Don't forget friction in the pipes! Matt Grisé PE*, LEED AP Sales Engineer Alliance Fire Protection *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 Brad Sent: Tuesday, June 15, 2010 12:39 PM To: [email protected]; [email protected] Subject: RE: Gravity Tanks i.e., if the water level is 280 feet 'above your head', then h=280 ft, v=134 ft/sec (same as the Law of Falling Bodies- if you were dropped from 280 ft, you would be going 134 ft/sec when you hit the ground). ft/sec*ft^2=ft^3/sec. If the flow is coming out of 4" pipe, ft^2=.09---- *134= 12 * 7.48= 90---- * 60= 5400 GPM. As the level 'above your head' drops, so does the velocity, so either use calculus, or call h the bottom of the tank, like I would have to do. It still seems like magic to me that by just using feet and seconds, given the rated psi and rpm ONLY, of a fire pump, I can calculate the diameter of the impeller (v=2*pi*r*f). It seems like magic bcoz for 15 years I tried to learn sprinkler calcs after the PEs had simplified it enough for me by factoring gravity out of the formulas. -----Original Message----- From: Brad [mailto:[email protected]] Sent: Tuesday, June 15, 2010 8:30 AM To: [email protected] Subject: RE: Gravity Tanks mgh=.5mv^2 m is the same on both sides so v= sq root 2gh h= v^2/2g first thing is forget about gallons, minutes, and psi- use feet and seconds: ft, ft^2, ft^3, sec, sec^2. ft/sec=(ft^3/sec)/ft^2) g=32.2 ft/sec^2 (if this project is on the earth). 7.48 gal/ft^3. water weighs 62.4 lbs/ft^3. -----Original Message----- From: Todd Williams [mailto:[email protected]] Sent: Tuesday, June 15, 2010 5:11 AM To: [email protected] Subject: Gravity Tanks Was there a thread on calculating flow from a gravity tanks a while back? I couldn't find it. I have to do a calculation on the first floor of a building fed from a gravity tank on the 28th floor Todd G. Williams, PE Fire Protection Design/Consulting Stonington, CT 860.535.2080 www.fpdc.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) _______________________________________________ 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)
