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-firesprinkler.org > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
