AS IEC 61511.3:2018 PDF
The objective of this Standard is to provide information on – (a) the underlying concepts of risk and the relationship of risk to safety integrity (see Clause A.4); (b) the determination of tolerable risk (see Annex K); (c) a number of different methods that enable the safety integrity level (SIL) for the safety instrumented functions (SIF) to be determined (see Annexes B through K); and (d) the impact of multiple safety systems on calculations determining the ability to achieve the desired risk reduction (see Annex J).
Safety instrumented systems (SIS) have been used for many years to perform safety instrumented functions (SIF) in the process industries. If instrumentation is to be effectively used for SIF, it is essential that this instrumentation achieves certain minimum standards and performance levels.
The IEC 61511 series addresses the application of SIS for the process industries. A process hazard and risk assessment is carried out to enable the specification for SIS to be derived.
Other safety systems are only considered so that their contribution can be taken into account when considering the performance requirements for the SIS. The SIS includes all devices and subsystems necessary to carry out the SIF from sensor(s) to final element(s).
The IEC 61511 series has two concepts which are fundamental to its application; SIS safety life-cycle and safety integrity levels (SIL).
The IEC 61511 series addresses SIS which are based on the use of Electrical (E)/Electronic (E)/Programmable Electronic (PE) technology. Where other technologies are used for logic solvers, the basic principles of the IEC 61511 series should be applied. The IEC 61511 series also addresses the SIS sensors and final elements regardless of the technology used. The IEC 61511 series is process industry specific within the framework of IEC 61508:2010.
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