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Question about FM Global Data Sheet 8-9 Table 8 "Ceiling-Level Protection Guidelines for Class

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SprinklerDesigner2

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Nov 30, 2006
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Question about FM Global Data Sheet 8-9 Table 8 "Ceiling-Level Protection Guidelines for Class 4 and Cartoned Unexpanded Plastic Commodities in Open-Frame Rack Storage Arrangements"

I have a 156,000 sq ft warehouse and when we started out the owner told me to design per NFPA #13 for rack storge of Class I through IV and cartoned plastic commodities. So easy enough I designed an ESFR system using K25.2 pendent sprinklers discharging at 25 psi per NFPA #13 "TABLE 23.6.1 ESFR Protection of Rack Storage of Group A Plastic Commodities".

Maximum storage height is 35' with maximum height of building at 40'.

The existing water supply is adequate but not great so we can't use anything smaller than a K25.2 sprinkler.

It was after I submitted preliminary plans that I learned FM Global was in the game when the owner passed this on to me from FM Global.

From FM Global said:
"The automatic sprinkler system designs should be based on flowing 40 psi from the 9 most remove K25.2 pendent quick-response heads in accordance with Table 8 of FM Global Property Loss Prevention Data Sheet 8-9, Storage of Class 1, 2, 3, 4 and Plastic Commodities. Please revise and provide complete hydraulic calculations to FM Global to verify the water supply is capable of meeting the anticipated sprinkler demands based off the new design information."

FM_Global_Table_8_nw5thf.jpg


I have nearly 50 years experience designing fire sprinkler systems but I admit over the last 20 years I have not had that much experience with FM Global just because we operate in an out of the way rural area. I've looked for it and it HAS to be in there somewhere but I can't locate the answer to these questions.

1. Using the K25.2 quick response (ESFR) heads I need to calculate 9 hydraulically most remote sprinklers which is easy to do but what is the layout of these heads? Using NFPA #13 it's generally 12 sprinklers with 4 sprinklers per line for 3 lines but what do I use per FM Global? Is it three heads per line for 3 lines or what?

2. And what about using the standard response K25.2 sprinkler with 9 sprinklers discharging at 30 psi? I know FM Global doesn't use the term ESFR but I am assuming their reference to Quick Response can be interpreted to ESFR. Given our water supply, less than 100 psi @ 1,500 gpm, the 9 K25.2 standard response sprinklers is definitively a better route to go what are some specific Tyco SIN numbers I can use?

Building is constructing using 12" bent metal purlins. Working with the structural steel people I am installing the branch lines in the purlin space so the deflectors do not exceed 18" below the roof deck in accordance with NFPA #13 Section 14.2.10.1.3.

And yes, I did try to contact FM Global but it appears everyone I need to talk to is on vacation so all I am trying to do is get a jump ahead over the weekend.

Any feedback would be most appreciated.
 
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Thank you very much and a big duh is on me!

I thought I had the latest data sheet but it was "Interim Revision October 2020" and Table 1a does not exist in that revision.

I checked and downloaded the latest "Interim Revision January 2022" and there is Table 1a staring me in the face.

Table 1a tells me 3 heads per line for 3 lines.
 
skdesigner,

I've been designing sprinkler systems for a good while seeing how my first copy of NFPA #13 was 1974. Hard to believe a half century ago.

Most of my systems were simple pipe schedule drawn on a drafting table and if hydraulics calculations were required we did those by hand because computers didn't yet exist.

Unless one was around back then they simply could not begin to guess at the changes in our industry.
 
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