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Click Below for Additonal SIL Information
Topics
 Articles: SIL
101 | SIL
102 | SIL
103
Calculating
SIL Suitability Levels
Choosing
an SIL System
LOPA:
Layer of Protection Analysis
Functional Safety Standards
The ANSI / ISA-84.00.01-1996 was the first standard developed by the
ISA SP84 committee to address the need to increase safety by systematically
reducing process risk. The standards are updated approximately every
5 years and the most recent version was released in 2004. The new
version adopts the IEC 61511 standard and adds the original 1996 version
of ANSI/ISA 84 as a “grandfather clause”.
IEC 61508 is an umbrella standard released by the International Electrotechnical
Committee in 1998 that is based on ANSI/ISA 84 and applies to all
industries. The IEC 61508 standard is viewed as the document that
vendors follow to receive certification for SIL suitability ratings
for products and system components.
IEC 61511 was released in 2003 and was developed specifically to address
functional safety in the process industry. This document is used by
end-users to successfully implement system safety throughout the entire
life-cycle of a system.
Please note, that if a system was implemented prior to the update
of the standards in 2004 and has been operating in a safe manner without
an increase in risks or safety incidents, then the system can be “grandfathered”
and does not need to comply with the ANSI / ISA 84 2004 update. However,
once significant changes are made to the system or if a safety issue
arises, the system will have to comply with the most recent version
of the standards.
It is important to note that none of the standards are prescriptive,
but are performance based. The standards present guidelines for best
practices, but do not identify procedures for specific implementation.
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