In message <of069c78e9.ebe4325a-on8025740f.004c2169-8025740f.004d8...@elekta.com>, dated Mon, 17 Mar 2008, chris.dup...@elekta.com writes:
>So how many levels of fault should we take into account in order to >fulfil the Risk Analysis requirements? This is one of those questions that no-one wants to answer. So I'll try. The reason that there isn't any 'official' answer is that with more than one simultaneous fault, chosen from all possible faults, nothing could ever be considered 'safe'. So, what you have to do is consider the consequences. If a fault creates a 'high risk' condition, then take care that its probability is very low. This is the case for the protective conductor connection of Class I equipment. However, it is a principle of standardization that specification of performance is much preferred to specifying design or construction. IEC 60335 has specified construction in this respect for a very long time, probably since before the above principle was recognized. Also, many household appliances generate their own vibration, which other products don't, so the need for a secure fixing is particularly great. Yet again, household appliances are still repairable items, so the service technician should not be easily able to forget to replace protective conductor connections. But ICT and multimedia equipment are less likely to be repaired these days, and technician training is better anyway, so the probability of an omitted connection is less. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk For very important information, please turn over. John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to emc-p...@ieee.org Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
