A SIL quantification approach to complex systems for guided transportation

摘要

This article adds to the information available on the use of Safety Integrity Levels (SILs) for evaluating the safety of guided transportation systems. First, the risk management process that is crucial to any such safety evaluations is examined. Then, the fundamentals of SIL are presented, with particular attention to its quantitative aspects. Several of the quantitative and qualitative methods that can be used to assign SIL to diverse subsystems, functions and/or equipment are also presented. Since these methods do not take the overall system's safety evaluation into account, this paper explains why only subsystems or functions are considered. It focuses on the problem of associating several safety functions with different or identical SIL as a means of identifying the equivalent of a system SIL. These functions are examined in terms of their use in successive sequences or in redundancy blocks. A quantitative approach to SIL, based on simulation, is introduced, and its implementation and results are presented.