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Functional Safety Play Book
279 members • Free
14 contributions to Functional Safety Play Book
May 28 •
Electrical final elements
Can anyone share their experience? Very practical two questions related to an issue which exists in many PFDavg calculations. What's your approach to a safety loop that includes typical electrical final elements, e.g. contactors? Although the IEC61508 and IEC61511 standards apply to electrical devices, many such solutions widely used in industry lack certification and reliability data. And if the data is available, it's usually related to PFH and is based on B10d - not well suitable for demand mode of operation calculations. Second one: how do you confirm their systematic capability?
1 like • Jun 29
@Richard Kelly Thanks for this Richard, very good advise and something I will look into as I am actually running the calc today. At the minute I have used generic data from SERH which gives an SU of 900 FITS, DU of 600 FITS and SFF of 60%. The Contactor used as an ABB 3 pole.
0 likes • 9d
Morning All, Just with regards to this one, has anyone got any thoughts on Mission Time considerations when the VSD itself has been installed for 10+ years. Does this need to be considered in the Mission Time even if the Safety Relay and Contractor are new?
Apr 9 •
IPL Management
Hi All, Just read an interesting article on the recent introduction of an ISA standard which provides guidance on the management of Independent Protection Layers - Low Integrity Protection Layers: ANSI/ISA-84.91.03-2025 Explained. This is an interesting subject as IPL's are an essential aspect when working out the target RRF of a SIF, however they are often forgotten about once the plant goes back into operation. Some sites do manage the maintenance of IPL's differently to non-safety loops, via a maintained IPL register, IPL validation and more stringent testing routines. However this is not always the case and a lot of the time IPL's just fall into the normal maintenance system as this article suggests. Would be interesting to hear from the group your thoughts on this subject .....
2 likes • May 10
Hi Sergio, great question. Personally this is not something I think you could came claim credit for twice in a LOPA, i.e. as a BPCS layer and Safety layer (if that’s what you are meaning) as there are too many points of CCF (the same initiator and same final element). It would be best to have a completely Independant second loop for my safety layer if you want to claim credit for an additional layer of protection. For safety system trips I would always design the trip signal to be repeated to the BPCS via software link (or if ifs a hardwired trip, using a second contact off the trip amp), however this would be for indication purposes only, Also note that whenever there’s an interaction from between the SIS and the BPCS the designer must be very careful to ensure that any BPCS failure does not have any affect on the SIS. So personally I would stray away from the idea you mentioned as I don’t see it serving much additional benefit from a risk reduction factor point of view. It would be best to go for two PT’s for two completely independent channels and ideally with separate final elements, although on some legacy plants sometimes the final elements are shared. In this case there must be a reduction in your IPL credit claim on the BPCS layer … This is just my opinion, would be good to hear what the others in the group think.
Apr 28 •
Incorporating FSM into the overall quality system
I'm interested in your experience regarding the technical implementation of functional safety management within an existing quality management system, e.g., ISO 9001. I am particularly interested in implementing this process for a consulting company that performs most tasks in the safety lifecycle. Any advice is welcome and I would be greatly appreciated.
0 likes • Apr 28
Hi Thomasz, I am not entirely sure I am reading your question correctly but are you referring to Functional Safety Audits? Independent FS audits should check the adequacy of company safety procedures against the requirements from the standard. Audits are also used to check the company procedures are actually being followed by the project …
Mar 25 •
T6A Symposium 2026
Good Morning All, Just to let you know the 61508 Association are holding a conference in York on November 25th this year. The event is free to join and looks to include a very good agenda regarding Functional Safety Compliance. I have attached the flyer for those that are interested 🙂
1 like • Apr 15
@Tomasz Barnert great stuff mate. I will be there so will be great to meet you!
Apr 14 •
Decision Review Update
Quick update — I’m feeling a bit under the weather this week, so I’m going to reschedule our deep dive review session to make sure I can give it the energy and focus it deserves. I’ll post the new date and time once I’m back on my feet — aiming for Friday if all goes well. In the meantime, if there’s a specific topic or question you’d like me to cover in that session, drop it in the comments below so I can build it into the updated plan. Appreciate your understanding, and I’ll catch you all very soon. – Richard
1 like • Apr 14
@Rob Connors this would be great also as I am likely to miss the sessions if during working hours …
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@anth-gunn-5750
Degree qualified Instrumentation & Control Engineer and FS Eng
Active 2d ago
Joined Mar 11, 2026
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