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.

A Proposed Bayesian Updating Approach to Update the Failure Probability of a Corrosion Defect After Performing Fitness for Service Based on API 579-1/ASME FFS-1

2016 ◽  
Author(s):  
S. Maleki ◽  
X. Cui
Keyword(s):  
Corrosion Rate ◽  
Failure Probability ◽  
Quantitative Method ◽  
Best Practice ◽  
Limit State ◽  
Bayesian Updating ◽  
Probability Of Failure ◽  
State Equation ◽  
Unconditional Probability ◽  
Probabilistic Technique

Using Risk-Based Inspection (RBI) and Fitness for Service (FFS) approaches to manage the integrity of pressure equipment has been the industries best practice for almost a decade. However, there had never been a procedural link between these two approaches in a way that when one performed FFS analysis on a defect, one could update the risk accordingly. This paper proposes a quantitative method to refresh the risk calculated in the RBI process when FFS analysis is completed on a locally thinned area. The proposed approach applies a probabilistic technique by considering the Remaining Strength Factor (RSF) from API 579-1/ASME FFS-1 as the limit state equation and assuming the corrosion rate as a distribution variable to estimate the unconditional probability of failure. This value is then modified using a Bayesian updating method allowing for the conditional probability to represent a new failure likelihood which could be utilized in the RBI planning.

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.

Pipeline Remaining Life Estimation Based on Concepts of Structural Reliability and Bayesian Inference

2014 ◽  
Author(s):  
Helio da Cunha Bisaggio ◽  
Theodoro Antoun Netto
Keyword(s):  
Structural Reliability ◽  
Limit State ◽  
Probability Of Failure ◽  
Operational Parameters ◽  
Simple Method ◽  
Life Estimation ◽  
Predicted Probability ◽  
Operational Life ◽  
Corrosion Defects ◽  
State Functions

In this paper, structural reliability concepts are used in conjunction with DNV Recommended Practice RP-F101 [1] formulation to establish the limit state functions of corroded pipes. The model takes into account the natural spread of material properties, geometric and operational parameters, and the uncertainties associated with the sizing of eventual corrosion defects to determine the probability of failure at a given time. Bayesian and reliability concepts are used to estimate the evolution of a pre-defined distribution of defects obtained, for instance, from an inspection campaign. By comparing the predicted probability of failure with the reliability acceptance criteria the operator can schedule defect repairs and establish inspection intervals with more confidence. Thus, a simple method to predict the probability of failure of a corroded pipeline along its operational life is proposed to provide the basis to develop a risk based maintenance strategy.

Pipeline Material Reliability Analysis Regarding to Probability of Failure Using Corrosion Degradation Model

2011 ◽  
Vol 422 ◽  
pp. 705-715 ◽  
Author(s):  
Patuan Alfon ◽  
Johny W. Soedarsono ◽  
Dedi Priadi ◽  
S Sulistijono
Keyword(s):  
Reliability Analysis ◽  
Oil And Gas ◽  
Oil And Gas Industry ◽  
Probability Of Failure ◽  
Distribution Method ◽  
Gas Industry ◽  
Internal Corrosion ◽  
Corrosion Failure ◽  
Calculation Results ◽  
External Corrosion

Reliability of equipment of the oil and gas industry is vital, whereas on pipeline transmission system, decreasing the integrity of the pipeline is generally caused by corrosion. Failure that occurs due to corrosion deterioration influenced by the environment within a certain time, and has exceeded the nominal thickness of the pipe so there is a failure. This study used the reliability analysis approach based on modeling corrosion degradation ratio that is determined by the amount of the corrosion rate externally and internally. Using the Weibull probabilistic distribution method, results that the reliability of pipeline will decrease with increasing lifetime. It was identified that internal corrosion has a major contribution to the remaining life of pipeline. From the calculation results obtained by external corrosion has the greatest reliability over 60 years, followed by internal corrosion less than 30 years and the least is by cumulative corrosion which is less than 20 years. From the value of reliability, it can be known probability of failure (POF) which is the anti reliability.

Effects of Inner Corrosion Defects Size on the Surface Strain of Oil and Gas Pipelines

2013 ◽  
Vol 740 ◽  
pp. 603-607
Author(s):  
Fang Jie Cheng ◽  
Hai We Zhao ◽  
Yun Long Wu ◽  
Wei Liu ◽  
Hong Yuan Cao ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Circumferential Strain ◽  
Oil And Gas ◽  
Reliability And Validity ◽  
Circumferential Direction ◽  
Surface Strain ◽  
Operating Pressure ◽  
Exponential Relationship ◽  
Proportional Relationship ◽  
Corrosion Defects

Inner corrosion defects have great effects on the life and safety of the oil and pipelines. To predict the safety by the surface strain and stress condition, ANSYS software was applied to analyze the effects of the inner corrosion defects size (diameter and depth) on the surface strain and stress value. The combined effects of defect diameter and depth on the circumferential direction strain of pipeline were obtained. The simulation results indicate that there is a linear relationship between circumferential direction strain and the defect diameter, an exponential relationship between circumferential strain and defect depth. Furthermore, there is a proportional relationship between the circumferential strain and the operating pressure of the pipeline. An empirical formula to calculate the surface strain used the defect diameter, depth and the operating pressure was developed based on the numerical simulation data. The experimental results verify the reliability and validity of this empirical formula for engineering prediction application.

scholarly journals The Use of Reliability Based Limit State Methods in Uprating High Pressure Pipelines

1998 ◽  
Author(s):  
Andrew Francis ◽  
Richard Espiner ◽  
Alan Edwards ◽  
Gary Senior
Keyword(s):  
Failure Probability ◽  
Probabilistic Analysis ◽  
Failure Modes ◽  
Limit State ◽  
Operating Conditions ◽  
Operating Pressure ◽  
New Materials ◽  
Limit State Design ◽  
The Impact ◽  
Transmission Pipelines

There is an increasing demand for operators of transmission pipelines to maximise the throughput of their pipeline systems. This can be achieved relatively easily with new pipelines, by using limit state design, new materials, novel fabrication techniques etc., Operators are also looking to maximise the throughput of existing transmission pipelines. Obviously, they are not able to make use of new materials etc., but limit state design concepts can be applied to show that a pipeline can be safely uprated to a higher design pressure. The limit state of an engineering structure or component is defined as the mathematical relationship between the parameters associated with a particular failure mode at the onset of failure. To assess the impact on pipeline integrity and safety, a limit state approach incorporating probabilistic analysis has been developed. The approach addresses all credible failure modes and takes account of uncertainties in the relevant parameters for each mode. The probabilistic approach takes the limit state approach a step further by describing the parameters as statistical distributions rather than single values. This allows failure probabilities to be computed which are a more meaningful measure of safety and allow areas of over conservatism (or under conservatism) to be identified. It is important to note that the approach is only as good as the limit states used and the data used to construct the distributions. Clearly uncertainties in both of these can exist and the absolute values of the computed probabilities must be viewed with caution. However, the strength of the approach lies in the relative values of the computed probabilities and previous ‘safe’ operation. If a system has a significant operational history with few or no failures and it can be shown that there is little change in the theoretical failure probability associated with a change in operating conditions, it can be inferred that few or no failures will occur in practice. The paper describes the above approach in detail and outlines a study carried out to determine the effect on pipeline integrity of uprating three pipelines from a current maximum operating pressure of 70 bar to an uprated pressure of 85 bar, exceeding the current design criteria. By application of the limit state approach incorporating probabilistic analysis, it is shown that there would be an insignificant change in failure probability as a result of uprating to 85 bar, and hence that the integrity of the pipelines is unimpaired by uprating.

Development of Reliability-Based Criteria for Corrosion Assessment

2018 ◽  
Author(s):  
Riski Adianto ◽  
Maher Nessim ◽  
Dongliang Lu
Keyword(s):  
Failure Probability ◽  
Limit State ◽  
Assessment Criteria ◽  
Ultimate Limit State ◽  
Operating Pressure ◽  
Safety Factors ◽  
Limit States ◽  
Feature Based ◽  
Corrosion Assessment ◽  
Ultimate Limit

Reliability-based corrosion assessment criteria were developed for onshore natural gas and low vapor pressure (LVP) pipelines as part of a joint industry project. The criteria are based on the limit states design (LSD) approach and are designed to achieve consistent safety levels for a broad range of pipeline designs and corrosion conditions. The assessment criteria were developed for two corrosion limit states categories: ultimate limit state, representing large leaks and ruptures; and leakage limit state, representing small leaks. For the ultimate limit state, a safety class system is used to characterize pipelines based on the anticipated severity of failure consequences as determined by pressure, diameter, product, population density and environmental sensitivity. Since the leakage limit state does not result in significant safety or environmental consequences, a single reliability target, applicable for all pipelines at all locations is used. The assessment criteria formulations are characterized by three elements: the equations used to calculate the characteristic demand (i.e. operating pressure) and capacity (i.e. burst pressure resistance at a corrosion feature); the characteristic values of the key input parameters for these formulas (such as diameter, pressure and feature depth); and the safety factors defining the characteristic demand as a ratio of characteristic capacity. The process used to calibrate safety factors and characteristic input parameter values that meet the desired reliability levels is described, and an assessment of the accuracy and consistency of the resulting checks in meeting the reliability targets is included. The assessment criteria include two methods of application: feature-based and section-based. The feature-based method divides the allowable failure probability equally between all features. It is simple to use, but conservative in nature. It is suitable for pipelines with a small number of corrosion features. The section-based method considers the failure probability of the corrosion features in a pipeline section as a group, and ensures that the total group failure probability is below the allowable threshold for the section. This method produces less conservative results than the feature-based method, but it requires more detailed calculations. It is suitable for all pipelines, and is particularly useful for those with a large number of features. The practical implications of the application of these criteria are described in the companion paper IPC2018-78608 Implementation of Reliability-based Criteria for Corrosion Assessment.

Reliability Analysis and Design Suggestion of Concrete Structure Bonded Rebars with Inorganic Material

2010 ◽  
Vol 163-167 ◽  
pp. 3586-3590
Author(s):  
Yu Guo Liang ◽  
Tian Bao Gao ◽  
Yu Deng
Keyword(s):  
Reliability Analysis ◽  
Inorganic Material ◽  
Limit State ◽  
State Equation ◽  
Analysis And Design ◽  
Design Suggestion ◽  
Testing Data ◽  
Calculation Results ◽  
First Order Second Moment ◽  
Second Moment Method

Based on the established limit state equation and connected with a large amount of statistic analysis of testing data, central point law in first order second moment method (FOSM) is adopted to the reliability analysis of bonded rebars with inorganic material. The adhesive anchorage design suggestion of bonded rebars with inorganic material is proposed. By means of comparing the calculation results to experimental results, it can be concluded that the calculation methods of anchorage length can be used to the calculation of designing concrete bonded rebars.

scholarly journals Reliability Analysis of Vertical Well Casing: Comparison of API 5C3 and ISO 10400

2018 ◽  
Vol 203 ◽  
pp. 01012
Author(s):  
Amirah Husna Abdul Halim ◽  
Zahiraniza Mustaffa ◽  
Do Kyun Kim
Keyword(s):  
Reliability Analysis ◽  
Design Method ◽  
Limit State ◽  
Probability Of Failure ◽  
Strength Parameter ◽  
Operating Pressure ◽  
Strength Model ◽  
Burst Strength ◽  
Vertical Well ◽  
Strength Models

Well casings are designed against burst strength pressure. The same formula is used in determining the remaining burst strength pressure of casing that suffered from wear. API 5C3 and ISO 10400 burst strength models are widely used to determine the burst strength pressure and the remaining strength of casing. This paper focus on the comparison of both burst strength models for its reliability assessment for vertical well casing. The limit state design method was used and adapted into this study to calculate the probability of failure for both burst strength models. The reliability analysis for both models is conducted using Monte Carlo simulation. The results show that ISO 10400 burst strength model can predict the probability of failure for vertical well casing when subjected to higher operating pressure compared to API 5C3 burst strength model. ISO 10400 burst strength model can predict probability of failure for higher operating pressure due to adaption of ultimate tensile strength as the strength parameter in the equation whereas API 5C3 has adopt yield strength as the strength parameter in the equation.

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