scholarly journals Quantitative Risk Assessment of Biogas Plant – Determination of Assumptions and Estimation of Selected Top Event

2019 ◽  
Author(s):  
Petr Trávníček ◽  
Luboš Kotek ◽  
Tomáš Koutný ◽  
Tomáš Vítěz
Keyword(s):  
Risk Assessment ◽  
Chemical Industry ◽  
Fault Tree Analysis ◽  
Quantitative Risk Assessment ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Hazardous Chemical ◽  
Biogas Plants

Biogas plants are a specific facility from the QRA (Quantitative Risk Assessment) methodologies' point of view, especially in the case of the determination of the event frequency of accident scenarios for biogas leakage from a gas holder and subsequent initiation. QRA methodologies determine event frequencies for different types of accident events related to vessels made of steel. Gas holders installed at biogas plants are predominantly made of other materials and are often integrated with the fermenter. It is therefore a specific type of gas holder, differing from that which is commonly used in the chemical industry. In addition, long-term experience is not available for the operation of biogas plants, unlike in the chemical industry. The event frequencies listed in the QRA methodologies are not relevant for the risk assessment of biogas plants. This work is focused on setting the prerequisites for QRA of biogas storage, including for example: information on hazardous chemical substances occurring at biogas plants, their classification, and information on the construction of integrated gas holders. For the purpose of the work, a scenario was applied where the greatest damage (to life or property) is expected. This scenario is the leakage of the total volume of hazardous gas substance from the gas holder and subsequent initiation. Based on this information, a "tree" was processed for "Fault Tree Analysis" (FTA), and frequencies were estimated for each event. Thereafter, an "Event Tree Analysis" was carried out. This work follows up on a discussion by experts on the determination of scenario frequencies for biogas plants that was conducted in the past.

scholarly journals Methodology for tunnel risk assessment using fault and event tree analysis

2021 ◽  
Author(s):  
Zlatko Zafirovski ◽  
Vasko Gacevski ◽  
Zoran Krakutovski ◽  
Slobodan Ognjenovic ◽  
Ivona Nedevska
Keyword(s):  
Risk Assessment ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Economic Consequences ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Geological Conditions ◽  
Hazard And Risk ◽  
Complex Solutions

The intense demand and construction of tunnels is accompanied by uncertainties. The reason for appearance of uncertainties are the complex solutions and conditions for these structures. Location and dimensions are becoming more challenging, and the construction is predicted in complexed geological conditions, leading to application of new approaches, methodologies and technologies by the engineers. Most of the uncertainties and unwanted events in tunnelling occur in the construction phase, which generally leads to economic consequences and time losses. For easier handling of the uncertainties, they should be anticipated and studied within a separate part of each project. One of the newer approaches to dealing with uncertainties is hazard and risk assessment and defining ways to deal with them i.e. management. Hazards and risks can be analysed qualitatively and quantitatively. The quantitative analysis, examines the causes and consequences in more detail way and gives explanation of the dependencies. With the quantitative approach, a more valuable information for decision-making can be provided. There are various models and methods used for the quantification of hazards and risks. This paper presents a methodology in which the fault tree analysis and event tree analysis are used in combination to obtain quantitative results. The fault tree analysis is used for assessment of various hazards and the different ways and reasons that cause them. The event tree analysis is a method for assessing the possible scenarios, which follow after a certain hazard i.e. the consequences that may occur in the project. These trees represent graphic models combined with a mathematical (probabilistic) model, which give the probability of occurrence of the risks.

scholarly journals Ανάπτυξη και εφαρμογή μεθοδολογίας εκτίμησης διακινδύνευσης σε ναυπηγεία

2015 ◽  
Author(s):  
Νικόλαος Φραγκιαδάκης
Keyword(s):  
Fuzzy Inference System ◽  
Fuzzy Inference ◽  
Fault Tree Analysis ◽  
Quantitative Risk Assessment ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Inference System ◽  
Tree Analysis ◽  
Neuro Fuzzy ◽  
Bow Tie

Στόχος αυτής της διατριβής είναι η δημιουργία μοντέλου που θα οδηγεί σε μια Ποσοτική Εκτίμηση Επαγγελματικής Διακινδύνευσης (Quantitative Risk Assessment, QRA) εργαζομένων στην ναυπηγική και ναυπηγοεπισκευαστική βιομηχανία με γνώμονα το εργατικό ατύχημα, επιχειρώντας να συμβάλλει στην αντιμετώπιση ενός προβλήματος που έχει σημαντικές κοινωνικές αλλά και οικονομικές διαστάσεις. Ακολουθήθηκαν δύο ανεξάρτητοι οδοί που συμπληρώνουν η μία την άλλη.Η πρώτη οδός οδήγησε στην ανάπτυξη ενός Αναλυτικού Μοντέλου, ικανό να περιγράφει τους μηχανισμούς σύνδεσης μεταξύ αιτίου- αιτιατού - συνεπειών εργατικών ατυχημάτων σε ναυπηγικές εργασίες και να οδηγεί υπό προϋποθέσεις σε μια ολοκληρωμένη QRA. Το μοντέλο στηρίχθηκε στον εντοπισμό και στην αξιολόγηση των πηγών κινδύνου, καθώς και άλλων επιβαρυντικών παραγόντων μέσα στο εργασιακό περιβάλλον ενός ναυπηγείου. Τεχνικές χρήσης επαγωγικών μοντέλων όπως τα δέντρα γεγονότων (Event Tree Analysis, ETA) και τα δέντρα σφαλμάτων (Fault Tree Analysis, FTA) χρησιμοποιήθηκαν. Τα επαγωγικά μοντέλα συνδέθηκαν τελικά σε μια ολοκληρωμένη δομή “BOW TIE”, στην οποία απεικονίζεται σαφώς η σχέση των γενεσιουργών αιτιών και των επιβαρυντικών παραγόντων που δύναται να οδηγήσουν στη δημιουργία ενός συμβάντος, καθώς και η πορεία από το συμβάν στις πιθανές συνέπειες μέσω των αμβλυντικών παραγόντων που συνθέτουν τα ανεξάρτητα επίπεδα προστασίας (Independent Layers of Protection, ILPs). Έτσι παρίστανται οι παράγοντες που συγκροτούν τη διακινδύνευση, δηλαδή η πιθανότητα ενός συμβάντος αφενός και οι πιθανές συνέπειες αφετέρου. Για την καλύτερη κατανόηση και τεκμηρίωση του μοντέλου διενεργήθηκαν τεχνικές ανάλυσης και αναγνώρισης κινδύνου για συγκεκριμένες χαρακτηριστικές περιπτώσεις (HAZID), κατασκευάστηκαν διαγράμματα ροής για αυτές τις περιπτώσεις και αριθμητικό παράδειγμα υπολογισμού της διακινδύνευσης για μια εκ των περιπτώσεων.Η δεύτερη οδός οδήγησε στην δόμηση ενός έμπειρου συστήματος, στηριζόμενου σε κανόνες ασαφούς λογικής και ασαφούς συμπερασμού, που χρησιμοποιεί την παρεχόμενη πληροφορία από δεδομένα εργατικών ατυχημάτων στη ναυπηγική βιομηχανία, τα οποία έχουν συγκεντρωθεί από ναυπηγοεπισκευαστικές μονάδες, μέσω της χρήσης στατιστικής ανάλυσης και με τη χρήση υπολογιστικών τεχνικών soft computing. Επιλέχθηκε η δημιουργία ενός «Ασαφούς Συστήματος Συμπερασμού» (Fuzzy Inference System, FIS) που στηρίζεται στα προσαρμοζόμενα νευρωνικά δίκτυα (Adaptive Neural Networks, AN). Τα καταγεγραμμένα δεδομένα στοιχεία υπέστησαν στατιστική επεξεργασία και καθορίστηκαν οι παράμετροι και τα δεδομένα για την τροφοδότηση, την εκπαίδευση και τον έλεγχο των αποτελεσμάτων του Προσαρμοζόμενου Νευρωνικού Ασαφούς Συστήματος Συμπερασμού (Adaptive Neuro-Fuzzy Inference System ANFIS).Το μοντέλο “BOW TIE” αποδείχθηκε ικανό να οδηγήσει σε ποιοτικά συμπεράσματα όπως ο εντοπισμός των πηγών κινδύνου, των επιβαρυντικών αλλά και των αμβλυντικών παραγόντων αλλά και να τεκμηριώσει ποσοτικά κάθε μέτρο βελτίωσης της ασφάλειας με στόχο τη μείωση της διακινδύνευσης.Το μοντέλο ANFIS αποδεδείχθηκε μια εφικτή μέθοδος προσομοίωσης της πολύπλοκης σχέσης μεταξύ των παραμέτρων που εμπλέκονται σε ένα εργατικό ατύχημα στη ναυπηγική βιομηχανία, εκμεταλλευόμενο ήδη υπάρχοντα και κατάλληλα στατιστικά επεξεργασμένα ιστορικά στοιχεία εργατικών ατυχημάτων, αποτελώντας ένα εργαλείο ικανό να κάνει προβλέψεις και να οδηγεί σε ασφαλή συμπεράσματα, σε μικρό υπολογιστικό χρόνο.

DAM RISK ASSESSMENT USING THE EVENT TREE ANALYSIS AND BAYESIAN NETWORKS

2019 ◽  
Author(s):  
RAFAE ANTONIO BRISEÑO-RAMIRO ◽  
VÍCTOR HUGO ALCOCER-YAMANAKA ◽  
ADRIÁN PEDROZO-ACUÑA ◽  
JOSÉ AGUSTIN BREÑA-NARANJO ◽  
RAMÓN DOMÍNGUEZ-MORA
Keyword(s):  
Risk Assessment ◽  
Bayesian Networks ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Dam Risk

Semi-Supervised Machine Learning Algorithms for Classifying the Imbalanced Protocol Flows

2014 ◽  
Vol 536-537 ◽  
pp. 809-814
Author(s):  
Lin Lin Li ◽  
Xiao Yi Zhang ◽  
Xia Zhang ◽  
Qing Li
Keyword(s):  
Fault Tree Analysis ◽  
Machine Learning Algorithms ◽  
Supervised Machine Learning ◽  
Event Tree ◽  
Level Crossing ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Minimal Cut Set ◽  
Risk Event ◽  
Precautionary Measures

The collision that between a car and a train is the main type of accidents in the case railway level-crossing, which is proved by the arrangement diagram analysing. The fault tree analysis and the event tree analysis are used to assess the level of the risk of the level-crossing quantificationally. Some conclusions can be drawn: the collision of the railway level-crossing that between a car and a train will happen 2.552 in a year, which can bring 0.061 equivalent fatalities. This paper puts forward some precautionary measures that based on the minimal cut set of the collision of the accident and the most probable or the highest risk event.

Risk Assessment in Bridge Construction Projects Using Fault Tree and Event Tree Analysis Methods Based on Fuzzy Logic

2015 ◽  
Vol 1 (3) ◽  
Author(s):  
Gholamreza Abdollahzadeh ◽  
Sima Rastgoo
Keyword(s):  
Fuzzy Logic ◽  
Traditional Approach ◽  
Fault Tree ◽  
Fault Tree Analysis ◽  
Mitigation Strategies ◽  
Fuzzy Arithmetic ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Risk Event

In this paper, interruption risk in construction activities of bridge projects is assessed in order to identify the main causes of its occurrence and also to determine the potential outcomes resulted from the risk occurrence. To do this, fault tree and event tree analysis (ETA) methods are applied. As the application of the traditional approach of these two methods is difficult in many cases due to limited access to information, fuzzy arithmetic can be considered as a useful tool. In this research, first, fault tree structure is created according to consequences resulted from the Delphi method. Then, the probability of risk occurrence is calculated by applying fault tree analysis (FTA) based on fuzzy logic. By establishing the structure of fault tree related to the failure risk of mitigation strategies, the main causes relating to failure of strategies are identified. The structure of the event tree is created using the obtained results; moreover, the expected monetary value (EMV) of risk event is computed. Finally, to validate the results obtained, a model is created by Monte Carlo simulation and then the results obtained by applying the two methods are compared. The EMV of the risk event evaluated in this paper is determined to be 9.93% of the project baseline cost.

A Survey of Early Design Risk and Reliability Methods and Their Impediments to Move Into Practice

2012 ◽  
Author(s):  
Bryan M. O’Halloran ◽  
Robert B. Stone ◽  
Irem Y. Tumer
Keyword(s):  
Research Methods ◽  
Failure Modes ◽  
Fault Tree Analysis ◽  
Event Tree ◽  
Reliability Engineering ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Early Design ◽  
Reliability Methods ◽  
Reliability Block Diagrams

This research surveys early design risk and reliability methodologies and discusses the impediments of moving these research methods into practice. Reliability engineering techniques exist primarily to help engineers better meet the needs of customers by extending design life and reducing the number of failures observed throughout the intended life. These efforts look at system components and functions, critical events, failure modes, and system characteristics to assess risk and reliability during the early design phase before detailed design has begun. Surveying early design reliability to identify underdeveloped areas of research contributes to an ongoing effort to increase the presence of reliability engineering earlier in design. In addition, this improves a researchers’ understanding of key consideration that need to be addressed during the development of the research so that it is useful in practice. Throughout this paper, four fundamental methods are identified and described including Event Tree Analysis, Fault Tree Analysis, Reliability Block Diagrams, and Failure Modes and Effects Analysis. Related methods, or those developed to solve limitations of the fundamental methods, are presented and compared to the fundamental methods. Finally, the impediments of moving research methods into practice are surveyed, then discussion is provided for the factors that improve this transition of research.

scholarly journals IT RISK IDENTIFICATION AND ASSESSMENT METHODOLOGY

2017 ◽  
Vol 2 ◽  
pp. 124
Author(s):  
Oskars Podziņš ◽  
Andrejs Romānovs
Keyword(s):  
Risk Assessment ◽  
Impact Analysis ◽  
Risk Identification ◽  
The Other ◽  
Qualitative Assessment ◽  
Event Tree ◽  
Structured Interviews ◽  
Event Tree Analysis ◽  
Tree Analysis ◽  
Other Hand

There are numerous methods for risk identification and risk assessment phases. Which for risk identification includes historical and systematic approach and inductive or theoretical analysis. One of the main reasons why risk identification is very helpful is that it provides justification in many cases for any large IT investment and other large undertakings. Without it organization probably wouldn’t be able to come to conclusion. Also in this phase business recognize the threats, vulnerabilities, and assets associated with its IT systems. Together with risk assessment phase risk management specialist is responsible for determining asset value, what's the value of the asset business is protecting, and risk acceptance level. Risk assessment on the other hand examines impact or consequence, as well as examines and evaluates the likelihood or probability of that adverse event happening. Risk assessment includes methods like Bayesian analysis, Bow Tie Analysis, brainstorming or structured interviews, business impact analysis, cause and consequence, cause-and-effect analysis, Delphi method, event tree analysis, fault tree analysis, hazard analysis, hazard and operational studies, and finally structured what if technique or SWIFT process. Risk assessment has two distinctive assessment types- quantitative and qualitative assessment. Quantitative assessment tries to put a monetary value on all risks. Qualitative assessment on the other hand rather look at it from a range of values like low, medium, high. The results of these phases are going to be documented in the risk assessment report and reported to senior management.

Risk Assessment of Hydrogen Production System by Dimethyl Ether Steam Reforming With the Use of Nuclear Power

2009 ◽  
Author(s):  
Kazuo Koguchi ◽  
Shigeo Kasai ◽  
Makoto Takahashi ◽  
Toshio Wakabayashi
Keyword(s):  
Risk Assessment ◽  
Heat Exchanger ◽  
Hydrogen Production ◽  
Dimethyl Ether ◽  
Steam Reforming ◽  
Nuclear Power ◽  
Average Frequency ◽  
Event Tree ◽  
Event Tree Analysis ◽  
Tree Analysis

Hydrogen is regarded as a clean fuel because it does not pollute when burned with air. In the case of commercial use, there is a need to research how to produce hydrogen more efficiency and large scale. Although there are some methods of hydrogen production, it can be considered that the heat of the nuclear reactor is promising method. In the recent studies on the hydrogen production with nuclear power, there has focused on the technical issues. Therefore, the object in this paper is to perform the risk assessment for a system of hydrogen production plant by Dimethyl Ether (DME) steam reforming with the use of nuclear power. First, one of the suitable systems with the DME steam reforming plant was selected PWR. A FMEA (Failure Mode and Effects analysis) was performed to identify initiating events. After identifying initiating events, event tree analysis (ETA) was performed to quantify the average frequency of an accident at this system. The result of the PSA, the safety of DME steam reforming plant with nuclear power depends on a rupture of reformer and heat exchanger between hydrogen and DME by the result of FMEA. Event tree analysis shows that the average frequency of hydrogen or DME explosion is 7.7×10−7 year−1 in the case of the rupture of the reformer and 1.9×10−8 year−1 in the case of the break of the heat exchanger.

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