Risk-Based Dependability Assessment of Digitalised Condition-Based Maintenance in Railway—Part II–Event Tree Analysis (ETA)

One vital contribution of Reliability-Centred Maintenance (RCM) is the definition of potential failure, which led to the concept of Condition-Based Maintenance (CBM) being accepted as one of the best ways of preventing functional failure. To enable CBM, the condition of an item must be monitored by Condition Monitoring (CM) of some critical functions. The CM results in collected data that represent the system’s condition in some way. Diagnostics and prognostics is then concerned with the interpretation of collected condition data and the conclusion drawn about the item’s current and future condition. On the basis of the diagnostic and prognostic information, decisions about appropriate CBM can be made. The purpose of the risk-based dependability assessment described in this paper, is to support a decision whether or not a railway infrastructure item should be covered by a new digitalised inspection solution for CM to enable improved CBM. Hence, the dependability assessment indicates ‘which’ functions or items that should be covered by a digitalised solution for inspection (CM) and ‘why’ they should be covered. ‘How’ the coverage should be solved, i.e., by which technical solutions, is not included in this paper. The proposed dependability assessment is based on stakeholder requirements, through a combination of a Failure Modes, Effects & Criticality Analysis (FMECA) and an Event Tree Analysis (ETA) with three major decision points where Maintenance Significant Items (MSIs) for further analysis are identified. This paper focuses on the ETA-part and the third MSI-selection of the proposed approach.