Re: [SystemSafety] SIL ratings to be scrapped?

From: Inge, James Mr < >
Date: Fri, 23 Aug 2013 10:41:05 +0100

It is possible that this rumour might relate to the current work underway to revise Def Stan 00-55, Requirements for Safety Related Software in Defence Systems.  

A system of SILs was defined Def Stan 00-56 Issue 2, Safety Management Requirements for Defence Systems (1996), which was also used in Def Stan 00-55. However, SILs were removed from the mandatory part of 00-56 in Issue 3 (2004) as part of the move to a goal-based approach to requirements setting. Instead, the guidance in 00-56 Part 2 discussed setting integrity requirements in generic terms, rather than using a specific SIL scheme. However, the guidance made it clear (in Annex C, section C.2) that SIL schemes could still be used where they were suitable.  

Def Stan 00-55 was made obsolescent by the release of 00-56 Issue 3, and has not been re-issued. However, new work is currently underway to revise both standards. I have not seen recent drafts, but it is likely that neither standard will define a system of SILs, or require use of a specific SIL scheme. That said, it is also likely that use of suitable standard that incorporates SILs or a similar concept could still be part of the argument to demonstrate compliance with either 00-55 or 00-56.  


          James Inge    

From: systemsafety-bounces_at_xxxxxx
[mailto:systemsafety-bounces_at_xxxxxx Of Dominey, Alan (UK)
Sent: 21 August 2013 16:59
To: safetyyork_at_xxxxxx Subject: Re: [SystemSafety] SIL ratings to be scrapped?  

I think there may have been a misunderstanding somewhere along the way here.  

UK MoD implemented the use of SILs into many of their projects a few years ago and these are now being replaced by

SIRs - Safety Integrity Requirements ( High / Medium / Low) . . . Don't know if this is a pointer in any direction . . .  

        Many Thanks



        Alan G. Dominey

        Electrical Safety Engineer

        Torpedo Capability Contract Project Surveillance Manager

        Spearfish Safety Group

Building 31, Broad Oak Business Park,

Airport Service Road, Portsmouth, Hampshire. PO3 5PQ

United Kingdom

7 Fax: +44 (0) 23 9222 6922

       Mob: +44 (0)7970 983792 <>  

         BAE Systems Integrated System Technologies Limited

         Registered Office: Warwick House, PO Box 87, Farnborough Aerospace Centre, Farnborough, Hants, GU14 6YU, UK.

         Registered in England & Wales No: 3456325  

         P don't print this e-mail unless you need to  

         This email, together with any attachments, is for the exclusive and confidential use of the addressee(s).

         Any other distribution, use or reproduction without the sender's prior consent is unauthorised and strictly prohibited.

         If you have received this message in error, please notify the sender by email immediately and delete the message from your

         computer without making any copies. All reasonable precautions have been taken to ensure no viruses are present in this e-mail.

         BAE SYSTEMS Electronics Limited cannot accept responsibility for loss or damage arising from the use of this e-mail or

         attachments and recommend that you subject these to virus checking procedures prior to use.      

From: systemsafety-bounces_at_xxxxxx
[mailto:systemsafety-bounces_at_xxxxxx Of Chris Hills
Sent: 21 August 2013 15:26
To: 'Bielefield Safety List'
Subject: [SystemSafety] SIL ratings to be scrapped?  

Hi all,  

I have just been taking to one of my customers who do control systems for industrial systems. They have been told by someone they are doing a system for that SIL ratings will "soon be scrapped". Apparently "It will be replaced by ALARP". This seems like a completely misunderstood half a message. Though usually on this sort of thing there is a grain of reality (if miss reported or miss represented) in there somewhere.  

I know I have not been paying attention over the summer but I haven't seen anything. Is there a move on any standard to change from SIL ratings for projects?    



Eur Ing Chris Hills BSc CEng MIET MBCS FRGS FRSA Technical Specialist Phaedrus Systems Ltd Tel: FREEphone 0808 1800 358 Vat GB860621831 Co Reg #04120771
Http:// <> chills_at_xxxxxx  

The System Safety Mailing List
systemsafety_at_xxxxxx Received on Fri Aug 23 2013 - 11:42:03 CEST

This archive was generated by hypermail 2.3.0 : Tue Jun 04 2019 - 21:17:05 CEST