I was hoping someone chimed in that actually new. It is my understanding each head operates at its required pressure during the test. For example, let's say we're testing a 0.4 density spacing 100 sq.ft. so 40 gpm. So we'd have a pressure during the test of 12.75 psi at the head. Now if the test had a mere 100 psi when the first head opened we'd flow 112 gpm. Seems like I'd want to list it for 1.12 gpm/sq.ft. then with one head operating? There are designs out there for 4 heads at whatever and x,xxx sq.ft. at whatever density. What if I only have 60 psi available and a real flat cure such that I don't need 100 psi? The test then becomes irrelevant because will I get control at 86 gpm or only 75% of the tested flow? Don't know, wasn't tested. Maybe we got control in the test because of the fire service term blitz attack and anything less is a fail if the first head isn't flowing 112 gpm.
Then think about variable speed pumps. I know they are not that popular but they exist. Arguably, there is very little (at least much less) over pressurization at any number of heads open. Testing like this is another reason we see a big difference between the number of calculated heads or heads that operate in the testing vs. the number of heads that operate in a fire. If someone had the resources this could be a place to further reduce the flow demands. Do some testing and show 1 head at x works with 3 heads at y and 6 heads at z and all of a sudden we're not calculating 20 heads. You as a designer see what you can pull off from choosing between a bunch of design points. Pipes shrink, pumps get smaller, tanks get smaller, sprinkler cost remain constant in actual dollars like they have for decades meaning with inflation they are way cheap. 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 Todd - Work Sent: Thursday, May 22, 2014 4:03 PM To: [email protected] Subject: Re: Overpressurizing Heads 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-firesprinkl > er.org > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.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
