If I didn't have a playpipe, I followed FM's conservative guidelines (from their Hydraulic Pocket Guide). 0.80 for outlets that were smooth and well rounded inside. And 0.70 when the outlet was square.
Travis From: Travis Mack, SET [mailto:[email protected]] Sent: Wednesday, February 22, 2017 5:45 PM To: [email protected] Subject: Re: Do Hydrant Butts have a K Factor? Or just use the formula in NFPA 291- Standard for Hydrant Marking and flow tests or something like that... Q = 29.83*d^2*Cd*P^0.5 d = hydrant outlet diameter in inches C = the outlet coefficient (0.7, 0.8 or 0.9) P = Pitot pressure that is measured Not everything has to be extremely complicated and thought out to the nth degree. If you are really so inclined, why not spend the next few years solving for Pi to the 1,000,000th point. And guess what...... if you assign K to be 29.83*d^2*Cd........ you get 168 for your example. Wow...sometimes the simplest methods are the best. There is a true phenomenon that causes many people problems - paralysis through analysis. Travis Mack, SET MFP Design, LLC 2508 E Lodgepole Drive Gilbert, AZ 85298 480-505-9271 fax: 866-430-6107 email:[email protected] http://www.mfpdesign.com https://www.facebook.com/pages/MFP-Design-LLC/92218417692 Send large files to us via: https://www.hightail.com/u/MFPDesign LinkedIn: https://www.linkedin.com/in/travismack On 2/22/2017 5:58 PM, Brad Casterline wrote: Say it's a 2.5" C=.9. I've tried to work this out a couple different ways: 1) a kind of long drawn out way, call it 'brad's way', and I get ~168. 2) a way i call the 'Bill Brooks back of napkin' way based on a few words he posted here a few years ago-- lightening fast, and i'll be damned if i dont get the same ~168! Basically, since K is the square feet area of the orifice he says 5*5*5.6=140, times (.9/.75) = 168. Anyway, if a hydrant butt has a K we could pretty quickly get the Q after the pitot'd P with Q=K*SQRT(P). thanks, Brad . _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
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