One more thing- I think when the 13 TC addresses density for unusually high ceilings they will do a better job than Factory Mutual has. For example: FM, LH, 29' CH, .1/1500+100=250. FM, LH, 31' CH, .2/2500+250=750. That is far too chunky- not smooth all all. There is an entrenched ceiling height cutoff of 20' in the mind of the Tech, PE, and AHJ, due to QR Reduction. What if everything stayed the same for less than 20', and for greater, only the density changed, for LH, OHI, and OHII? I modeled the 'example for demonstration purposes only' and came up with 5.76 minutes, 5566 kW. 5566/1700=3.27, x .1=.327, divided 40 = .008 gpm/ft^2/ft celing height. This would be the LH Ceiling Height Factor. The Factor for OHI would then be .012, and .016 for OHII. And per 13, LH, 30' CH, 30*.008 = 0.24/1500+100=460. A few years ago I posted this .008 Factor based on less simple modeling and reasoning, but because I was advocating it for all ceiling heights, and questioned minimum 7 psi end head, it got lost in the chaos of me being ripped to shreds by some whom, smelling blood, jumped into the middle of the thread.
It is just a suggestion for some kind of starting point, and really only because 13 states that ~sprinklers are necessary AND effective at heights above fifty feet~ Go Chiefs! Brad Casterline On Jan 2, 2016 11:52 AM, "Brad Casterline" <[email protected]> wrote: > There is currently just one thing Rahe, in 13, that I think might not work > as indicated (example for demonstration purposes only): > > Light Hazard, 40 foot ceiling height, 200F, QR, Standard Coverage. > .1/1500, and 1/2" orifice is fine. > The problem is that it takes ~7 minutes for the sprinklers to activate, > and based on full scale tests of the growth rate the heat realease rate by > then is ~7,000 kW. > > According to Dr. Jason Floyd in his work with the Cloud Ceiling Studies, > the typical Light Hazard heat release rate is about 1,700 kW, which .1/1500 > works fine for. > > I hope 13 addresses this sometime soon but in the meantime consulting > engineers might want to consider what Factory Mutual has to say about > minimum orifice size and density based on ceiling height, not occupancy. > > (man it feels good to let that go after keeping it bottled up inside for > quite some time) > > Me > On Dec 31, 2015 12:54 PM, "Brad Casterline" <[email protected]> > wrote: > >> Thanks Rahe. >> Just to try to clarify, 13 shows sidewalls with a wall, or soffit, and >> soffits normally protrude from a wall. Apparently some manufacturer's data >> says they can be used with a wall or beam, but I doubt what was envisioned >> was "back-to-back" sidewalls with a beam between them, which would be >> required by 13 and the data, but likely a beam say, 8" from a "real wall", >> and only on the interior side, to better look like the pictures in 13. >> And please note, the activation times I showed really don't mean much-- I >> used a space of X by Y by Z, open on the end opposite the fire, with a >> certain heat release and fire growth rate. Changing any of those would >> change the activation times. >> The interesting thing is difference with and without the beam, and that >> is what I meant by the margin of error being tenths of a second. In other >> words, I don't try to predict anything, I like keeping all things the same >> but one, say deflector distance, and seeing what the difference is, >> according to the model that is :) >> >> Brad >> On Dec 31, 2015 12:06 PM, "Rahe Loftin - 7PMC" <[email protected]> >> wrote: >> >>> I got it. I was thinking that you had sidewalls 8 inches apart back to >>> back and another set 8 feet from them. Very interesting test. It is >>> always interesting to find things in NFPA 13 that mysteriously do not >>> work, >>> as indicated, in real life. >>> >>> >>> >>> *Success Through Code Compliance* >>> >>> *Rahe Loftin, PE * >>> *Regional Fire Protection Engineer* >>> *General Services Administration* >>> *Region 7 - TX, OK, NM, AR, LA* >>> *Facilities Management & Support 7PMC* >>> *c - 817-371-3102* >>> *o - 817-978-7299* >>> >>> On Wed, Dec 30, 2015 at 1:04 PM, Brad Casterline <[email protected] >>> > >>> wrote: >>> >>> > Rhae, >>> > No, 8" apart is correct. This is a continuation of the ~do sidewalls >>> need a >>> > wall discussion~ but I made it new because I don't know how to trim >>> threads >>> > using my phone. >>> > Very interesting stuff. >>> > When looking at activation only I use a heat detector because the same >>> RTI >>> > algorithm is used for upright, pendent, sidewall, and heat detector. >>> > It is interesting to note that the 12" deep beam affects the near sprk >>> like >>> > an 18" draftstop affects a water curtain sprk-- it disrupts the heat >>> flow, >>> > delaying activation a few seconds. I think an 18" draft stop is used to >>> > contain an 18" "build down" of 'cold smoke', per floor, when openings >>> are >>> > required to be protected. >>> > On Dec 30, 2015 12:30 PM, "Rahe Loftin - 7PMC" <[email protected]> >>> > wrote: >>> > >>> > > Brad, >>> > > Should your post say 8' apart instead of 8"? >>> > > >>> > > >>> > > >>> > > *Success Through Code Compliance* >>> > > >>> > > *Rahe Loftin, PE * >>> > > *Regional Fire Protection Engineer* >>> > > *General Services Administration* >>> > > *Region 7 - TX, OK, NM, AR, LA* >>> > > *Facilities Management & Support 7PMC* >>> > > *c - 817-371-3102* >>> > > *o - 817-978-7299* >>> > > >>> > > On Wed, Dec 30, 2015 at 11:07 AM, Brad Casterline < >>> > [email protected]> >>> > > wrote: >>> > > >>> > > > Modeled: >>> > > > (2) heat detectors, 8" below ceiling, 8" apart, with and without >>> 12" >>> > deep >>> > > > beam centered between them. >>> > > > >>> > > > Results without-- >>> > > > Both near and far side heads activate at 90.5 seconds. >>> > > > Margin of error a few tenths of a second. >>> > > > >>> > > > Results with-- >>> > > > near side=93.8 seconds. >>> > > > far side=115.0 seconds. >>> > > > Same margin of error. >>> > > > >>> > > > Head scratching -- >>> > > > 1) I doubt in real life two heads 8" apart would activate within >>> tenths >>> > > of >>> > > > a second of each other, my feel is more like a few, enough for one >>> to >>> > > > cold-solder the other. >>> > > > 2) in a model the spray pattern of a sidewall can be straight out, >>> but >>> > in >>> > > > real life I think enough would be splashed backward to cause 1). >>> > > > >>> > > > For 30 years, if I thought beyond what the book said about max >>> > deflector >>> > > > distance I thought "ok, the heat rises, hits the bottom of the >>> deck, >>> > and >>> > > > starts coming down, and when this heat gets, say, 12" down the head >>> > > pops". >>> > > > Well, 10 years ago I realized that that is normal-- and the >>> emergency >>> > is >>> > > > where the heated air is travelling horizontally five to ten feet >>> per >>> > > second >>> > > > across the head. >>> > > > 10 years ago is also when I first heard "ceiling jet". I really >>> > resented >>> > > a >>> > > > Code Person telling me anything about sprinklers but, after 3 >>> months of >>> > > > getting my sprinkler (oops i mean head) around mass and the metric >>> > system >>> > > > learning the first things about FDS, it started sinking in that the >>> > > ceiling >>> > > > jet is really where is at re: activation. >>> > > > >>> > > > Brad C >>> > > > >>> > > > Ps- this new thread is tied to the recent "can sidewalls..." >>> thread. >>> > > > Ps2- Ron, I'm not too sick, tired (or lazy), to look stuff up-- i >>> just >>> > > > don't have access to commentary, and I was curious, but it can >>> wait. >>> > > > Ps3- Ron2-----please don't be a stranger >>> > > > _______________________________________________ >>> > > > Sprinklerforum mailing list >>> > > > [email protected] >>> > > > >>> > > > >>> > > >>> > >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>> > > > >>> > > _______________________________________________ >>> > > Sprinklerforum mailing list >>> > > [email protected] >>> > > >>> > > >>> > >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>> > > >>> > _______________________________________________ >>> > Sprinklerforum mailing list >>> > [email protected] >>> > >>> > >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>> > >>> _______________________________________________ >>> Sprinklerforum mailing list >>> [email protected] >>> >>> http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org >>> >> _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
