Gruhn, P.
Rockwell Automation, Houston, Texas
is a global process safety consultant with Rockwell Automation in Houston, Texas. He is an ISA Fellow; a member of the ISA 84 standard committee (on safety instrumented systems); a developer and instructor of ISA courses on safety systems; the author of two ISA textbooks, two chapters in other books and over two dozen published articles; and the developer of the first commercial safety system software modeling program. Mr. Gruhn has a BS degree in mechanical engineering from the Illinois Institute of Technology. He is a licensed professional engineer (PE) in Texas, and is an ISA 84 expert.
The ISA 84 (IEC 61511) standard on safety instrumented systems (SISs) in the process industries states that assessments and audits are required to determine that functional safety has been achieved and maintained.
For decades, process industries have used different forms of safety control based on what was available in the market. The simple answer to the question of whether SIS devices need to be certified is, "No," but operators and the industry as a whole continue to ask for certification anyway. Why is this?