Dear Dan You are correct, an IEC 61508 SIL is a property of an overall safety-related function or system.
It cannot be applied to a constituent part. However, IEC 61508 gives you a list of the things that you need to provide safety-related systems designers with, so that they can decide how to use your product to achieve the IEC 61508 SIL they require. These include data on the product's : a) Quantified failure probability b) Hardware fault tolerance c) The techniques that you used to avoid and control systematic faults (in both hardware and software, not forgetting EMC) d) To what degree your product or its components have been ‘proved-in-use’ Note: SIL ratings are defined in IEC 61508 and this is probably what your customer was asking about - but the acronym "SIL" could possibly be used by other standards or guides, so you should check that IEC 61508's SILs is what they were really interested in. All the very best! Keith Armstrong www.cherryclough.com In a message dated 04/05/02 13:56:46 GMT Daylight Time, dan.kin...@heapg.com writes: > Subj:SIL Ratings > Date:04/05/02 13:56:46 GMT Daylight Time > From:<A HREF="mailto:dan.kin...@heapg.com";>dan.kin...@heapg.com</A> > To:<A > HREF="mailto:emc-p...@majordomo.ieee.org";>emc-p...@majordomo.ieee.org</A> > Sent from the Internet > > A customer called this week and asked what our SIL rating is on one of our > products (Programmable Logic Controller). I had never heard of a SIL > rating. I went to the web and discovered SIL stands for Safety Integrity > Level and is addressed in IEC61508. My impression, from the web search, is > that a SIL analysis would be accomplished on a large manufacturing process > and the outcome would be based on the attributes of all of the components > of > the process, i.e.. sensors, controllers, output devices. I haven't seen > anything on the web that indicates the individual components have a SIL > rating. Does anyone have any experience with either SIL ratings or > IEC61508 > who might be able to shed some light? > Dan Kinney > Lead Qualification Engineer > Horner APG, LLC > Indianapolis, IN
