Another picture cause I'm having fun. The tank bone is connected to the pump bone. The pump just flow the 450 gpm to the sprinks at the required pressure but adding the 250 sends the demand pressure too far north on the supply curve. The pump is then connected to a Tee bone and the Tee bone is connected to 100 feet of pipe to the sprinks and 400' of pipe to the hydrant bone. When the 1500 gpm reaches the hydrant bone it's at 20 psi (and let's say it's at 20 without the pump), but that's OK 'cause the FD brings another pump to the party just for the hydrant and the hoselines (by the way auto-correct fixed homeliness to homeliness). The tank has enough actual capacity to run both sprinks and hydrant for an hour. Why do I need that extra 250 gpm added to the sprink calc when it's already available and adding it causes me to buy a different, perhaps more expensive pump. Brent is agreement with my overall thinking here (though I think he has the hydrant on the way to building instead of past it) but there's nothing that allows me to ignore the 250 unless I take the sprinkler demand out of the one tank and add a second tank just for it. And if I need a pump for both sprinks and hydrant then I need a second. Obviously this isn't a big deal, and may literally be a stupid question. I've already spent more time on it than would ever occur in the cost of sizing the pump to take care of the unusual theoretical question but it just bugged me. And Roland, the other point you bring up may take many scotches to discuss in San Antonio. And when are you in town. We have many paper targets needing a good killing.
On Thu, Jun 30, 2011 at 10:05 AM, Roland Huggins <[email protected] > wrote: > You're crossing into a nebulous area when you attempt to connect reality > and methodology (better known as the twilight zone where the whole court is > out of order). In the same vane, we could debate the fact that 80+% of fire > are controlled by no more than 3 sprinklers and ask why have a 1500 sf > remote area (or even 900 sf with QR). Bottom line is that we have X amount > for sprinkler (that exceed the actual demand) and a simultaneous Y amount > for hose demand (for those cases that have some mop-up) producing the only > reality that counts - that being that it works. Occasional variances are > granted to reduce the hose demand but in looking at it, I'm having a > difficult time connecting those dots. What is the relevance of having 1500 > gpm hose demand when discussing the ability to supply the sprinkler and a > reduced hose demand unless you plan to turn off the sprinklers and run only > a manual response? Apples to oranges. I Like them both but not together. > > Roland > > > On Jun 30, 2011, at 8:43 AM, Ron Greenman wrote: > > It was just rhetorical. I was thinking what if I'm boosting the tank >> pressure to just what I need (think steepish curve) to operate the sprinks >> at the 450 gpm. That gets the 1500 gpm to the hydrant at over 0 psi and >> the >> engine takes it to whatever the FD wants. So I'm showing a steep drop in >> pressure with supply and a rise in demand to almost the magic line. Then I >> have to add the horizontal 250 gpm and I'm slightly north of the supply >> curve. Easy enough to fix with a better designed pump but why should I >> have >> to fix it? As for gpm the tank has sufficient capacity to cover duration >> for >> both hydrant and system operating simultaneously so I meet that water >> supply >> quantity demand in spades. Why do I need to include that 250 gpm when I >> have >> more than enough water for simultaneous operation? What if that pump that >> will do the job without adding the hose stream is cheap and forcing the >> addition of the hose stream increases my cost? Why do I need to spend the >> money for a different pump to flatten a curve that meets need? And why do >> I >> need to add it if I have one tank but not if two tanks? This has mostly to >> do with what is on the piece of paper and that horizontal line from 450 >> gpm >> to 700 gpm and how that interacts with the other diagonal line heading >> downhill and to the right. The pump is undersized to cover the pressure at >> the gpm required when this extra and arbitrary 250 gpm is added to the >> curve >> but the 250 gpm is covered by the 1500 gpm and engine psi boost at the >> hydrant, and would be OK if each was supplied by it's own tank (the >> hydrant >> is only on the pump because it and the building and a future building are >> 10 >> feet higher than the base of the tank and the the single pump (which will >> be >> sized to handle the extra code required 250, but the tank is oversized and >> capacious enough to cover both buildings burning and using the hydrant at >> the same time for an hour) is the cost-effective. It just struck me as one >> of those things that could happen (the supply pressure issue). >> > > ______________________________**_________________ > Sprinklerforum mailing list > Sprinklerforum@firesprinkler.**org <[email protected]> > http://fireball.firesprinkler.**org/mailman/listinfo/**sprinklerforum<http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum> > > For Technical Assistance, send an email to: [email protected] > > To Unsubscribe, send an email to:Sprinklerforum-request@** > firesprinkler.org <to%[email protected]> > (Put the word unsubscribe in the subject field) > -- Ron Greenman Instructor Fire Protection Engineering Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: ASEE, SFPE, ASCET, NFPA, AFSA, NFSA, AFAA, NIBS, WSAFM, WFC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [email protected] To Unsubscribe, send an email to:[email protected] (Put the word unsubscribe in the subject field)
