Bearings are critical in today’s mechanisms, and their reliability is continuously improving. Yet, working under high loads for long periods, bearings will degrade and eventually fail. An unpredicted bearing failure can lead to total and catastrophic failures of machines and may even lead to human injuries that result in substantial economic losses and reductions in production. Determining a bearing’s remaining useful life (RUL) has become an important topic in many industrial fields. Vibration signals are the most used representation for understanding a bearing’s health status. Using different algorithms, time-domain vibration signals can be transformed into time-frequency domain signals that help indicate a bearing’s status. For instance, this thesis investigates spectrograms and scalograms to visually represent a bearing’s health condition using a short-time Fourier transform (STFT) and a continuous wavelet transform (CWT). Both representations are plotted as a function of time and frequency and can detect the bearing’s working condition. However, spectrograms are advantageous in revealing frequency changes along the time axis, while scalograms facilitate the detection of abrupt changes. Combined with a convolutional neural network (CNN), these plots can be used to interpret bearing RUL. The strength of CNNs lie in their ability to identify and detect features in images, including such tasks as image classification, using share-weight architectures, convolutional layers, and kernels. This thesis explores CNNs combined with spectrograms and scalograms using the PRONOSTIA dataset to perform bearing RUL predictions and explore relationships between prognosis and diagnosis for bearing faults analysis.

In the oil and gas industry, statistical methods have been used for corrosion analysis for various asset systems such as pipelines, storage tanks, and so on. However, few industrial standards and guidelines provide comprehensive stepwise procedures for the usage of statistical approaches for corrosion analysis. For example, the UK HSE (2002) report "Guidelines for the use of statistics for analysis of sample inspection of corrosion" demonstrates how statistical methods can be used to evaluate corrosion samples, but the methods explained in the document are very basic and do not consider risk factors such as pressure, temperature, design, external factors and other factors for the analyses. Furthermore, often the industrial practice that uses linear approximation on localised corrosion such as pitting is considered inappropriate as pitting growth is not uniform. The aim of this research is to develop an approach that models the stochastic behaviour of localised corrosion and demonstrate how the influencing factors can be linked to the corrosion analyses, for predicting the remaining useful life of components in oil and gas plants. This research addresses a challenge in industry practice. Non-destructive testing (NDT) and inspection techniques have improved in recent years making more and more data available to asset operators. However, this means that these data need to be processed to extract meaningful information. Increasing computer power has enabled the use of statistics for such data processing. Statistical software such as R and OpenBUGS is available to users to explore new and pragmatic statistical methods (e.g. regression models and stochastic models) and fully use the available data in the field. In this thesis, we carry out extreme value analysis to determine maximum defect depth of an offshore conductor pipe and simulate the defect depth using geometric Brownian motion in Chapter 2. In Chapter 3, we introduce a Weibull density regression that is based on a gamma transformation proportional hazards model to analyse the corrosion data of piping deadlegs. The density regression model takes multiple influencing factors into account; this model can be used to extrapolate the corrosion density of inaccessible deadlegs with data available from other piping systems. In Chapter 4, we demonstrate how the corrosion prediction models in Chapters 2 and 3 could be used to predict the remaining useful life of these components. Chapter 1 sets the background to the techniques used, and Chapter 5 presents concluding remarks based on the application of the techniques.

Orientador: Ariene Gimenes Fernandes Van Dender / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-03T22:25:48Z (GMT). No. of bitstreams: 1 Alves_RosaMariaVercelino_D.pdf: 5293051 bytes, checksum: 173b3b436555b3d5de8b3a01b60feee3 (MD5) Previous issue date: 2004 / Resumo: Requeijão cremoso é um produto genuinamente brasileiro, sendo classificado como um tipo de queijo processado obtido pelo cozimento de uma massa de queijo fresco de sais fundentes, água e creme de leite. Atualmente esse produto é acondicionado principalmente em copos de vidro com sistema de fechamento metálico de fácil abertura, ficando durante sua comercialização, exposto a luz em gôndolas dos refrigeração. Pelo fato de não serem encontrados dados em literatura sovre principais fatores que interferem em sua vida util, a introdução de novas alternativas para este segmento acaba sendo limitada. Assim, o objetivo desse trabalho foi estudar o efeito da disponibilidade de oxigênio e de incidência de luz sobre a estabilidade do requeijão cremoso através da ánálise comparativa da sua estabilidade quando acondicionado em diferentes tipos de embalagem, na ausência e presença de luz, determinando os efeitos das caracteristicas de barreira ao oxigênio, à umidade e à luz da embalagem e da quantidade de oxigênio disponivel no espaço-livre nas caracteristicas microbiológicas, fisico-quimicas e sensoriais do produto, ao longo da estocagem refrigerada. O produto foi produzido na planta piloto do TECNOLAT/ITAL a partir de uma massa obtida por acidificação direta de leite aquecido a 80°C. O produto foi acondicionado em cinco diferentes tipos de embalagens (copo de vidro com tampa metálica abre-fácil, copo de vidro termosselado, pode plástico de polipropileno termosselado, bisnagas plásticas coextrudadas e de polietileno). De maneira geral, não foram observadas alterações microbiologicas no requeijão cremoso acondicionado nos cinco tipos de embalagens indicando condições adequadas de processo e fechamento das embalagens em estudo. Também não se observaram alterações fisico-quimicas do produto, pois as variações observadas encontravam-se dentro dos padrões normais para requeijão cremoso. Quanto ao indice de proteólise, este indicou estabilidade do sistema protéico do produto em todas as em balagens até 150 doas de estocagem e até 180 dias no copo de vidro com tampa metálica abre fácil. Os resultados de TBA, quando indicavam diferenças entre as amostras provinientes das diferentes embalagens expostas ou não à luz, oxidação do produto era muito acentuada e o mesmo já havia sidp rejeitado na análise sensorial. Em ausência de luz, a disponibilidade de oxigênio, seja presente no espaço-livre, seja por permeação pela embalagem, não afeta a perda de qualidade do requeijão cremoso para periodos de estocagem de até 150 dias a 10°C e 180 dias a 4°C. Também verificou-se que em ausência de luz, o efeito das temperaturas de estocagem estudadas, 10°C e 4°C foi pouco significativo. Entretanto, a perda de qualidade de requeijão cremoso é significamente maior se a estocagem do produto acondicionado nas embalagens for sob exposiçãoà luz, quando observou-se alteração na fase lipidica levando à alteração sensorial do produto com requeijão e definição de final de vida útil. Sob exposição à luz, o efeito de uma alta taxa de transmissão ao oxigênio foi observado, uma vez que a estabilidade do produto foi menor quando acondicionado na bisnaga PE em compração com a obtida na estrutura da bisnaga Coex. Também verificou-se que o volume de oxigênio disponivel afeta a estabilidade do produto de forma que, a partir de uma determinada concentração de oxigênio, seja por volume de gases no espaço-livre, ou seja por permeação, as reações de fotoxidação são muito aceleradas, uma vez que não foi observada diferença significativa no produto do vidro selado (VS), no pote de polipropilrno (pote PP) e na bisnaga Coes (EVOH como camada barreira ao oxigênio). E, sob exposição à luz, em condições de menor volume de oxigênio disponivel no espaço-livre da embalagem, a redução da pressão parcial de oxigênio no espaço-livre permite um éríodo de vida útil maior para o produto, porque menor é a disponibilidade de oxigênio no produto para ser consumido nas reações fotoxidativas (situação do VAF). Entre as embalagens estudadas, o vidro com sistema de fechamento por vácuo (VAF) foi o que preservou por mais tempo a qualidade inicial do produto, uma vez que apresenta a situação de minima disponibilidade de oxigênio. recomenda-se que caso se opte pela utilização de embalagens plásticas, que seja dada preferência para as com pigmentação do material, que garanta proteção contra a incidência de luz, aumentado assim a estabilidade do produto / Abstract: Creamy Requeijão is a genuinamente Brazilian product, being classified as a type of processed cheese gotten by the baking of a mass of cool cheese of you leave fundentes, water and cream of milk. Currently this product is conditioned mainly in glass cups with system of metallic closing of easy opening, being during its commercialization, displayed the light in gondolas of the refrigeration. For the fact not to be joined data in literature sovre main factors that intervene with its util life, the introduction of new alternatives for this segment finishes being limited. Thus, the objective of this work was to study the effect of the availability of oxygen and incidence of light on the stability of the creamy requeijão through ánálise comparative of its stability when conditioned in different types of packing, in the absence and presence of light, determining the effect of the caracteristicas of barrier to the oxygen, the humidity and the light of the packing and the amount of oxygen disponivel in the space-free one in the microbiological, fisico-quimicas and sensorial caracteristicas of the product, the long one of the cooled stockage. The product was produced in the plant pilot of the TECNOLAT/ITAL from a mass gotten for direct acidificação of warm milk 80°C. The product was conditioned in five different types of packings (glass cup with open-easy metallic cover, termosselado glass cup, can plastic of termosselado polypropylene, coextrudadas plastic longs loaf of french bread and of polyethylene). In general way, microbiologicas alterations in the creamy requeijão conditioned in the five types of packings had not been observed indicating adequate conditions of process and closing of the packings in study. Also fisico-quimicas alterations of the product had not been observed, therefore the observed variations met inside of the normal standards for creamy requeijão. How much to the indice of proteólise, this indicated stability of the protéico system of the product in all in balagens up to 150 donates of stockage and up to 180 days in the glass cup with metallic cover it opens easy. The TBA results, when they indicated differences between the provinientes samples of the different packings displayed or not to the light, oxidation of the product was very accented and the same already it had sidp rejected in the sensorial analysis. In light absence, the availability of oxygen, either present in the space-free one, either for permeação for the packing, does not affect the loss of quality of the creamy requeijão for periodos of stockage of up to 150 days 10°C and 180 days 4°C. Also it was verified that in light absence, the effect of the studied temperatures of stockage, 10°C and 4°C were little significant. However, the loss of quality of creamy requeijão is significamente bigger if the stockage of the product conditioned in the packings will be under exposiçãoà light, when alteration in the lipidica phase was observed taking to the sensorial alteration of the product with requeijão and definition of end of useful life. Under exposition to the light, the effect of one high tax of transmission to the oxygen was observed, a time that the stability of the product lesser when was conditioned in long loaf of french bread PE in compração with the gotten one in the structure of the Coex long loaf of french bread. Also it was verified that the volume of oxygen disponivel affects the stability of the form product that, from one determined oxygen concentration, either for volume of gases in the space-free one, or either for permeação, the fotoxidação reactions very are sped up, a time that were not observed significant difference in the product of the stamped glass (VERSUS), in the pot of polipropilrno (pot PP) and in the Coes long loaf of french bread (EVOH as layer barrier to the oxygen). E, under exposition to the light, in conditions of lesser volume of oxygen disponivel in the space-free one of the packing, the reduction of the partial pressure of oxygen in the space-free one allows one éríodo of bigger useful life for the product, because lesser it is the availability of oxygen in the product to be consumed in the fotoxidativas reactions (situation of the VAF). Between the studied packings, the glass with system of closing for vacuum (VAF) was what it preserved for more time the initial quality of the product, a time that presents the situation of minima oxygen availability sends regards that in case that if opts to the use of plastic packings, that is given preference for the ones with pigmentação of the material, that guarantees protection against the light incidence, increased thus the stability of the product / Doutorado / Doutora em Tecnologia de Alimentos

Yes / Diagnostics and prognostics have significant roles in the reliability enhancement of systems and are focused topics of active research. Engineered systems are becoming more complex and are subjected to miscellaneous failure modes that impact adversely their performability. This everincreasing complexity makes fault diagnostics and prognostics challenging for the system-level functions. A significant number of successes have been achieved and acknowledged in some review papers; however, these reviews rarely focused on the application of complex engineered systems nor provided a systematic review of diverse techniques and approaches to address the related challenges. To bridge the gap, this paper firstly presents a review to systematically cover the general concepts and recent development of various diagnostics and prognostics approaches, along with their strengths and shortcomings for the application of diverse engineered systems. Afterward, given the characteristics of complex systems, the applicability of different techniques and methods that are capable to address the features of complex systems are reviewed and discussed, and some of the recent achievements in the literature are introduced. Finally, the unaddressed challenges are discussed by taking into account the characteristics of automotive systems as an example of complex systems. In addition, future development and potential research trends are offered to address those challenges. Consequently, this review provides a systematic view of the state of the art and case studies with a reference value for scholars and practitioners.

Inledning Deloitte gjorde 2013 en granskning av Jönköpings kommun som visade på att rutiner saknades avseende omprövning av nyttjandeperiod för materiella anläggningstillgångar. Detta skulle kunna innebära att det även finns brister i kommunala bolag, varför en jämförelse mellan kommunala och privata bolag görs. Syfte Syftet med studien är att förklara och analysera sambandet mellan ägaridentitet och omprövning av nyttjandeperiod för materiella anläggningstillgångar i svenska fastighetsbolag. Metod Studien har en deduktiv ansats och en kvantitativ forskningsstrategi. En tvärsnittsdesign har gjorts där datan samlats in i form av sekundärdata genom granskning av årsredovisningar. Datan, som utgörs av ett slutgiltigt urval om 405 bolag, har kompletterats med kvalitativa intervjuer med fem revisorer. Slutsats Den statistiska analysen visar ingen signifikans för sambandet mellan omprövning av nyttjandeperiod och ägaridentitet. Det som dock verkar påverka benägenheten att ompröva nyttjandeperiod är vilken revisionsbyrå bolaget anlitar. Bolag som anlitar Deloitte eller en annan revisionsbyrå än Big 4 är mer benägna att ompröva nyttjandeperiod än bolag som anlitar övrigarevisionsbyråer. / Introduction An inspection of Jönköping’s municpality made by Deloitte in 2013 showed a lack of routines regarding reviewing of useful life for tangible fixed assets. This could imply a lack of routines in municipal corporations as well, and because of this a comparison is made between municipal and private corporations. Purpose The aim of this study is to explain and analyze the relationship between owner identity and reviewing of useful life for tangable fixed assets in Swedish real estate corporations. Method The following is a quantitative study based on a deductive approach and a cross-sectional design. Data has been collected as secondary data through examiniation of annual reports. The data, which consists of a final selection of 405 corporations, has been complemented through qualitative interviews with five auditors. Conclusion The statistical analysis shows no significant relationship between reviewing of useful life and owner identity. However, a factor that seems to affect the propensity to review useful life is depending on which audit firm the corporation uses. Corporations that use Deloitte or another audit firm than Big 4 tend to review useful life to a greater extent that those who use other audit firms.

We consider the prediction algorithm and performance evaluation for prognostics and health management (PHM) problems, especially the prediction of remaining useful life (RUL) for the milling machine cutter and lithium ‐ ion battery. We modeled battery as a voltage source and internal resisters. By analyzing voltage change trend during discharge, we made the prediction of battery remain discharge time in one discharge cycle. By analyzing internal resistance change trend during multiple cycles, we were able to predict the battery remaining useful time during its life time. We showed that the battery rest profile is correlated with the RUL. Numerical results using the realistic battery aging data from NASA prognostics data repository yielded satisfactory performance for battery prognosis as measured by certain performance metrics. We built a battery test platform and simulated more usage pattern and verified the prediction algorithm. Prognostic performance metrics were used to compare different algorithms.

Le pronostic industriel vise à étendre le cycle de vie d’un dispositif physique, tout en réduisant les couts d’exploitation et de maintenance. Pour cette raison, le pronostic est considéré comme un processus clé avec des capacités de prédiction. En effet, des estimations précises de la durée de vie avant défaillance d’un équipement, Remaining Useful Life (RUL), permettent de mieux définir un plan d’action visant à accroitre la sécurité, réduire les temps d’arrêt, assurer l’achèvement de la mission et l’efficacité de la production.Des études récentes montrent que les approches guidées par les données sont de plus en plus appliquées pour le pronostic de défaillance. Elles peuvent être considérées comme des modèles de type boite noire pour l’ étude du comportement du système directement `a partir des données de surveillance d’ état, pour définir l’ état actuel du système et prédire la progression future de défauts. Cependant, l’approximation du comportement des machines critiques est une tâche difficile qui peut entraîner des mauvais pronostic. Pour la compréhension de la modélisation du pronostic guidé par les données, on considère les points suivants. 1) Comment traiter les données brutes de surveillance pour obtenir des caractéristiques appropriées reflétant l’ évolution de la dégradation? 2) Comment distinguer les états de dégradation et définir des critères de défaillance (qui peuvent varier d’un cas `a un autre)? 3) Comment être sûr que les modèles définis seront assez robustes pour montrer une performance stable avec des entrées incertaines s’ écartant des expériences acquises, et seront suffisamment fiables pour intégrer des données inconnues (c’est `a dire les conditions de fonctionnement, les variations de l’ingénierie, etc.)? 4) Comment réaliser facilement une intégration sous des contraintes et des exigence industrielles? Ces questions sont des problèmes abordés dans cette thèse. Elles ont conduit à développer une nouvelle approche allant au-delà des limites des méthodes classiques de pronostic guidé par les données. / Prognostics and Health Management (PHM) aims at extending the life cycle of engineerin gassets, while reducing exploitation and maintenance costs. For this reason,prognostics is considered as a key process with future capabilities. Indeed, accurateestimates of the Remaining Useful Life (RUL) of an equipment enable defining furtherplan of actions to increase safety, minimize downtime, ensure mission completion andefficient production.Recent advances show that data-driven approaches (mainly based on machine learningmethods) are increasingly applied for fault prognostics. They can be seen as black-boxmodels that learn system behavior directly from Condition Monitoring (CM) data, usethat knowledge to infer its current state and predict future progression of failure. However,approximating the behavior of critical machinery is a challenging task that canresult in poor prognostics. As for understanding, some issues of data-driven prognosticsmodeling are highlighted as follows. 1) How to effectively process raw monitoringdata to obtain suitable features that clearly reflect evolution of degradation? 2) Howto discriminate degradation states and define failure criteria (that can vary from caseto case)? 3) How to be sure that learned-models will be robust enough to show steadyperformance over uncertain inputs that deviate from learned experiences, and to bereliable enough to encounter unknown data (i.e., operating conditions, engineering variations,etc.)? 4) How to achieve ease of application under industrial constraints andrequirements? Such issues constitute the problems addressed in this thesis and have ledto develop a novel approach beyond conventional methods of data-driven prognostics.

O setor aeroportuário apresentou forte crescimento nos últimos anos, ressaltando as ineficiências na gestão de sua infraestrutura e de seus ativos, especialmente no Brasil. Assim, com a exaustão das técnicas tradicionais para a redução de custos, as empresas necessitam buscar melhorias apoiadas no uso de métodos mais complexos a fim de aumentar a produtividade de seus ativos. Desta forma, desponta a necessidade de modelos para a identificação da vida útil e análise da substituição econômica de ativos, uma vez que estas informações auxiliam na tomada de decisão e conduzem a melhores planos de manutenção, reduzindo as perdas do processo. Assim sendo, este trabalho tem por objetivo propor e aplicar uma sistemática para avaliação da substituição de ativos no setor aeroportuário, apoiado em modelos adequados às especificidades do setor através do estudo das suas variáveis. Para isto, são identificados os elementos que influenciam na vida útil dos ativos e, posteriormente, modelos de identificação de vida útil e substituição econômica de ativos são propostos e aplicados em um aeroporto brasileiro de grande porte. Pode-se concluir que a sistemática produziu resultados consistentes e que auxiliam a decisão de substituição de ativos de uma forma estruturada. / In the past years, an increase in aviation transport can be noticed and it highlights inefficiencies in asset management, especially in Brazil. Hence, the exhaustion of traditional techniques to cost reduction lead companies to seek improvements supported by more complex methods in order to increase productivity of their assets. Thus, it is crucial to develop models for useful life identification and economic replacement of assets, since these information assist the decision making process and lead to better maintenance plans, reducing wastage. As a result, the main objective of this work is develop and apply a systematic for evaluation of asset replacement in airports, supported by models that consider the specificities of the aviation sector and its particular variables. In this direction, elements that influence assets useful life are identified and, then, models for useful life identification and economic replacement of assets are developed and applied in an important Brazilian airport. It can be concluded that the systematic have produced consistent results and can assist in asset replacement decision in a structured form.

The action of chlorine in concrete structures of sea coastal cities has been the focus of research data due to its importance in the context of durability guarantee. It has been studied the production mechanisms of the ion chlorine, its deposition on the concrete surface and, eventually, its pathological action. From these data, several norms indicate protection measures to be specified by the projectors, minimizing the percolation of this ion through the cover layer of the concrete. In spite of the present Brazilian norm of planning concrete structures9 indicates classes of environmental aggressiveness to the concrete structures in coast areas, it does not correlate any content or deposition rate of chlorine, making clear the existence of a normative gap. This work exposes the fulfillment of bibliographical research related to the production of the ion chlorine, its transportation and deposition mechanisms on the surface of concrete structures; an experimental field and laboratorial study catching the chlorine at points located in the city of Maceió, from the shore to the coastal table lowlands10. To quantify the ion content, the Mohr s method11 was used. It could be seen an increase in the levels of chlorine deposition in places situated close to shore and a decrease when going further into the continent, being the chlorine found 14 km off the coast. From these results, it was evaluated the perspective of useful life of concrete structures located at each point of collecting, making use of several normative specifications12. The results show that there was a significant gain of useful life when using the criteria of the American norm for structures located in the splashing tide areas, while the Brazilian norm is that which presents smaller projection of useful life in the sea coast areas. / A ação do cloreto nas estruturas de concreto em cidades litorâneas vem sendo foco de pesquisa dada sua importância no contexto da garantia de durabilidade. Tem sido estudado tanto os mecanismos de produção do íon cloreto, sua deposição sobre a superfície do concreto e consequentemente sua ação patológica. A partir daí, diversas normas indicam medidas de proteção a serem especificadas pelos projetistas, minimizando a percolação desse íon através da camada de cobrimento do concreto. Apesar da atual norma brasileira para projeto de estrutura em concreto5 indicar classes de agressividade ambiental às estruturas de concreto em região costeira, não correlaciona a nenhum teor ou taxa de deposição de cloreto, deixando clara a existência de uma lacuna normativa. Este trabalho se propõe a efetuar uma pesquisa bibliográfica quanto à produção do íon cloreto, seus mecanismos de transporte e deposição na superfície das estruturas de concreto; um estudo experimental de campo e laboratorial, captando o cloreto em pontos dispostos na cidade de Maceió, desde a orla até os tabuleiros6. Para quantificar o teor do íon utilizou-se o método de Mohr7. Observou-se um aumento nas taxas de deposição de cloreto em pontos situados à beira mar, e uma diminuída à medida que adentra ao continente, tendo sido detectado o cloreto além de 14 km da costa. Através desses resultados foi avaliada a perspectiva de vida útil das estruturas de concreto, face ao ataque por cloretos, para as estruturas situadas em cada ponto de coleta, utilizando-se diversas especificações normativas8. Os resultados mostram que obtem-se um significativo ganho de vida útil utilizando-se os critérios da norma americana para estruturas situadas na zona de respingo de maré, enquanto que a norma brasileira é a que apresenta menor projeção dessa vida útil em regiões marinhas.

O setor aeroportuário apresentou forte crescimento nos últimos anos, ressaltando as ineficiências na gestão de sua infraestrutura e de seus ativos, especialmente no Brasil. Assim, com a exaustão das técnicas tradicionais para a redução de custos, as empresas necessitam buscar melhorias apoiadas no uso de métodos mais complexos a fim de aumentar a produtividade de seus ativos. Desta forma, desponta a necessidade de modelos para a identificação da vida útil e análise da substituição econômica de ativos, uma vez que estas informações auxiliam na tomada de decisão e conduzem a melhores planos de manutenção, reduzindo as perdas do processo. Assim sendo, este trabalho tem por objetivo propor e aplicar uma sistemática para avaliação da substituição de ativos no setor aeroportuário, apoiado em modelos adequados às especificidades do setor através do estudo das suas variáveis. Para isto, são identificados os elementos que influenciam na vida útil dos ativos e, posteriormente, modelos de identificação de vida útil e substituição econômica de ativos são propostos e aplicados em um aeroporto brasileiro de grande porte. Pode-se concluir que a sistemática produziu resultados consistentes e que auxiliam a decisão de substituição de ativos de uma forma estruturada. / In the past years, an increase in aviation transport can be noticed and it highlights inefficiencies in asset management, especially in Brazil. Hence, the exhaustion of traditional techniques to cost reduction lead companies to seek improvements supported by more complex methods in order to increase productivity of their assets. Thus, it is crucial to develop models for useful life identification and economic replacement of assets, since these information assist the decision making process and lead to better maintenance plans, reducing wastage. As a result, the main objective of this work is develop and apply a systematic for evaluation of asset replacement in airports, supported by models that consider the specificities of the aviation sector and its particular variables. In this direction, elements that influence assets useful life are identified and, then, models for useful life identification and economic replacement of assets are developed and applied in an important Brazilian airport. It can be concluded that the systematic have produced consistent results and can assist in asset replacement decision in a structured form.