Let's say you used option #3 and opened the valve all the way and the velocity was only 5 FPS. Why would that velocity ever be more than 5 FPS? Even in the case of a dry pipe valve or pre action? You could break the main off at the riser and you'd still only have 5 FPS velocity.
Alternate: You used option #1 and flushed per 24. While you may get an initial in rush of greater than 10 FPS it will be short lived as your water in the system compresses the air that remains in the system. If you have delivery time software, it's really interesting to watch the simulation of the water compressing the air in branch lines that don't have open outlets. (Outside of the fire area.) Besides let's say you have a 500 Gallon dry system. The water to fill that to pressure will be less than 500 gallons by more than 1/2, so in reality your only flowing say 250 gpm in one minute. (Time to outlet) Remember 24 say's min underground size is 6" unless you Hyd. Calc. the underground. 6" DIP flowing 250 GPM is 2.5 FPS. Flowing 500 Gpm is 5 FPS, and 1000 GPM is (you guessed it) 10 FPS. So if you have a 6" underground you'd need a 2000 Gallon dry system to flow over 10 FPS average. Yes I admit the initial flow for the first 200 gallons may exceed 10 FPS, but then the average would drop off as pressure built.(Keep in mind that 200 Gallons is less than the volume of 150 LF of 6" pipe) Thom McMahon, SET Firetech, Inc. 2560 Copper Ridge Dr P.O. Box 882136 Steamboat Springs, CO 80488 Tel: 970-879-7952 Fax: 970-879-7926 -----Original Message----- From: sprinklerforum-boun...@firesprinkler.org [mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Art Tiroly Sent: Friday, April 02, 2010 10:30 AM To: sprinklerforum@firesprinkler.org Subject: RE: Underground flushing velocities One concern I have is for dry pipe and preaction systems. The in-rush to fill the system will have a short term high velocity flow that will pick up any debris in the fire line and move it into the riser. Should that be added to the flushing proceedure or is it a special case that that does not warrant attention? -----Original Message----- From: sprinklerforum-boun...@firesprinkler.org [mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Roland Huggins Sent: Wednesday, March 31, 2010 2:06 PM To: sprinklerforum@firesprinkler.org Subject: Re: Underground flushing velocities What it actually says is: shall not be less than ONE of the following. So as long as you meet ANY one of the following you comply. As for why all the discussion on 10 ft/s, that is the golden rule and they had to talk about something so they talked a lot about that. What about all the discussion in the Handbook about sizing the remote area by counting sprinklers despite the fact that even with the right number, the actual size can be too small and NOT be in compliance. What about the Handbook text that states: "In the field, actual flushing is normally done without measuring the flow rate. Flushing is normally accomplished at the maximum flow rate AVAILABLE from the water supply as permitted by 10.10.1.2.3(3)." So yes, 2 fps is acceptable as long as it is what is produced by the system demand and has nothing to do with a call by the AHJ. You guys are unnecessarily beating yourselves up. Now having said that, what you put in your spec's (especially where stuff glows in the dark and the DOE is happy to apply the golden rule), is a different story. Roland On Mar 31, 2010, at 10:37 AM, Law, Kevin W wrote: > The key is the requirement states it shall not be less than ANY one of > the following. > > Therefore, the very minimum flow rate will be 10ft/sec line velocity. > > If your system cannot under any condition flow a minumum of 10ft/sec > then you would have to get a ruling from the AHJ to allow that. > > Nuff said > > > Kevin Law, PE > Bechtel National, Inc. > Waste Treatment Project > Fire Protection Engineering > Work (509) 371-3280 > Cell (509) 531-5715 > > > -----Original Message----- > From: sprinklerforum-boun...@firesprinkler.org > [mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of > craig.pr...@ch2m.com > Sent: Wednesday, March 31, 2010 10:20 AM > To: sprinklerforum@firesprinkler.org > Subject: RE: Underground flushing velocities > > So if the max. velocity is only 2fps there's no issue? > > Then why the talk of 10fps in the appendix with mention of high > velocity and Table relating to 10fps? > > If any velocity was acceptable then why not just say it doesn't matter > or say nothing at all? > > > Craig L. Prahl, CET > Fire Protection Specialist > Mechanical Department > CH2MHILL > Lockwood Greene > 1500 International Drive > PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - > 864.599.8439 craig.pr...@ch2m.com http://www.ch2m.com > > > -----Original Message----- > From: sprinklerforum-boun...@firesprinkler.org > [mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Roland > Huggins > Sent: Wednesday, March 31, 2010 12:51 PM > To: sprinklerforum@firesprinkler.org > Subject: Re: Underground flushing velocities > > The 10 fps applies only to option 2, not all the options. As long as > you meet any ONE of the options, where's the beef? > > The objective is to keep loose objects in the main from potentially > blocking the sprinkler system. Option 2 assures us that we will > remove the loose objects. The other options assure us that the > objects will not reach the system since the maximum possible velocity > (being less than 10 ft/s) has removed the objects that will move at > system demand (which would be the likely lowest velocity). Option 3 > allows us to simply open multiple outlets and let it flow whatever > flows without having to prove anything. > > Roland > > On Mar 30, 2010, at 1:47 PM, <craig.pr...@ch2m.com> > <craig.pr...@ch2m.com > wrote: > >> NFPA 24 says the following: >> >> NFPA 24: 10.10.2.1.3 The minimum rate of flow shall be not less than >> one of the following: >> (1) Hydraulically calculated water demand flow rate of the system, >> including any hose requirements >> (2) Flow necessary to provide a velocity of 10 ft/sec (3.1 m/sec) in >> accordance with Table 10.10.2.1.3 >> (3) Maximum flow rate available to the system under fire conditions >> >> >> >> >> >> Debate is whether that means that the flow rate dictates the velocity >> and it has no absolute requirement or the minimum is 10fps. >> >> Based on wording in the Appendix it would appear that 10fps is the >> desired minimum. >> >> So for example I have a flow rate of 8000 gpm (fire flow per local >> AHJ) and the line size ends up being 24" Vel= 6.74 fps. Is that >> acceptable per NFPA 24, 10.10.2.1.3? There are issues with the >> distance between source and pump suction and larger pipe equal less >> friction loss but also lowers velocities. >> >> I read it that it can be less than any one of the following with >> 10fps being the minimum. Sometimes simpler wording for non-FP >> types would make life easier. <sigh> >> >> Thought, comments, etc????????? >> >> Craig L. Prahl, CET >> Fire Protection Specialist >> Mechanical Department >> CH2MHILL >> Lockwood Greene >> 1500 International Drive >> PO Box 491, Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - >> 864.599.8439 craig.pr...@ch2m.com http://www.ch2m.com >> >> _______________________________________________ >> Sprinklerforum mailing list >> Sprinklerforum@firesprinkler.org >> http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum >> >> For Technical Assistance, send an email to: supp...@firesprinkler.org >> >> To Unsubscribe, send an email >> to:sprinklerforum-requ...@firesprinkler.org >> (Put the word unsubscribe in the subject field) >> > > _______________________________________________ > Sprinklerforum mailing list > Sprinklerforum@firesprinkler.org > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: supp...@firesprinkler.org > > To Unsubscribe, send an email > to:sprinklerforum-requ...@firesprinkler.org > (Put the word unsubscribe in the subject field) > _______________________________________________ > Sprinklerforum mailing list > Sprinklerforum@firesprinkler.org > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: supp...@firesprinkler.org > > To Unsubscribe, send an email > to:sprinklerforum-requ...@firesprinkler.org > (Put the word unsubscribe in the subject field) > _______________________________________________ > Sprinklerforum mailing list > Sprinklerforum@firesprinkler.org > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: supp...@firesprinkler.org > > To Unsubscribe, send an email > to:sprinklerforum-requ...@firesprinkler.org > (Put the word unsubscribe in the subject field) > _______________________________________________ Sprinklerforum mailing list Sprinklerforum@firesprinkler.org http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: supp...@firesprinkler.org To Unsubscribe, send an email to:sprinklerforum-requ...@firesprinkler.org (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list Sprinklerforum@firesprinkler.org http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: supp...@firesprinkler.org To Unsubscribe, send an email to:sprinklerforum-requ...@firesprinkler.org (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list Sprinklerforum@firesprinkler.org http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: supp...@firesprinkler.org To Unsubscribe, send an email to:sprinklerforum-requ...@firesprinkler.org (Put the word unsubscribe in the subject field)
