Estágio realizado na Sakthi Portugal, SA, e orientado pela Eng. Helena Coimbra / Tese de mestrado integrado. Engenharia Metalúrgica e de Materiais. Universidade do Porto. Faculdade de Engenharia. 2010

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Risk management is essential for the construction industry to successfully fulfill project objectives. Several studies were conducted in the past decade to support quantitative risk analysis. These studies were based on using some of the commonly used techniques such as risk matrix, decision trees, Monte Carlo, and sensitivity analysis. However, some of these techniques are limited because they either do not support quantitative risk analysis, or are difficult to be utilized due to the required amount of data to support quantitative risk analysis. To address such limitations, a comprehensive framework was developed, based on combining three well-known techniques in reliability engineering, i.e., failure mode and effect analysis, fault trees, and event trees with fuzzy logic. Fuzzy logic and failure mode and effect analysis were first combined to provide an answer to the problem of identifying of critical risk events through the development of a fuzzy expert system software package named Risk Criticality Analyzer. To support quantitative risk analysis in the construction industry, fault tree and event tree were combined, and fuzzy logic is used to solve both of them. Fuzzy arithmetic operations on fuzzy numbers were used to represent logical gates in the fault tree structure, and to conduct event tree analysis. To automate solving both fault trees and event trees, Fuzzy Reliability Analyzer was designed and implemented using Visual Basic.net. Both tools were then validated through case studies. The results indicate that by using the proposed methodology, the risk can be assessed effectively and efficiently. The proposed framework presented in this research provides the contribution of combining fuzzy logic with failure mode and effect analysis, fault trees, and event trees in a comprehensive framework to support risk identification, risk assessment, and risk response. Since the proposed framework is based on using linguistic terms, risk analysts are offered a more convenient and practical framework to conduct risk analysis. The proposed framework was able to address several limitations attributed to the conventional application of failure mode and effect analysis and offered a generic framework that can be adapted to fit any industry or organization. / Construction Engineering and Management

This research is aimed at addressing problems in the field of asset management relating to risk analysis and decision making based on data from a Supervisory Control and Data Acquisition (SCADA) system. It is apparent that determining risk likelihood in risk analysis is difficult, especially when historical information is unreliable. This relates to a problem in SCADA data analysis because of nested data. A further problem is in providing beneficial information from a SCADA system to a managerial level information system (e.g. Enterprise Resource Planning/ERP). A Hierarchical Model is developed to address the problems. The model is composed of three different Analyses: Hierarchical Analysis, Failure Mode and Effect Analysis, and Interdependence Analysis. The significant contributions from the model include: (a) a new risk analysis model, namely an Interdependence Risk Analysis Model which does not rely on the existence of historical information because it utilises Interdependence Relationships to determine the risk likelihood, (b) improvement of the SCADA data analysis problem by addressing the nested data problem through the Hierarchical Analysis, and (c) presentation of a framework to provide beneficial information from SCADA systems to ERP systems. The case study of a Water Treatment Plant is utilised for model validation.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The railway transportation system is fundamental in sustaining the economic activities of a country, by providing a safe, reliable and relatively affordable means of transporting people and goods; hence, the need to ensure its ongoing reliability is of paramount importance. The principle and applications of rail reliability have been reviewed, and reliability improvement in rail infrastructure has been investigated using failure mode and effect analysis (FMEA). Reliability improvement is a continuous process that is geared to meeting dynamic changes in operation and stakeholders’ expectations. Recently, growth has occurred in the amount of rail transport traffic utilisation undertaken, together with the degradation of the infrastructure involved. Such deterioration has amplified the operating risks, leading to an inadequacy in rail track maintenance and inspection that should have kept abreast with the changes. The result has been increased rail failures, and subsequent derailments. A case study of the Passenger Rail Agency of South Africa (PRASA) Metrorail maintenance policy was reviewed to evaluate its maintenance strategy and identifying the potential critical failure modes, so as to be able to recommend improvement of its reliability, and, thus, its availability. On the basis of the case study of PRASA Metrorail maintenance strategy and its performance, it is recommended that PRASA Metrorail change its maintenance policy through employing a cluster maintenance strategy for each depot. / AFRIKAANSE OPSOMMING: Die spoorwegvervoerstelsel is fundamenteel om die ekonomiese bedrywighede van ’n land te ondersteun deur die voorsiening van ’n veilige, betroubare en betreklik bekostigbare manier om mense en goedere te vervoer. Dus is dit van die allergrootste belang om die voortgesette betroubaarheid daarvan te verseker. Die beginsels en toepassings van spoorbetroubaarheid is hersien en die betroubaarheidsverbetering van spoorinfrastruktuur met behulp van foutmodus-eneffekontleding (“FMEA”) ondersoek. Betroubaarheidsverbetering is ’n voortdurende proses om tred te hou met dinamiese bedryfsveranderinge sowel as verskuiwings in belanghebbendes se verwagtinge. Die hoeveelheid spoorvervoerverkeer het onlangs beduidend toegeneem, terwyl die betrokke infrastruktuur agteruitgegaan het. Dié agteruitgang het die bedryfsrisiko’s verhoog, en lei tot ontoereikende spoorweginstandhouding en -inspeksie, wat veronderstel was om met die veranderinge tred te gehou het. Dit gee aanleiding tot ’n toename in spoorwegfoute en gevolglike ontsporing. ’n Gevallestudie is van die instandhoudingsbeleid van die Passasierspooragentskap van Suid- Afrika (PRASA) Metrorail onderneem om dié organisasie se instandhoudingstrategie te beoordeel en die moontlike kritieke foutmodusse te bepaal. Die doel hiermee was om verbeteringe in stelselbetroubaarheid en dus ook stelselbeskikbaarheid voor te stel. Op grond van die gevallestudie van die PRASA Metrorail-instandhoudingstrategie en -prestasie, word daar aanbeveel dat PRASA Metrorail sy instandhoudingsbeleid verander deur ’n klusterinstandhoudingsplan vir elke depot in werking te stel.

Este trabalho apresenta um método de análise de confiabilidade de sistemas novos em desenvolvimento, no qual se utiliza como referência dados predominantemente qualitativos. O método proposto está organizado em três fases, as quais são subdivididas em etapas que constituem as atividades a serem realizadas. A primeira fase é a análise FMEA, que visa definir e identificar falhas potenciais do sistema ainda em seus estágios iniciais de conceituação e projeto. A segunda fase é a análise de confiabilidade, que tem como objetivo gerar dados quantitativos para uma análise aprimorada da confiabilidade do sistema a partir de dados qualitativos coletados na fase da análise FMEA. A terceira fase consiste na análise comparativa e visa, além de comparar os resultados obtidos previamente, propor uma forma de integração destes. O método proposto foi aplicado em dois sistemas principais de um sistema de transporte sobre trilhos: o sistema de propulsão e o sistema de controle. Com o intuito de integrar as duas técnicas, propôs-se uma nova forma de calcular o risco, denominado RPNI, que leva em consideração o índice de severidade, a probabilidade de ocorrência, a probabilidade de detecção e o índice de impacto. A partir desse valor, foi então possível determinar os componentes considerados prioritários para os sistemas e propor as medidas cabíveis, tendo em vista as metas de segurança e a confiabilidade do sistema em desenvolvimento. / This work presents a method for the reliability analysis of a new system under development, which uses qualitative data as predominant reference. The proposed method is organized in three phases, which are subdivided in activities to be accomplished. The first phase employs the FMEA to define and identify potential failures in the early stages of conceptualization and system design. The second phase contemplates a mathematical reliability analysis, providing quantitative data for an enhanced analysis of system reliability from qualitative data collected at the first phase. The third phase, named comparative analysis, compares the previous results and proposes an integrated prioritization. The proposed method was applied in two major systems of a transportation system on guideways: the propulsion and the control systems. In order to integrate the FMEA and the mathematical analysis, a different form to calculate the risk, named RPNI, was proposed, which considers the severity index, occurrence probability, detection probability and the impact index. Using the RPNI, it was possible to determine system priority components and to propose appropriate measures to increase the safety and reliability goals of the system under development.

Este trabalho apresenta um método de análise de confiabilidade de sistemas novos em desenvolvimento, no qual se utiliza como referência dados predominantemente qualitativos. O método proposto está organizado em três fases, as quais são subdivididas em etapas que constituem as atividades a serem realizadas. A primeira fase é a análise FMEA, que visa definir e identificar falhas potenciais do sistema ainda em seus estágios iniciais de conceituação e projeto. A segunda fase é a análise de confiabilidade, que tem como objetivo gerar dados quantitativos para uma análise aprimorada da confiabilidade do sistema a partir de dados qualitativos coletados na fase da análise FMEA. A terceira fase consiste na análise comparativa e visa, além de comparar os resultados obtidos previamente, propor uma forma de integração destes. O método proposto foi aplicado em dois sistemas principais de um sistema de transporte sobre trilhos: o sistema de propulsão e o sistema de controle. Com o intuito de integrar as duas técnicas, propôs-se uma nova forma de calcular o risco, denominado RPNI, que leva em consideração o índice de severidade, a probabilidade de ocorrência, a probabilidade de detecção e o índice de impacto. A partir desse valor, foi então possível determinar os componentes considerados prioritários para os sistemas e propor as medidas cabíveis, tendo em vista as metas de segurança e a confiabilidade do sistema em desenvolvimento. / This work presents a method for the reliability analysis of a new system under development, which uses qualitative data as predominant reference. The proposed method is organized in three phases, which are subdivided in activities to be accomplished. The first phase employs the FMEA to define and identify potential failures in the early stages of conceptualization and system design. The second phase contemplates a mathematical reliability analysis, providing quantitative data for an enhanced analysis of system reliability from qualitative data collected at the first phase. The third phase, named comparative analysis, compares the previous results and proposes an integrated prioritization. The proposed method was applied in two major systems of a transportation system on guideways: the propulsion and the control systems. In order to integrate the FMEA and the mathematical analysis, a different form to calculate the risk, named RPNI, was proposed, which considers the severity index, occurrence probability, detection probability and the impact index. Using the RPNI, it was possible to determine system priority components and to propose appropriate measures to increase the safety and reliability goals of the system under development.

Este trabalho apresenta um método de análise de confiabilidade de sistemas novos em desenvolvimento, no qual se utiliza como referência dados predominantemente qualitativos. O método proposto está organizado em três fases, as quais são subdivididas em etapas que constituem as atividades a serem realizadas. A primeira fase é a análise FMEA, que visa definir e identificar falhas potenciais do sistema ainda em seus estágios iniciais de conceituação e projeto. A segunda fase é a análise de confiabilidade, que tem como objetivo gerar dados quantitativos para uma análise aprimorada da confiabilidade do sistema a partir de dados qualitativos coletados na fase da análise FMEA. A terceira fase consiste na análise comparativa e visa, além de comparar os resultados obtidos previamente, propor uma forma de integração destes. O método proposto foi aplicado em dois sistemas principais de um sistema de transporte sobre trilhos: o sistema de propulsão e o sistema de controle. Com o intuito de integrar as duas técnicas, propôs-se uma nova forma de calcular o risco, denominado RPNI, que leva em consideração o índice de severidade, a probabilidade de ocorrência, a probabilidade de detecção e o índice de impacto. A partir desse valor, foi então possível determinar os componentes considerados prioritários para os sistemas e propor as medidas cabíveis, tendo em vista as metas de segurança e a confiabilidade do sistema em desenvolvimento. / This work presents a method for the reliability analysis of a new system under development, which uses qualitative data as predominant reference. The proposed method is organized in three phases, which are subdivided in activities to be accomplished. The first phase employs the FMEA to define and identify potential failures in the early stages of conceptualization and system design. The second phase contemplates a mathematical reliability analysis, providing quantitative data for an enhanced analysis of system reliability from qualitative data collected at the first phase. The third phase, named comparative analysis, compares the previous results and proposes an integrated prioritization. The proposed method was applied in two major systems of a transportation system on guideways: the propulsion and the control systems. In order to integrate the FMEA and the mathematical analysis, a different form to calculate the risk, named RPNI, was proposed, which considers the severity index, occurrence probability, detection probability and the impact index. Using the RPNI, it was possible to determine system priority components and to propose appropriate measures to increase the safety and reliability goals of the system under development.

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Through identifying failure manufacturing companies compete in today’s world to gain beneficial attributes. The purpose if this thesis is to develop a model towards identifying failure and the root cause. The model developed to identify failure and the root cause toward it, which should result it decrease in failure time (nonfunction machine). The developed model has tested and analyzed in a manufacturing company. The model has been established through studies based on preventive and predictive maintenance: FMEA & RCA.