Process safety is more than a PLC
Jack Smith, Editor -- AppliedAutomation, 2/1/2008
Charlie Fialkowski is quick to point out that Safety Instrumented System design is all about the process for this issue of AppliedAutomation. Designing a large SIS includes some activities that are outside the realm of the control engineer.
In one entry in Fialkowski’s blog (www2.sea.siemens.com/News/Blogs), he wrote, “You would think that the simple word 'safety’ would be so well understood by now that – well – even a caveman could get it. Unfortunately, I find we are still struggling to come to a consensus.”
Process safety is more than just the sensors, the logic solver or the final element – it’s all of these. But don’t stop there. Beyond this system, there is the process. A refinery has different safety concerns than a chemical plant. The concepts and philosophies are the same, but the devil is in the details.
The ISA 84.00.01-2004 (IEC 61511) standard describes safety system performance requirements – Safety Integrity Level – for the overall system. Fialkowski puts the issue of risk into perspective. He covers the SIS design steps within the safety life cycle from concept to decommissioning.
Process safety is more than a PLC. However, as Fialkowski wrote in another blog entry, “A safety PLC is required for all but SIL 1, and even with that comes baggage – makes one wonder why anyone would elect to go outside the slew of certified offerings.”
