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- Preventive maintenance of critical assets based on degradation mechanisms and failure forecastPublication . Sobral, José; Guedes Soares, CarlosWhen dealing with critical physical assets it is very important to monitor some parameters just to observe and predict the potential time to failure and thus establish a preventive maintenance activity avoiding the unwanted failure occurrence and its consequences. According to periodic (or continuous) data gathered along the time concerning selected parameters it is possible to observe tendencies and determine time to failure, assuming a pre-defined value as the critical one, corresponding to asset failure. The present paper deals with this type of condition monitoring outlining the importance of predicting time to failure and illustrating it with an example where the evolution of a degradation parameter on time for several similar assets is observed and, based on that, the time to failure is determined, allowing to establish the right moment for maintenance for these type of assets operating in these conditions.
- Increasing availability through maintainability growth using partial Multi Criteria Decision Making (pMCDM)Publication . Sobral, José; Ferreira, L. A.In the last decades considerations about equipments' availability became an important issue, as well as its dependence on components characteristics such as reliability and maintainability. This is particularly of outstanding importance if one is dealing with high risk industrial equipments, where these factors play an important and fundamental role in risk management when safety or huge economic values are in discussion. As availability is a function of reliability, maintainability, and maintenance support activities, the main goal is to improve one or more of these factors. This paper intends to show how maintainability can influence availability and present a methodology to select the most important attributes for maintainability using a partial Multi Criteria Decision Making (pMCDM). Improvements in maintainability can be analyzed assuming it as a probability related with a restore probability density function [g(t)].
- Availability of fire pumping systems under periodic inspectionPublication . Sobral, José; Ferreira, L. A.Fire pumping systems are often used for firefighting in the majority of buildings, can they be residential, commercial, industrial or any other type. These systems are responsible for the needed water flow and pressure on manual or automatic devices installed for building protection purposes. Thus, it is very important to assure their availability when an undesirable fire event occurs. This paper focuses fire pumping systems' availability when they are submitted to regular periodic inspections or tests. These inspections or tests are performed to observe the system behavior and detect potential hidden failures of some component or subsystem. The methodology proposed in this paper is focused in the first stage on the analysis of the probability of failure on demand of critical equipment and analyzing the probability of success of this important stage. It is also shown the influence of inspection or tests frequency on the desired availability of the fire pumping system.