A case study of safety integrity level assessment and verification: Electronics division product line evaluation and analysis

Abstract With the adoption of IEC 61511 (Functional safety—Safety instrumented systems for the process industry sector) and ANSI/ISA‐84.00.01‐2004 (IEC 61511 Mod, Functional safety: safety instrumented systems for the process industry sector, Parts 1–3) standards, Air Products and Chemicals has made a concerted effort to provide a standardized approach to the design and implementation of safety instrumented systems following the safety lifecycle model. This presentation provides a case study describing the methodology used during the safety integrity level (SIL) assessment and verification of existing electronics division product lines. SIL assessment was accomplished through the use of hazard identification; likelihood, consequence, and risk analysis. Each of the electronics division product's safety instrumented function (SIF) was identified during SIL Assessment, making use of both layer of protection analysis (LOPA) and consequence analysis. A target SIL was determined for each SIF through quantitative and qualitative analysis. SIL Verification was accomplished using fault tree analysis in order to determine the average probability of failure on demand (PFDAVG) of each SIF. This analysis was a joint collaboration between the process safety and process controls engineering teams. © 2007 American Institute of Chemical Engineers Process Saf Prog, 2008