Maybe I am missing something, but when they do a full scale fire test, doesn't the first head that opens operate in that condition?
Todd G Williams, PE Fire Protection Design/Consulting Stonington, CT www.fpdc.com 860-535-2080 (ofc) > On May 22, 2014, at 1:26 PM, John Denhardt <[email protected]> > wrote: > > FWIW - A few cycles ago, NFPA 13 was modified to limit pressure at the > sprinkler to 175psig for storage and extra hazard occupancies . > > John > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of Cahill, Christopher > Sent: Thursday, May 22, 2014 12:05 PM > To: [email protected] > Subject: RE: Overpressurizing Heads > > The fire goes out with 1-3 heads is the answer. I hear you in that is a > great question I have thought of many times. Success rate of sprinklers tells > us not to worry. I think the better question is to focus on the high > challenge fires like high piled storage where drop size is more important. I > wonder with a 20 psi EFSR that sees 80 psi? Correct me if I'm wrong but all > the testing labs control the sprinkler pressure at the head to the minimum > required during the fire tests? For example has there ever been a test with > a 120 psi pump with pipe sized as it would be in the field so the first head > sees basically 120 - elevation? > > Chris Cahill, PE* > Associate Fire Protection Engineer > Burns & McDonnell > Phone: 952.656.3652 > Fax: 952.229.2923 > [email protected] > www.burnsmcd.com > *Registered in: MN > > > Proud to be #14 on FORTUNE's 2014 List of 100 Best Companies to Work For > > > > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of Richard Mote > Sent: Thursday, May 22, 2014 10:38 AM > To: [email protected] > Subject: RE: Area/Density Method and Walls > > HydraCALC has a box you can check on the calculation menu for doing a source > calc. That brings up a question I have been asking for years. I know from > direct observation when I was testing sprinklers for Star that increases in > pressure can materially affect droplet size and distribution pattern. If we > have a system designed to work a 50 psi @ 250 gpm. What happens to the spray > pattern and droplet size when the fire department come along and starts > pumping 500gpm @ 100 psi into the system. Part of the reason for the minimum > pressure requirements for Residential sprinklers is that, that was the > minimum pressure required to pass all the UL testing. If you do the math the > pressure required does not always matchup with sqrt of P = Q/K. So what > happens to the distribution and droplet size when you install residential > sprinkler in residential portions of a 13 occupancy and give it two or three > times the minimum starting pressure. > > > Richard Mote ET > Designer > Rowe Sprinkler Systems, Inc. > PO Box 407 > Middleburg, PA 17842 > P- 877-324-ROWE > F- 570-937-6335 > [email protected] > www.rowesprinkler.com > > > > > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of Steve Leyton > Sent: Thursday, May 22, 2014 11:09 AM > To: [email protected]; [email protected] > Subject: RE: Area/Density Method and Walls > > I think most software can do that. We've been using FPE for a long while and > the software has a toggle feature between "Demand" and "Supply" calculations. > The later being a model of system performance at 0 psi remaining at Source. > > SL > > > > > > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of [email protected] > Sent: Thursday, May 22, 2014 7:38 AM > To: [email protected]; [email protected] > Subject: RE: Area/Density Method and Walls > > I don't know if Hydracad or SprinkCad has the same option as HASS but HASS > puts out a secondary calc called Full Flow. We looked at this and were a bit > surprised of the results. Basically when we calculate a system all we are > doing is proving that we can achieve the required minimum flow and pressure > within the hydraulically remote area. When you're done you end up with a > comparison of REQUIRED versus AVAILABLE pressure and flow. AS long as the > REQUIRED is less than the AVAILABLE all is good. > > What you don't see is what actually could be discharged based on the ACTUAL > pressure and flow. For example if you have a 250 gpm sprinkler demand with a > required BOR pressure of 50 psi and the water supply can provide 1000 gpm at > 125 psi, your FULL FLOW conditions will discharge MUCH more than the 250 > minimum required. > > So when there is a robust water supply your LH system can easily discharge > rates closer to an EH system. > > Also consider the statistical data of most fires being controlled by one to > three sprinklers and we're calculating more than that so you can see where > the difference between physics and reality come into play. > > Craig L. Prahl, CET > Fire Protection Group Lead > CH2MHILL > Lockwood Greene > 1500 International Drive > Spartanburg, SC 29303 > Direct - 864.599.4102 > Fax - 864.599.8439 > CH2MHILL Extension 74102 > [email protected] > > > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of Brad Casterline > Sent: Thursday, May 22, 2014 9:54 AM > To: [email protected] > Subject: RE: Area/Density Method and Walls > > "The designed system has little to do with physics or reality." > > Roland, I did not want to take your statement out of context completely, > because I know how much that hurts sometimes, so I did not trim this thread. > > I am always trying to quantify things as best I can so here is my shot: > > At the time calculations were being accepted into NFPA 13 the 'reality' was > that pipe scheduled systems had worked for 90 years. > In order for proposed changes to be accepted (then and now I guess) an > equivalency of some sort had to be shown, and that is where the 'physics' > came in, along these lines: given a certain water supply, what flows will a > scheduled system produce? Now, for the sake of economy, how much can we beef > it up here and slim it down there and still get equivalent results; mix a > little fluid mechanics theory with a lot of water flow measurements and... > BOOM! the density/area curves where born. > > So calculated systems using the density/area curves are nothing more than > reconfigured pipe scheduled systems at their roots. > > This is just my current understanding, and if it is mostly correct, it makes > real and perfect physical sense (to me anyway) ;) > > Brad Casterline, SET > > ps- I think calcs were a quantum leap in fire sprinkler design, and I think > the future WILL involve 'fire having something to do with it'. > > > -----Original Message----- > From: Brad Casterline [mailto:[email protected]] > Sent: Wednesday, May 21, 2014 12:12 PM > To: 'Roland Huggins'; 'SprinklerFORUM' > Subject: RE: Area/Density Method and Walls > > Three people took NFPA 13 from pipe scheduled to calculated: > Jack Wood, Lin McCool, and Hasu Doshi. > The Density/Area Curves "had nothing to do with fire" according to Hasu, the > only one of the three still alive. > The calculations were performed to see if they could get mains from 8" to 6" > by making the lines a little bigger and still get the same total flow. > So Chris, if you were pipe scheduling your set-up you would ignore the walls, > right? So there is your answer. > When I said I would consider any barrier I mean I would see in full color 3D > the flames and smoke and sprinkler spray of what I think would probably > happen, but what I would calc and print and walk the 40 feet to where my > supervising FPE of ~35 years, Hasu Doshi, is, I will have ignored the walls. > Hope that helps Cecil. > > Brad Casterline > Designer Member, AFSA > > -----Original Message----- > From: Roland Huggins [mailto:[email protected]] > Sent: Wednesday, May 21, 2014 10:41 AM > To: SprinklerFORUM > Subject: Re: Area/Density Method and Walls > > Actually a good question. > > Generally speaking you ignore the walls (exception the room design of course > and others like small systems where you simply add additional water to the > calc). The designed system has little to do with physics or reality. I've > yet to see a pendent sprinkler discharge water in a 10X13 rectangle, the > amount of water hitting the flow is NOT equal to the assigned density (even > IF it did flow uniformly throughout the pattern which it doesn't), friction > loss through fittings is not well accounted for from an academic standpoint, > if you move the sprinkler an additional 6" off a wall it will greatly > increase the required pressure but do you think it will really affect the > performance, unbounded fires do burn in a relative circle but the design as > never been based on that etc etc. The reality of the design is that it is a > well defined process whereby different people get relatively similar results > AND IT WORKS to control the fire. > > As such, for a new design, the approach ensures that a fire located anywhere > will be controlled by assigning the remote area in the most hydraulically > demanding location regardless of walls. When modifying a system, you will > not find anything that relaxes this conservative approach. So if you are > looking for a get out of jail card, get comfortably because you're staying in > jail. Now as an engineer evaluating a modification, one could challenge the > conventions of the standard and I believe still have an adequate system. > If one is thinking to avoid lawsuits, don't be an engineer (or contractor for > that matter). I know of a case where the building burned down and the > control valve was known to be closed and RECORDED as such for 6 months before > the fire.The contractor is still being sued - UFB. > > Somewhat what Cecil said with a touch of my opinion that is not I say not > (think of the big chicken from Looney Tunes Foghorn Leghorn pronouncing > that) to be considered an interpretation for NFPA 13 or any other NFPA > standard (with a few less THE's). > > Roland Huggins, PE - VP Engineering > American Fire Sprinkler Assn. --- Fire Sprinklers Saves Lives > Dallas, TX > http://www.firesprinkler.org > > > > > > On May 20, 2014, at 5:12 PM, Cahill, Christopher <[email protected]> > wrote: > >> I can't believe I'm asking this question after all these years. >> Anyway, > swallowing pride and asking. >> >> 2010 NFPA 13 strict Density/Area method 11.2.3.2 and 22.4.4.1.1. >> Great > big room being subdivided. Existing system with a new wall added between > heads on a BL. Contractor had to add a head on one side to preserve the > existing spacing (area) of the heads. Without head over 130 sq.ft. I take > the 1.2 ^.5 of the area and get 46.5' required along the BL. Original system > lets say calc'd 5 heads on the BL. But now in the same 46.5' there are 6 > heads on the BL. Do I ignore the wall and require a new calc? What if the > wall is rated 1 hour do I ignore it? >> >> I looked all over and can't seem to find anything definitive. Room >> design > is out so not a consideration. 22.4.4.1.1.1 simply says all the heads in the > 46.5'. I can't find anything that says either to count the wall as a break > so measure 46.5' from the wall in each direction and still see if there are 5 > head or ignore it and there are now 6 heads. I find 11.1.2 that clarifies to > extend the density or not. I don't think that's applicable exactly. The > question is not about whether to extend the density on either side. Let's > just say it's all OH. >> >> It gets a little more complex as on the one side of the wall they cut >> a > head in on the BL but on the other side there is a perpendicular new wall and > they come off same BL and arm over to two more head so if I ignore the walls > there are now 8 heads off the 1 BL. >> >> Prefer a code section or written reference 'cuz this is going to be a >> big > deal if we ignore the walls. Ordinarily with unrated walls they are ignored > in density/area (of course can't find that reference). I think I'm getting > tripped up with the rated portion? Or maybe I'm just tired???? >> >> Chris Cahill, PE* >> Associate Fire Protection Engineer >> Burns & McDonnell >> Phone: 952.656.3652 >> Fax: 952.229.2923 >> [email protected]<mailto:[email protected]> >> www.burnsmcd.com<http://www.burnsmcd.com/> >> *Registered in: MN >> >> >> Proud to be #14 on FORTUNE's 2014 List of 100 Best Companies to Work >> For >> >> >> >> >> _______________________________________________ >> 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 > _______________________________________________ > 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
