Ron, By "pig" do you mean inflatable plug like Cherne manufacturer's? If so, I didn't know those were used for "cleaning". I guess it would work as long as there is accountability and it gets out of the ug before the fire...
Scott Futrell (763) 425-1001 Office (612) 759-5556 Cell -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Ron Greenman Sent: Tuesday, March 30, 2010 4:03 PM To: [email protected] Subject: Re: Underground flushing velocities The objective is to move the water fast enough to move the crap and to move enough water that there's enough flow to get the stuff to the outlet so I think (dangerous) flow rate is more important. If I put my big thumb over the end of your 24" pipe I'll get good velocity but stuff might get hung up at the thumb end 'cause I got a little hole. I'm just cleaning out debris so I can manually remove it if I get it to the end. If moving a lot of water was the issue so that any given slug of water could be traced as fully moving along the pipe and I was trying to scrub the pipe walls, and it was moving slow I'd probably fail. I don't need to scrub the walls of a new pipe, just move the loose stuff like gloves, 2x4s, rags, tools and bedsheets (yes, I've found a bed sheet, came from a hospital in an area where there were no hospitals) then velocity is key. If I can't scrub because velocity is too low unless I try to restrict exiting volume then I can always scrub with a pig. So after all that I'm agreeing that the velocity (10fps) is the bottom limiting factor. But it isn't really clearly stated. On Tue, Mar 30, 2010 at 1:47 PM, <[email protected]> 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 > [email protected] > http://www.ch2m.com > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum > > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email to:[email protected] > (Put the word unsubscribe in the subject field) > -- Ron Greenman Instructor Fire Protection Engineering Bates Technical College Tacoma, WA Member: SFPE, ASCET, NFPA, AFSA, NFSA AFAA, NIBS, WSAFM, WFC _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
