IEC 61511-2:2003(E) FUNCTIONAL SAFETY-SAFETY INSTRUMENTED sYSTEMSFOR THE PROCESS INDUSTRY SECTOR-Part 2: Guidelines for the application of IEC 61511-1
Scope
IEC 61511-2 provides guidance on the specification，design，installation，operation andmaintenance of Safety instrumented Functions and related safety instrumented system asdefined in lEC 61511-1.This standard has been organized so that each clause and subclausenumber herein addresses the same clause number in lEC 61511-1(with the exception of theannexes).
2Normative references
No further guidance provided.
3 Terms, definitions and abbreviations
No further guidance provided except for 3.2.68 and 3.2.71 of lEC 61511-1.
3.2.68 A safety function should prevent a specified hazardous event.For example,"preventthe pressure in vessel #ABC456 exceeding 100 bar." A safety function may be achieved bya) a single safety instrumented system (SIs), or
b) one or more safety instrumented systems and/or other layers of protection.
In case b), each safety instrumented system or other layer of protection has to be capable ofachieving the safety function and the overall combination has to achieve the required riskreduction (process safety target).
3.2.71 Safety instrumented functions are derived from the safety function，have anassociated safety integrity level (SIL) and are carried out by a specific safety instrumentedsystem (SlS).For example, "close valve #XY123 within 5 s when pressure in vessel #ABC456reaches 100 bar". Note that components of a safety instrumented system may be used by
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