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In rack sprinklers water demand

In rack sprinklers water demand

(OP)
Greetings colleagues,

I have a room that will store chemicals in plastic bins in racks of two rows. The room has ceiling sprinkler but we will be installing in rack sprinklers in both rows. For the hydraulic calculation I'm considering 7 active sprinklers per level (14 total) plus a hose demand of 500 gpm. Do I need to balance this demand with the ceiling sprinklers and supply the water demand for both? I had the notion that if the in rack sprinklers work properly it would prevent the ceiling sprinklers from activating simultaneously unless it was a really intense fire.

RE: In rack sprinklers water demand

What standard are you using, what are the chemicals any hazardous?? What is the ceiling design?

RE: In rack sprinklers water demand

(OP)
Sorry, NFPA 13. Chemicals are non hazardous, they are for cleaning purposes. The ceiling design is for an OH (.20 gpm/sq. ft., 1,500 sq. ft. fire area) facility with a 250 gpm hose allowance.

RE: In rack sprinklers water demand

(OP)
Wet pipe system. 5.6 K for ceiling sprinklers, 11.2 for in rack.

RE: In rack sprinklers water demand

If plastic bins are involved they may need to be considered a Group A Platic. Which depending on height of storage and clearance to the ceiling may also involve upgrades to the ceiling system. Also check miscellaneous storage if the room is less than 1000 sq ft.

RE: In rack sprinklers water demand

(OP)
Thank you LCREP. The storage area is 1,300 sq ft., rack height is 12 ft., room height is 25 ft.

RE: In rack sprinklers water demand

You have a problem based on the 2013 ed of 13 for grp a plastic max clearance is 10'. I do not know if the 2016 ed of 13 addresses this or perhaps FM Data sheet 8-9. Can they store higher to reduce the clearance?

RE: In rack sprinklers water demand

Wouldn't par. 12.1.3.4.5 of NFPA 13 solve the clearance problem?

12.1.3.4.5 Where the clearance to ceiling exceeds 10 ft (3.0 m) for Section 16.3 or Section 17.2, protection shall be based upon the storage height that would result in a clearance to ceiling of 10 ft (3.0 m) or providing one level of supplemental, quick-response in-rack sprinklers located directly below the top tier of storage and at every flue space intersection.

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