Very good points Bill and Wayne: 2007 NFPA 13: Chapter 17.3
I bet with 98% confidence that NFPA 13 intended the maximum horizontal spacing of in-rack sprinklers for plastic storage in open, double- and multiple-row racking at heights >= 25 ft to be a). 10 ft for double pallet bays (for lack of a better name), and b). 5 ft for single pallet load bays. The true intention is eagerly sought, regardless of winning a bet or not. The 10 ft horizontal maximum spacing "bet" is based on Note to Figure 17.3.1.2 and Note in Figures 17.3.1.4.3(a-d). The 5 ft horizontal maximum spacing "bet" is based on Figure 17.3.4.1.4. Coincidence as to the 10:5 ft maximum horizontal in-rack sprinkler spacing relative to the 2:1 pallet loading/bay? I think one item that bears repeating, is the intention to put an in-rack sprinkler *in the transverse flue, *not simply comply with the maximum horizontal spacing of in-rack sprinkler, wherever that spacing lands within the bay. Now, if I were the AHJ, and any contractor of honesty presented me with rack columns having a 10' 4" transverse flue spacing, and the sprinkler designer wanted to go with the "install in-rack sprinklers every-2-pallets" horizontal spacing strategy... I would *strongly* consider giving a variance of 4-inches on this maximum 10 ft iin-rack horizontal spacing. Was I present at all or even more than a handful of UL or FM in-rack full-scale fire tests, to fully know the implications of this variance? No. But are many of the results from these tests presented as monograph or video literature publicly available, and the essential findings from these same tests, distilled as text into Annex A and B comments? Sure they are. Have I reviewed them? You can bet that I have. Are there some compensatory mitigations that I as the AHJ might ask of our stakeholders, were I the AHJ stakeholder to grant such a variance to the team? Sure, there are. If those mitigations decreased sprinkler activation time, or increased water delivery density, then those would be good mitigations, in that order. Exercise of "good judgment" is the lubrication that keeps the customer coming back for more...to borrow a mixed metaphor from that Conservative party leader across the pond who -- two days on, at the Hague -- may "give us more." Most young professionals strive to learn the rules; many older professionals struggle to remember the exceptions. Consideration of both, rather than dogmatic overconfidence and/or blind allegiance to just one ideology, is often more than enough to put a wind at our back as we go down the path of delivering good decisions. scot deal Excelsior Fire/Risk Engineering On Tue, Jan 15, 2013 at 11:09 PM, Bill Brooks <[email protected]>wrote: > In my case the rack uprights were 10' 4" but with only two pallet loads. It > caused the addition of an extra sprinkler even after much writing and > attempted explaining of the rack uprights being the transverse flue. I > don't think this was the intent but it sure is written this way. It's an > unusual looking in-rack arrangement. > > Bill Brooks > > William N. Brooks, P.E. > Brooks Fire Protection Engineering Inc. > 372 Wilett Drive > Severna Park, MD 21146-1904 > 410-544-3620 > 410-544-3032 FAX > 412-400-6528 Cell > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of å... .... > Sent: Tuesday, January 15, 2013 1:38 PM > To: [email protected] > Subject: Maximum in-rack sprinkler spacing - plastic over 25ft > > Wayne: > > You make a good point. > > Per NFPA 13 in-rack sprinkler layouts, I don't perceive that a gap between > pallets constitutes a formal transverse flue. I think the transverse flue > is > formed by the steel column of the racking structure. > > Wayne, you are correct in that 2007 NPFA 13 Figure 17.3.1.2(a) includes the > exception-to-the-rule of having in-rack sprinklers in each transverse flue > (TF) for plastic storage in open racks two-or-more-bays deep, [1] that > stores commodities at heights 25+ ft.. NFPA 13 however, mitigates the > reduction of in-rack sprinklers (particularly, but not exclusively) at > every > transverse flue. For the case of Figure 17.3.1.2(a), this mitigation calls > for horizontal barriers above each level of in-rack sprinkler *with > face-sprinklers*. Does our situation you are describing contain such > horizontal barriers in the racking scheme? > > One *could* assume (at least I do) that the horizontal spacing between in > rack sprinklers in Figure 17.3.1.2(a) is not to exceed 10 ft, as this is > maximum width of two pallets mentioned in Note 7 of this Figure. This > maximum horizontal spacing between in-rack sprinklers is enforced even if > metal racking support columns are spaced greater than 10 ft apart. > > > [1] new criteria added to this comment. > > scot deal > Excelsior Fire > > > > On Tue, Jan 15, 2013 at 4:03 PM, Dewayn > e Martinez <[email protected]> wrote: > > > Thanks Scot, > > What is confusing is that you are allowed to have more loads in the > > vertical as long as you don't go past 10ft spacing but nothing is > > mentioned for the horizontal spacing. > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://fireball.firesprinkler.org/mailman/private/sprinklerforum/attachments/20130116/709d2e29/attachment.html> _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum
