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Determining the SIL

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yennyffer duran Moderated by: Michel Houtermans	Thursday 28 December 2006 3:10:35 pm Determining the SIL I'm pretty new in this area and I'd like to know about how to determine the SIL for a process. I'm working on a pilot plant and I know that after doing the HAZOP study I would be able to determine the SIL for each node analized on the HAZOP, my confusion is how I decide the SIL for the whole plant (is it the most restrictive SIL). Is there any procedure to determine the SIL of the whole plant? I need this SIL to design the SIS
Jonas Krueger	Wednesday 03 January 2007 10:53:13 am Re: Determining the SIL As far as I know it is not common to determine the SIL of a whole plant. You only determine the SIL of an individual safety loop. A plant has therefore many SIL's. See IEC 61511.
Michel Houtermans	Thursday 04 January 2007 9:31:01 am Re: Determining the SIL As said in the previous post there is no plant level SIL. But in order to design you SIS you must make sure that the common elements of your SIS, usually the logic solver, is of the highest SIL concerning the loops it integrates. In other words one SIL 1 loop , one SIL 2 loop, and one SIL 3 loop integrated into one logic solver means that the logic solver needs to be of SIL 3. The f ield instrumentation for example can then still be SIL 1, 2 or 3 depending on the loop.