Layer Of Protection Analysis: Pilot study, method development and application on a hydraulic braking system

Within the safety analysis industry there are a variety of tools used to ensure reliability and security of systems, ranging from mostly qualitative approaches to mostly quantitative. One safety analysis method that lies in between these two is called Layers Of Protection Analysis (LOPA). LOPA is known as a “semi-quantitative” approach that uses a mix of quantitative and qualitative approaches to draw conclusions. In this masters thesis the LOPA approach is demonstrated, in addition to being developed into two alternate LOPA approaches, known as MarkovLOPA and RBDLOPA. These two developed approaches use the concept of Markov chains and Reliability block diagram (RBD) respectively, to extend the applicability of the traditional LOPA methodology. Furthermore, a conventional hydraulic braking system (CHB), which includes ABS/TCS- and ESP functionality was analysed by these three methodologies. The results of the analysis show that in the analysis by LOPA and RBDLOPA 4- and 3 out of 10 scenarios need slight improvements and only 1 scenario for MarkovLOPA. Additionally, the validity of the alternative approaches are analysed by a sensitivity analysis, showing irregularities in the results, leading to the conclusion that further research and development is required prior to industrial applications of the approaches