Search results for "Fault Tree Analysi"

An imprecise Fault Tree Analysis for the estimation of the Rate of OCcurrence Of Failure (ROCOF)

2013

Abstract The paper proposes an imprecise Fault Tree Analysis in order to characterize systems affected by the lack of reliability data. Differently from other research works, the paper introduces a classification of basic events into two categories, namely Initiators and Enablers . Actually, in real industrial systems some events refer to component failures or process parameter deviations from normal operating conditions ( Initiators ), whereas others refer to the functioning of safety barriers to be activated on demand ( Enablers ). As a consequence, the output parameter of interest is not the classical probability of occurrence of the top event, but its Rate of OCcurrence (ROCOF) over a s…

Safety analysis in the LBE-Cooled XADS plant through an integrated use of HAZOP, FAULT TREE and thermalhydraulic transient analyses

2004

A detailed description of possible accidental scenarios, with their frequency of occurrence and their consequences, taking into account both internal and external causes that might contribute to them, can be attained by using the most important risk analysis methodologies (HAZard and OPerability studies, HAZOP; Event Tree, ET; Fault Tree, FT; etc.). As it is known, the Fault Tree methodology is aimed at the evaluation of the frequency of an undesired accidental event (Top Event, TE), and is used to describe this one as a combination of primary events identified, for example, by a HAZOP analysis [1]. However, the classic HAZOP analysis, while allowing to perform an exhaustive study of the ex…

Trattamento dell'incertezza epistemica nell'analisi affidabilistica

ATLAS technical coordination expert system

2019

When planning an intervention on a complex experiment like ATLAS, the detailed knowledge of the system under intervention and of the interconnection with all the other systems is mandatory. In order to improve the understanding of the parties involved in an intervention, a rule-based expert system has been developed. On the one hand this helps to recognise dependencies that are not always evident and on the other hand it facilitates communication between experts with different backgrounds by translating between vocabularies of specific domains. To simulate an event this tool combines information from different areas such as detector control (DCS) and safety (DSS) systems, gas, cooling, vent…

Reliability Analysis of Systems Containing Complex Control Loops

1986

Abstract Many Process Plants employ complex control and trip systems to improve process safety. Reliability prediction requires determination of the failure mechanisms followed by quantification of the failure rates. The fault tree technique is often used for reliability prediction. Fault tree construction is a skilled task and can be complex for systems containing multiple protective devices. The paper compares 3 approaches to the problem of fault tree construction. The problems of quantification and common mode failure is also considered.

Epistemic uncertainty in fault tree analysis approached by the evidence theory

2012

Abstract Process plants may be subjected to dangerous events. Different methodologies are nowadays employed to identify failure events, that can lead to severe accidents, and to assess the relative probability of occurrence. As for rare events reliability data are generally poor, leading to a partial or incomplete knowledge of the process, the classical probabilistic approach can not be successfully used. Such an uncertainty, called epistemic uncertainty, can be treated by means of different methodologies, alternative to the probabilistic one. In this work, the Evidence Theory or Dempster–Shafer theory (DST) is proposed to deal with this kind of uncertainty. In particular, the classical Fau…

TREEZZY2, a Fuzzy Logic Computer Code for Fault Tree and Event Tree Analyses

2004

In conventional approach to reliability analysis using logical trees methodologies, uncertainties in system components or basic events failure probabilities are approached by assuming probability distribution functions. However, data are often insufficient for statistical estimation, and therefore it is required to resort to approximate estimations. Moreover, complicate calculations are needed to propagate uncertainties up to the final results. In our work, in order to take account of the uncertainties in system failure probabilities, the methodology based on fuzzy sets theory is used both in fault tree and event tree analyses. This paper just presents our work in this issue, which resulted…

Risk Assessment and Analysis

2014

Once threats are identified, they must be assessed or evaluated, which is the objective of this chapter. There is usually a large number of threats, making it impossible or unprofitable to analyze them all, meaning selection of the threats that will be addressed is important. It is a decision-making process; an example is proposed and solved by one of the many techniques available. The chapter proposes a very standard requested study, which is the assessment of the economic and financial risks of a project. This is done through a real-life-example, followed by another appraisal, this time devoted to economic issues, as well as another for transportation, introducing the important concept of…

A New Approach for the Reliability of Vehicular Ad Hoc Networks

2018

Vehicular ad hoc networks (VANET), a subset of Mobile Ad hoc Networks (MANETs), is a wireless communication technology applied to transportation, referring to a set of smart vehicles used on the road. These vehicles provide communication services among one another (V2V) or with Road Side Infrastructure (V2I). The main benefits of VANET are enhancing road safety, reducing energy use and emissions, and giving information services. Reliability is one of the most critical issues related to VANET since the information transmitted is distributed in an open access environment. We focused in this paper, on the reliability of VANET as a function of reliable hardware and their functionality taking in…

Operational and financial effectiveness of e-collaboration tools in supply chain integration

2004

This paper develops a comprehensive model of supply chain integration and uses it to analyze and assess the operational and financial effectiveness of different e-collaboration tools at various levels of supply chain integration. This model is also used to evaluate the importance of the sequence in which e-collaboration tools are adopted in supply chain integration. Computational results from a validated system dynamics simulation model with different implementation sequences of e-collaboration tools and different financial scenarios show that local financial constraints can also severely impact operational and financial performance of the entire supply chain. (C) 2003 Elsevier B.V. All rig…