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.

Influence of Human Error on Structural Reliability

2017 ◽  
Author(s):  
Eric Brehm ◽  
Robert Hertle ◽  
Markus Wetzel
Keyword(s):  
Human Error ◽  
Structural Reliability ◽  
Failure Modes ◽  
Structural Model ◽  
Limit State ◽  
Design Procedure ◽  
Material Strength ◽  
Limit States ◽  
The Impact

In common structural design, random variables, such as material strength or loads, are represented by fixed numbers defined in design codes. This is also referred to as deterministic design. Addressing the random character of these variables directly, the probabilistic design procedure allows the determination of the probability of exceeding a defined limit state. This probability is referred to as failure probability. From there, the structural reliability, representing the survival probability, can be determined. Structural reliability thus is a property of a structure or structural member, depending on the relevant limit states, failure modes and basic variables. This is the basis for the determination of partial safety factors which are, for sake of a simpler design, applied within deterministic design procedures. In addition to the basic variables in terms of material and loads, further basic variables representing the structural model have to be considered. These depend strongly on the experience of the design engineer and the level of detailing of the model. However, in the clear majority of cases [1] failure does not occur due to unexpectedly high or low values of loads or material strength. The most common reasons for failure are human errors in design and execution. This paper will provide practical examples of original designs affected by human error and will assess the impact on structural reliability.

Evaluation of the Effect of Yield to Tensile (Y/T) Ratio on the Structural Integrity of Offshore Pipeline by Limit State Design Approach

2006 ◽  
Author(s):  
Gianluca Mannucci ◽  
Giuliano Malatesta ◽  
Giuseppe Demofonti ◽  
Marco Tivelli ◽  
Hector Quintanilla ◽  
...  
Keyword(s):  
Structural Reliability ◽  
Failure Modes ◽  
Structural Integrity ◽  
Limit State ◽  
Minor Effect ◽  
Offshore Pipelines ◽  
Limit State Design ◽  
A Minor ◽  
Probabilistic Failure Analysis ◽  
Failure Probabilities

Nowadays specifications require strict Yield to Tensile ratio limitation, nevertheless a fully accepted engineering assessment of its influence on pipeline integrity is still lacking. Probabilistic analysis based on structural reliability approach (Limit State Design, LSD) aimed at quantifying the yield to tensile strength ratio (Y/T) influence on failure probabilities of offshore pipelines was made. In particular, Tenaris seamless pipe data were used as input for the probabilistic failure analysis. The LSD approach has been applied to two actual deepwater design cases that have been on purpose selected, and the most relevant failure modes have been considered. Main result of the work is that the quantitative effect of the Y/T ratio on failure probabilities of a deepwater pipeline resulted not so big as expected; it has a minor effect, especially when Y only governs failure modes.

Plastic hinges mechano-reliability analysis in the beams of RC frames structures

2020 ◽  
Vol 17 (5) ◽  
pp. 719-732
Author(s):  
Leyla Bouzid ◽  
Mohand Hamizi ◽  
Naceur-Eddine Hannachi ◽  
Aghiles Nekmouche ◽  
Karim Akkouche
Keyword(s):  
Compressive Strength ◽  
Yield Stress ◽  
Failure Probability ◽  
Limit State ◽  
State Function ◽  
Concrete Compressive Strength ◽  
Plastic Hinges ◽  
Content Type ◽  
Steel Bars ◽  
The Impact

Purpose The purpose of this study is to establish a relationship between causes and effects, the respect of materials characteristics values [concrete compressive strength (fc) and steel yield stress (fy)] and the norms of the construction dispositions value (covers). This study is motivated by the post-seismic damages related to the plastification of the reinforced concrete (RC)/beams sections, named plastic hinges. The results are given by fragility curves representing the failure probability (Pf) of the plastic hinges versus covers value. Design/methodology/approach A mechanical-reliability coupling methodology is proposed and performed on three frames (three, six and nine storey). For each frame, seven covers the value of reinforcement steel bars has been taken into account in the beams. After definition of the limit state function G(x), a process of idea to twin-track; deterministic and probabilistic, is considered. Thus, numerical simulations are carried out under ETABS© software, to extract a soliciting moments Ms(x). Then, ultimate moments Mu(x), the result of reliability approach are calculated using Monte Carlo Simulations. In this step, two random variables; concrete compressive strength in 28 days of age (fc) and steel yield stress (fy), have been studied. Findings In the mechanical study, the results show that, the first plastic hinge appears at the beams for all frames. In the reliability study, the (fy) variation shows that all plastic hinges are in failure domain, nevertheless, the (fc) variation leads to have all sections in the safety domain, except A7 and B7 models. The failure probability (Pf) calculation according to (fc) and (fy) shows that an absolute error of 0.5 cm in the steel bars covers can switch the frame from the safety domain to the failure domain. Originality/value The plastic hinges reliability of the RC/ frame structures is independent on the high of the structure. The (fc) random variable according to the used distribution law does not affect the reliability (safety or failure). However, the impact of the steel yield stress variation (fy) is not negligible. The errors in covers affect considerably the strength of the elements.

scholarly journals Multi-Scale Analysis of Integrated C1 (CH4 and CO2) Utilization Catalytic Processes: Impacts of Catalysts Characteristics up to Industrial-Scale Process Flowsheeting, Part I: Experimental Analysis of Catalytic Low-Pressure CO2 to Methanol Conversion

Catalysts ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 505 ◽  
Author(s):  
Hamid Reza Godini ◽  
Mohammadali Khadivi ◽  
Mohammadreza Azadi ◽  
Oliver Görke ◽  
Seyed Mahdi Jazayeri ◽  
...  
Keyword(s):  
Catalytic System ◽  
Low Pressure ◽  
Operating Conditions ◽  
Industrial Scale ◽  
Operating Pressure ◽  
Scale Analysis ◽  
Methanol Production ◽  
Multi Scale ◽  
The Impact ◽  
Multi Scale Analysis

A multi-aspect analysis of low-pressure catalytic hydrogenation of CO2 for methanol production is reported in the first part (part I) of this paper. This includes an extensive review of distinguished low-pressure catalytic CO2-hydrogenation systems. Specifically, the results of the conducted systematic experimental investigation on the impacts of synthesis and micro-scale characteristics of the selected Cu/ZnO/Al2O3 model-catalysts on their activity and stability are discussed. The performance of the investigated Cu/ZnO/Al2O3 catalysts, synthesized via different methods, were tested under a targeted range of operating conditions in this research. Specifically, the performances of these tested Cu/ZnO/Al2O3 catalysts with regard to the impacts of the main operating parameters, namely H2/CO2 ratio (at stoichiometric -3-, average -6- and high -9- ratios), temperature (in the range of 160–260 °C) and the lower and upper values of physically achievable gas hourly space velocity (GHSV) (corresponding to 200 h−1 and 684 h−1, respectively), were analyzed. It was found that the catalyst prepared by the hydrolysis co-precipitation method, with a homogenously distributed copper content over its entire surface, provides a promising methanol yield of 21% at a reaction temperature of 200 °C, lowest tested GHSV, highest tested H2/CO2 ratio (9) and operating pressure (10 bar). This is in line with other promising results so far reported for this catalytic system even in pilot-plant scale, highlighting its potential for large-scale methanol production. To analyze the findings in more details, the thermal-reaction performance of the system, specifically with regard to the impact of GHSV on the CO2-conversion and methanol selectivity, and yield were experimentally investigated. Moreover, the stability of the selected catalysts, as another crucial factor for potential industrial operation of this system, was tested under continual long-term operation for 150 h, the reaction-reductive shifting-atmospheres and also even after introducing oxygen to the catalyst surface followed by hydrogen reduction-reaction tests. Only the latter state was found to affect the stable performance of the screened catalysts in this research. In addition, the reported experimental reactor performances have been analyzed in the light of equilibrium-based calculated achievable performance of this reaction system. In the performed multi-scale analysis in this research, the requirements for establishing a selective-stable catalytic performance based on the catalyst- and reactor-scale analyses have been identified. This will be combined with the techno–economic performance analysis of the industrial-scale novel integrated process, utilizing the selected catalyst in this research, in the form of an add-on catalytic system under 10 bar pressure and H2/CO2 ratio (3), for efficiently reducing the overall CO2-emission from oxidative coupling of methane reactors, as reported in the second part (part II) of this paper.

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.

Thermo-Mechanical Analysis of a Laser Diode Chip in an Opto-Electronic Package

2009 ◽  
Author(s):  
Satish C. Chaparala ◽  
Lawrence C. Hughes ◽  
Jae Kwak ◽  
Seungbae Park
Keyword(s):  
Laser Diode ◽  
Failure Modes ◽  
Operating Conditions ◽  
Image Correlation ◽  
Fe Model ◽  
Substrate Thickness ◽  
Assembly Process ◽  
Package Design ◽  
The Impact ◽  
Dic Technique

It is a well-known fact that the lasers have wide variety of applications in diverse fields from medicine to communications [1]. Laser packaging involves appropriate materials selection and design to ensure that the laser performance meets the required specifications. In this paper, we present a GaAs based laser diode package design. The package design enables the laser diode chip to withstand the thermo-mechanical strains that are induced during the package assembly process as well as during the operating conditions. Excessive stresses in the chips could causes cracks in the chip. Excessive strains could cause un-desired spectral characteristics in the emitted light [2]. Therefore, the objective is to design a package that is tested and characterized to avoid these failure modes. This study presents numerical and experimental investigation of thermo-mechanical strains induced due to coefficient of thermal expansion (CTE) mismatch between various package components during assembly process. Finite element (FE) analysis is used to predict the displacements, tensile strains and stresses in the chip at various assembly processes. Digital Image Correlation (DIC) technique was used to measure the strains in the laser diode. Earlier, other researchers have used photo-luminescence methods and spectroscopic methods etc to measure packaging induced strains in the laser package [3]–[9]. The authors are not aware of any prior work where the DIC technique is applied on a very small chip for strain measurements Good correlation in displacements and strains was obtained between the model and the measurements, increasing confidence in the model. In addition, experiments were conducted to estimate the fracture strength of the GaAs to predict the chip failure based on the maximum principal stress criterion. The FE model was later used to conduct parametric study to analyze the impact of other factors on the chip stress such as substrate thickness, voids, thermal gradients in the package, surface irregularities in the chip etc. Experiments and model indicated that the designed package was robust enough and does not cause any damage to the chip.

Effects of Various Types of Distribution on Probabilistic Method and FAD

2007 ◽  
Vol 353-358 ◽  
pp. 2561-2564
Author(s):  
Ouk Sub Lee ◽  
Dong Hyeok Kim
Keyword(s):  
Failure Probability ◽  
Probabilistic Method ◽  
Limit State ◽  
Random Variables ◽  
Reliability Estimation ◽  
Probabilistic Methods ◽  
State Function ◽  
Operating Pressure ◽  
Lognormal Distributions ◽  
Reliability Method

The reliability estimation of pipeline is performed in accordance with the probabilistic methods such as the FORM (first order reliability method) and the SORM (second order reliability method). A limit state function has been formulated with help of the FAD (failure assessment diagram). Various types of distribution of random variables are assumed to investigate its effect on the failure probability. It is noted that the failure probability increases with the increase of the dent depth, the operating pressure and the outside radius, and the decrease of the wall thickness. Furthermore it is found that the failure probability for the random variables having the Weibull distribution is larger than those of the normal and the lognormal distributions.

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.

scholarly journals Вплив промислових очищувальних рідин на анодно-окисне захисно-декоративне покриття отримане у розчині хромового ангідриду

2021 ◽  
pp. 117-124
Author(s):  
Олексій Денисович Попов ◽  
Анатолій Іванович Долматов ◽  
Володимир Федорович Сорокін
Keyword(s):  
Oxide Coating ◽  
Operating Conditions ◽  
Water Soluble ◽  
Chemical Compositions ◽  
Operating Pressure ◽  
Washing Machine ◽  
Technological Parameters ◽  
The Stability ◽  
The Impact

The subject of research in this article is the anode-oxide coating of aluminum parts of the hull type of aircraft engine units and aircraft units under the influence of cleaning fluids of different nature and chemical compositions. The purpose of this work is to experimentally test, the effect of different cleaning fluids, under different operating conditions and on different equipment for the stability of the anode-oxide protective coating. Many experiments have been performed on three types of washing machines: jet and immersion washing machine, which works on all types of water-soluble detergents, washing machine cleaning in vacuum or low-pressure environment, uses modified alcohols or hydrocarbon solvents as a washing liquid, and specialized stand for cleaning parts with aviation kerosene, aviation fuel TS-1 or jet A-1. Flushing modes were, covered throughout the range of operation of this equipment. The operating conditions of engines and units and the need to use an anode-oxide coating of parts are determined. The main types of liquids for washing parts are considered. For each of the experiments a special technology of these studies was determined, as technological parameters, parameters that can change and affect the stability of the coating, were set the following temperature, detergent concentration, operating time, operating pressure in the detergent supply system. The change of each of these parameters was, carried out with the fixation of other technological parameters to determine the direct indicators of the impact of each of the parameters and to establish the growth of their impact on the anode-oxide coating. The conditions under which the coating is destroyed and the percentage of its damage from the total surface of the part are determined, and the quality of cleaning the part by particle size distribution and visual method was, also determined. It is determined that the greatest negative effects on the anodic oxide coating in the solution of chromic anhydride are acidic and alkaline water-soluble pore cleaning liquids, so they have the best quality of cleaning from contaminants, for which a range of indicators is determined at which the coating does not deteriorate.

scholarly journals Multiple Failure Modes Reliability Modeling and Analysis in Crack Growth Life Based on JC Method

2017 ◽  
Vol 2017 ◽  
pp. 1-5 ◽  
Author(s):  
YuanTao Sun ◽  
Chao Liu ◽  
Qing Zhang ◽  
XianRong Qin
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Normal Distribution ◽  
Crack Growth ◽  
Failure Probability ◽  
Failure Modes ◽  
Limit State ◽  
State Equations ◽  
Multiple Failure Modes ◽  
Joint Failure

The fatigue crack growth (FCG) phenomenon generally exists in large mechanical structures. Due to the influences of varied kinds of random factors, the safety evaluation of structure in FCG is under great uncertainty. In this paper, based on the reliability theory, the limit state equations of fracture failure and static strength failure were derived firstly, and the parameters in those equations were regarded as random variables that follow the normal distribution or log-normal distribution. According to the limit state equations, the JC method (equivalent normalizing method) was used to calculate the reliability indexes under the different failure modes of structure in every stress cycle. Based on the reliability indexes and correlation of the two failure modes, the joint failure probability was obtained. In the end, a specific computation example was given, and the curve of joint failure probability in multiple failure modes was used for comparison with the result of single failure mode. The results indicated that the reliability analysis based on multiple failure modes was more reasonable, and the evaluation of reliability could be obtained in fatigue crack growth process.

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