SAFETY INTEGRITY LEVEL (SIL) ALLOCATION ON MONORAIL ROLLING STOCK

摘要

Railroad and transit projects are increasingly referencing and requiring compliance with the CENELEC railway standards, and the Independent Safety Assessment (ISA) is a key element of the safety certification and homologation process. The Quantitative Risk Analysis (QRA) which includes the Safety Integrity Level (SIL) allocation to the Safety Functions (SFs) is one of the major elements in the development of a Safety Management System (SMS) for the railroad and transit systems. This paper presents the experience with SIL allocation to the Safety functions designed on the Monorail Rolling Stock, which is essential for the Safety Management System to be successful in delivering IEC 61508 / CENELEC standards (EN 50126/8/9) based railroad and transit systems. This paper introduces the concept of SIL, interpretation of SIL in the different standards such as IEC61508, EN50126, EN50128 and EN50129; methods of defining Tolerable Hazard Rate, ALARP principle, and experience of SIL allocation on the Monorail Rolling Stock. The study of SIL allocation on the Monorail Rolling Stock comprises of the characteristics of the Monorail system, general approach of SIL allocation, functional analysis, identification of required SIL, example discussion, assignment of safety functions to systems, and the identification of alternate risk reduction measures. The conclusion is summarized at the end of the paper.