintain and safely manage the depleted uranium hexafluoride (UF{sub 6}) stored in approximately 50,000 carbon steel cylinders. The cylinders are located at three DOE sites: the ETTP site (K-25) at Oak Ridge, Tennessee; the Paducah Gaseous Diffusion Plant (PGDP) in Paducah, Kentucky, and the Portsmouth Gaseous Diffusion Plant (PORTS) in Portsmouth, Ohio. The System Requirements Document (SRD) (LMES 1997a) delineates the requirements of the project. The appropriate actions needed to fulfill these requirements are then specified within the System Engineering Management Plan (SEMP) (LMES 1997b). This report documents activities that in whole or in part satisfy specific requirements and actions stated in the UF{sub 6} Cylinder Project SRD and SEMP with respect to forecasting cylinder conditions. The results presented here supercede those presented previously (Lyon 1995, 1996, 1997, 1998, 2000). Many of the wall thickness projections made in this report are conservative, because they are based on the assumption that Corrosion trends will continue, despite activities such as improved monitoring, relocations to better storage, and painting
Homero Castaneda - One of the best experts on this subject based on the ideXlab platform.
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statistical analysis of spatial distribution of External Corrosion defects in buried pipelines using a multivariate poisson lognormal model
Structure and Infrastructure Engineering, 2020Co-Authors: Xiangrong Wang, Hui Wang, Fujian Tang, Homero Castaneda, Robert Y LiangAbstract:It is well recognised that the severity of pipeline External Corrosion is highly related to the corrosivity of the surrounding soil environment. However, in practice, the explicit effects of the so...
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a clustering approach for assessing External Corrosion in a buried pipeline based on hidden markov random field model
Structural Safety, 2015Co-Authors: Hui Wang, Robert Y Liang, Ayako Yajima, Homero CastanedaAbstract:Abstract This paper describes the use of a clustering approach based on hidden Markov random field to extract potential homogeneous segments from a large length right-of-way of a pipeline structure with heterogeneous soil properties. This approach extends the conventional finite mixture model so that the spatial correlation of External Corrosion sites can be taken into consideration. An algorithm is established for classifying Corrosion defects using soil properties from an in-situ survey and location information from in-line inspection reports. The categorized Corrosion defects reveal the hidden patterns of Corrosion degradation in different segments along a pipeline structure. Stochastic simulation is employed to test this clustering approach. An example involving a 110-km pipeline interval is employed to illustrate the implementation of the clustering approach. The results indicate that the process of External Corrosion propagation in a buried pipeline is position-dependent and is highly related to the soil environment. In addition, the results show that this phenomenon can be interpreted by segmentation using the proposed clustering method. A clustering-based inspection strategy is discussed as a way to apply the present approach.
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Bayesian Modeling of External Corrosion in Underground Pipelines Based on the Integration of Markov Chain Monte Carlo Techniques and Clustered Inspection Data
Computer-Aided Civil and Infrastructure Engineering, 2014Co-Authors: Hui Wang, Robert Y Liang, Ayako Yajima, Homero CastanedaAbstract:In this study, a model is developed to assess External Corrosion in buried pipelines based on the uni- fication of Bayesian inferential structure derived from Markov chain Monte Carlo techniques using clustered inspection data. This proposed stochastic model com- bines clustering algorithms that can ascertain the simi- larity of Corrosion defects and Monte Carlo simulation that can give an accurate probability density function es- timation of the Corrosion rate. The metal loss rate is cho- sen as the indicator of Corrosion damage propagation, obeying a generalized extreme value (GEV) distribution. Bayesian theory was employed to update the probability distribution of metal loss rate as well as the GEV param- eters in order to account for the model uncertainty. The proposed model was validated with direct and indirect inspection data extracted from a 110-km buried pipeline system.
