Risk Assessment of the Light Rail Train Braking Systems by Failure Mode, Effects and Criticality Analysis (FMECA): A Case Study of Addis Ababa Light Rail Train

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Addis Ababa University


Many light rail train accidents have occurred in recent years despite the development of modern design technology and better safety standards implying there will always be some risk associated with the system. This has been attributed to many reasons, and one of the major contributions is system failures. System failures are normally related to maintenance methods and implementation by an organization. These system failures can prove to be costly and have very high safety-related consequences that may lead to catastrophic events. However these can be eliminated/minimized through selection of effective maintenance practices. Many systems, such as the traction system, the braking system, etc. are utilized in light railway trains, and each system must perform its function effectively and efficiently. This research focused on the braking system due to the identified accumulated minor failures and its crucial role in human mass transportation. The main goal of this thesis research is to identify the most risky components of the light rail braking system using the Failure Mode Effects and Criticality Analysis approach. This approach determines the likelihood of failure, severity, and failure mode detectability and assigns a numerical score to each failure mode to obtain the Risk Priority Number, which is a product of these three ratings. Most Current Failure Mode Effects and Criticality Analysis methods use the risk priority number to evaluate the risk of failure and suggest a maintenance practice. This thesis study makes a significant contribution by proposing a maintenance selection model based on the acquired risk findings and an estimated maintenance repair cost due to component failure utilizing the fuzzy logic mat lab tool. This model aimed to assist in decision-making for maintenance practices of light rail systems. Data was gathered from the Addis Ababa light rail transit using prior failure record analysis, an unstructured interview, and a research questionnaire. 42 failure modes, 22minor events (do not reduce adhesion), 20 major events (reduce brake adhesion) mainly observed on the mechanical components were detected throughout the assessment. The failure assessment revealed that brake pads among other components possess a high risk for the braking system. As obtained by the proposed model, condition-based maintenance and total productive maintenance are suitable for the safety of the light rail braking system.



Risk assessment, train braking system, fuzzy logic, maintenance strategy, Failure Mode, Effect, Criticality Analysis (FMECA)