Browsing by Author "Parreira, Rui"
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- Control Charts Limits Flexibility Based on the Equipment ConditionsPublication . Lampreia, Suzana Paula Gomes Fernando da Silva; Vairinhos, Valter Martins; Lobo, Victor J. A. S.; Parreira, Rui; Requeijo, José GomesCondition Based Maintenance became an important development in industrial and transport equipment maintenance efforts. Many statistical methodologies have been applied in this area. These methodologies are usually applied off-line: after the data is collected. We propose an online, real-time condition monitoring system based on a modified control chart, applied to engine parameters. These charts should be flexible enough and its control limits should reflect the equipment state, the manufacturer specifications and onboard meteorological conditions. In this study we will develop a methodology to specify flexible chart control limits. The experimental equipment is a combined diesel or gas propulsion system. Two phases will be assumed. In phase 1 the equipment and historical data are analyzed, studying historical data, which leads to the definition of equipment parameters. In phase 2, new data is obtained by simulation, and the Exponentially Weighted Moving Average charts are applied considering flexible limits.
- Opportunistic Maintenance Based on CUSUM Control ChartsPublication . Lampreia, Suzana Paula Gomes Fernando da Silva; Vairinhos, Valter Martins; Lobo, Victor J. A. S.; Parreira, Rui; Requeijo, José GomesThe use of a Ship Maintenance Management System is fundamental for the good performance of equipments and the entire platform. Over the systematic maintenance, the opportunistic maintenance is a concept that aims to minimize outages and costs preventing undesirable failures. To implement this kind of maintenance statistical methodologies must be used. The Cumulative Sum charts have a very good performance applied to processes control in quality control. We proposed the use of Modified Cumulative Sum control charts to equipment maintenance.The data under study are observations of cooling water and oil temperatures from a diesel generator. In the first phase, we will apply traditional control charts, and, in the second phase, the Cumulative charts with a certain Average Run Length will be used. Then we will compare the results and extract conclusions, presenting measures for improvement.
- Ourivesaria arcaica em Portugal. O brilho do poderPublication . Correia, Virgílio Hipólito; Parreira, Rui; Silva, Armando Coelho Ferreira da