[SystemSafety] EN 50128 in an IEC 61508 envelope

[Daniel Grivicic]

Dear Peter,

On Thu, Mar 8, 2018 at 7:22 PM, Peter Bernard Ladkin <ladkin at causalis.com>
wrote:

> Daniel,
>
> On 2018-03-08 06:37 , Daniel Grivicic wrote:
> >
> > A safety case has been developed and a claim is made to EN50128. Is it
> fair, for example within the
> > safety case requirements, to claim that "requirements in 50128 are met
> as they are met in 61508"?
> > Certainly not a blanket claim but one in a context in a limited way.
>
> "Fair" is not the question. Acceptable is the question. The answer is no.
>
> Thank you.


> EN 50128 has certain specific requirements for the safety case. You have
> to meet them, one by one.
> There is nothing in EN 50128 which says that a safety case which has been
> found acceptable for IEC
> 61508 requirements is also acceptable to fulfil the requirements of EN
> 50128. It follows there is no
> way available to you at present to invoke such a phenomenon to demonstrate
> fulfilment of the
> requirements for EN 50128.
>

This is what I have begun to understand and it is now clear.

>
>
>
> None of this means that there isn't significant commonality between the
> two sets of requirements.
> Maybe someone could propose such a TS to CEN/CENELEC?
>
>
>From what I have read, EN50128 takes a very different approach to
IEC61508, especially from a subset persepctive where the tools
available have inbuit checking
(LVL). Rail requires significantly more assurance using the same tools
for a similar estimated level of risk. It is, granted, in a differnt
domain to the petrochemical domain where
typically "Safety PLCs" land.

Cheers,

Daniel.


>
>
>
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