It is perhaps just as important to know what is NOT specified as what is required in the many clauses referenced by the safety life-cycle. Many projects involving functional safety and SIS get off on the wrong footing by making the false assumption that simply copying the life-cycle from the standard will be sufficient.
- NO guidance on WHO is responsible for each SIS safety life-cycle activity. Management and planning is therefore critical.
- NO specific techniques are mandated e.g. HAZOP, LOPA etc. The duty holder must decide which techniques to use and provide procedures.
- NO requirements for safety functions that are not instrumented (e.g. relief valves), or for other non-instrumented safety-related activities which may reduce risk. Other standards will apply to those.
- IEC 61511 is NOT a means for manufacturers to make claims about SIL capability of their devices. Only conformance to IEC 61508 can provide that.
- IEC 61511 is NOT a means for manufacturers or others to make SIL claims about embedded software or applications with full variability software languages.
- NO specific SIL is specified for any particular application.