Hello Rich I am somewhat alarmed by a paragraph in your email!! In it you indicated that:
"When I evaluate a product, I look for the physical energy sources, *and then determine if the energy sources are hazardous or no*t. Unlike Risk Assessment, this is easy and repeatable and not subjective. For example, all primary circuits are hazardous energy circuits that can cause injury (electric shock, thermal, fire, and maybe more) and safeguards must be provided. " Does this effort not expose the safety engineer to litigation? Personally I liked using the UL (NRTL) specs as one had an objective source. On Sat, Feb 12, 2022 at 3:00 PM Richard Nute <ri...@ieee.org> wrote: > * This message originated outside of DISH and was sent by: ri...@ieee.org > <ri...@ieee.org> * > ------------------------------ > > > > > > I don’t like the Risk Assessment process because it is highly subjective > and not very repeatable. > > > > When I was with Hewlett Packard, three of us developed “Hazard Based > Safety Engineering,” HBSE. The basis for HBSE was James J. Gibson’s > (Cornell University) research into child injury from auto accidents. > Gibson said: > > > > “Injuries to a living organism can be produced only by some energy > interchange. Consequently, a most effective way of classifying sources of > injury is according to the forms of physical energy involved. The analysis > can thus be exhaustive and conceptually clear. Physical energy is either > mechanical, thermal, radiant, chemical, or electrical.” > > > > In a moving automobile, the automobile and its passengers have kinetic > (mechanical) energy. In an accident, the kinetic energy of the automobile > is dissipated in crumpling parts. The kinetic energy of the passengers is > dissipated in injuries to the body. Seat belts transfer the passenger > kinetic energy to the automobile. Air bags slow the rate of kinetic energy > transfer to the automobile. > > > > HBSE identified the magnitudes each kind of physical energy necessary to > cause injury. We called this “hazardous” energy. Then, HBSE went on to > specify safeguards that would attenuate or prohibit hazardous energy > interchange. > > > > When I evaluate a product, I look for the physical energy sources, and > then determine if the energy sources are hazardous or not. Unlike Risk > Assessment, this is easy and repeatable and not subjective. For example, > all primary circuits are hazardous energy circuits that can cause injury > (electric shock, thermal, fire, and maybe more) and safeguards must be > provided. > > > > Best regards, > > Rich > > > > > > *From:* Douglas E Powell <doug...@gmail.com> > *Sent:* Friday, February 11, 2022 11:37 AM > *To:* EMC-PSTC@LISTSERV.IEEE.ORG > *Subject:* Re: [PSES] EN 62368-1 : 2020 Ed 3 > > > > In my view, the Risk Assessment should never be treated as a 'get out of > jail' card or panacea. Instead, it is only a starting point for a safe > design and should be done near the beginning of a project, not the end. I > agree with what Rich says, I've seen a lot of subjective assessments by > cross-functional teams, with variability based on personal risk tolerance > or risk aversion. There are any number of articles pointing to why humans > are not very good at assessing risk (Google search > <https://www.google.com/search?q=humans+are+not+very+good+at+assessing+risk> > ). > > > > When using FMEA for risk assessment, I always stress that the RPN factors > of probability of occurrence, severity, and detection be quantified > separately without regard to the other factors, not an easy task. There is > also the problem of RPN vs Criticality (severity x occurrence). If using > the RPN, there is the possibility that Detection can dilute the RPN number > to a point below the threshold for action. So in my view, Criticality alone > should be used to trigger action. > > > > Kenneth Ross wrote a very good article last month on Navigating the Safety > Hierarchy; for me, it was an excellent refresher on how I should use > risk assessment more effectively ( > https://incompliancemag.com/article/navigating-the-safety-hierarchy/ > <https://incompliancemag.com/article/navigating-the-safety-hierarchy/> > ). > > > > -Doug > > > > Douglas E Powell > > Laporte, Colorado USA > - > ---------------------------------------------------------------- > > 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 < > emc-p...@ieee.org> > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieee-pses.org/emc-pstc.html > <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/ > <http://product-compliance.oc.ieee.org/> > can be used for graphics (in well-used formats), large files, etc. > > Website: http://www.ieee-pses.org/ > <http://www.ieee-pses.org/> > Instructions: http://www.ieee-pses.org/list.html (including how to > unsubscribe) > <http://www.ieee-pses.org/list.html> > List rules: http://www.ieee-pses.org/listrules.html > <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> > -- Charles Grasso Dish Technologies (c) 303-204-2974 (h) 303-317-5530 (e ) charles.gra...@dish.com (e2) chasgra...@gmail.com - ---------------------------------------------------------------- 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 <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>
