Mark, That may work out on the plains with your crappy water pressures but here (at the hydrants I use for teaching this procedure) I have a static (city residual) at about 75 psi. When I flow a separate hydrant I get a velocity of around 35 psi and a residual drop at my control hydrant of about 2 psi. I then have to open a third hydrant (and usually I need the steamer port) to get the recommended 10% (at least 67.5 psi or lower for 75 psi static) for an accurate residual reading and the velocity drops to maybe 32 psi. This is medium pressures for the area. In some places in Seattle (the waterfont for one) the city static during peak hours is 120-130 psi and as high 150-160 psi at off hours. Lots of pretty tall buildings around here without pumps.
On Fri, Jul 22, 2011 at 9:02 AM, Smith, Steven D. (CSFD) < [email protected]> wrote: > Any hard data showing comparisons of dual/single hydrant testing out there? > > -----Original Message----- > From: [email protected] [mailto: > [email protected]] On Behalf Of Mark Sornsin > Sent: Friday, July 22, 2011 9:54 AM > To: [email protected] > Subject: RE: Convert Pitot to actual residual?? > > The residual pressure in a single hydrant test would be a bit lower, i.e. > more conservative due to the friction losses incurred from the water moving > up the hydrant barrel. The larger the flows, the less accurate > (conservatively) the test becomes. > I generally avoid these situations, but when you don't need a lot of flow > for your design it is reasonably accurate (e.g. residential or light hazard > designs for sure). > > Mark A. Sornsin, PE | Fire Protection Engineer > Ulteig Engineers, Inc. |Fargo, ND > Direct: 701. 280.8591 | www.ulteig.com > > > -----Original Message----- > From: [email protected] [mailto: > [email protected]] On Behalf Of Matt Grise > Sent: Friday, July 22, 2011 10:46 AM > To: '[email protected]' > Subject: RE: Convert pitot to actual residual?? > > My understanding is that single hydrant tests are not as accurate as double > hydrant flow tests. You are trying to figure out how much pressure you can > get from the system when it is discharging a certain amount of water. If you > test the flowing hydrant, I imagine the pressure would read lower since the > water would have a pretty high velocity. (just thinking out loud there... I > have not researched it) > > Matt Grisé PE*, LEED AP > Sales Engineer > Alliance Fire Protection > 130 w 9th Ave. > North Kansas City, MO 64116 > > *Licensed in KS & MO > > 913.888.0647 ph > 913.888.0618 f > 913.927.0222 cell > www. AFPsprink.com > > > -----Original Message----- > From: [email protected] [mailto: > [email protected]] On Behalf Of Smith, Steven D. > (CSFD) > Sent: Friday, July 22, 2011 10:41 AM > To: [email protected] > Subject: RE: Convert pitot to actual residual?? > > What if a pressure gauge was installed on the other outlet of the hydrant > from which the water is flowed and pitot reading is taken? > > IOW, is it possible to have the test and flow hydrant one in the same? > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Vince > Sabolik > Sent: Friday, July 22, 2011 9:08 AM > To: [email protected] > Subject: Re: Convert pitot to actual residual?? > > Ron, > > Ron, > > Yeah figured so. I just thought that someone may have had one of those > 'rule of thumb' thingys laying around. > > Seems to me THAT should be possible, no? > > I just wanted this to guestimate the design ahead of doing another test. > > BTW, sorry about the double posts. I'm having an argument with me this > morning. > > > > At 10:58 AM 7/22/2011, you wrote: > >Vince, > > > >Since you don't have a residual, which is the left over energy in the > system > >measured in psi at the non-flowing hydrant, while flowing through that > >circular orifice you're screwed and the test has to be re-done. Once > you > >have actual flow and residual you can calculate flow at any residual > >pressure (changes with the size of orifice) or residual at any flow. > >Unfortunately static minus velocity (the pitot reading) doesn't equal > >residual. Life and understanding the world would be so much easier if > it ran > >on magic and religion instead of physics. > > > >Vince Sabolik, West Tech Fire Protection, Inc. > 11351 Pearl Road / Strongsville, Ohio 44136 440 > 238-4800 Fax 440 238-4876 > ____________________________________________________________________ > > > _______________________________________________ > 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) > _______________________________________________ > 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) > > > _______________________________________________ > 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 Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: ASEE, SFPE, ASCET, NFPA, AFSA, NFSA, AFAA, NIBS, WSAFM, WFC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) _______________________________________________ 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)
