Linear assets are among the largest and most important engineered systems; their reliability is of the utmost importance. This thesis presents an overview of the reliability estimation methods used for the various types of linear assets, both observation- and statistically-based. While observation-based reliability monitoring and estimation methods are necessarily particular to a certain type of asset, statistically-based methods developed for one type can potentially inform those used for another. Therefore, this thesis looks to point out commonalities in the methods for the statistical evaluation of the reliability of various types of linear assets, develop and extend reliability models and methods with this knowledge, and suggest how maintenance strategies may be improved. To help illustrate and test the models described in this paper a case study was conducted with a utility operator; this thesis shows the modelling results from the study, and demonstrates the model’s use in a maintenance decision model.

Thesis (MSc (Logistics)--University of Stellenbosch, 2007. / There exists, for any connected graph G, a minimum set of vertices that, when removed, disconnects G. Such a set of vertices is known as a minimum cut-set, the cardinality of which is known as the connectivity number k(G) of G. A connectivity preserving [connectivity reducing, respectively] spanning subgraph G0 ? G may be constructed by removing certain edges of G in such a way that k(G0) = k(G) [k(G0) < k(G), respectively]. The problem of constructing such a connectivity preserving or reducing spanning subgraph of minimum weight is known to be NP–complete. This thesis contains a summary of the most recent results (as in 2006) from a comprehensive survey of literature on topics related to the connectivity of graphs. Secondly, the computational problems of constructing a minimum weight connectivity preserving or connectivity reducing spanning subgraph for a given graph G are considered in this thesis. In particular, three algorithms are developed for constructing such spanning subgraphs. The theoretical basis for each algorithm is established and discussed in detail. The practicality of the algorithms are compared in terms of their worst-case running times as well as their solution qualities. The fastest of these three algorithms has a worst-case running time that compares favourably with the fastest algorithm in the literature. Finally, a computerised decision support system, called Connectivity Algorithms, is developed which is capable of implementing the three algorithms described above for a user-specified input graph.

Process plants come with a wide variety of engineering challenges. Each process has uniqueoperating conditions that require careful operation and maintenance programs to keep the process equipment in a condition that is safe for operation. A pilot-scale plant was built in Luleå to demonstrate the possibility of carbon dioxide removal from blast furnace gas usingthe Sorption Enhanced Water Gas Shift (SEWGS) technology. One of the challenges facingthe SEWGS pilot plant was the lack of a maintenance plan which was the motivation for this thesis. The aim of this thesis was to create a maintenance plan for the SEWGS pilot plant. Studying the process conditions of the pilot plant was the starting point since an understanding of the unique operating conditions was necessary for creating a maintenance plan for the pilot plant’s equipment. The Reliability-centered maintenance (RCM) method was chosen to create the maintenance plan. The study began with determining the objectives and contents of the analysis. The next step was a functional failure analysis in the form of a Failure Mode and Effect Criticality Analysis (FMECA) covering all the equipment in the plant. Afterwards the failure consequences were assessed based on a criticality assessment matrix to determine which equipment necessitate the performance of maintenance activities. The maintenance plan was created based upon the criticality of the equipment and the selected maintenance activities were based on the recommendations of manufacturers. The failure analysis found that the blast furnace gas compressor is the most critical for the process. The boiler and superheater have been found to be highly critical due to the dangerous safety consequences of their failure. In addition, all pressure safety valves have been found to be highly critical due to the hidden nature of their failure. The maintenance plan addresses these critical items and other less critical items while some non-critical items have been removed from the plan due to the negligible consequences of their failure.

abstract: Infant mortality rate of field deployed photovoltaic (PV) modules may be expected to be higher than that estimated by standard qualification tests. The reason for increased failure rates may be attributed to the high system voltages. High voltages (HV) in grid connected modules induce additional stress factors that cause new degradation mechanisms. These new degradation mechanisms are not recognized by qualification stress tests. To study and model the effect of high system voltages, recently, potential induced degradation (PID) test method has been introduced. Using PID studies, it has been reported that high voltage failure rates are essentially due to increased leakage currents from active semiconducting layer to the grounded module frame, through encapsulant and/or glass. This project involved designing and commissioning of a new PID test bed at Photovoltaic Reliability Laboratory (PRL) of Arizona State University (ASU) to study the mechanisms of HV induced degradation. In this study, PID stress tests have been performed on accelerated stress modules, in addition to fresh modules of crystalline silicon technology. Accelerated stressing includes thermal cycling (TC200 cycles) and damp heat (1000 hours) tests as per IEC 61215. Failure rates in field deployed modules that are exposed to long term weather conditions are better simulated by conducting HV tests on prior accelerated stress tested modules. The PID testing was performed in 3 phases on a set of 5 mono crystalline silicon modules. In Phase-I of PID test, a positive bias of +600 V was applied, between shorted leads and frame of each module, on 3 modules with conducting carbon coating on glass superstrate. The 3 module set was comprised of: 1 fresh control, TC200 and DH1000. The PID test was conducted in an environmental chamber by stressing the modules at 85°C, for 35 hours with an intermittent evaluation for Arrhenius effects. In the Phase-II, a negative bias of -600 V was applied on a set of 3 modules in the chamber as defined above. The 3 module set in phase-II was comprised of: control module from phase-I, TC200 and DH1000. In the Phase-III, the same set of 3 modules which were used in the phase-II again subjected to +600 V bias to observe the recovery of lost power during the Phase-II. Electrical performance, infrared (IR) and electroluminescence (EL) were done prior and post PID testing. It was observed that high voltage positive bias in the first phase resulted in little/no power loss, high voltage negative bias in the second phase caused significant power loss and the high voltage positive bias in the third phase resulted in major recovery of lost power. / Dissertation/Thesis / M.S. Engineering 2011

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.

O objetivo geral deste trabalho é propor um instrumento de avaliação do nível de habilidades técnicas ofensivas do basquetebol para atletas e escolares de 10 a 11 anos. A mostra do estudo é de 64 meninos, dentre eles, 48 são escolares e 16 são atletas de basquetebol. Os testes propostos passaram primeiramente por um processo de validação de conteúdo, sendo considerado como válido, e posteriormente por uma validação de construto, através do método de grupos diferenciados, ao qual também teve os critérios atendidos. As habilidades técnicas a serem avaliadas são: drible, passe e arremesso. A reprodutibilidade dos testes foram avaliadas através de coeficientes de correlação intra-classe e correlação de alpha de Cronbach.Na verificação da objetividade foi utilizado também correlações intra-classe e alpha de Cronbach. Foi analisado a assimetria (skewness) e o achatamento (kurtosis) da curva. O teste de Shapiro Wilk foi utilizado para verificar a normalidade dos dados dos atletas. Foi utilizado um nível de significância de 5% para todas as análises. Para o estabelecimento de critérios de seleção em escolares a metodologia utilizada foi a técnica multivariada da Análise da Função Discriminante. Os resultados apresentados em relação a objetividade foram expressos através de alphas de Cronbach de 0,97. A reprodutibilidade dos dados de arremesso apresentou um aplha Cronbach de 0,88. Sobre os dados de passe a reprodutibilidade manifestou um alpha de 0,83, enquanto no drible foi de 0,96. Quanto ao estabelecimento de critérios de performance através da análise da função discriminante, demonstrou que todas a as variáveis utilizadas na equação entre elas, passe, drible e arremesso, tem poder de discriminar atletas e escolares. / The overall aim of this work isto propose a tool for assessing lhe level of technichal skills for offensive basketaball athletes and schollchildren of 10 to 11 years. The sample is 64 childrens, amog them, 48 are scholars and 16 are basketball players. The proposed tests passed first trough a process of content validation, being considered as valid, and later by a construct validation, through the method of differentiated groups, which had also met the criteria. The technichal skills to be assessed are dribbling, passing and shooting. The reliability of tests were evaluated using intra class correlation coefficients and Cronbach’s alpha correlation. On verification of intra evaluator reliability was also used intra-class correlations and Cronbach’s alpha. We analyzed the simetry (skewness) and flatenning (kurtosis) of the curve. The Shapiro Wilk test was used to verify the normality of the data of athletes. We used a significance level of 5% for all analyzes. To estabilish selection criteria in students the methodology used was the technique of multivariate analysis is discriminant function analysis. The results presented in relation to objectivity were expressed by Cronbach’s alphas of 0.97. The reproducibility of the data presented a shooting Cronbach alpha of 0.88. About the passing, the reproducibility showed na alpha of 0.83, while the dribbling was used discriminant function analysis and the result was shown that all variables used in this model, including, passing, dribbling and shooting has power to discriminate school athletes.

Este trabalho apresenta um método de elaboração e aplicação de um plano de manutenção baseado nos preceitos da MCC aplicado em uma indústria de bebidas. O método contempla: i) Escolher o processo a ser estudado e realizar levantamento de dados; ii) identificar os conjuntos e subconjuntos que impactam na confiabilidade; iii) levantar a taxa de falhas desses subconjuntos; iv) desenvolver uma FMEA para levantamento dos maiores riscos associados ao equipamento em estudo e v) estabelecer planos de ação da manutenção mais adequado, visando à redução dos riscos levantados na FMEA. A aplicação da proposta é ilustrada através de um estudo real realizado em um processo de envase de uma linha de produção de refrigerantes. A aplicação do método permitiu identificar com precisão os conjuntos e subconjuntos que tinham maior impacto na confiabilidade do equipamento em questão. Entre os principais resultados obtidos, destacam-se: i) ampliação do faturamento em cerca de um milhão por ano, ii) ampliação da satisfação e moral das pessoas, iii) redução do uso de horas extras, iv) redução de 10% no descarte de produtos não conformes, v) possibilidade de adiar em cerca de um ano investimentos de ampliação da linha, e vi) redução dos níveis de estoque, uma vez que existe maior grau de certeza de que o item vai manter sua função pelo período estabelecido. / This paper presents a method for preparation and application of a maintenance plan based on precepts of the MCC applied in a beverage industry. The method comprises: i) Choose the process to be improved and perform data collection; ii) identify assemblies and sub-assemblies that impact on reliability; iii) compute the failure rate of these sub-assemblies; iv) develop a FMEA for computation of major risks associated with the equipment under study and v) establishment of an action plan comprising the most appropriate maintenance activities, aimed at reducing the risks estimated by the FMEA. The implementation of the proposal is illustrated by a study performed in a real process of packaging in a production line of soft drinks. The application of the method allowed identifying more accurately the assemblies and sub-assemblies that had the greatest impact on the reliability and availability of the equipment in question. Among the main results obtained we emphasize: (i) the expansion of sales in about a million a year, (ii) greater satisfaction and morale of the employees, (iii) reduction of overtime, (iv) reduction of 10% in non-compliant products, (v) possibility of postpone expansion investments in about a year, and (vi) reduction of inventory levels, since there is greater certainty that the item will keep your function for the established period.

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.

O objetivo geral deste trabalho é propor um instrumento de avaliação do nível de habilidades técnicas ofensivas do basquetebol para atletas e escolares de 10 a 11 anos. A mostra do estudo é de 64 meninos, dentre eles, 48 são escolares e 16 são atletas de basquetebol. Os testes propostos passaram primeiramente por um processo de validação de conteúdo, sendo considerado como válido, e posteriormente por uma validação de construto, através do método de grupos diferenciados, ao qual também teve os critérios atendidos. As habilidades técnicas a serem avaliadas são: drible, passe e arremesso. A reprodutibilidade dos testes foram avaliadas através de coeficientes de correlação intra-classe e correlação de alpha de Cronbach.Na verificação da objetividade foi utilizado também correlações intra-classe e alpha de Cronbach. Foi analisado a assimetria (skewness) e o achatamento (kurtosis) da curva. O teste de Shapiro Wilk foi utilizado para verificar a normalidade dos dados dos atletas. Foi utilizado um nível de significância de 5% para todas as análises. Para o estabelecimento de critérios de seleção em escolares a metodologia utilizada foi a técnica multivariada da Análise da Função Discriminante. Os resultados apresentados em relação a objetividade foram expressos através de alphas de Cronbach de 0,97. A reprodutibilidade dos dados de arremesso apresentou um aplha Cronbach de 0,88. Sobre os dados de passe a reprodutibilidade manifestou um alpha de 0,83, enquanto no drible foi de 0,96. Quanto ao estabelecimento de critérios de performance através da análise da função discriminante, demonstrou que todas a as variáveis utilizadas na equação entre elas, passe, drible e arremesso, tem poder de discriminar atletas e escolares. / The overall aim of this work isto propose a tool for assessing lhe level of technichal skills for offensive basketaball athletes and schollchildren of 10 to 11 years. The sample is 64 childrens, amog them, 48 are scholars and 16 are basketball players. The proposed tests passed first trough a process of content validation, being considered as valid, and later by a construct validation, through the method of differentiated groups, which had also met the criteria. The technichal skills to be assessed are dribbling, passing and shooting. The reliability of tests were evaluated using intra class correlation coefficients and Cronbach’s alpha correlation. On verification of intra evaluator reliability was also used intra-class correlations and Cronbach’s alpha. We analyzed the simetry (skewness) and flatenning (kurtosis) of the curve. The Shapiro Wilk test was used to verify the normality of the data of athletes. We used a significance level of 5% for all analyzes. To estabilish selection criteria in students the methodology used was the technique of multivariate analysis is discriminant function analysis. The results presented in relation to objectivity were expressed by Cronbach’s alphas of 0.97. The reproducibility of the data presented a shooting Cronbach alpha of 0.88. About the passing, the reproducibility showed na alpha of 0.83, while the dribbling was used discriminant function analysis and the result was shown that all variables used in this model, including, passing, dribbling and shooting has power to discriminate school athletes.

Este trabalho apresenta um método de elaboração e aplicação de um plano de manutenção baseado nos preceitos da MCC aplicado em uma indústria de bebidas. O método contempla: i) Escolher o processo a ser estudado e realizar levantamento de dados; ii) identificar os conjuntos e subconjuntos que impactam na confiabilidade; iii) levantar a taxa de falhas desses subconjuntos; iv) desenvolver uma FMEA para levantamento dos maiores riscos associados ao equipamento em estudo e v) estabelecer planos de ação da manutenção mais adequado, visando à redução dos riscos levantados na FMEA. A aplicação da proposta é ilustrada através de um estudo real realizado em um processo de envase de uma linha de produção de refrigerantes. A aplicação do método permitiu identificar com precisão os conjuntos e subconjuntos que tinham maior impacto na confiabilidade do equipamento em questão. Entre os principais resultados obtidos, destacam-se: i) ampliação do faturamento em cerca de um milhão por ano, ii) ampliação da satisfação e moral das pessoas, iii) redução do uso de horas extras, iv) redução de 10% no descarte de produtos não conformes, v) possibilidade de adiar em cerca de um ano investimentos de ampliação da linha, e vi) redução dos níveis de estoque, uma vez que existe maior grau de certeza de que o item vai manter sua função pelo período estabelecido. / This paper presents a method for preparation and application of a maintenance plan based on precepts of the MCC applied in a beverage industry. The method comprises: i) Choose the process to be improved and perform data collection; ii) identify assemblies and sub-assemblies that impact on reliability; iii) compute the failure rate of these sub-assemblies; iv) develop a FMEA for computation of major risks associated with the equipment under study and v) establishment of an action plan comprising the most appropriate maintenance activities, aimed at reducing the risks estimated by the FMEA. The implementation of the proposal is illustrated by a study performed in a real process of packaging in a production line of soft drinks. The application of the method allowed identifying more accurately the assemblies and sub-assemblies that had the greatest impact on the reliability and availability of the equipment in question. Among the main results obtained we emphasize: (i) the expansion of sales in about a million a year, (ii) greater satisfaction and morale of the employees, (iii) reduction of overtime, (iv) reduction of 10% in non-compliant products, (v) possibility of postpone expansion investments in about a year, and (vi) reduction of inventory levels, since there is greater certainty that the item will keep your function for the established period.