Keep in mind that you started with a nominal K factor of 5.6. Per Table 6.2.3.1 (NFPA 13 - 2007), the range for the K factor under laboratory testing conditions was 5.3 to 5.8. Just talking out loud, but I wonder if that correction is really that important when the reality is the base number could be off by 0.5 to start.
Look at NFPA 13 - 2013 and see if these adjustments are still required. My educated guess is that they have been deleted based on this argument. Check the ROP and the ROC from last cycle if you are interested. John - This is my personal opinion and not an official interpretation by the NFPA 13's technical committee. John August Denhardt, P.E., FSFPE Strickland Fire Protection Incorporated 5113 Berwyn Road College Park, Maryland 20740 Office Telephone Number: 301-474-1136 Mobile Telephone Number: 301-343-1457 FIRE SPRINKLERS SAVE LIVES - Can you live without them? -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Brad Casterline Sent: Tuesday, June 11, 2013 7:52 AM To: [email protected] Subject: adjusting the K-Factor with our bare hands >From NFPA 13-2007, 22.4.4.5.1, we are required to, among other things, adjust the K-Factor. Using the Hazen-Williams friction formula, 62.4 lb/ft3 / 144 in2 = .433 lb/in2/ft(h). If we have an AF solution at 65.5 lb/ft3, / 144 = .455 lb/in2/ft(h). If K=5.6, and we assume P=7 PSI.: 7/.433=16.166 ft(h). 7/.455=15.385 ft(h).* 15.385/16.166=.952. sqrt(.952)=.976, x 5.6 = 5.46. There is a chart in 13 showing a 50% glycerin solution at about -10F weighing about 15% more than 100% water: 62.4 x 1.15 = 71.76. 71.76/144=.498. 7/.498=14.056 ft(h). 14.056/16.166=.869. sqrt(.869)=.932, x 5.6 = 5.22. If I had to fab the pipe today and formalize the submittal tomorrow (after googling centipoises for several hours) I would calc it like it was 'all wet', using K=5.22. * converting PSI to feet of head(h) it is seen that the denser the solution, the 'shorter' it is. Since v=sqrt(2gh), the shorter it is the slower it is. Making the adjustment based on "h", we have to take the square root of the ratio, i.e., (K=Q/sqrtP). If adjusted based on velocity we would use the ratio itself (square feet=cubic feet per second divided by feet per second): sqrt(2*32.2*16.166)=32.266 ft/sec. sqrt(2*32.2*15.385)=31.477 ft/sec. 31.477/32.266=.976. The above is simply the type of thing I enjoy doing and like to share, hoping it will cause no harm, to be taken or left as one sees fit. thanks, Brad Casterline, NICET IV Fire Protection Division FSC, Inc. P: 913-722-3473 [email protected] www.fsc-inc.com Engineering Solutions for the Built Environment _______________________________________________ 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
