scholarly journals The Forecasting Residual Life of Corroding Pipeline based on Semi-Probabilistic Method

2010 ◽  
Vol 1 (2) ◽  
pp. 1-6 ◽  
Author(s):  
Noor N.M. ◽  
Yahaya N. ◽  
Ozman N.A.N ◽  
Othman S.R.
Keyword(s):  
Standard Deviation ◽  
Residual Life ◽  
Probabilistic Method ◽  
Time To Failure ◽  
Operating Pressure ◽  
Safety Factors ◽  
Internal Corrosion ◽  
Maintenance Schedule ◽  
Operating Strategies ◽  
Pipeline Failures

In general, the prediction of pipeline residual life can effectively assist pipeline operators to evaluate future safe operating strategies including re-inspection and appropriate maintenance schedule. As a result it can minimize the possibility of pipeline failures until it reaches its designed lifetime. A semi-probabilistic methodology for predicting the remaining strength of submarine pipelines subjected to internal corrosion based on Recommended Practice RP-F101 by Det Norske Veritas (DNV) is described in this paper. It is used to estimate the maximum allowable operating pressure of the corroding pipelines based on series of pigging data, which represents corrosion pit location and dimension. The introduction of partial safety factors in the DNV code to minimise the effect of uncertainties due to the defect sizing has improved the reliability of pipeline assessment methodology. Nevertheless, the code is still regarded as a fully deterministic approach due to its incapability of predicting the remaining life of corroded pipeline. Thus, we have added prediction capabilities to the capacity equation by introducing a standard deviation model of future defect depth. By doing so, the variation of safety factors of the capacity equation can be fully manipulated in which prediction of future pipeline residual life becomes feasible. The paper demonstrates calculation and prediction of pipeline residual life subjects to internal corrosion. The results shows the standard deviation of corrosion parameter affected the value of partial safety factor as corrosion progressing, hence amplify the conservatism of time to failure.

Control of Internal Pipeline Corrosion Based Upon an Evaluation of Risk: A Case for Change

1996 ◽  
Author(s):  
David J. Richardson
Keyword(s):  
Oil And Gas ◽  
Management Strategies ◽  
Hydraulic Simulation ◽  
Internal Corrosion ◽  
Maintenance Schedule ◽  
Root Cause ◽  
Pipeline Segment ◽  
Regulatory Bodies ◽  
Pipeline Failures

Pipeline failures attributed to internal corrosion are increasing throughout the oil and gas producing industry(1) suggesting that commonly accepted practices continue to allow failures to occur. The article describes a “Maintenance Management System” for prevention of internal corrosion of pipelines that provides advances compared with conventional management strategies. The “System” recognizes and addresses root-cause issues that contribute to internal pipeline damage and failures. It provides a genuine improvement in pipeline confidence to the Management of operating companies, and the Regulatory bodies. The “System” combines pipeline hydraulic simulation technology with corrosion engineering science to assess the severity of the operational hazards within each pipeline segment. Besides providing a numerical ranking of the operational risk, the “System” generates a maintenance schedule appropriate to the assessment. What is more important, the day-to-day schedule is updated immediately upon any change in the corrosion hazard profile. By means of a Case Study, the article demonstrates how, in our opinion, improvements in both information management, and scheduling of maintenance activities can narrow the scope of investigative projects, while at the same time provide enhanced confidence in pipeline integrity.

Texture and Microstructure Effects on Electromigration Behavior of Aluminum Metallization

1991 ◽  
Vol 225 ◽  
Author(s):  
D. B. Knorr ◽  
K. P. Rodbell ◽  
D. P. Tracy
Keyword(s):  
Grain Size ◽  
Standard Deviation ◽  
Pure Aluminum ◽  
Time To Failure ◽  
X Ray Diffraction ◽  
Aluminum Films ◽  
Failure Data ◽  
Transmission Electron ◽  
Aluminum Metallization ◽  
Microstructure Effects

ABSTRACTPure aluminum films are deposited under a variety of conditions to vary the crystallographic texture. After patterning and annealing at 400°C for 1 hour, electromigration tests are performed at several temperatures. Failure data are compared on the basis of t50 and standard deviation. Microstructure is quantified by transmission electron microscopy for grain size and grain size distribution and by X-ray diffraction for texture. A strong (111) texture significantly improves the electromigration lifetime and decreases the standard deviation in time to failure. This improvement correlates with both the fraction and sharpness of the (111) texture component.

Markovian Analysis of Aging Distributed Systems Remaining Life

2014 ◽  
Author(s):  
Anna Bushinskaya ◽  
Sviatoslav Timashev
Keyword(s):  
Distributed Systems ◽  
Markov Process ◽  
Residual Life ◽  
Limit State ◽  
Real Life ◽  
Random Variable ◽  
Operating Pressure ◽  
Remaining Life ◽  
Failure Pressure ◽  
The Moment

Correct assessment of the remaining life of distributed systems such as pipeline systems (PS) with defects plays a crucial role in solving the problem of their integrity. Authors propose a methodology which allows estimating the random residual time (remaining life) of transition of a PS from its current state to a critical or limit state, based on available information on the sizes of the set of growing defects found during an in line inspection (ILI), followed by verification or direct assessment. PS with many actively growing defects is a physical distributed system, which transits from one physical state to another. This transition finally leads to failure of its components, each component being a defect. Such process can be described by a Markov process. The degradation of the PS (measured as monotonous deterioration of its failure pressure Pf (t)) is considered as a non-homogeneous pure death Markov process (NPDMP) of the continuous time and discrete states type. Failure pressure is calculated using one of the internationally recognized pipeline design codes: B13G, B31Gmod, DNV, Battelle and Shell-92. The NPDMP is described by a system of non-homogeneous differential equations, which allows calculating the probability of defects failure pressure being in each of its possible states. On the basis of these probabilities the gamma-percent residual life of defects is calculated. In other words, the moment of time tγ is calculated, which is a random variable, when the failure pressure of pipeline defect Pf (tγ) > Pop, with probability γ, where Pop is the operating pressure. The developed methodology was successfully applied to a real life case, which is presented and discussed.

Substantiation of probabilistic safety factors as a factor for optimizing the metal consumption of pipelines and the permissible operating pressure

2021 ◽  
pp. 364-371
Author(s):  
Юрий Григорьевич Матвиенко ◽  
Дмитрий Александрович Кузьмин ◽  
Владимир Васильевич Зацаринный ◽  
Максим Сергеевич Пугачев ◽  
Владимир Вячеславович Потапов
Keyword(s):  
Safety Factor ◽  
Probability Of Failure ◽  
Fracture Probability ◽  
Operating Pressure ◽  
Pipe Steels ◽  
Safety Factors ◽  
Metal Consumption ◽  
Load Variation ◽  
Coefficients Of Variation ◽  
The Given

Проведен анализ влияния коэффициентов вариации сопротивления материала разрушению и коэффициентов вариации нагрузки на вероятность разрушения и, следовательно, на коэффициенты запаса по характеристикам сопротивления материала разрушению при заданных показателях вероятности разрушения. Снижение неопределенности в условиях нагружения и повышение качества материала позволяют снизить коэффициенты запаса по пределу текучести и вязкости разрушения для заданных целевых показателей безопасности. На примере трубных сталей марок Ст 20 и 16ГС показана возможность снижения коэффициента запаса по пределу текучести до значений n = 1,45 при коэффициенте вариации нагрузки 0,1 и сохранении целевого показателя безопасности в терминах вероятности разрушения на уровне 10. Возможность снижения коэффициентов запаса по пределу текучести и вязкости разрушения при заданных целевых показателях безопасности в терминах вероятности разрушения позволяет оптимизировать металлоемкость и максимальные допустимые давления в эксплуатируемых трубопроводах. The analysis of the influence of the coefficients of variation of the material resistance and the coefficients of the load variation on the probability of failure as well as on the safety factors for the characteristics of the material resistance to failure has been done at given indicators of the probability of failure. Reducing uncertainty under loading conditions and improving material quality allow reducing the safety factors against fracture and collapse for given targets safety. Using the example of pipe steels of grades St 20 and 16GS, it seems possible to reduce the safety factor against collapse up to 1.45 with a load variation coefficient of 0.1 and maintaining the safety target in terms of the fracture probability at the level of 10. The possibility of reducing the safety factors against collapse and fracture at the given target safety indicators in terms of the fracture probability allows optimizing the metal consumption and the maximum allowable pressures in the operating pipelines.

scholarly journals A modified fouling index (MFI40) and fouling predicting approach for ultrafiltration of secondary effluents

2018 ◽  
Vol 9 (1) ◽  
pp. 67-82 ◽  
Author(s):  
B. J. Cai ◽  
I. Baudin ◽  
H. Y. Ng
Keyword(s):  
Standard Deviation ◽  
Treatment Process ◽  
Pilot Scale ◽  
Operating Pressure ◽  
Combined Effects ◽  
Positive Role ◽  
Secondary Effluents ◽  
Pre Treatment ◽  
Modified Fouling Index ◽  
Turbidity Increase

Abstract Fouling indices for evaluating fouling propensity of secondary effluents (SEF) as feed of ultrafiltration (UF) systems are important parameters for the design and operation of the UF process. However, limited fouling indices have been developed and applied for UF feedwater. This study (i) established a modified UF fouling index (MFI40) by raising operating pressure from 30 psi in a traditional MFI test to 40 psi. Standard deviation of MFI40 tests was lower than that of traditional MFI by 68.6%, indicating better stability and repeatability of MFI40. It (ii) investigated the combined effects of UF feedwater characteristics on MFI40. Biopolymers and turbidity played a dominant and secondary positive role in the MFI40, respectively. The effect of conductivity on MFI40 changed from positive to negative with a turbidity increase. It also (iii) validated the MFI40 in both laboratory- and pilot-scale UF membrane units, and UF fouling rates were linearly correlated to the MFI40 of their feeds, and (iv) explored the practical use of the MFI40. It was applied to determine the maximum allowable UF feedwater quality (MFI40max), which could be used to select an appropriate pre-treatment process. A fouling predicting model was established based on the feedwater MFI40 and the operating flux, with an average predicting error of 26.8%.

Hydrostatic Retesting of Existing Pipelines

1984 ◽  
Vol 106 (3) ◽  
pp. 362-368
Author(s):  
J. F. Kiefner ◽  
T. P. Forte
Keyword(s):  
Growth Rate ◽  
Time To Failure ◽  
Operating Pressure ◽  
Pipe Material ◽  
Rate Data ◽  
Time Intervals ◽  
Large Pressure ◽  
Pressure Cycle ◽  
Long Time ◽  
Test Pressure

An analytical model is presented for predicting hydrostatic retest intervals in liquid pipelines which are subjected to frequent large pressure cycles. The model utilizes pressure cycle history, hydrostatic test history, and fatigue crack growth rate data for the pipe material to calculate time to failure for the largest possible defect which could have survived a previous hydrostatic test. An example problem is described which shows the value of maximizing the margin between test pressure and operating pressure in order to achieve long time intervals between tests.

Analysis of the Partial Safety Factor Method Using Probabilistic Techniques

2010 ◽  
Author(s):  
B. A. Lindley ◽  
P. M. James
Keyword(s):  
Probabilistic Method ◽  
Probability Of Failure ◽  
Safety Factors ◽  
First Order Reliability Method ◽  
First Order ◽  
Target Probability ◽  
Reliability Method ◽  
Input Parameters ◽  
Partial Safety Factors ◽  
Hand Calculation

Partial Safety Factors (PSFs) are scaling factors which are used to modify the input parameters to a deterministic fracture mechanics assessment in order to consider the effects of variability or uncertainty in the values of the input parameters. BS7910 and SINTAP have adopted the technique, both of which use the First Order Reliability Method (FORM) to derive values for PSFs. The PSFs are tabulated, varying with the target probability of failure, p(F), and the Coefficient of Variance (COV) of the variable. An accurate assessment of p(F) requires a probabilistic method with enough simulations. This has previously been found to be time consuming, due to the large number of simulations required. The PSF method has been seen as a quick way of calculating an approximate, conservative value of p(F). This paper contains a review of the PSF method, conducted using an efficient probabilistic method called the Hybrid probabilistic method. The Hybrid probabilistic method is used to find p(F) at a large number of assessment points, for a range of different PSFs. These p(F) values are compared to those obtained using the PSF method. It is found that the PSF method was usually, and often extremely, conservative. However there are also cases where the PSF method was non-conservative. This result is verified by a hand calculation. Modifications to the PSF method are suggested, including the establishment of a minimum PSF on each variable to reduce non-conservatisms. In light of the existence of efficient probabilistic techniques, the non-conservatisms that have been found in the PSF method, coupled with the impracticality of completely removing these non-conservatisms, it is recommended that a full probabilistic assessment should generally be performed.

Reliability Estimation for PVC Pipe Using Probability Theory and Stress Intensity Factor

2008 ◽  
Author(s):  
O. S. Lee ◽  
D. H. Kim ◽  
H. M. Kim ◽  
H. B. Choi
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Wall Thickness ◽  
Failure Probability ◽  
Probabilistic Method ◽  
Reliability Estimation ◽  
State Function ◽  
Operating Pressure ◽  
Reliability Method

In this paper, the reliability estimation of Polyvinyl chloride (PVC) pipelines is performed by utilizing the probabilistic method, which accounts for the uncertainties in the load and resistance parameters in the limit state function (LSF). The LSF is formulated with the help of fracture control concept including the stress intensity factor (SIF) for the pipeline having crack or crack like defects. The common cracks found at pipeline can be assumed as semi-elliptical shape and the main load is hoop stress due to the internal pressure. The FORM (first order reliability method) and the SORM (second order reliability method) are carried out to estimate the failure probability of pipeline utilizing the SIF for semi-elliptical crack. The reliability is assessed using this failure probability. It is found that the failure probability increases with the operating pressure, and the decrease of the pipeline wall thickness, and the increase of the crack depth, the crack length, the outside diameter of pipeline. The failure probability increases when the initial crack approaches to a semi-circle shape of crack and the failure probability steeply increases at the ratios of larger than 0.5 of a/t and larger than 30 of D/t. Moreover, it is recognized that the effects of the fracture toughness and the pipe wall thickness on the failure probability are the significant one.

k-OUT-OF-n SYSTEM WITH SELF-LOOP UNITS

2005 ◽  
Vol 12 (01) ◽  
pp. 61-73 ◽  
Author(s):  
K. JENAB ◽  
B. S. DHILLON
Keyword(s):  
Standard Deviation ◽  
Generating Function ◽  
Analytical Approach ◽  
Failure Detection ◽  
Moment Generating Function ◽  
System Failure ◽  
Time To Failure ◽  
Flow Graph ◽  
Recovery Mechanisms

This paper presents an analytical approach for a k-out-of-n system with units having the failure detection, isolation, and recovery mechanisms. The approach uses the flow-graph concept and moment generating function (MGF) to analyze the reliability of the k-out-of-n system with self-loop units. This newly developed analytical approach provides the probability of system failure, system mean, and standard deviation time to failure. A solved example is presented to demonstrate the application of the approach.

RELIABILITY PROPERTIES OF MEAN TIME TO FAILURE IN AGE REPLACEMENT MODELS

2010 ◽  
Vol 17 (01) ◽  
pp. 15-26 ◽  
Author(s):  
G. ASHA ◽  
N. UNNIKRISHNAN NAIR
Keyword(s):  
Residual Life ◽  
Stochastic Orders ◽  
Mean Residual Life ◽  
Time To Failure ◽  
Mean Time To Failure ◽  
Replacement Model ◽  
The Mean ◽  
Age Replacement ◽  
The Relationship ◽  
Mean Time

In this article some properties of the mean time to failure in an age replacement model is presented by examining the relationship it has with hazard (reversed hazard) rate and mean (reversed mean) residual life functions. An ordering based on mean time to failure is used to examine its implications with other stochastic orders.

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