Re: [SystemSafety] Preliminary Hazard Analysis - Approaches

From: jean-louis Boulanger < >
Date: Wed, 24 Apr 2013 12:55:45 +0200


Hello
The pha is done without knowledge of the breakdown The Idea is select the set of fear event related to your system

Le mercredi 24 avril 2013, M Mencke a écrit :

>
> Dear all,
>
>
>
> I have seen different approaches to Preliminary Hazard Analysis in the
> railway sector.
>
>
>
> I have come across a top-down method, which (roughly) involves the
> following steps:
>
>
>
> Use of an “Example Railway Hazard List” based on the hazardous events
> modeled by RSSB’s Safety Risk Model. The hazardous events are classified
> according to the type of event. For example, Collision, Fire, etc.
>
>
>
> The events on this list are linked to the functions of the system being
> analysed. For example, avoiding a collision between two passenger trains
> can be considered a function of the signaling system.
>
>
>
> The functions identified are broken down into components, modules, etc.,
> therefore linking them to the top hazard.
>
>
>
> This sounds similar to a Fault Tree Analysis; my question is, is it useful
> to apply this approach during initial design stages?
>
>
>
> From my point of view, if you select the top hazards which you consider to
> be mitigated by your system from a list at the beginning of your analysis,
> you could overlook some significant hazards which may be generated by a
> (sub)system/function failure that you did not initially identify.
>
>
>
> Personally, I prefer a bottom-up approach. It seems to me that by
> analyzing failures of system functions through the application of keywords,
> etc., effects on the subsystem and the system can be easily identified,
> whereas the other way round, you have to be very familiar with the effects
> in order to be able to work downwards.
>
>
>
> Any opinions would be appreciated.
>
>
>
> Kind regards,
>
>
>
> Myriam.
>
>
>

-- 
Mr Jean-louis Boulanger



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