Review on Corrosion of Underground Pipelines Using Reliability (original) (raw)
Related papers
Reliability Assessment of Underground Pipelines Under Active Corrosion Defects
Reliability assessment of underground pipeline steel structures for hydrocarbon transmission and distribution systems under active corrosion defects has been investigated. The aim of this work is to obtain a decision-making tool for risk-based inspection and maintenance program. The basic idea consists in statistical analysis of corrosion defect measurements in a buried pipeline as to sort out the corresponding depths and lengths after several years of service. As a result steady corrosion rate model is proposed to estimate the growth in the dimensions of corrosion defects. Then, a degradation model based on ASME modified B31G standard is used as a mechanical model in order to assess the failure probability or the reliability index through defect dimensions and associated uncertainties. Meanwhile, the main assumption of the probabilistic analyses for corroded pipelines is the randomness of load and resistance parameters determining the limit state functions. The statistical distribution of the uncertainties in the parameters involved in the limit state functions is modeled using normal and lognormal distributions. The reliability software PHIMECA is used to compute the reliability index β and the probability of failure Pf, when increasing dimensions of the defect within the respective measured values of depth and length during inspection and maintenance operations. The reliability calculation allows carrying out the sensitivity of the variables according to their importance, their mean value and their coefficient of variation. The probability of failure and reliability index are obtained assuming in one hand constant depth of defect with increasing length and in the other hand a relationship between the depth to length corrosion defect ratio is given as a function of reliability index β. The latter can be used as a parameter for risk-based inspection and maintenance operations.
Failure Probability Assessment for Pipelines under the Corrosion Effect
American Journal of Mechanical Engineering, 2014
In this work, a numerical method was developed, by a reliability mechanical coupling, in order to define the reliability index and probability of failure evolutions for pipelines under corrosion effect. The chosen model, takes into account uniform and localized corrosion. Thus, the hardness and tensile tests were worked out to characterize the mechanical properties of pipelines material. Once the model was defined, a simulation was carried out by the software Phemica. The importance factors were also estimated. A methodology has been presented for the reliability analysis of pipelines subjected to localized corrosion. The variables influencing the reliability are treated as random variables and represented by suitable statistical distributions. An approximate limit state function was developed. Advanced first-order second moment reliability theory was employed for the estimation of the probability of pipeline failure by Phimeca software logiciel. From a numerical investigation, it was found that both defect depth and fluid pressure have significant influences on pipeline reliability.
International Journal of Pressure Vessels and Piping, 2006
Lifetime management of underground pipelines is mandatory for safe hydrocarbon transmission and distribution systems. Reliability analysis is recognized as a powerful decision-making tool for risk-based design and maintenance. Both the residual stresses generated during the manufacturing process and in-service corrosion reduce the ability to resist internal and external loading. In this study, the residual stress distribution in large diameter pipes has been characterized experimentally in order to be coupled with the corrosion model. During the pipe lifetime, residual stress relaxation occurs due to the loss of pipe thickness as material layers are consumed by corrosion. The reliability-based assessment of residual stress effects is applied to underground pipelines under a roadway, with and without active corrosion. It has been found that the residual stress greatly increases the failure probability, especially in the early stage of the pipe lifetime.
Reliability based integrity assessment of steel pipelines under corrosion
Corrosion Engineering Science and Technology
Currently, the assessment of mechanical integrity of pipelines damaged by corrosion is performed through deterministic procedures and, in special cases, by using random variables. Rigorously, the calculations require the use of probabilistic methods because they provide the proper framework to include explicitly the uncertainties involved. Some recent treatments consider the corrosion events to be independent, which may lead to errors in estimating the failure probability of the pipeline. In this paper, pipeline integrity is assessed in terms of failure probability and recent models are utilised that estimate the resistance to failure using improved representations of the corrosion defect. Also, a simplified way to consider the space correlation between different segments of a corroding steel pipeline is introduced and the procedure is applied to the specific case where the defect geometry is modelled to be of parabolic shape. The geometrical and mechanical pipeline properties are considered to be random variables; their mean values are taken from experimental results and the interdependence between them is characterised using the model's correlation matrix.
Structure and infrastructure engineering, 2015
(2015): Reliability-based temporal and spatial maintenance strategy for integrity management of corroded underground pipelines, Structure and Infrastructure Engineering, a graduate School aIceS, rWtH aachen university, aachen, germany; b department of Statistics, texas a&M university, college Station, tX, uSa; c department of civil engineering, the university of akron, akron, OH, uSa; d department of Material Science and engineering, national corrosion center, texas a&M university, college Station, tX, uSa ABSTRACT In this work, a novel stochastic model framework for predicting the external corrosion growth in buried pipeline structures has been developed, and a reliability-based temporal and spatial maintenance strategy is presented. The spatial correlation of soil properties is modelled via hidden Markov random field. The temporal correlation of the corrosion rate is characterised by the geometric Brownian bridge process. A Bayesian inferential framework is employed to estimate the model parameters of the corrosion growth model using in-line inspection data. The proposed corrosion growth model was validated with actual inspection data. In the reliability analysis, the impact of device detectability is considered and hence the estimated failure probability is more realistic. The proposed maintenance strategy is directly based on the time-specific and location-specific failure probability. The application of the proposed model and maintenance strategy is illustrated through a real-life pipeline system. The results indicate that the proposed maintenance strategy is an adaptive and dynamic scheme that is able to improve the efficiency of inspections.
Pipelines Reliability Analysis Under Corrosion Effect and Residual Stress
2015
This work focuses on a development of a finite element model that simulates corrosion phenomenon and its influence on structure rupture (pipelines). Subsequently, the pitting effect on reliability and pipelines lifetime is studied. In this paper, the investigated structure material is characterized experimentally, in order to determine the maximum strength and stress resistance. Therefore, a numerical model was developed under ANSYS code to simulate different loads to obtain the stress concentration factor as the stresses could surpass the yielding limit in the corrosion impact, and to determine the Von Mises stress. A corrosion model and residual stresses used in the literature are coupled with the probabilistic model to find the limit state function. Thus, failure probability and structure reliability index under the effect of pitting corrosion phenomena are calculated and the obtained results are discussed and analyzed.
Reliability of pipelines with corrosion defects
International Journal of Pressure Vessels and Piping, 2008
This paper aims at assessing the reliability of pipelines with corrosion defects subjected to internal pressure using the first-order reliability method (FORM). The limit-state function is defined based on the results of a series of small-scale experiments and threedimensional non-linear finite element analysis of the burst pressure of intact and corroded pipelines. A sensitivity analysis is performed for different levels of corrosion damage to identify the influence of the various parameters in the probability of burst collapse of corroded and intact pipes. The Monte Carlo simulation method is used to assess the uncertainty of the estimates of the burst pressure of corroded pipelines. The results of the reliability, sensitivity and uncertainty analysis are compared with results obtained from codes currently used in practice. r
Reliability Estimation and Risk-Cost Optimisation of Underground Pipelines
The safety of infrastructure facilities is the primary objective of any civil engineering design. A large section of underground pipelines in the UK are classified as structurally deficient and functionally obsolete. Due to low visibility, condition assessment and rehabilitation of underground pipelines are frequently neglected until a catastrophic failure occurs. Providing an acceptable level of service and overcoming the practical difficulties, the concerned industry has to plan how to operate, maintain and renew (repair or replace) the pipeline systems under the budget constraints. This research is focused on estimating pipe reliability and deciding when and how interventions are needed to prevent unexpected failures of flexible underground metal pipelines subject to externally applied loadings and pipe material corrosion during the whole service life at the optimal cost. The time-dependent reliability due to corrosion induced excessive deflection, buckling, wall thrust and bendi...
Numerical model for estimating time-dependent reliability of a corroding pipeline over its lifetime
International Journal of Advanced Structural Engineering
This work aims to evaluate time-dependent reliability of a pipeline under corrosion impact over its lifetime. A finite element corrosion model was proposed, and an empirical power low model is also used and coupled with a probabilistic model for evaluating reliability index about a limit state function. The failure probability of structure was determinate for deferent corrosion rate (low, moderate and high rates), considering corrosion depth. Form method and Monte Carlo simulation are used for evaluating the structure reliability. The impact of applying both effect of corrosion and residual stress is shown which is appears a significant failure probability of the studied pipeline. The found results are analyzed and discussed.