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FIRE SERVICE AND GENERAL FIRE SAFETY TOPICS => Technical Advice => Topic started by: Revol on July 23, 2015, 11:19:56 AM

Title: BR 187 External Fire Spread
Post by: Revol on July 23, 2015, 11:19:56 AM

Has anyone else noticed this ...

The old BR 187 (1991) tables for % of unprotected area within a given unprotected area (UPA) assumed that if the width of the rectangle was greater than 120m then the next column 'no limit' could be applied. As such the same percentage of unprotected area applied to a rectangle that was 140 meters wide or 240 meters wide. The guidance also contained Appendix A giving Melinek's formulae for calculating UPA. This method assumes that if the width is greater than 140 m then a value of 140 m may be used. .... still with me? ... well IN the new BR 187 (2014) all of the tables now stop at 130 meters, the 'no limit' column has been removed. In addition the Appendix A seems to have gone.

Any thoughts?

Title: Re: BR 187 External Fire Spread
Post by: Revol on August 04, 2015, 09:53:56 AM

Any one?

Title: Re: BR 187 External Fire Spread
Post by: Phoenix on August 04, 2015, 05:26:16 PM

Well, I have noticed now that you've pointed it out.  Thanks.

I have just done a large warehouse well over 130m wide and just used the maximum figure from the table (old or new) as I would have done before.  The increments are so small at such large widths that I don't think there is any need for them.

If you think about a point centrally located and facing a 140m wide wall of burning building, any additional width is going to be at a pretty oblique angle to the point and over 70m away - I don't think that the extra width will make much difference to the heat energy the point receives when compared to the radiated heat coming from the portion of the wall facing it more directly.

So I would advise carrying on using the tables as before, assuming no limit for high widths and as for Appendix A there could be a number of reasons why it has disappeared.  It would be nice if someone could offer an explanation.  I guess there could be a few reasons.  

Maybe it was found to be wrong in some way - but then a better option would have been to correct it and leave it in.  That would not have produced the doubt we now have over the validity of the content.  

Or maybe it hasn't been found to be wrong but confidence in it has waned so it was thought best to exclude it.

Or maybe it was just considered superfluous.

Title: Re: BR 187 External Fire Spread
Post by: John Webb on August 04, 2015, 07:43:08 PM

If the 2014 edition has any editorial attribute, it may be worth ringing up or e-mailing them at BRE Ltd. and asking about this. Also check the intro to the new edition - they sometimes comment there on alterations to the previous edition. Sorry I can't help any more, but it wasn't my area of work and all but 3 or 4 of my former colleagues have now retired, so I can't ask them!

Title: Re: BR 187 External Fire Spread
Post by: wee brian on August 05, 2015, 12:17:00 PM

Richard Chitty at BRE is your man - he's been there for decades JW so maybe you do know him.

Title: Re: BR 187 External Fire Spread
Post by: John Webb on August 06, 2015, 04:38:03 PM

Brian - yes, know Richard very well - but I'd heard he'd retired a couple of weeks ago!

Title: Re: BR 187 External Fire Spread
Post by: wee brian on August 07, 2015, 01:41:57 PM

I knew it was soon. Blimey, what will we do without him....

Title: Re: BR 187 External Fire Spread
Post by: colin todd on August 07, 2015, 09:19:05 PM

Scary thing is I used to work in same department as his dad!