Activity: Talk or presentation › Oral presentation
Current trend in infrastructural asset management is towards risk-based (a.k.a. reliability centered) maintenance, promising better performance at lower cost. By maintaining crucial components more intensively than less important ones, dependability increases, while costs decrease. This requires good insight in the effect of maintenance on the dependability and their associated costs. To gain these insights, we propose a novel framework, Fault maintenance trees (FMTs), integrating fault tree analysis with maintenance. We support many dependability measures, such as the system reliability and availability, as well as costs over time, split into different cost components. FMTs are based on fault trees (FTs), a popular method in reliability engineering. We augment FTs in three ways: - A new rate-dependency gate models cases where a trigger (e.g. installation failure) causes components to fail at a higher rate. - Maintenance models specify the effects of maintenance on components. We allow various phases of degradation in components. Inspections take action depending on the degradation, and repairs remove or reduce degradation. - Costs, where consider the cost of maintenance actions, as well as the cost of downtime and failures. Technically, our framework is realized via statistical model checking, a state-of-the-art tool for flexible modeling and simulation. Our compositional approach is flexible and extensible. We apply our framework to two industrial case studies. First, we collaborated with ProRail to analyze the electrically insulated joint, a major cause of disruptions in train service. Our analysis points out that (1) the current maintenance policy is cost-optimal for the current joint design, and (2) a new design developed by RailPro offers significant cost savings. The second case study concerns a pneumatic compressor and was provided by NedTrain. Our analysis points out the importance of the service frequency, and that a periodic overhaul is likely not cost-effective.