Politiques de Tests Partiels & Systèmes de Sécurité

International audienceA set of general formulas is proposed for the probability of failure on demand (PFD) assessment of MooN architecture (i.e. k-out-of-n) systems subject to partial and full tests. Partial tests (e.g. visual inspections, imperfect testing) may detect only some failures, whereas owing to a full test, the system is restored to an as good as new condition. Following the proposed approach and according to an example, performance estimations of the system and test policies are presented, by using the feedback from partial and full tests. An optimization of the partial test distribution is also proposed, which allows reducing the average probability of system failure on demand (PFDavg)

Probability of Failure of Safety-Critical Systems Subject to Partial Tests

A set of general formulas is proposed for the probability of failure on demand (PFD) assessment of MooN architecture (i.e. k-out-of-n) systems subject to proof tests. The proof tests can be partial or full. The partial tests (e.g. visual inspections, partial stroke testing) are able to detect only some system failures and leave the others latent, whereas the full tests refer to overhauls which restore the system to an as good as new condition. Partial tests may occur at different time instants (periodic or not), up to the full test. The system performances which are investigated are the system availability according to time, the PFD average in each partial test time interval, and the total PFD average calculated on the full test time interval. Following the given expressions, parameter estimations are proposed to assess the system failure rates and the partial test effectiveness according to feedback data from previous test policies. Subsequently, an optimization of the partial test strategy is presented. In the 2oo6 system given as example, an improvement of about 10% of the total PFD average has been obtained, just by a better (non-periodic) distribution of the same number of partial tests, in the full test time interval

Linhas gerais para construção de um modelo de avaliação de impacto da inovação aplicável a organizações de pesquisa agropecuária

This article is focused on a conceptual model of the innovation impact assessment process, especially directed to agricultural research organisations. This research proposes an existing methodology based on a literature review. The innovative contributions of this article are I. theoretical lines for constructing a model of impact assessment as a base for a future data based management system; II. a conceptual base of innovation impact assessment process that considers a cross-cut view of sustainability, integrating the environmental, social, policy, and economic dimensions. This article intends to present a theoretical model addressed to research and innovation organisations that will contribute to fulfilling the United Nations’ sustainable development goals towards more productive and sustainable agriculture and accomplishing stakeholder challenges and demands.  This article is focused on a conceptual model of the innovation impact assessment process, especially directed to agricultural research organisations. This research proposes an existing methodology based on a literature review. The innovative contributions of this article are I. theoretical lines for constructing a model of impact assessment as a base for a future data based management system; II. a conceptual base of innovation impact assessment process that considers a cross-cut view of sustainability, integrating the environmental, social, policy, and economic dimensions. This article intends to present a theoretical model addressed to research and innovation organisations that will contribute to fulfilling the United Nations’ sustainable development goals towards more productive and sustainable agriculture and accomplishing stakeholder challenges and demands.  This article is focused on a conceptual model of the innovation impact assessment process, especially directed to agricultural research organisations. This research proposes an existing methodology based on a literature review. The innovative contributions of this article are I. theoretical lines for constructing a model of impact assessment as a base for a future data based management system; II. a conceptual base of innovation impact assessment process that considers a cross-cut view of sustainability, integrating the environmental, social, policy, and economic dimensions. This article intends to present a theoretical model addressed to research and innovation organisations that will contribute to fulfilling the United Nations’ sustainable development goals towards more productive and sustainable agriculture and accomplishing stakeholder challenges and demands.  Este artigo está focado em um modelo conceitual de avaliação de impacto, especialmente direcionado a organizações de pesquisa agropecuária. Baseado em revisão de literatura, suas contribuições inovadoras são: I. linhas teóricas para a construção de um modelo de avaliação de impacto como base para um futuro sistema de gestão; II. uma base conceitual para avaliação de impacto de inovação que leva em conta uma perspectiva transversal de sustentabilidade, integrando as dimensões ambiental, social, política e econômica. O artigo apresenta um modelo teórico aplicável a organizações de pesquisa e inovação em sintonia com os Objetivos de Desenvolvimento Sustentável das Nações Unidas, bem como buscando uma lógica sistêmica que atenda aos desafios e demandas das partes interessadas da instituição de pesquisa.

Fiabilité des Capteurs-Transmetteurs intégrant des Fonctionnalités Numériques

These works are part of a PhD thesis performed at the INERIS, under the scientific supervision of the UTT, and about the reliability of digital-based transmitters. These systems are commonly described as “intelligent” since they are able to perform innovative functionalities such as self-diagnoses, error measurement corrections, self-adjustments, and on-line reconfigurations. Moreover, they may take advantage of a bidirectional digital communication to perform “cooperating” operations. First, an “intelligent transmitter” modelling has been developed, which includes material and functional interactions, and reliability analyses have been proposed based on this model, dealing with uncertainties linked to system behaviours under faulty conditions. Then, “intelligent transmitters” taking part of control systems have been considered, taking the system elements interactions into account, as well as the process influences, using a dynamic reliability framework

Dependability Issues for Intelligent Transmitters and Reliability Pattern Proposal

International audienceNew technologies make way for "intelligent" transmitters by integrating new functionalities: error measurement corrections, self-adjustment, self-diagnosis for measurement and transmitter status, on-line reconfiguration, and digital bidirectional communication. Industrialists are taking advantage of more accurate measurements, cost reductions and facilities. For industrial risk prevention, new dependability issues are arising. Functionalities such as self-diagnosis and digital communication seem to be in favour of control systems availability. On the other hand, the high amount of electronics and programmable units implies new failure causes and modes which are usually not well known. In this paper, dependability issues for intelligent transmitters are discussed and a reliability model is proposed. By using a Goal Tree - Success Tree (GTST) technique, both functional and material aspects of an intelligent transmitter pattern are included. Material-material, material-function, and function-function relationships are then demonstrated in Master Logic Diagrams (MLD). These results are proposed as support for further case studies. For example, the impact of any material failure on any function, and the reliability of the main functions, can be assessed using this kind of model. Other dependability tools can take advantage of this reliability pattern, for example when the behavioural aspects of complex systems are undetermined

Dynamic Reliability Modeling of Cooperating Digital-Based Systems

International audienceDynamic reliability explicitly handles the interactions between the stochastic behavior of system components and the deterministic behavior of process variables. However, its industrial level applications are still limited, notably due to the inherent complexity of the theory and the lack of a generic modeling framework. The increased use of digital-based systems has also introduced additional modeling challenges related to the interactions between cooperating digital components. For solving these challenges, the present paper first extends the mathematical framework of dynamic reliability to handle 1) information and data computed and exchanged between digital components; and 2) random parameter deviations. A formalized Petri net approach is then proposed to perform the corresponding reliability analyses, using a finite element method. Finally, the framework's effectiveness is demonstrated on a simplified model of a nuclear reactor case study

Capteurs Intelligents : Nouvelles Technologies et Nouvelles Problématiques pour la Sûreté de Fonctionnement

New technology allows intelligent sensors by integrating new functionalities: error measure correction, self-calibration, self-diagnosis of measures and sensor status, reconfiguration, digital communication. Industrialists take advantage of more accurate measurements, cost reductions and use facilities. For industrial safety, new dependability issues appear. Some functionalities as self-diagnosis and digital communication seem to be in favour of control systems availability. On the other hand, the high amount of electronics and programmable units implies new failure causes and modes. Availability assessments of intelligent sensors are quite low in literature. Moreover, “intelligent” functionalities are usually not taken into account. In this paper, a discussion about dependability issues and modelling is presented. An approach is proposed. Both functional and structural decompositions of the system are included which allow representing sensor functionalities and types of dependencies. Failures make up the third part of the model. First analyses show the consequences of these failures on sensor functions and the corresponding failure modes during time. An infrared gas sensor is used for example. Some tools for availability assessment of complex systems can take advantage of these results, especially when dysfunctional behaviour is not well known

Reliability Study of an Intelligent Transmitter

International audienceAn intelligent transmitter reliability study has to deal with several issues: various interactions between both material elements and functions; behaviors of components as programmable units and software which are difficult to predict when faults or failures occur, as well as the consequences on functions processing. A “3-step model” is therefore proposed to include both functional and material aspects, using Goal Tree–Success Tree (GTST), and setting faults and failures as a third full part. Then, Master Logic Diagrams (MLD) aim to represent several types of relationships between faults or failures, material elements, and functions. Probabilities are used for MLD components to take the indeterminate relationships into account. Quantitative assessments are then performed, using an infrared gas transmitter as an example: total relationships between any fault or failure and any function, probabilities of malfunction and failure modes. Moreover, uncertainty analyses show that even if input relationship data are uncertain, precise results can be obtained. These properties make the proposed model especially suitable for evaluating the reliability of intelligent transmitters. Finally, some design issues are discussed, taking advantage of the proposed model

Design of complex safety-related systems in accordance with IEC 61508

International audienceAccording to IEC 61508, a safety-related system is regarded as type B if it presents a high complexity (i.e. the failure mode of at least one component is not well defined, or the behaviour under fault conditions cannot be completely determined), or if there is insufficient data to support claims for failure rates. This paper proposes a modelling method adapted to the evaluation of failure probabilities for systems with uncertain behaviour under fault conditions. To this aim, weighted “continuous gates” are introduced in a fault tree framework. By acting on weight values, it is then allowed to continuously graduate system part architectures between series and parallel structures. An intelligent transmitter is used as example. Probabilities of failure on demand are assessed, with both failure rates and behaviour uncertainty analyses. Results tend to show that the lack of knowledge in system behaviour can be partially handled by this kind of approach

Optimization of maintenances following proof tests for the final element of a safety-instrumented system

2019 The Authors Safety-instrumented systems (SISs) have been widely installed to prevent accidental events and mitigate their consequences. Mechanical final elements of SISs often become vulnerable with time due to degradations, but the particulars in SIS operations and assessment impede the adaption of state-of-art research results on maintenances into this domain. This paper models the degradation of SIS final element as a stochastic process. Based on the observed information during a proof test, it is essential to determine an optimal maintenance strategy by choosing a preventive maintenance (PM) or corrective maintenance (CM), as well deciding what degree of mitigation of degradation is enough in case of a PM. When the reasonable initiation situation of a PM and the optimal maintenance degree are identified, lifetime cost of the final element can be minimized while keeping satisfying the integrity level requirement for the SIS. A numerical example is introduced to illustrate how the presenting methods are used to examine the effects of maintenance strategies on cost and the average probability of failure on demands (PFDavg) of a SIS. Intervals of the upcoming tests thus can be updated to provide maintenance crews with more clues on cost-effective tests without weakening safety