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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Risk-based reliability assessment of subsea control module for offshore oil and gas production

Umofia, Anietie Nnana January 2014 (has links)
Offshore oil and gas exploitation is principally conducted using dry or wet tree systems, otherwise called the subsea Xmas tree system. Due to the shift to deeper waters, subsea production system (SPS) has come to be a preferred technology with attendant economic benefits. At the centre of the SPS is the subsea control module (SCM), responsible for the proper functioning and monitoring of the entire system. With increasing search for hydrocarbons in deep and ultra-deepwaters, the SCM system faces important environmental, safety and reliability challenges and little research has been done in this area. Analysis of the SCM reliability then becomes very fundamental due to the huge cost associated with failure. Several tools are available for this analysis, but the FMECA stands out due to its ability to not only provide failure data, but also showcase the system’s failure modes and mechanisms associated with the subsystems and components being evaluated. However, the technique has been heavily challenged in various literatures for several reasons. To close this gap, a novel multi-criteria approach is developed for the analysis and ranking of the SCM failures modes. This research specifically focusses on subsea tree-mounted electro-hydraulic (E-H) SCM responsible for the underwater control of oil and gas production. A risk identification of the subsea control module is conducted using industry experts. This is followed by a comprehensive component based FMECA analysis of the SCM conducted with the conventional RPN technique, which reveals the most critical failure modes for the SCM. A novel framework is developed using multi-criteria fuzzy TOPSIS methodology and applied to the most critical failure modes obtained from the FMECA evaluation using unconventional parameters. Finally, a validation of these results is performed using a stochastic input evaluation and SCM failure data obtained from the offshore industry standard reliability database, OREDA.
2

Risk-based Reliability Assessment of Subsea Control module for Offshore Oil and Gas production

Umofia, Anietie Nnana 09 1900 (has links)
Offshore oil and gas exploitation is principally conducted using dry or wet tree systems, otherwise called the subsea Xmas tree system. Due to the shift to deeper waters, subsea production system (SPS) has come to be a preferred technology with attendant economic benefits. At the centre of the SPS is the subsea control module (SCM), responsible for the proper functioning and monitoring of the entire system. With increasing search for hydrocarbons in deep and ultra-deepwaters, the SCM system faces important environmental, safety and reliability challenges and little research has been done in this area. Analysis of the SCM reliability then becomes very fundamental due to the huge cost associated with failure. Several tools are available for this analysis, but the FMECA stands out due to its ability to not only provide failure data, but also showcase the system’s failure modes and mechanisms associated with the subsystems and components being evaluated. However, the technique has been heavily challenged in various literatures for several reasons. To close this gap, a novel multi-criteria approach is developed for the analysis and ranking of the SCM failures modes. This research specifically focusses on subsea tree-mounted electro-hydraulic (E-H) SCM responsible for the underwater control of oil and gas production. A risk identification of the subsea control module is conducted using industry experts. This is followed by a comprehensive component based FMECA analysis of the SCM conducted with the conventional RPN technique, which reveals the most critical failure modes for the SCM. A novel framework is developed using multi-criteria fuzzy TOPSIS methodology and applied to the most critical failure modes obtained from the FMECA evaluation using unconventional parameters. Finally, a validation of these results is performed using a stochastic input evaluation and SCM failure data obtained from the offshore industry standard reliability database, OREDA.
3

Reliability of PV Modules: Dependence on Manufacturing Quality and Field Climatic Conditions

January 2017 (has links)
abstract: This is a two-part thesis assessing the long-term reliability of photovoltaic modules. Part 1: Manufacturing dependent reliability - Adapting FMECA for quality control in PV module manufacturing This part is aimed at introducing a statistical tool in quality assessments in PV module manufacturing. Developed jointly by ASU-PRL and Clean Energy Associates, this work adapts the Failure Mode Effect and Criticality Analysis (FMECA, IEC 60812) to quantify the impact of failure modes observed at the time of manufacturing. The method was developed through analysis of nearly 9000 modules at the pre-shipment evaluation stage in module manufacturing facilities across south east Asia. Numerous projects were analyzed to generate RPN (Risk Priority Number) scores for projects. In this manner, it was possibly to quantitatively assess the risk being carried the project at the time of shipment of modules. The objective of this work was to develop a benchmarking system that would allow for accurate quantitative estimations of risk mitigation and project bankability. Part 2: Climate dependent reliability - Activation energy determination for climate specific degradation modes This work attempts to model the parameter (Isc or Rs) degradation rate of modules as a function of the climatic parameters (i.e. temperature, relative humidity and ultraviolet radiation) at the site. The objective of this work was to look beyond the power degradation rate and model based on the performance parameter directly affected by the degradation mode under investigation (encapsulant browning or IMS degradation of solder bonds). Different physical models were tested and validated through comparing the activation energy obtained for each degradation mode. It was concluded that, for the degradation of the solder bonds within the module, the Pecks equation (function of temperature and relative humidity) modelled with Rs increase was the best fit; the activation energy ranging from 0.4 – 0.7 eV based on the climate type. For encapsulant browning, the Modified Arrhenius equation (function of temperature and UV) seemed to be the best fit presently, yielding an activation energy of 0.3 eV. The work was concluded by suggesting possible modifications to the models based on degradation pathways unaccounted for in the present work. / Dissertation/Thesis / Masters Thesis Chemical Engineering 2017
4

Failure analysis of railway switches and crossings for the purpose of preventive maintenance.

Jalili Hassankiadeh, Seyedahmad January 2011 (has links)
In the Swedish railway network there are about 12000 units of track switches and crossings, which at 13000 Km, make up about 5.5 percent of the total track length. However, the maintenance cost for S&C is more than 13 percent of the total maintenance cost which is high in comparison with their proportion. The aim of the project is to conduct research into classification of the different modes of failure in S&C components and to perform a statistical analysis to converge the data in order to determine the most important failures that occur in turnouts.
5

Kvalitetssäkring av monteringsmoment vid Fasta Motorers F11-montering utifrån en process-, felläges- och effektanalys / Quality assurance of assembly operations at fixed motors F11-assembly based on a process failure mode and effect analysis

Dalung, Emma, Johansson, Mikael January 2012 (has links)
I detta examensarbete har möjligheten att kvalitetssäkra en monteringsbana vid Parker Hannifin Manufacturing Sweden AB:s anläggning i Trollhättan utretts. Syftet med studien var att förbättra kvalitetssäkringen vid Fasta Motorers F11-montering och arbetet baserades på en tidigare utarbetad felläges- och effektanalys. För att styrka kundperspektivet genomfördes en undersökning av vad kunderna reklamerar, i form av PQP-anmälningar samt NCMR-rapporter. Genom att därefter identifiera kritiska monteringsmoment i felläges- och effektanalysen, PQP-anmälningar och NCMR-rapporter, var en prioritering möjlig att utföra. Prioriteringen resulterade i att feltyperna felvridet lagerhus, felplock av material samt kuggfel ansågs vara de mest kritiska att kvalitetssäkra. Målet med arbetet var att reducera det totala risktalsvärdet, vilket var möjligt genom en konceptgenerering samt ett konceptval för de specifika prioriteringarna. I samband med konceptgenereringen undersöktes, genom intervjuer med berörd personal, specifika kundbehov. Dessa kundbehov omarbetades därefter till målspecifikationer för att underlätta genereringen av koncept. Då informativa koncept var framtagna återstod ett val av det bäst lämpade konceptet. Valet utfördes med två olika metoder, screening och scoring samt 3P, för att ytterligare säkerställa att rätt koncept valts. Det var därmed möjligt att uppdatera felläges- och effektanalysen med de valda åtgärderna och då påvisa att syftet var uppnått. Syftet med kvalitetssäkringen uppnåddes genom att sänka det totala risktalsvärdet med 47,5 procent mot det tidigare risktalsvärdet, 6415. / In this thesis an investigation has been made in order to find possibilities to assure the quality at an assembly line at Parker Hannifin Manufacturing Sweden AB:s facility in Trollhättan. The purpose with the study was to improve the quality assurance at Fixed Motors F11-assembly line, where the work was based on an already conducted process-FMEA. In order to verify and further investigate the customer perspective, an inquiry was also done to see what customers complained about, this with help of PQP, Product Quality Problems, and NCMR, Nonconformance reports. By analyzing the process-FMEA, PQP and NCMR reports an identification and prioritization of critical failures were made. The result from these steps was three failures, incorrect positioning of the bearing house, picking of incorrect material and incorrect gear timing. These three were considered to be the most critical failures to quality assure. The aim with the quality work were set to reduce the total RPN, Risk Priority Number, of the process-FMEA, which was rendered by applying a concept generation and a concept selection for the specific failures. In relation with the concept selection, interviews were made with staff that was considered important and vital for the project. This was made to identify specific customer needs regarding solutions to the three failures. From these needs a target specification was developed to ease the generation of concepts. After generating a number of well specified concepts, a concept selection was made using the two methods screening and scoring and an additional Parker method called 3P to further establish that the right concepts was chosen. Further it was then possible to update the process-FMEA with the chosen concept solutions and by doing that reaching the project aim. By implementing the solutions it was possible to reduce total RPN, 6415, with 47,5 percent.
6

Developing a Risk Assessment Model for non-Technical Risk in Energy Sector

Almashaqbeh, Sahar, Munive-Hernandez, J. Eduardo, Khan, M. Khurshid 28 February 2018 (has links)
Yes / Risk Management is one of the most relevant approaches and systematic applications of strategies, procedures and practices management that have been introduced in literatures for identifying and analysing risks which exist through the whole life of a product ,a process or services. Therefore, the aim of this paper is to propose a risk assessment model that will be implemented to the energy sector, particularly to power plants. This model combines the Analytic Hierarchy Process (AHP) technique with a new enhanced Balance Score Card (BSC). AHP is constructed to determine the weights and the priorities for all perspectives and risk indicators that involved in the BSC. The novelty in this paper is not only in using the BSC for risk assessment, but also, in developing a new BSC with six perspectives, which are sustainability perspective; economic; learning and growth; internal and operational business process; supply chain and customer/demand perspective. Another three contributions of this paper are firstly, including the sustainability dimension in BSC, and covering nine risk categories, which comprise 84 risk indicators that have been distributed across the six risk BSC perspectives. Secondly, assessing the non-technical risks in power plants and finally, this research will concentrate on the strategic level instead of the operational level where the majority of researches focus on latter but the former is far less researched. The created model will provide an effective measurement for the risks particularly, in the power plants sector. The results of this study demonstrate that the supply chain risks perspective is the keystone for the decision making process. Furthermore, these risk indicators with the new structure of BSC with six perspectives, help in achieving the organisation mission and vision in addition to affording a robust risk assessment model. The inputs of this model are composed from a previous stage using a modified Failure Mode and Effect Analysis (FMEA) (which has been used the Exponential Weighted Geometric Mean (EWGM)) to understand and analyse all risks, after which, the results of the developed FMEA which are the Risk Priority Numbers (RPN’s), have been used to build the AHP-BSC risk model. These risks are collected with difficulty from various literatures. This study will be validated in the next stage in power plants in the Middle East. / Hashemite University, Jordan
7

PROFITABILITY IMPROVEMENT OF CONSTRUCTION FIRMS THROUGH CONTINUOUS IMPROVEMENT USING RAPID IMPROVEMENT PRINCIPLES AND BEST PRACTICES

Fekadu Debella (9155963) 29 July 2020 (has links)
<p>The internal and external challenges construction companies face such as variability, low productivity, inefficient processes, waste, uncertainties, risks, fragmentation, adversarial contractual relationships, competition, and those resulting from internal and external challenges such as cost overruns and delays negatively affect company performance and profitability. Though research publications abound, these challenges persist, which indicates that the following gaps exist. Lean construction, process improvement, and performance improvement research have been conducted wherein improvement principles, and best practices are used to ameliorate performance issues, but several knowledge gaps exist. Few companies use these improvement principles and best practices. For those companies applying improvements, there is no established link between these improvements and performance/profitability to guide companies. Further, even when companies use improvement principles and best practices, they apply only one or two, whereas an integrated application of these improvement principles and best practices would be more effective. The other gap the author identified is the lack of strategic tools that construction companies can use to improve and manage their profitability. This thesis tried to fill the knowledge gap, at least partially, by developing a two-part excellence model for profitability improvement of construction companies. The excellence model lays out strategies that would enable companies to overcome the challenges and improve their profitability. The excellence model also gives an iterative and recursive continuous improvement model and flowchart to improve the profitability of construction companies. The researcher used high impact principles, guidelines, and concepts from the literature on organizational effectiveness, critical success factors, strategic company profitability growth enablers, process improvement, and process maturity models, performance improvement, and organizational excellence guidelines to develop the two-part excellence model.</p> <p>The author also translated the two-part excellence model into the diagnostic tool and Decision Support System (DSS) by use of process diagrams, fishbone diagrams, root cause analysis, and use of improvement principles, countermeasures and best practices at the most granular (lowest intervention) levels to do away with root causes of poor performance. The author developed the diagnostic tool and Decision Support System (DSS) in Access 2016 to serve as a strategic tool to improve and manage the profitability of construction companies. The researcher used improvement principles, and best practices from scientific and practitioner literature to develop company and project process flow diagrams, and fishbone (cause and effect) diagrams for company, department, employee, interactions and project performance for the profitability improvement, which are the engines of the diagnostic tool and DSS. The diagnostic tool and DSS use continuous improvement cycles iteratively and recursively to improve the profitability of construction companies from the current net profit of 2-3 percent to a higher value.</p>

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