"Area of Sprinkler Operation" Calculation

[eduardotci]

Hi everyone
I'm new to NFPA and I'm trying to define the GPM needed for an OH2 with a K-8 sprinkler and an Indoor Storage with an ESFR 25.2-k sprinkler. I'm using the Density Area Method but still I'm not sure what's the choosing point criteria on a curve on NFPA 13 Figure 11.2.3.1.1.
There's a big difference between 300 gpm (1500 ft2*0.2) and 800 gpm (4000 ft2*0.2) in the case for the OH group 2, is it there steps or rules to follow to determine a point on the curve?

Thank you

 

[MatthewJWillis]

Way more than can be listed or enumerated on here.

What is your role in this if I may ask?

R/
Matt

 

[eduardotci]

I'm the CAD designer, but as I said I'm new to this.

 

[MatthewJWillis]

There is a big difference between 300 and 800.
But you also mentioned ESFR.
2 very different animals.
A quick check of the ESFR using a generic criteria means around 2200 gpm.

You are asking for very specific information in a general way.
We can provide general stuff, but I think you will need to discuss these items with the design professional?

R/
Matt

 

[TravisMack]

Typically, on the curves, you choose the point with highest density and lowest area. The equates to the least amount of water.

You don't do the 0.2/4000. You reduce the density when you increase the area. You would do 0.15 / 4000 which comes out to 600 gpm, not 800 gpm.

The most helpful situation is in storage applications. If you can get the density under 0.25 gpm / sq ft then you can increase the spacing to 130 sq ft in lieu of the 100 sq ft limitation when the densities are in excess of 0.25 gpm/ sq ft.

It is good to ask these questions, but the answers come with time and experience. Keep asking... keep learning!!

ESFR is an entirely different animal. Do not attempt those designs until you have a very good basis of fire sprinkler system layout. Mistakes with ESFR cost ALOT to fix. Obstruction rules are crazy strict.

Travis Mack
MFP Design, LLC

http://www.mfpdesign.com

"Follow" us at

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[LCREP]

Oh yea ESFR will kill you if you do not know what you are doing. I once had a 750,000 sq.ft.warehouse inspection they had ESFR 22" below the metal deck, 1st ESFR job they ever designed and installed. They were not happy with me when I told them the max was 14" NOT 22", they had to take it all down and put it back up......I do not think they made $$$$ on that job! They did not send me the plans to review as I had asked, this was on the final, new building, oh well .....