Having paid the bills on these for years I can tell you that the safety side the other side of the pond has never really inspected to a list safety of components (they would charge you based on the number of components they chose to control) but they never did a product inspection to see if they were being used. They did a process inspection. Once a year, I believe they sent someone out to go over my QA process - but they never glanced at the multiple products being built. It has some sense to it, but on the other hand if I desire I can defeat a process both short term and long term, but if you happen to pick up a product they might be significantly different. The US version of the evaluation only looks at the process up front to be comfortable that you can build the same thing twice in a row with some repeatability, and that you have any necessary production line equipment, it's used, and its calibrated. I don't have any argument with your notes below. I would only say that there is a certain sense to the critical components list in the safety standards. During that evaluation they are running test trying to determine what happens a product type (all computer for example), have a history of similar failures. A power supply output component fails short or open for example. In fact this is a bit of a critical component within a critical component. If the power supply was a recognized component then 90% of the testing for hazardous output during failure was done on the power supply itself, and UL has a file on that construction and those components that must be robust or fail in some mode they determine to leave the rest of the system without undo hazard. Since it is a recognized component, they pay those factories a visit and inspect to see if the output components are different that the original product. They will have a series of components, and their alternate components, that reflect the specific testing required. When it comes to my end unit 1) I avoid most of the test required to insure a component failure won't cause my system to erupt in flames. 2) They compare the model number on that power supply to the one I submitted in my end unit (and alternatives if I thought ahead), and have some confidence that at least that part of the design didn't change from what was tested, and it can be expected to react the same way during the short circuit tests etc. Some of the components are pretty generic. A PCB is most often characterized only by it being UL recognized and its flame rating. If it's not a main power board it may not even have the exact manufacturers name and model number associated with it. It will have some mark that allows the inspector to determine that some, rather than a specific, recognized manufacture produced the PCB and because of that it is more likely than not that the flame rating is the same (or better). I don't need to know exactly the clock type, the processor type etc, I short of know that if these things fail they are anchored to a component that isn't won't propagate flame. So there is some sense to the critical list for safety things, again maybe not all inclusive but better than that stick thing.
UL has altered its course over the years. It used to be that when they showed up unannounced they would inspect only what was being built and to which their logo was being attached. That meant that if there was nothing being built I didn't have to pay them an arm and a leg. They discovered the error with that cash flow conundrum and now do process inspections if I'm not building anything for which they can be legitimately concerned. A movie project using cellulose nitrate for example. If they don't have their logo attach to it they couldn't complain that I was building a fire hazard. Now if I'm not building anything they still stick me with a minimum $800 dollar visit. I would like to think the change was part of joining the EU under the CB scheme test facility - even if I don't fully appreciate that process method of control - being both suspicious by nature and cheap by pure joy I simply choose to believe it was another method from taking a buck (ha pence, Ruble, Rupee, Kroner, or Confederate dollar, etc out of my pocket. Gary From: Ed Price [mailto:[email protected]] Sent: Wednesday, March 13, 2013 3:25 PM To: [email protected] Subject: Re: [PSES] Critical component in EMC report Well, just about as I expected, EMC compliance can't be defined by some set of "critical components." Everything in a product is "critical", as well as the component placement and installation. An inspector can't use a checklist of "critical components" to ensure continuing EMC compliance because the EMC situation isn't as easy as a component inventory. Even if all the EMC "critical components" were present, a re-routed wire or a slight difference in a mechanical dimension could make a huge difference. Maybe for something like Safety, a list of "critical components" is acceptable (it's better than nothing, but I don't think Safety is all that much simpler than EMC either). Maybe I'm just not seeing the bigger picture, but to me, a component list is a pretty poor aid to ensuring any continuing product compliance. Ed Price WB6WSN Chula Vista, CA USA From: Bayo Olabisi [mailto:[email protected]] Sent: Wednesday, March 13, 2013 2:51 PM To: [email protected] Subject: Re: [PSES] Critical component in EMC report What's critical for product safety isn't always critical for EMC - they are two compliance domains and 3rd party lab reports treat them as such. While EMC involves assessment to regulatory limits for emissions (potential for interference) or immunity to external interference, product safety tends to address potential for electric shock, fire, and other hazards. EMC reports document EUT test setups, instrumentation used, etc to assure repeatability of test data, product safety reports conversely document critical components, and some EUT test setups. One other point (for US based folks) - critical components are typically checked by the certifying agency versus the report during routine field inspections post-production, though such routine inspections aren't done for EMC. ________________________________ From: Scott Xe <[email protected]<mailto:[email protected]>> To: [email protected]<mailto:[email protected]> Sent: Wednesday, March 13, 2013 11:48 AM Subject: [PSES] Critical component in EMC report It is common not to have critical component list in EMC reports issued from 3rd party laboratories. Those information are essential to track if the correct parts to be used in mass production. What is main reason not to have it as a common practice in the field? Thanks and regards, Scott - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]<mailto:[email protected]>> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]<mailto:[email protected]>> Mike Cantwell <[email protected]<mailto:[email protected]>> For policy questions, send mail to: Jim Bacher <[email protected]<mailto:[email protected]>> David Heald <[email protected]<mailto:[email protected]>> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
