The Machinery Directive requires consideration of possible misuse as part of the risk assessment. Depending on the product I could easily see using an indoor only rated power supply outdoors as possible misuse. In that case depending on the risk/hazard it could mean using an outdoor rated power supply or not or looking closer at the consequences of using a particular indoor only rated supply outdoors. I could see this extending to non-machinery.
-Dave -----Original Message----- From: Brian O'Connell [mailto:oconne...@tamuracorp.com] Sent: Tuesday, April 05, 2016 8:34 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] "For indoor use only" on External Power Supply The current *style* is the Risk Assessment. The RA is an assumed probability. Dunno, as much of the supposed 'probability' for failure does not map well with resultant MTBF numbers. The sample space is not the probability space, but probability space does contain a sample space. American engineers are taught statistics without adequate measure theory; that is, this side of the pond uses stuff based on combinatorics - not always conducive to the existing finite sample space. The measure of the result of safeguards, while codified by many medical equipment standards, does not necessarily provide a repeatable model for revealing the effectiveness of safeguards. Data from observations (Type Tests?) has problems (other than the obvious mundane calculations for measurement uncertainty) because the 'experiments' (aka, the tests), are not designed to be randomized experiments. From a simplistic working engineer's POV, there should never be a pathological integral in this stuff. By my feeble understanding, we have a mathematical process that strives for a countable infinite, in order to explain why a coin may never or continually comes up heads. A non-countable infinite makes for unclean and intractable theoretical basis. While there are textbooks that provide measure theory for use in probability theory, the usage is scoped for graduate-level math geeks, and it seems to be all sigma algebra. There are some engineering processes (HALT,HASS,SR332) that are using bayesian analysis, but the initial calculation of both posteriors and a priori to remove uncertainty for electrical equipment failures is difficult for mortals. But once you build your database with good RMA (failure data) and ATP (production data), the dynamic updates yields very tangible and useable results. But how do we get to a legit RA for our new box about to go to production? Not trivial for power conversion equipment, at least. So how safe is it to sit at your computer and read this? Probably about 0.1, or more, or less... Brian From: Richard Nute [mailto:ri...@ieee.org] Sent: Tuesday, April 05, 2016 3:10 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] "For indoor use only" on External Power Supply OTOH, apart from instructions and symbols, how else can manufacturers begin to address the issue of “risk reduction” other than making the products “absolutely safe”? Most products are absolutely safe for all practical purposes. As you read this, you are safe. And, you are acting like you are absolutely safe; that is, you are taking no precautions against an injury. Most safety requires two independent safeguards. Safeguards are considered reliable for the lifetime of the product. So, for an injury to occur, you have the probability of failure of two safeguards, both of which are supposed to be reliable for the product lifetime. Multiplication of the two probabilities yields an extremely small number which means the product is absolutely safe for two lifetimes. Driving across town involves much higher probabilities of safeguard (driver behavior) failure than typical product safeguard failures. Most of us recognize that our safety and that of others depends on our behavior (adherence to driving rules). I would not use the term “absolute safety” to describe the activity of driving across town. Best regards, Rich Ps: This should trigger much discussion! - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to <emc-p...@ieee.org> 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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
