Avoidance is a factor in calculating PLr in ISO 13849-1 Safety of machinery — Safety-related parts of control systems — Part 1: General principles for design. We include PLr in our risk assessments as well for reference since some of the same elements that go into PLr go into the risk calculation.
-Dave From: Mike Sherman ----- Original Message ----- [mailto:msherma...@comcast.net] Sent: Thursday, April 14, 2016 9:45 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] SV: [PSES] EU's new approach directive transitions Regarding "avoidabiility": 1. I used it typically for mechanical/kinetic hazards, such as being hit by a robot, where human reflex times were relevant. I did not use it for most other risk assessments (e.g., shock, explosion). 2. I gave it a scale of 0 to 1, then subtracted it from 1: risk formula then was S*L*(1-A). This keeps the highest score corresponding to the highest risk. This approach was easily understood by those on the risk assessment team. Mike Sherman Graco Inc. ________________________________ From: "John Woodgate" <jmw1...@btinternet.com> To: "EMC-PSTC" <EMC-PSTC@LISTSERV.IEEE.ORG> Sent: Thursday, April 14, 2016 7:23:27 AM Subject: Re: [PSES] SV: [PSES] EU's new approach directive transitions I think that introducing the third factor is good, but care is needed. We have S-factor, L-factor and A-factor, but ‘avoidability’ is a positive word and doesn’t go well with the biggest number meaning the worst case. It might be better to change the third factor to Unavoidability, so all three factors work in the same way. But I think we still need to know S*L as well as S*L*U in order to get the full picture. Multiplication actually discards (or hides, often irretrievably) data, a point to bear in mind when considering any algorithm. I agree that the actual scale doesn’t matter technically, it’s just that big numbers are more likely to register with powerful non-technical people. ‘On a scale of 1 to 125, the SLU is only 5’ or ‘On a scale of 1 trillion, the SLU is only 4%.’ From: ce-test, qualified testing bv - Gert Gremmen [mailto:g.grem...@cetest.nl] Sent: Thursday, April 14, 2016 12:52 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] SV: [PSES] EU's new approach directive transitions In the medical RA where I got a bit of experience a third factor is used to classify the avoidability of risk. Avoidability of the risk. So the risk number is severity times likelihood times avoidability (why doesn't MS Word like this word ?) - To use the comet example, it cannot be avoided, so risk number 5. - A chain saw approaches rather quick, but can be avoided if vigilant, so number 4. - The user gets tired , so stop using the chain saw, can be number 2 - Avoid getting pinched by the elevator door is easy so number 1 The exact numbers makes no difference, as long as the scale is the same for all your projects. RA is not to make a difference between, just to prioritize risks. if too much risk end up with the same number, just extend the scale 1-10 or 1-100 if you need to. Once you see the list of risks ordered, it is more easy to say: “Below a risk number of 20 I feel safe, and above we will (try to) fix them” The RA process is thus an iterative process, governed by the risk management process. The RA process might be need repetition for different users, such as operators service agents domestic animal (yes! LVD) third age and disabled people children Regards, Ing. Gert Gremmen Approvals manager ------------------------------------------------------------------------------------ + ce marking of electrical/electronic equipment + Independent Consultancy Services + Compliance Testing and Design for CE marking according to EC-directives: - Electro Magnetic Compatibility 2004/108/EC - Electrical Safety 2006/95/EC - Medical Devices 93/42/EC - Radio & Telecommunication Terminal Equipment 99/5/EC + Improvement of Product Quality and Reliability testing + Education Web: www.cetest.nl<http://www.cetest.nl> (English) Phone : +31 10 415 24 26 ------------------------------------------------------------------- This e-mail and any attachments thereto may contain information that is confidential and/or protected by intellectual property rights and are intended for the sole use of the recipient(s) named above. Any use of the information contained herein (including, but not limited to, total or partial reproduction, communication or distribution in any form) by persons other than the designated recipient(s) is prohibited. If you have received this e-mail in error, please notify the sender either by telephone or by e-mail and delete the material from any computer. Thank you for your co-operation. From: John Woodgate [mailto:jmw1...@btinternet.com] Sent: Thursday 14 April 2016 12:48 To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] SV: [PSES] EU's new approach directive transitions A scale of 1 to 5 has been considered too coarse, but again ‘where to stop?’ 1 to 1000 gives, perhaps, a better impression of the RA of a comet strike to non-technical managers and politicians, but in these days of big numbers, there is a case for 1 to 1 million. From: McCallum, Andy [mailto:andy.mccal...@mottmac.com] Sent: Thursday, April 14, 2016 10:02 AM To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] SV: [PSES] EU's new approach directive transitions Rich If you have not done a risk assessment previously it can be daunting – where do you draw the line with “what if”. In the UK rail industry an example could be “What happens if the train is hit by a comet”. Answer everyone dies. So what mitigation can you do – run trains in tunnels deep in rock so the train is protected. That’s not practical so the ALARP principal is introduced (As low as reasonably practical). Also risk is about the likelihood of an event – so a comet strike chances of happening are so low that it can be ignored. Your RA could be enormous if you tried to include every risk that was possible (rumour is someone did consider a comet strike but I have not seen it!). So product knowledge and common sense need to be applied. Consider the risks for your product assign them a risk rating ( say 1 – 5 where 1 is no risk and 5 is risk of death) and then assign a likelihood (1 is incredibly unlikely and 5 is a daily occurrence). Multiply 1 by the other and you have a risk score somewhere between 1 and 25. So a comet strike is likely to a consequence of death (score 5) but is incredibly unlikely (Score 1) total risk score 5. Any reasonable mitigation? No that’s the best you will get move on the next risk. Hope that helps Andy From: Gary Swale [mailto:gary.sw...@ditchwitch.com] Sent: 14 April 2016 00:48 To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: Re: [PSES] SV: [PSES] EU's new approach directive transitions >>I don’t have experience in RA, so I guess I can’t do it.<< No, not experience in RA, experience and knowledge about the product. The RA is all about presenting "what if" scenarios to product experts and the experts then work to lower the risk through design, safeguards, and information. ________________________________________ From: Richard Nute [ri...@ieee.org] Sent: Wednesday, April 13, 2016 6:19 PM To: Gary Swale; EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> Subject: RE: [PSES] SV: [PSES] EU's new approach directive transitions “… Risk Assessment is a qualitative (estimate based on experience) venture.” I don’t have experience in RA, so I guess I can’t do it. I guess I have to hire someone who has RA experience. This is very much like the certification house manager who told me that product safety is an art that takes many years (and products) of experience to master. As a product manufacturer (compared to a certification house), my experience is limited and I would not likely master the art. 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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>
