Shenwei zhang | Western University Canada (original) (raw)

Papers by Shenwei zhang

Research paper thumbnail of Inverse Gaussian process-based corrosion growth model for energy pipelines considering the sizing error in inspection data

Corrosion Science, 2013

This paper describes an inverse Gaussian process-based model to characterize the growth of the de... more This paper describes an inverse Gaussian process-based model to characterize the growth of the depth of corrosion defects on underground energy pipelines based on inspection data. The model is formulated in a hierarchical Bayesian framework, which allows consideration of uncertainties from different sources. The Markov Chain Monte Carlo (MCMC) simulation techniques are used to evaluate the probabilistic characteristics of the model parameters by incorporating the defect depths reported by multiple in-line inspections (ILIs) as well as the prior knowledge about these parameters. The bias and random scattering error associated with the ILI tool as well as the correlation between the random scattering errors associated with different ILI tools are considered in the analysis. An example involving real ILI data collected from an in-service pipeline is employed to illustrate the application of the growth model. The results indicate that the model in general can predict the growth of corrosion defects reasonably well. The proposed model can be used to facilitate the development and application of reliability-based pipeline corrosion management.

Research paper thumbnail of Improved Surface Loading Stress Analysis Method Considering Protection Measures

This paper presents a methodology to evaluate pipe stress induced by surface vehicle loading at u... more This paper presents a methodology to evaluate pipe stress induced by surface vehicle loading at uncased road crossings that are protected by mat or bridging. When vehicles cross an existing pipeline, additional circumferential and longitudinal pipe stresses induced by surface vehicle loadings should be comprehensively considered to ensure pipe integrity and safe operation. Surface protection measures are sometimes installed to distribute the surface loading away from pipe centerline and reduce “footprint pressure”. A modified CEPA equation was proposed to calculate the radius of relative stiffness (or effective length) of mat and was validated by comparing with results from continuum FEA. The effective length calculated by the modified equation demonstrates good consistency with the FEA-predicted effective length. An approach was proposed to evaluate the pipe stress with user-defined free span of bridging, which provide flexibility for optimizing bridging protection in the field. A tool was developed to facilitate the assessment of surface loading stress of pipeline with mat or bridging protection. Case studies were presented to demonstrate the application of the proposed methods and the effect of mat thickness or bridging free span on the reduction of live load stress. The proposed methods will benefit pipeline operators with derived cost-effective protection measures for vehicle crossing while assuring safety of pipeline operation.

Research paper thumbnail of Model error assessment of burst capacity models for energy pipelines containing surface cracks

International Journal of Pressure Vessels and Piping, 2014

ABSTRACT This paper develops the probabilistic characteristics of the model errors associated wit... more ABSTRACT This paper develops the probabilistic characteristics of the model errors associated with five well-known burst capacity models/methodologies for pipelines containing longitudinally-oriented external surface cracks, namely the Battelle and CorLAS™ models as well as the failure assessment diagram (FAD) methodologies recommended in the BS 7910 (2005), API RP579 (2007) and R6 (Rev 4, Amendment 10). A total of 112 full-scale burst test data for cracked pipes subjected internal pressure only were collected from the literature. The model error for a given burst capacity model is evaluated based on the ratios of the test to predicted burst pressures for the collected data. Analysis results suggest that the CorLASTM model is the most accurate model among the five models considered and the Battelle, BS 7910, API RP579 and R6 models are in general conservative; furthermore, the API RP579 and R6 models are markedly more accurate than the Battelle and BS 7910 models. The results will facilitate the development of reliability-based structural integrity management of pipelines.

Research paper thumbnail of An Efficient Methodology for the Reliability Analysis of Corroding Pipelines

Journal of Pressure Vessel Technology, 2014

This paper describes an efficient methodology that utilizes the first order reliability method (F... more This paper describes an efficient methodology that utilizes the first order reliability method (FORM) and system reliability approaches to evaluate the time-dependent failure probabilities of a pressurized pipeline at a single active corrosion defect considering three different failure modes, i.e., small leak, large leak, and rupture. The criteria for distinguishing small leak, large leak, and rupture at a given corrosion defect are established based on the information in the literature. The wedge integral and probability weighting factor methods are used to evaluate the probabilities of small leak and burst, whereas the conditional reliability index method is used to evaluate the probabilities of large leak and rupture. Two numerical examples are used to illustrate the accuracy, efficiency and robustness of the proposed methodology. The proposed methodology can be used to facilitate reliability-based corrosion management programs for energy pipelines.

Research paper thumbnail of Time-dependent reliability assessment for corroding pipelines based on imperfect inspection data

This paper presents a methodology to evaluate the time-dependent system reliability of pressurize... more This paper presents a methodology to evaluate the time-dependent system reliability of pressurized pipelines containing multiple active metal-loss corrosion defects and subjected to at least one inline inspection (ILI). The methodology incorporates an inverse Gaussian process-based corrosion growth model, and separates three distinctive failure modes, namely small leak, large leak and rupture. The hierarchical Bayesian method and Markov Chain Monte Carlo (MCMC) simulation are employed to evaluate the model parameters based on data obtained from high-resolution inline inspections. An example involving an in-service gas pipeline is used to validate the developed corrosion growth model and illustrate the proposed methodology for the system reliability analysis. The impact of the growth model on the reliability of pipelines is investigated through the comparative analysis in the example. The proposed methodology will facilitate the application of reliability-based pipeline corrosion management programs.

Research paper thumbnail of Cost-based optimal maintenance decisions for corroding natural gas pipelines based on stochastic degradation models

This paper investigates the optimal inspection interval for newly-built onshore underground natur... more This paper investigates the optimal inspection interval for newly-built onshore underground natural gas pipelines with respect to external metal-loss corrosion by considering the generation of corrosion defects over time and time-dependent growth of individual defects. The non-homogeneous Poisson process is used to model the generation of new defects and the homogeneous gamma process is used to model the growth of individual defects. A realistic maintenance strategy that is consistent with the industry practice and accounts for the probability of detection (PoD) and sizing errors of the inspection tool is incorporated in the investigation. Both the direct and indirect costs of failure are considered. A simulation-based approach is developed to numerically evaluate the expected cost rate at a given inspection interval. The minimum expected cost rule is employed to determine the optimal inspection interval. An example gas pipeline is used to examine the impact of the cost of failure, PoD, the excavation and repair criteria, the growth rate of the defect depth, the instantaneous generation rate of the generation model and defect generation model on the optimal inspection interval through parametric analyses. The results of the investigation will assist engineers in making the optimal maintenance decision for corroding natural gas pipelines and facilitate the reliability-based corrosion management.

Research paper thumbnail of Inverse Gaussian process-based corrosion growth model for energy pipelines considering the sizing error in inspection data

Corrosion Science, 2013

This paper describes an inverse Gaussian process-based model to characterize the growth of the de... more This paper describes an inverse Gaussian process-based model to characterize the growth of the depth of corrosion defects on underground energy pipelines based on inspection data. The model is formulated in a hierarchical Bayesian framework, which allows consideration of uncertainties from different sources. The Markov Chain Monte Carlo (MCMC) simulation techniques are used to evaluate the probabilistic characteristics of the model parameters by incorporating the defect depths reported by multiple in-line inspections (ILIs) as well as the prior knowledge about these parameters. The bias and random scattering error associated with the ILI tool as well as the correlation between the random scattering errors associated with different ILI tools are considered in the analysis. An example involving real ILI data collected from an in-service pipeline is employed to illustrate the application of the growth model. The results indicate that the model in general can predict the growth of corrosion defects reasonably well. The proposed model can be used to facilitate the development and application of reliability-based pipeline corrosion management.

Research paper thumbnail of Improved Surface Loading Stress Analysis Method Considering Protection Measures

This paper presents a methodology to evaluate pipe stress induced by surface vehicle loading at u... more This paper presents a methodology to evaluate pipe stress induced by surface vehicle loading at uncased road crossings that are protected by mat or bridging. When vehicles cross an existing pipeline, additional circumferential and longitudinal pipe stresses induced by surface vehicle loadings should be comprehensively considered to ensure pipe integrity and safe operation. Surface protection measures are sometimes installed to distribute the surface loading away from pipe centerline and reduce “footprint pressure”. A modified CEPA equation was proposed to calculate the radius of relative stiffness (or effective length) of mat and was validated by comparing with results from continuum FEA. The effective length calculated by the modified equation demonstrates good consistency with the FEA-predicted effective length. An approach was proposed to evaluate the pipe stress with user-defined free span of bridging, which provide flexibility for optimizing bridging protection in the field. A tool was developed to facilitate the assessment of surface loading stress of pipeline with mat or bridging protection. Case studies were presented to demonstrate the application of the proposed methods and the effect of mat thickness or bridging free span on the reduction of live load stress. The proposed methods will benefit pipeline operators with derived cost-effective protection measures for vehicle crossing while assuring safety of pipeline operation.

Research paper thumbnail of Model error assessment of burst capacity models for energy pipelines containing surface cracks

International Journal of Pressure Vessels and Piping, 2014

ABSTRACT This paper develops the probabilistic characteristics of the model errors associated wit... more ABSTRACT This paper develops the probabilistic characteristics of the model errors associated with five well-known burst capacity models/methodologies for pipelines containing longitudinally-oriented external surface cracks, namely the Battelle and CorLAS™ models as well as the failure assessment diagram (FAD) methodologies recommended in the BS 7910 (2005), API RP579 (2007) and R6 (Rev 4, Amendment 10). A total of 112 full-scale burst test data for cracked pipes subjected internal pressure only were collected from the literature. The model error for a given burst capacity model is evaluated based on the ratios of the test to predicted burst pressures for the collected data. Analysis results suggest that the CorLASTM model is the most accurate model among the five models considered and the Battelle, BS 7910, API RP579 and R6 models are in general conservative; furthermore, the API RP579 and R6 models are markedly more accurate than the Battelle and BS 7910 models. The results will facilitate the development of reliability-based structural integrity management of pipelines.

Research paper thumbnail of An Efficient Methodology for the Reliability Analysis of Corroding Pipelines

Journal of Pressure Vessel Technology, 2014

This paper describes an efficient methodology that utilizes the first order reliability method (F... more This paper describes an efficient methodology that utilizes the first order reliability method (FORM) and system reliability approaches to evaluate the time-dependent failure probabilities of a pressurized pipeline at a single active corrosion defect considering three different failure modes, i.e., small leak, large leak, and rupture. The criteria for distinguishing small leak, large leak, and rupture at a given corrosion defect are established based on the information in the literature. The wedge integral and probability weighting factor methods are used to evaluate the probabilities of small leak and burst, whereas the conditional reliability index method is used to evaluate the probabilities of large leak and rupture. Two numerical examples are used to illustrate the accuracy, efficiency and robustness of the proposed methodology. The proposed methodology can be used to facilitate reliability-based corrosion management programs for energy pipelines.

Research paper thumbnail of Time-dependent reliability assessment for corroding pipelines based on imperfect inspection data

This paper presents a methodology to evaluate the time-dependent system reliability of pressurize... more This paper presents a methodology to evaluate the time-dependent system reliability of pressurized pipelines containing multiple active metal-loss corrosion defects and subjected to at least one inline inspection (ILI). The methodology incorporates an inverse Gaussian process-based corrosion growth model, and separates three distinctive failure modes, namely small leak, large leak and rupture. The hierarchical Bayesian method and Markov Chain Monte Carlo (MCMC) simulation are employed to evaluate the model parameters based on data obtained from high-resolution inline inspections. An example involving an in-service gas pipeline is used to validate the developed corrosion growth model and illustrate the proposed methodology for the system reliability analysis. The impact of the growth model on the reliability of pipelines is investigated through the comparative analysis in the example. The proposed methodology will facilitate the application of reliability-based pipeline corrosion management programs.

Research paper thumbnail of Cost-based optimal maintenance decisions for corroding natural gas pipelines based on stochastic degradation models

This paper investigates the optimal inspection interval for newly-built onshore underground natur... more This paper investigates the optimal inspection interval for newly-built onshore underground natural gas pipelines with respect to external metal-loss corrosion by considering the generation of corrosion defects over time and time-dependent growth of individual defects. The non-homogeneous Poisson process is used to model the generation of new defects and the homogeneous gamma process is used to model the growth of individual defects. A realistic maintenance strategy that is consistent with the industry practice and accounts for the probability of detection (PoD) and sizing errors of the inspection tool is incorporated in the investigation. Both the direct and indirect costs of failure are considered. A simulation-based approach is developed to numerically evaluate the expected cost rate at a given inspection interval. The minimum expected cost rule is employed to determine the optimal inspection interval. An example gas pipeline is used to examine the impact of the cost of failure, PoD, the excavation and repair criteria, the growth rate of the defect depth, the instantaneous generation rate of the generation model and defect generation model on the optimal inspection interval through parametric analyses. The results of the investigation will assist engineers in making the optimal maintenance decision for corroding natural gas pipelines and facilitate the reliability-based corrosion management.