ISA accepted the 2nd edition of IEC 61511, “Functional Safety — Safety Instrumented Systems for the Process Industry Sector,” as the replacement for the current U.S. national standard, ANSI/ISA 84.00.01-2004. Unlike the previous edition, the latest U.S. and international versions don’t differ at all.
However, the “grandfather clause" now appears in clause 5, serving as a reminder that leaving an SIS “as is” demands a formal determination that it is achieving functional and safety integrity requirements, which must be determined by an assessment of the design, maintenance, inspection, testing and operating records for the installed system.
Our sister website Chemical Processing examines some IEC 61511 requirements that should be considered when determining whether an SIS can be left as-is.
