No prollem. You don't have to apply theoreticals however - Elkhart has some friction loss data on line for hose and commonly used fittings. If you assume the flow rate of 250gpm from a Class 1, common practice for many FD's is to put down a section of 2½" rubber suction hose and then connect a gated wye that is sized for their preferred attack line, usually 1½" or 1¾". If you assume an 8' section of suction hose, 250gpm through a gated wye and 125gpm down a 100' length of lined synthetic 1½" hose, you get a loss of 45-55psi depending on variables. Which supports the TC's finding of 150psi back in 1993. And which is why I (and others) have been pushing to include more forward language in both the standard and annex regarding "performance based" design.
SL -----Original Message----- From: Sprinklerforum on behalf of Brad Casterline Sent: Wed 9/17/2014 6:54 AM To: [email protected] Subject: RE: Water Velocity No problem Steve, thanks for the reply. Until a few months ago, all I new about NFPA 14 was the written word, and that AHJs in Kansas City were not adverse to allowing 65 PSI at the top in lieu of 100 (existing buildings). Any way, after having done a standpipe calc that included the loss for the valve, nipple and tee I thought what the heck why not include the nozzle and hose also. I totally guessed the coefficient of discharge of a 2.5" nozzle to be .75, which gave me K=92.2, Q=250, P=7.352, and flowing through 100 feet gave me about 62 PSI at the SP connection. That is when I posted the 'why 100 PSI' and got an excellent education (as usual on this Forum). For 250 through the 1.5" equipment though I came up with more than the 150 you cite (and I did not have to derive the PSI at the nozzle part). Then Monday I got a notice from AFSA that NFPA 14 is open for public comment, so naturally I started dwelling on "why raise the minimum 35 PSI when the reasoning being used would require raising it at least 85 PSI? Why not go all the way or leave it alone, since the FD will be there when they are being used anyway"? The question I have now, and I should save it for Friday due to its laugh value, is; Do you foresee the 14 Technical Committee saying something like "OOps, let's back up to a simpler place and time, 65 it is again!" Not only pump people, but PR valve people would have to tighten their belts, no? :) Thanks again sir, Brad Casterline -----Original Message----- From: Steve Leyton [mailto:[email protected]] Sent: Tuesday, September 16, 2014 8:20 PM To: [email protected] Subject: RE: Water Velocity I've been buried today, so apologies for late answer. I have a story, but it's anecdotal and I wasn't in the room during the 1993 cycle. However, the source of this information is VERY reliable and served on the 14 committee for a very long time. By the 1993 cycle, selectable flow nozzles were displacing smooth bore/straight stream tips. The first one, Select-A-Flow, was rated at 100psi. Smaller diameter attack lines with shapeable tips were being adopted nationwide, so the TC set about determining whether or not 65psi was the right number. They determined that the correct number was 150psi, to allow enough loss in the hose and fittings to provide 100 at the tip. Between ROP and ROC, there was an uproar as the only happy stakeholders were pump manufacturers. So in the second half of the cycle, they arrived at 100 as an increase that wouldn't get NITMAM'd off the floor of the code hearing. It was political, not performance based. If anyone's ever heard me do a presentation or just pontificate on standpipes, then you've heard me say that I think they should be designed for the equipment that the serving FD is using. However, FD's have purchasing agents who stick to budgets and some cities change tips when the time and price are right. Changing equipment (and NOT failure of the PRV's as commonly thought) was the main reason that inside attack streams couldn't be developed at the Meridian Plaza fire. My opinion and someone else's story only ... SML -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Brad Casterline Sent: Monday, September 15, 2014 7:53 PM To: [email protected] Subject: Re: Water Velocity BTW, while I got you, 14 is standpipes right? Your specialty, and open for public opinion? 65 at the top was just right for the old 2.5 inch but 100 is inadequate for the modern, smaller packs-- any comments on that conundrum? _______________________________________________ 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
