So I'm assuming you've verified that AFFF and not AR-AFFF is the suitable solution and that 3% not 6% or other is also suitable? Typically unless you have some cookbook material you're dealing with, make a call to one of the foam reps and run the material by them to verify type of concentrate, concentration, and flow rates. 0.30 gpm/sf is pretty high for a foam-water system unless you've got some extenuating circumstances going on.
10 minutes is standard baseline for NFPA 16. But it can vary depending on conditions and Underwriter. You didn't state the type of foam system so the assumption here is something like a foam-water sprinkler system. Foam Concentrate Tank sizing: Density x design area x 1.15 = GPM x % concentration x duration = tank size. 0.30 gpm/sf x 2500 sf x overage or imbalance factor = 862.5 GPM x 3% concentration x 15 minute duration= 388 gallons. Use a 400 gallon tank. Imbalance or overage fact is typically in the 10-15% range since sprinkler system do not actually flow at 100% of design criteria. Mathematically .30 x 3000 = 900 gpm but if you look at your calcs you'll see when it's all said and done calculated flow will be more and ACTUAL flow will always exceed design. There are other factors to consider again depending on the specific hazard and type of foam system you are designing. Craig L. Prahl, CET Fire Protection Group Lead CH2MHILL Lockwood Greene 1500 International Drive Spartanburg, SC 29303 Direct - 864.599.4102 Fax - 864.599.8439 CH2MHILL Extension 74102 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bob Sent: Wednesday, February 26, 2014 1:58 PM To: [email protected] Subject: AFFF Bladder Tank Sizing I have a NFPA 30 project where I need to size a bladder tank for 3% AFFF solution. I have looked but can't find any info on sizing the tank. I am assuming that I need to take the gpm flowing x .03 x 15 min duration. The only thing I have found for a safety factor in in 409 where it uses 1.15. For example, 750 gpm x .03 = 22.5 x 15 = 337.5 x 1.15 = 388.125 gal. Does this sound right? Thank you, Bob Knight, CET III 208-318-3057 www.firebyknight.com _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
