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.

Practical Methodology of Predictive Maintenance for Pipelines

2010 ◽  
Author(s):  
S. A. Timashev ◽  
A. V. Bushinskaya
Keyword(s):  
Wall Thickness ◽  
Pipe Wall ◽  
Residual Life ◽  
Real Life ◽  
Life Time ◽  
Predictive Maintenance ◽  
Operating Pressure ◽  
Pipe Material ◽  
Remaining Life ◽  
Corrosion Rates

Predictive maintenance (PdM) is the leading edge type of maintenance. Its principles are currently broadly used to maintain industrial assets [16]. Yet PdM is as yet not embraced by the pipeline industry. The paper describes a comprehensive practical risk based methodology of predictive maintenance of pipelines for different criteria of failure. For pipeline systems the main criterion is integrity. One of the main causes of loss of containment is pipe wall defects which grow in time. Any type of analysis of pipeline state (residual life time, probability of failure (POF), etc.,) is based on the sizes of discovered defects, which are assessed during the ILI or DA. In the developed methodology pipeline strength is assessed using one of the five internationally recognized design codes (the B31G, B31mod, DNV, Battelle, Shell 92). The pipeline POF is calculated by the comprehensive Gram-Charlier-Edgeworth method [14]. Having in mind that the repair actions are executed on particular cross-sections of the pipeline, the POF are calculated for each defect present in the pipeline. When calculating POFs, the defect sizes (depth, length and width), wall thickness and pipe diameter, SMYS of the pipe material, the radial and longitudinal corrosion rates, and operating pressure (OP) are considered random variables each distributed according to its PDF. In the proposed method of PdM of pipelines the remaining life time can be assessed using following criteria: POF = Qth; dd = 80%wt; SMOP = MAOP; ERF = MAOP/SMOP, if ERF ≥ 1, the pipeline needs immediate repair; dd = 100%wt. Here Qth is the ultimate permissible POF, dd is the depth of the most dangerous defect, wt is pipe wall thickness, SMOP is the maximal safe operating pressure SMOP = DF·Pf, MAOP is the Maximum Allowable Operating Pressure, Pf is the failure pressure, DF is the design factor (for B31Gmod DF = 1.39), ERF is the Estimated Repair Factor. The above criteria are arranged in descending order according to the growing level of their severity in time. The prediction of future sizes of growing defects and the pipeline remaining life time are obtained by using consistent assessments of their corrosion rates CRs. In the PdM methodology these CRs may be considered as deterministic, semi-probabilistic or fully stochastic values. Formulas are given for assessing the CRs using results of one ILI, two consecutive ILI, with or without verification measurements, and for the case when several independent types of measurements are used to assess the defect sizes. The paper describes results of implementation of the developed methodology on a real life pipeline. The time to reach each of the limit states given above was calculated, using results of two consecutive ILI divided by a three year interval. Knowledge of these arrival times permits minimizing the maintenance expenditures without creating any threats to its integrity and safety.

Determination of Optimal Reserve between Two Machines in Series with the Repair Time has Change of Distribution after the Truncation Point

GIS Business ◽  
2019 ◽  
Vol 14 (6) ◽  
pp. 577-585
Author(s):  
T. Vivekanandan ◽  
S. Sachithanantham
Keyword(s):  
Real Life ◽  
Random Variable ◽  
Repair Time ◽  
Inventory Level ◽  
Optimal Size ◽  
Truncation Point ◽  
In Series ◽  
Optimal Reserve ◽  
Optimal Inventory Level ◽  
Two Machines

In inventory control, suitable models for various real life systems are constructed with the objective of determining the optimal inventory level.  A new type of inventory model using the so-called change of distribution property is analyzed in this paper. There are two machines M1 and M2  in series and the output of M1 is the input of M2. Hence a reserve inventory between M1 and M2 is to be maintained. The method of obtaining the optimal size of reserve inventory, assuming cost of excess inventory, cost of shortage and when the rate of consumption of M2  is a constant, has already been attempted.  In this paper, it is assumed that the repair time of M1  is a random variable and the distribution of the same undergoes a change of distribution  after the truncation point X0 , which is taken to be a random variable.  The optimal size of the reserve inventory is obtained under the above said  assumption . Numerical illustrations are also provided.

Dynamic performance evaluation of multi – state systems under non – homogeneous continuous time Markov process degradation using lifetimes in terms of order statistics

2017 ◽  
Vol 231 (3) ◽  
pp. 255-264 ◽  
Author(s):  
Funda Iscioglu
Keyword(s):  
Markov Process ◽  
Order Statistics ◽  
Continuous Time ◽  
Dynamic Performance ◽  
Real Life ◽  
State Change ◽  
Transition Rates ◽  
Lifetime Analysis ◽  
Complete Failure ◽  
Effect Of Age

In multi-state modelling a system and its components have a range of performance levels from perfect functioning to complete failure. Such a modelling is more flexible to understand the behaviour of mechanical systems. To evaluate a system’s dynamic performance, lifetime analysis of a multi-state system has been considered in many research articles. The order statistics related analysis for the lifetime properties of multi-state k-out-of-n systems have recently been studied in the literature in case of homogeneous continuous time Markov process assumption. In this paper, we develop the reliability measures for multi-state k-out-of-n systems by assuming a non-homogeneous continuous time Markov process for the components which provides time dependent transition rates between states of the components. Therefore, we capture the effect of age on the state change of the components in the analysis which is typical of many systems and more practical to use in real life applications.

Effect of Lu¨ders Bands on the Bending Capacity of Steel Tubes

2010 ◽  
Author(s):  
Julian F. Hallai ◽  
Stelios Kyriakides
Keyword(s):  
Limit State ◽  
Solution Procedure ◽  
Inhomogeneous Deformation ◽  
Pure Bending ◽  
Steel Tubes ◽  
Deformation Regime ◽  
Bending Capacity ◽  
The Moment ◽  
T Values ◽  
Structural Instabilities

In several offshore applications hot-finished pipe that often exhibits Lu¨ders bands is bent to strains of 2–3%. Lu¨ders banding is a material instability that leads to inhomogeneous plastic deformation in the range of 1–4%. It can precipitate structural instabilities and collapse of the pipe. Experiments and analysis are used to study the interaction of the prevalent structural instabilities under bending with Lu¨ders banding, with the objective of providing guidance to the designer. Pure bending experiments on tubes of various D/t values reveal that Lu¨ders bands result in the development of inhomogeneous deformation in the structure, in the form of coexistence of two curvature regimes. Under rotation controlled bending, the higher curvature zone(s) gradually spreads while the moment remains essentially unchanged. For relatively low D/t tubes with relatively smaller Lu¨ders strain, the whole tube eventually is deformed to the higher curvature, subsequently entering the usual hardening regime where it continues to deform uniformly until the expected limit state is reached. For higher D/t tubes and/or for materials with longer Lu¨ders strain, the structure collapses during the inhomogeneous deformation regime. This class of problems is analyzed using 3D finite elements and an elastic-plastic constitutive model with an up-down-up material response. It will be demonstrated that the solution procedure followed can simulate the experiments with consistency.

Do We Need a Safe Excavation Pressure for Dented Pipelines: How Should it Be Defined?

2018 ◽  
Author(s):  
Muntaseer Kainat ◽  
Doug Langer ◽  
Sherif Hassanien
Keyword(s):  
Fracture Mechanics ◽  
Boundary Conditions ◽  
Structural Reliability ◽  
Limit State ◽  
Stress And Strain ◽  
Operating Pressure ◽  
Fitness For Purpose ◽  
Element Analysis ◽  
Overburden Pressure ◽  
Conflicting Objectives

Pipeline operators’ utmost priority is to achieve high safety measures during the lifecycle of pipelines including effective management of integrity threats during excavation and repair processes. A single incident pertaining to a mechanical damage in a gas pipeline has been reported previously which resulted in one fatality and one injury during investigation. Some operators have reported leaking cracks while investigating rock induced dents. Excavation under full operating pressure can lead to changes in boundary conditions and unexpected loads, resulting in failure, injuries, or fatalities. In the meantime, lowering operating pressure during excavation can have a significant impact on production and operational availability. The situation poses two conflicting objectives; namely, maximizing safety and maximizing operational availability. Current pipeline regulations require that operators have to ensure safe working conditions by depressurizing the line to a level that will not cause a failure during the repair process. However, there are no detailed guidelines on how an operator should determine a safe excavation pressure (SEP) level, which could lead to engineering judgment and subjectivity in determining such safety level. While the pipeline industry relies on well-defined fitness for purpose analyses for threats such as crack and corrosion, there is a gap in defining a fitness for purpose for dents and dents associated with stress riser features in order to set an SEP. Stress and strain based assessment of dents can be used in this matter; however, it requires advanced techniques to account for geometric and material nonlinearity. Additionally, loading and unloading scenarios during excavation (e.g. removal of indenter, overburden pressure, etc.) drive a change in the boundary conditions of the pipe that could lead to leakage. Nevertheless, crack initiation or presence within a dent should be considered, which requires the incorporation of crack geometry and application of fracture mechanics in assessing a safe excavation pressure. Recently, there have been advancements in stress and strain based finite element analysis (FEA) of dents coupled with structural reliability analysis that can be utilized to assess SEP. This paper presents a reliability-based approach to determine a safe excavation pressure for dented liquid pipelines. The approach employs nonlinear FEA to model dents interacting with crack features coupled with uncertainties associated with pipe properties and in-line-inspection information. A fracture mechanics-based limit state is formulated to estimate the probability of failure of dents associated with cracks at different levels of operating pressure during excavation. The application of the developed approach is demonstrated through examples within limited scope. Recommended enhancements and future developments of the proposed approach are also discussed.

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.

scholarly journals Investigation of the structure of cement conglomerates

2021 ◽  
Vol 266 ◽  
pp. 03005
Author(s):  
D. N. Shabanov ◽  
E. Trambitsky ◽  
E. Borovkova
Keyword(s):  
Strain State ◽  
Residual Life ◽  
Experimental Studies ◽  
Cement Stone ◽  
Virtual Model ◽  
Structural Studies ◽  
Acoustic Sensors ◽  
Cement Pastes ◽  
The Moment ◽  
Physical And Chemical

This article describes the structural studies of a cement conglomerate, its evolution from the moment of formation to the loss of operational properties. Physical and chemical phenomena and interactions of various elements of cement stone are considered. The study of its rheology includes creating a virtual model and monitoring the formation of the structure of cement pastes by acoustic emission (AE). The results of combined experimental studies to determine the residual life of cement stone samples using AE and tensometry methods are presented. The authors created a complex for monitoring the stress-strain state of artificial conglomerates, which includes both internal and acoustic sensors.

scholarly journals Secukinumab Loss of Efficacy Is Perfectly Counteracted by the Introduction of Combination Therapy (Rescue Therapy): Data from a Multicenter Real-Life Study in a Cohort of Italian Psoriatic Patients That Avoided Secukinumab Switching

2022 ◽  
Vol 15 (1) ◽  
pp. 95
Author(s):  
Giovanni Damiani ◽  
Giulia Odorici ◽  
Alessia Pacifico ◽  
Aldo Morrone ◽  
Rosalynn R. Z. Conic ◽  
...  
Keyword(s):  
Combination Therapy ◽  
Rescue Therapy ◽  
Therapeutic Option ◽  
Real Life ◽  
Chronic Inflammatory Disease ◽  
Life Study ◽  
Secondary Failure ◽  
The Moment ◽  
Effective Drugs

Since psoriasis (PsO) is a chronic inflammatory disease, patients may experience a drug failure also with very effective drugs (i.e., secukinumab) and, consequently, dermatologists have two therapeutic options: switching or perform a combination therapy (rescue therapy) to save the drug that had decreased its efficacy. At the moment no studies focused on combination/rescue therapy of secukinumab, so we performed a 52-weeks multicenter retrospective observational study that involved 40 subjects with plaque psoriasis that experienced a secondary failure and were treated with combination therapy (ciclosporin (n = 11), MTX (n = 15), NB-UVB (n = 7) and apremilast (n = 7)). After 16 weeks of rescue/combination therapy, PASI and a DLQI varied respectively from 8 [7.0–9.0] and 13 [12.0–15.0], to 3 [2.8–4.0] and 3 [2.0–3.3]), suggesting a significant improvement of daily functionality and quality of life. Results were maintained at 52 weeks. No side effects were experienced during the study. Secukinumab remains a safety and effective drug for PsO patients also in the IL-23 and JAK inhibitors era. The rescue therapy is a valid therapeutic option in case of secukinumab secondary failure.

scholarly journals Tornumonkpe Distribution: Statistical Properties and Goodness of Fit

2021 ◽  
pp. 12-22
Author(s):  
Barinaadaa John Nwikpe
Keyword(s):  
Goodness Of Fit ◽  
Real Life ◽  
Mathematical Expression ◽  
Information Criterion ◽  
Moment Generating Function ◽  
Data Sets ◽  
The Moment ◽  
The One ◽  
Coefficient Of Skewness ◽  
New Distribution

A new sole parameter probability distribution named the Tornumonkpe distribution has been derived in this paper. The new model is a blend of gamma (2,  and gamma(3  distributions. The shape of its density for different values of the parameter has been shown.  The mathematical expression for the moment generating function, the first three raw moments, the second and third moments about the mean, the distribution of order statistics, coefficient of variation and coefficient of skewness has been given. The parameter of the new distribution was estimated using the method of maximum likelihood. The goodness of fit of the Tornumonkpe distribution was established by fitting the distribution to three real life data sets. Using -2lnL, Bayesian Information Criterion (BIC), and Akaike Information Criterion(AIC) as criterial for selecting the best fitting model, it was revealed that the new distribution outperforms the one parameter exponential, Shanker and Amarendra distributions for the data sets used.

Reliability-Based Assessment Method of Buried Pipeline at Fault Crossings

2020 ◽  
Author(s):  
Qian Zheng ◽  
Xiaoben Liu ◽  
Hong Zhang ◽  
Samer Adeeb
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Finite Element Model ◽  
Limit State ◽  
Element Model ◽  
Normal Operation ◽  
Operating Pressure ◽  
Peak Strain ◽  
Highly Nonlinear ◽  
Fault Displacement

Abstract The tectonic fault, which is one of the most common geohazards in field, poses great threat to buried pipe segments. Pipes will process to buckling or fracture due to large strain induced by continuously increasing ground displacements during earthquakes. Therefore, it is imperative to conduct safety analysis on pipes which are buried in seismic areas for the sake of ensuring normal operation. However, the highly nonlinearity of pipe response restricts the proceeding of reliability assessment. In this study, a hybrid procedure combining finite element method and artificial neural network is proposed for reliability-based assessment. First of all, the finite element model is developed on ABAQUS platform to simulate pipe response to strike-slip fault displacements. Thus, the strain demand value (the peak strain value obtained by finite element model in each design case) can be collected for database establishment, which is the preparation for neural network training. Thoroughness of the strain demand database can be achieved by a fully comprehensive calculation with consideration of influencing factors involving pipe diameter and wall thickness, operating pressure, magnitude of fault displacement, intersection angle between pipeline and fault plane, and characteristic value of backfill mechanics. Sequentially, Back Propagation Neural Network (BPNN) with double hidden layers is trained based on the developed database, and the surrogate strain demand prediction model can be obtained after accuracy verification. Hence, the strain-based limit state function can be respectively determined for tensile and compressive conditions. The strain capacity term is simply assumed based on published papers, the strain demand term is naturally superseded by the surrogate BPNN model, and Monte Carlo Simulation is employed to compute the probability of failure (POF). At last, the workability of the proposed approach is tested by a case study in which basic variables are referred to the Second West-to-East natural gas transmission pipeline project. It indicates that ANN is a good solver for reliability problems with implicit limit state functions especially for highly nonlinear problems. The proposed method is capable of computing POFs, which is an exploratory application for reliability research on pipes withstanding fault displacement loads.

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