Establishment of limit state equation for buried pipeline corrosion defects

2015 ◽  
pp. 1815-1821
Author(s):  
Zhenyong Zhang ◽  
Qingmei Jiang ◽  
Bin Guo
Keyword(s):  
Limit State ◽  
State Equation ◽  
Buried Pipeline ◽  
Corrosion Defects ◽  
Pipeline Corrosion

Identification of the Cause of Variability of Probability of Failure for Burst Models Recommended by Codes/Standards

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Mainul Hasan ◽  
Faisal Khan ◽  
Shawn Kenny
Keyword(s):  
Failure Probability ◽  
Oil And Gas ◽  
Limit State ◽  
Probability Of Failure ◽  
State Equation ◽  
Operating Pressure ◽  
Moment Methods ◽  
First Order Second Moment ◽  
Corrosion Defects ◽  
External Corrosion

Failure probability of oil and gas pipelines due to external corrosion defects can be estimated using corrosion growth model and the evaluation of remaining strength. Codes/standards have been developed for the assessment of the remaining strength of corroded pipeline. The remaining strength and the operating pressure were considered to develop the limit state equation and consequently the failure probability of the burst models recommended by codes/standards. In the present paper, comparative analyses of the failure probability estimated by the codes/standards were conducted, using Monte Carlo simulation and first order second moment methods. The analysis revealed that the failure probability of the burst models recommended by codes/standards varies significantly for the same defects size. The study further explored the cause of variability in failure probabilities. The study observed that different defect shape specifications (rectangular, parabolic, etc.) and different stress concentration factor derivations (different contributions of l) for burst pressure estimation are responsible for high variability in the probability of failure. It is important to reduce variability to ensure unified risk-based design approach considering any codes/standards.

An Array of Multielectrodes for Locating, Visualizing, and Quantifying Stray Current Corrosion

CORROSION ◽  
10.5006/2828 ◽  
2018 ◽  
Vol 74 (10) ◽  
pp. 1093-1101 ◽  
Author(s):  
Ke Wang ◽  
Facundo Bob Varela ◽  
Mike Yongjun Tan
Keyword(s):  
Cathodic Protection ◽  
Laboratory Simulation ◽  
Buried Pipeline ◽  
Stray Current ◽  
Simulation Experiments ◽  
Corrosion Rates ◽  
Pipeline Corrosion ◽  
Probe Array

An array of multielectrode corrosion probes, designed based on a series of coupled wire beam electrodes (WBEs), has been devised as a new tool for locating, visualizing, and quantifying the effects of stray currents on buried pipeline corrosion. It has been demonstrated in laboratory simulation experiments that this WBE probe array is capable of detecting stray current corrosion affected sites along a pipeline, visualizing stray current corrosion patterns and corrosion rates, and evaluating the efficiency of cathodic protection against stray current corrosion. Based on these results, two applications of this WBE probe array have been proposed for stray current corrosion survey and monitoring.

Reliability of Buried Pipeline Using a Theory of Probability of Failure

2006 ◽  
Vol 110 ◽  
pp. 221-230 ◽  
Author(s):  
Ouk Sub Lee ◽  
Dong Hyeok Kim ◽  
Seon Soon Choi
Keyword(s):  
Failure Probability ◽  
Probability Of Failure ◽  
Operating Conditions ◽  
Reliability Estimation ◽  
Design Parameters ◽  
Buried Pipeline ◽  
Safety Level ◽  
First Order ◽  
Reliability Method ◽  
Corrosion Defects

The reliability estimation of buried pipeline with corrosion defects is presented. The reliability of corroded pipeline has been estimated by using a theory of probability of failure. And the reliability has been analyzed in accordance with a target safety level. The probability of failure is calculated using the FORM (first order reliability method). The changes in probability of failure corresponding to three corrosion models and eight failure pressure models are systematically investigated in detail. It is highly suggested that the plant designer should select appropriate operating conditions and design parameters and analyze the reliability of buried pipeline with corrosion defects according to the probability of failure and a required target safety level. The normalized margin is defined and estimated accordingly. Furthermore, the normalized margin is used to predict the failure probability using the fitting lines between failure probability and normalized margin.

Reliability Analysis of Fatigue Crack Growth with JC Method Based on Scientific Materials

2011 ◽  
Vol 63-64 ◽  
pp. 882-885 ◽  
Author(s):  
Xiao Li Zou
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Normal Distribution ◽  
Crack Growth ◽  
Reliability Index ◽  
Limit State ◽  
State Equation ◽  
Fatigue Reliability ◽  
Crack Propagation Process ◽  
Log Normal

Since the fatigue crack propagation process from initial size till final fracture is affected by lots of random factors, it is difficult to evaluate the fatigue reliability. Based on reliability theory, the first order second moment method ( JC method) is adopted to analyze and compute the fatigue reliability. To account for the uncertainties of material resistance, the parameters in the deterministic fatigue crack growth rate equation and material fracture toughness are taken as random variables with Normal distribution or Log-Normal distribution. Consequently, the limit state equation of fatigue crack growth is derived. The fatigue reliability index at any moment is calculated iteratively through JC method. As a computation example, the curve of fatigue crack growth reliability index with time is presented.

Characterization of Limit State for Seismic Fragility Assessment of T-Joints in Piping System

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Ankit R. Dubey ◽  
Abhinav Gupta ◽  
Sung Gook Cho
Keyword(s):  
Limit State ◽  
Experimental Studies ◽  
State Equation ◽  
Cyclic Behavior ◽  
Piping System ◽  
Damage State ◽  
T Joints ◽  
Performance Function ◽  
A Performance

Abstract Fragility assessment requires characterization of a component or system's performance through a performance function/limit-state equation. The exceedance of limit-state is representative of failure or damage state. For the purposes of evaluating piping fragility, characterizing the behavior of T-joints through an appropriate performance function is critical, as failures in piping are generally localized at the location of T-joints, elbows, and nozzles. Past studies have utilized a monotonic rotation-based performance function. However, the existing criteria does not account for the effect of cyclic behavior. As observed during prior experimental studies, the T-joint behavior under cyclic loading is different from that under monotonic loading, and therefore, it is important to include the effects of cyclic behavior while characterizing a performance function. Moreover, the monotonic rotation-based performance function could not replicate all the leakage locations observed during experimental studies on a full-scale two-story piping system. Therefore, it is important to develop a new limit-state for accurate piping fragility assessment. This paper presents the development of a new limit state which considers the cyclic behavior of a T-joint and quantifies the number of cycles to failure.

MECHANICAL SIMULATION AND ELECTROCHEMICAL CORROSION IN A BURIED PIPELINE WITH CORROSION DEFECTS SITUATED IN PERMAFROST REGIONS

2020 ◽  
pp. 2150002
Author(s):  
XIAOLI LI ◽  
LI CHEN ◽  
XIAOYAN LIU ◽  
YU ZHANG ◽  
LIFU CUI
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Simulation Analysis ◽  
Electrochemical Corrosion ◽  
Frost Heave ◽  
Buried Pipeline ◽  
Mechanical Coupling ◽  
Finite Element Software ◽  
Corrosion Defects ◽  
Permafrost Regions

The geological environment along a buried pipeline in permafrost regions is complex, where differential frost heave often occurs. To understand the changes in the stress behavior of pipeline structures caused by corrosion while laying them in permafrost regions, we established a thermo-mechanical coupling model of buried pipeline with corrosion defects by using finite element software. Numerical simulation analysis of buried pipeline was conducted. The effects of the frost heave length, the length of the transition section, the corrosion depth, and the corrosion length on the stress displacement were obtained. These analyses showed that the stresses and displacements of the pipeline with corrosion defects in permafrost regions can be simulated by using the finite element software numerical simulation method. Afterward, the corrosion resistances of pipelines with different corrosion lengths and depths were investigated via an electrochemical testing method. These results can provide some useful insights into the possible mechanical state of buried pipeline with regard to their design and construction, as well as some useful theoretical references for simulating real-time monitoring and safety analysis for their operation in permafrost regions.

Validity of the LAPA Method for Assessment of Defects Reported by In-Line Inspection Tools

2004 ◽  
Author(s):  
Richard Fletcher ◽  
Louis Fenyvesi
Keyword(s):  
Alternative Assessment ◽  
Reliable Method ◽  
Burst Pressure ◽  
Independent Validation ◽  
Defect Profile ◽  
Corrosion Defects ◽  
Pipeline Corrosion

Over recent years, RSTRENG has gained acceptance as a reliable method of assessing the effect of pipeline corrosion defects, while reducing the conservatism inherent in some of the alternative assessment models. The Length Adaptive Pressure Assessment (LAPA) algorithm has been developed to apply an adaptation of the RSTRENG methodology directly to the results of a magnetic in-line inspection. Adoption of the LAPA technique offers substantial accuracy and efficiency benefits over the more conventional processes, but the industry requires confirmation of the method’s validity before it can take advantage of these. The paper will describe the LAPA validation work performed by PII, and independent validation undertaken by TransCanada Pipelines and other pipeline operators. The independent validation took the form of a comparison of LAPA-based burst pressure calculations with RSTRENG calculations based on direct infield measurements of the defect profile. TransCanada also performed a series of burst tests to quantify the accuracy of the LAPA calculations.

Topology optimization of continuum structures with uncertain-but-bounded parameters for maximum non-probabilistic reliability of frequency requirement

2015 ◽  
Vol 23 (16) ◽  
pp. 2557-2566 ◽  
Author(s):  
Bin Xu ◽  
Lei Zhao ◽  
Yi Min Xie ◽  
Jiesheng Jiang
Keyword(s):  
Topology Optimization ◽  
Reliability Index ◽  
Optimization Problems ◽  
Mass Density ◽  
Limit State ◽  
Optimization Procedure ◽  
State Equation ◽  
Outer Loop ◽  
Continuum Structures ◽  
Beso Method

A method for the non-probabilistic reliability optimization on frequency of continuum structures with uncertain-but-bounded parameters is proposed. The objective function is to maximize the non-probabilistic reliability index of frequency requirement.The corresponding bi-level optimization model is built, where the constraints are applied on the material volume in the outer loop and the limit state equation in the inner loop. The non-probabilistic reliability index of frequency requirement is derived by the analytical method for the continuum structure with the uncertain elastic module and mass density. Further, the sensitivity of the non-probabilistic reliability index with respect to the design variables is analyzed. The topology optimization in the outer loop is performed by a bi-directional evolutionary structural optimization (BESO) method, where the numerical techniques and the optimization procedure of BESO method are presented. Numerical results show that the proposed BESO method is efficient, and convergent optimal solutions can be achieved for a variety of optimization problems on frequency non-probabilistic reliability of continuum structures.

Reliability Calculation of Design Point Method for Orthotropic Plate

2013 ◽  
Vol 639-640 ◽  
pp. 1029-1032
Author(s):  
Jian Hua Cheng ◽  
Jian Min Xiong ◽  
Jin Zhi Zhou
Keyword(s):  
Orthotropic Plate ◽  
Evaluation Method ◽  
Stress Amplitude ◽  
Limit State ◽  
State Equation ◽  
Point Method ◽  
Fatigue Reliability ◽  
Design Point ◽  
Reliability Calculation ◽  
Fatigue Damage Accumulation

The design point method is a commonly-used method on fatigue reliability analysis. It is put forward, based on Palmgren-Miner linear fatigue damage accumulation rule, that the evaluation method of fatigue reliability for orthotropic plate in this article. It is analyzed the random variables of limit state equation of single component, established the three parameters of stress amplitude , fatigue life and constant , and derived the calculation method on reliability index of design point method, which would provide evidence for consequent design of Orthotropic Plate.

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