Critical Review of Reliability Centred Maintenance (RCM) for Asset Management in Electric Power Distribution System

The purpose of maintenance is to extend equipment lifetime or at least the mean time to the next failure. Maintenance too incurs expenditures that result in very costly consequences when not performed or performed too little, and it may not even be economical to perform it too frequently. Therefore the two costs must be balanced. In the past, this balance had been estimated by extrapolating the experience obtained from existing systems and using the rule - of – thumb methods. Nowadays, the tempo of advanced and softiscated research in that direction has rendered such rule – of – thumb methods obsolete. The literature works describing the reliability centred maintenance methods for managing distribution assets have grown until the papers can now be numbered in thousands. This paper presents critical review of the various existing methods that have been developed by different reseachers and proposes a probabilistic model that will provide a quantitative connection between reliability and maintenance, a link missing in all the heuristic approaches

AFTI/F-16 digital flight control system experience

The Advanced Flighter Technology Integration (AFTI) F-16 program is investigating the integration of emerging technologies into an advanced fighter aircraft. The three major technologies involved are the triplex digital flight control system; decoupled aircraft flight control; and integration of avionics, pilot displays, and flight control. In addition to investigating improvements in fighter performance, the AFTI/F-16 program provides a look at generic problems facing highly integrated, flight-crucial digital controls. An overview of the AFTI/F-16 systems is followed by a summary of flight test experience and recommendations

Preliminary human safety assessment (PHSA) for the improvement of the behavioral aspects of safety climate in the construction industry

Occupational safety in the construction industry still represents a relevant problem at a global level. In fact, the complexity of working activities in this sector requires a comprehensive approach that goes beyond normative compliance to guarantee safer working conditions. In particular, empirical research on the factors influencing the unsafe behavior of workers needs to be augmented. Thus, the relationship between human factors and safety management issues following a bottom-up approach was investigated. In particular, an easy-to-use procedure that can be used to better address workers' safety needs augmenting the company's safety climate and supporting safety management issues was developed. Such an approach, based on the assessment of human reliability factors, was verified in a real case study concerning the users of concrete mixer trucks. The results showed that the majority of human failures were action and retrieval errors, underlining the importance of theoretical and practical training programs as a means to improve safety behavior. In such a context, information and communication activities also resulted beneficially to augment the company's safety climate. The proposed approach, despite its qualitative nature, allows a clearer understanding of workers' perceptions of hazards and their risk-taking behavior, providing practical cues to monitor and improve the behavioral aspects of safety climate. Hence, these first results can contribute to augmenting safety knowledge in the construction industry, providing a basis for further investigations on the causalities related to human performances, which are considered a key element in the prevention of accidents

Wind turbine condition monitoring strategy through multiway PCA and multivariate inference

This article states a condition monitoring strategy for wind turbines using a statistical data-driven modeling approach by means of supervisory control and data acquisition (SCADA) data. Initially, a baseline data-based model is obtained from the healthy wind turbine by means of multiway principal component analysis (MPCA). Then, when the wind turbine is monitorized, new data is acquired and projected into the baseline MPCA model space. The acquired SCADA data are treated as a random process given the random nature of the turbulent wind. The objective is to decide if the multivariate distribution that is obtained from the wind turbine to be analyzed (healthy or not) is related to the baseline one. To achieve this goal, a test for the equality of population means is performed. Finally, the results of the test can determine that the hypothesis is rejected (and the wind turbine is faulty) or that there is no evidence to suggest that the two means are different, so the wind turbine can be considered as healthy. The methodology is evaluated on a wind turbine fault detection benchmark that uses a 5 MW high-fidelity wind turbine model and a set of eight realistic fault scenarios. It is noteworthy that the results, for the presented methodology, show that for a wide range of significance, a in [1%, 13%], the percentage of correct decisions is kept at 100%; thus it is a promising tool for real-time wind turbine condition monitoring.Peer ReviewedPostprint (published version

Analysis and Insights from a Dynamical Model of Nuclear Plant Safety Risk

In this paper, we expand upon previously reported results of a dynamical systems model for the impact of plant processes and programmatic performance on nuclear plant safety risk. We utilize both analytical techniques and numerical simulations typical of the analysis of nonlinear dynamical systems to obtain insights important for effective risk management. This includes use of bifurcation diagrams to show that period doubling bifurcations and regions of chaotic dynamics can occur. We also investigate the impact of risk mitigating functions (equipment reliability and loss prevention) on plant safety risk and demonstrate that these functions are capable of improving risk to levels that are better than those that are represented in a traditional risk assessment. Next, we analyze the system response to the presence of external noise and obtain some conclusions with respect to the allocation of resources to ensure that safety is maintained at optimal levels. In particular, we demonstrate that the model supports the importance of management and regulator attention to plants that have demonstrated poor performance by providing an external stimulus to obtain desired improvements. Equally important, the model suggests that excessive intervention, by either plant management or regulatory authorities, can have a deleterious impact on safety for plants that are operating with very effective programs and processes. Finally, we propose a modification to the model that accounts for the impact of plant risk culture on process performance and plant safety risk. We then use numerical simulations to demonstrate the important safety benefits of a strong risk culture.Nonlinear Dynamical Systems, Process Model, Risk Management

De-perimeterisation as a cycle: tearing down and rebuilding security perimeters

If an organisation wants to secure its IT assets, where should the security mechanisms be placed? The traditional view is the hard-shell model, where an organisation secures all its assets using a fixed security border: What is inside the security perimeter is more or less trusted, what is outside is not. Due to changes in technologies, business processes and their legal environments this approach is not adequate anymore.\ud This paper examines this process, which was coined de-perimeterisation by the Jericho Forum.\ud In this paper we analyse and define the concepts of perimeter and de-perimeterisation, and show that there is a long term trend in which de-perimeterisation is iteratively accelerated and decelerated. In times of accelerated de-perimeterisation, technical and organisational changes take place by which connectivity between organisations and their environment scales up significantly. In times of deceleration, technical and organisational security measures are taken to decrease the security risks that come with de-perimeterisation, a movement that we call re-perimeterisation. We identify the technical and organisational mechanisms that facilitate de-perimeterisation and re-perimeterisation, and discuss the forces that cause organisations to alternate between these two movements