Ha your CB Physics serve you well! The "static" we measure when other flows are going on is really Pn. A true static is Pt. Pt=Pn+Pv so without other flows Pt=Pn+0.
I know during a flow test people are taking showers, flushing toilets, watering lawns, etc, and your analogy to a sprinkler system where we would have to know all the nodes is good. I imagine a flow test though as temporarily considering those nodes negligible (out of necessity), like pin holes in the main and we are pitoting the end of the main. It is the only way we can justify using the flow test results as the basis for the pipe sizing. We rarely know what the details are between the source and the hydrant so we (me anyway) say the flow test must be a measure of the loss, and based on that I can work backward to say "WOW, a 120# drop flowing 265 is absolutely the ugliest I've ever heard of... why?...", and 60,000 feet of 6" at C=140 is one of the "facts" that would fit. DISCLAIMER. I was an English Major when I dropped out of college. Brad http://www.mail-archive.com/sprinklerforum%40lists.firesprinkler.org/msg3908 4.html -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of [email protected] Sent: Sunday, February 22, 2015 1:25 PM To: [email protected] Subject: Re: Hydraulic Calculations with two water sources According to my cowboy physics, if there were no out flows in the municipal system, and you performed the flow test again, there would be a much higher flow rate and higher residual pressure. DISCLAIMER. My physics degree is from the U of HK. Mark at Aero 602 820-7894 Sent from my iPhone > On Feb 22, 2015, at 10:37 AM, "Brad Casterline" <[email protected]> wrote: > > Hello Mark! > > Thanks- it is an interesting problem and I have tried to figure it out up > one side and down the other. I think if everyone turned their water off > while I got a true Static it would be higher. And if they left it off while > I measured 265 GPM @ 8 PSI wouldn't the drop be greater (drop being the sum > of the velocity head and the friction head)? So you are right because under > those conditions I would state as being "fact" a storage tank that is higher > AND farther away than the first one :) (I think). > > I am now dwelling on Paul's original "... storage tank at 610 feet about the > POC...". I thought he must have meant above instead of about, and in Kansas > 610 feet above the POC means "upstream" of the POC because we don't even > have buildings that tall here. But names like Nor Cal and Morgan Hill got me > thinking it might really be above, and if so the new tank would make the > "static" 610x.433= 264 PSI at the POC, which would be an increase. > > thanks again man, > Brad > > -----Original Message----- > From: Sprinklerforum [mailto:[email protected]] > On Behalf Of [email protected] > Sent: Saturday, February 21, 2015 1:17 PM > To: [email protected] > Subject: Re: Hydraulic Calculations with two water sources > > Hi Brad and all, > I think you're missing the fact that the city water main serves many(maybe > thousands) of users between the possibly elevated tank and hydrant #2. The > static pressure you're reading at that hydrant is actually the residual > pressure remaining in the line after many thousand GPM is distributed to > users along the way. Without knowing all those flow points (hydraulic nodes) > it is impossible for you to calculate the information you are presenting as > fact. Aside from that, I agree that a meeting with the water purveyor is a > necessary step in the design. > > Mark at Aero > 602 820-7894 > > Sent from my iPhone > >>> On Feb 21, 2015, at 9:59 AM, "Brad Casterline" <[email protected]> >> wrote: >> >> Paul, >> >> I have been thinking more about this and re-reading the excellent > responses >> and learning. I think it is important to get an accurate sketch before you >> finalize the calculations. I would want to meet with the water department >> and draw the picture the numbers and your current understanding show for >> Hydrant #2: >> If the source for #2 is a storage tank its elevation would be 128/.433= > ~296 >> feet above the hydrant. It would also be about 10 miles away because > flowing >> 265 through 6" UG (minimum if serving hydrants) it would take about 60,000 >> feet of pipe and fittings to burn 120 PSI. This is not impossible but it > is >> strange that after all that the FD is left with 8 psi at 265 GPM to try to >> do something with, when 376 feet over and 50 feet down is hydrant #1 with > 40 >> @ 750! >> >> thanks and good luck, >> Brad >> >> -----Original Message----- >> From: Sprinklerforum > [mailto:[email protected]] >> On Behalf Of Brad Casterline >> Sent: Friday, February 20, 2015 10:02 AM >> To: [email protected] >> Subject: RE: Hydraulic Calculations with two water sources >> >> Thanks Paul. The first thing I noticed yesterday was that the static >> difference between #1 and #2 did not correspond to the elevation > difference. >> And 120 PSI worth of Pf+Pv from the source to the hydrant is 5-6 times > more >> than one would expect if it is serving hydrants. >> I can see 128,108,265. Is there any way something might have been jotted >> down wrong when the information was communicated? >> >> Brad >> >> -----Original Message----- >> From: Sprinklerforum > [mailto:[email protected]] >> On Behalf Of Paul Cetani >> Sent: Friday, February 20, 2015 9:12 AM >> To: [email protected] >> Subject: RE: Hydraulic Calculations with two water sources >> >> Hey Brad, >> This test was conducted by the water company and doesn't really sound > right >> to us either but, because of the water situation in California, they will >> not perform a new test. >> >> Paul B. Cetani >> Exec. Vice President >> >> Nor Cal Fire, Inc. >> 16840 Joleen Way, Bldg A >> Morgan Hill, CA 95037 >> T 408-776-1580 >> F 408-776-1590 >> [email protected] >> www.norcalfire.com >> >> CONFIDENTIALITY NOTICE: This message and any document accompanying it may >> contain confidential information >> belonging to the sender. The information is intended only for the use of >> individual or entity named above. If you are not the intended recipient, > or >> the employee or agent responsible to deliver this message to the intended >> recipient, you are hereby notified that any disclosure, copying or taking > of >> any action in reliance on the contents of this information is strictly >> prohibited. If you have received this transmission in error, please >> immediately notify us by telephone to arrange for return of the documents. >> >> >> -----Original Message----- >> From: Sprinklerforum > [mailto:[email protected]] >> On Behalf Of Brad Casterline >> Sent: Friday, February 20, 2015 6:08 AM >> To: [email protected] >> Subject: RE: Hydraulic Calculations with two water sources >> >> >> Paul, >> >> I am curious about the hydrant #2 flow test: >> >> "The closest hydrant from this water source (hydrant #2) is >> 50 feet higher in elevation than hydrant #1. Hydrant #2 has a static of >> 128psi, residual of 8psi, and a flow of 265gpm." >> >> If you have time will you post any additional details you know about it >> please? >> >> thanks, >> Brad >> >> _______________________________________________ >> 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 >> >> _______________________________________________ >> 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 > _______________________________________________ > 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 _______________________________________________ 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
