I have to say that my FAVORITE emails are the ones that contain the phrase, "Steve is correct." I never get tired of reading that ...
SML -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Tony Eggster Sent: Tuesday, March 15, 2016 8:01 AM To: [email protected] Subject: Re: Standpipe Calc: Adding City Demand to Pumper Truck? All that confirms my suspicions. I always calc to the FDC but when I came across these plans I tried to find justification in '14 and saw the material in the annex which set off a lot more questions. Good to know guys, thanks! On Mon, Mar 14, 2016 at 4:13 PM, Tom Duross <[email protected]> wrote: > Steve is correct. A simple 151@0 to 150@1000 (or 1250) supply line, > regardless of city supply flow unless of course you can't supply the > pumper with 1000 or 1250 gpm supply. The reason for the 150 psi > demand pressure is the system is hydro'd to 200. You can use the two > (2) uppermost FDV's on the HMD standpipe flowing 250 each for the > standpipe required flow of 500 and then the uppermost FDV on each > remaining standpipe at 250 each to a max of 1000 for a sprinklered > building or 1250 for partially or a non-sprinklered building. All > flows must have a minimum residual of 100 psi but I do what Steve says > and shoot for 105. You can use K factors of 25 and > 50 at the minimum residual of 105 to make your standpipe calc's easier > and the FDC is the supply point. Remember not to calc a hole in the > pipe but to include the tee, nipple and valve. > TD > > > Tony: > > You (or the submitter) are over-simplifying what the annex says. It's > not the intent that you take the city flow test and add it to the pumper > curve. > NFPA 1901 sets the basic performance curve for a pumper at 150 PSI/1,000 > GPM. NFPA 13E is the standard for FD Operations for buildings equipped > with sprinklers and standpipes - that standard goes into the company > engineer's procedure for calculating the discharge pressure of the pump > based on suction pressure, friction loss in hose and other variables. But > the bottom line is that it's all targeted at discharging 150 PSI > residual at > 1,000 GPM. This has NOTHING to do with pressure at the FDC; it has to do > with calculating the performance of the apparatus. What gets to the FDC > is > up to the engineer. > > Which is why 7.7.4 states, "When the system demand to be supplied by > the fire department at the fire department connection is being > determined, the local fire department shall be consulted regarding the water > supply > available from a fire department pumper." FROM A FIRE DEPARTMENT PUMPER. > It's up to the incident commander and his or her engineer to determine > the suction pressure and set their discharge to whatever is required > to make their programmed starting pressure. And based on the > nationwide standard and best practices, that is almost certain to be > 150 PSI at the prescribed flow rate. The engineer will calculate the > friction loss in the discharge hose that's connected to the building. > If you are reviewing plans that show > 150 PSI residual plus a positive suction head at that flow rate as the > inlet pressure, then that is almost certainly not correct. > > To answer your question, if I have a building with two (750 GPM) or > three or more (1,000 GPM) standpipes, we plug in a "flow test" static > pressure of > 151 > PSI and a residual of 150 PSI at the target flow rate and we run the calc' > using the FDC as the "city connection". We plug in a 500 PSI hose stream > allowance at the most remote standpipe outlets and at 250 GPM hose > streams at those points in the bulk main system where the other risers take > off. > We > allow 5 PSI for loss in a standard hose valve so the minimum pressure > at any node is 105 PSI. > > The foregoing is my opinion only and does not represent the opinion of > or any manner of interpretation by NFPA or the Technical Committee on > Standpipes. > > Steve Leyton > > > Quick question: I'm reviewing some plans for a manual class I > standpipe and the designer added the city flow test to the usual > 1000gpm fire pumper curve in order to keep all the pipe down to 4". I > see in the NFPA 14 appendix that you can do this but personally I've > always just calculated solely to the pumper curve. How do you guys do > it? > > Also, I'm assuming that if you do factor in city supply wouldn't that > frequently require high pressure pipe and fittings depending on city > supply psi? > > _TONY > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.org > _______________________________________________ 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
