Reza, You first need to establish the design criteria for your facility. So let's say it's just a factory as you stated and they do mostly machining type work, no special hazards or anything like that, we can take a look in NFPA 13 (2007), in A.5.3.2 and we'll see that we would have an Ordinary Hazard Group II occupancy. Then go to Figure 11.2.3.1.1 (Density/Area Curves) and you will see that for an Ordinary Hazard Group II you could have a density of 0.20 gpm sq. ft with a design area of 1,500 sq. ft. In Table 11.2.3.1.2 For OH II your hose stream allowance is 250 gpm. So .20 gpm/sf x 1,500 sf give you 300 gpm sprinkler demand plus 250 gpm hose gives you 550 total system demand. This is bare minimum and it is often recommended to add at least 10%-15% to that since we don't end up with exactly .20 gpm/sf from each head when they're calculated. So with that in mind you could have a demand of 605-630 +/- gpm of system demand.
For this application the head spacing could vary, say we used 130 sq. ft per sprinkler (just for discussion) so in that 1,500 sq. ft you'd end up calculating approximately 12 sprinklers. This is a real basic overview and not intended to include or encompass every aspect of hydraulic calculations, system design or other variables. Craig L. Prahl, CET Fire Protection Group 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.lg.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Reza Esmaeili Sent: Thursday, September 13, 2007 7:41 AM To: [email protected] Subject: Water demand for fire protection system! Hi all, I have a bit problem in calculating my water demand for a theory project like below: Assume that there is a factory protected with a wet pipe sprinkler system, 4 fire boxes and 4 external hydrants on main ring. According to NFPA-13 i conclude that for example I should consider 20 sprinklers active and from my hydraulic calculations I concluded that my sprinklers demand would be 643 Gpm. I also assumed 2 fire boxes active and from my hydraulic calculations I concluded that for example flow rate for first fire box is 142 Gpm and second is 156 Gpm, So the total demand for hose streams is (142+156) = 295 Gpm. I also have 4 external hydrants on main ring, should I assume that at least one hydrants will work at the same time with my sprinklers and 2 fire boxes? If the answer is yes, then I will active one hydrant and my hydraulic calculations I concluded that my hydrant demand is 860 Gpm. So I have following demands: 1- Wet pipe sprinkler system ------------------------------- Demand: 643 Gpm 2- Hose streams (Fire boxes) ------------------------------ Demand: 295 Gpm 3- External Hydrants on main ring------------------------- Demand: 860 Gpm Now I conclude that my total water demand is (643 + 295 + 860 )= 1798 Gpm. My questions are as below: A- Should I assume that my external hydrants will work at the same time with sprinklers and 2 fire boxes? and should I include them in total water demand? B- Should I assume exactly 295 Gpm for my hose streams? or NFPA has standard for water demand of hose streams( Ex. 250 or 500 Gpm) ? C- What is my right total demand in your idea? I know that my questions may surprise you, becuase I am a beginner, I would appreciate if you answer in details to know where I am wrong. Thanks, Reza --------------------------------- Don't let your dream ride pass you by. Make it a reality with Yahoo! Autos. _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
