Requirements for selection of components and subsystems

1 The first objective of the requirements of this clause is to specify the requirements for the selection of components or subsystems which are to be used as part of a safety instrumented system. 

No reproduction or networking permitted without license from IHS 

1 Components and subsystems selected for use as part of a safety instrumented system for SIL 1 to SIL 3 applications shall either be in accordance with lEC 61508-2 and lEC 61508-3, as appropriate, or else they shall be in accordance with 11.4 and 11.5.3 to 11.5.6, as appropriate. 

1 There are some considerations for selecting components and sub-systems to be used in a SIS. The first option is that the components be designed in accordance with lEC 61508-2 (requirements for electrical/electronic/programmable electronic safety-related systems) and lEC 61508-3 (software requirements). The second option is to use components and sub-systems that are known to be reliable through extensive use in similar service and in a similar environment. 

Whichever option is chosen, it has to be demonstrated that the component or subsystem 

The requirement of c) can be satisfied either by compliance with lEC 61508-2 and lEC 61508-3 or by the prior use requirements in 11.5 of this standard. 

3 Requirements for the selection of components and subsystems based on prior use 

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Requirements for selection of components and subsystems, field devices, and interface refer guide in the standard. 

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