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).
On Thu, Jun 30, 2011 at 8:15 AM, Roland Huggins <[email protected]>wrote: > Lets start over again since I think the birds have already grabbed the > bread crumbs. > > You have a supply tank for both sprinklers and hydrants. After the pump, > the hydrant and sprinkler paths diverge. Do you need to add the hose demand > to the sprinkler calc - right? What difference would this be from a > street main supplying both? The two tank comparison is the same as two > separate municipal supplies feeding each. I must be missing something since > I see no potential confusion so take another stab at 'splainin'. > > Roland > > > > On Jun 29, 2011, at 12:59 PM, Ron Greenman wrote: > > Right and that is accounted for. I can flow both hydrant and sprinks >> simultaneously for the total duration of each. I may or may not need a >> pumper at the hydrant. This is actually more of a pressure question and is >> just theoretical. If the hose stream portion of the sprinkler demand >> crosses >> the the supply curve from the pump so I don't have the required flow at >> with >> the hose stream but there is more on-site water than I need to flow both >> (and that is not subject to demand fluctuations from other users) I can >> adjust my pump curve. The question though is why should I need to add that >> demand on the sprinkler calc where the supply to the sprinks and the >> supply >> to the hydrant diverge? This is akin to doing a rack calc and an overhead >> calc and then adding an arbitrary extra amount of gpm at the common point >> of >> divergence from the main after you've balanced the two. There's no problem >> to overcome since in the actual case the hose demand can be added without >> causing the problem but it did bring up the question of why does it need >> inclusion in the first place under these conditions. The obvious parent >> answer is because I (the code) say. All the exceptions are for process >> water >> and when there are only sprinklers on the tank. If I had a small elevated >> tank for the sprinks only and another for the hydrant only I wouldn't have >> to include hose stream but when I combine the both in the same tank I do. >> Doesn't make sense to me. >> > > ______________________________**_________________ > 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)
