Hi Folks Having just logged on this morning, I am somewhat surprised at some of the comments against the concept of "standard definitions" for "safety critical", "compliance critical", etc. The very fact that this thread was started in one country and has spread across national boundaries with a wide range of opinions is evidence of the confusion that exists and the need for clarifications.
After all we do already a huge range of definitions in the International Electrotechnical Vocabulary (IEV) - and an additional number in individual standards - for the very purpose of making life more straightforward for all us, and avoiding confusion, reinventing the wheel, etc. I was not, and am not, arguing that IEC committees and test authorites should define absolutely what is, and what is not, a "safety critical", "safety related", a "compliance critical" (etc) component. What I am saying, at least at this stage, is that the general meanings of these terms (and/or of any other terms that are chosen) shall be clarified in that forum so that - from one person/test house/authority/country to another - we can avoid confusion between component "standards-compliance critical" and overall equipment/system "safety critical" - a distinction on which most of us (at least those have realised the difference!) already seem to agree. That is not to say that there is no overlap between the terms as a single component can be one or the other - OR BOTH - dependent on what it is and what its function(s) and failure mode(s) is (are). In fact, as is quite obvious, that a component (e.g a transistor bias resistor in an SELV circuit) in a specific item of equipment may not be "compliance critical" for that equipment, but could be "safety critical" in the context of the role that equipment (or the system into which it is then integrated) such that if the component fails (etc) the overall equipment/system fails or fails to operate in a manner which ensures that safety is assured. For example: resistor in fuel feed valve in aircraft engine fails to open circuit-> fuel valve does not open ->engine stops but no fire, etc.-> plane falls out of sky = UNSAFE condition!! After the general definitions have been agreed, then, maybe, we can go further by concensus between all the interested parties in the definitions of - particularly - "compliance critical" components which is what I think sparked this whole thread off! Regards John Allen Thales Defence Communications Division Bracknell, UK ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: pstc_ad...@garretson.org Dave Heald davehe...@mediaone.net For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
