by Paul Gruhn, P.E., CFSE
This paper summarizes the differences between the first and second editions of IEC 61511.
Historical Background The ISA (International Society of Automation) 84 standard (“Application of Safety Instrumented Systems for the Process Industries”) was first published in 1996. During the time of its development, the IEC (International Electrotechnical Commission) was working on the 61511 standard (“Functional Safety: Safety Instrumented Systems for the Process Industry Sector”). Some members of the ISA 84 committee were also members of the IEC 61511 committee. In essence, the ISA 84 committee had direct involvement (along with all the other national committees) in the creation of the IEC 61511 standard. IEC 61511 was published in 2003.
ISA and IEC, like many standards development organizations, try and put their standards through a 5 year review and development cycle. In the early 2000’s the ISA 84 committee felt that the more recent 61511 standard was a considerable improvement compared to its original work, and the committee agreed to adopt 61511 as the 2nd edition of ISA 84. The only change was the addition of the “grandfather clause” (1.y) which comes from a US regulation. ISA 84 (IEC 61511 mod) 2nd edition was released in 2004.
It has been over 10 years since the first release of IEC 61511. That committee has worked diligently to create a 2nd edition. A CD (Committee Draft) went out for review and comment by the national committees in 2012. The FDIS (Final Draft International Standard) went out to the committee in November 2015. The standard is expected to be released in 2016. Note that there may still be editorial changes to the standard, but no further technical changes will be accepted for this edition. The ISA 84 committee will then decide whether to accept the 2nd edition of IEC 61511 as the 3rd edition of ISA 84, or whether they may wish to make any changes. Considering the desire for international design practices and standards, changes would be unlikely.