Performance-based standards: safety instrumented functions and safety integrity levels

This paper discusses two international performance-based standards, ANSI/IS A S84.01 and IEC d61508 and the requirements they place upon companies that rely on electrical, electronic and programmable electronic systems to perf orm safety functions. Performance-based regulations are also discussed and common safety elements between the standards and regulations are identified . Several risk analysis techniques that can be used to comply with the afor ementioned requirements are discussed and a simple example is used to illus trate the use, advantages and disadvantages of the techniques. The evaluati on of safety integrity level (Sn) of the Safety Instrumented System (SIS) i n terms of the probability to fail to function is outside the scope of this paper. (C) 2000 Elsevier Science B.V. All rights reserved.