All very good info. I'd like to add 1 comment: If you're going to flow a larger port, be sure you've got enough water behind it to get a FULL stream.
Years ago, I was advised to pitot the pumper connection instead of the 2 1/2". The pitot pressure dropped to 0 (zero!) when placed in the dead center. The supplying water mains simply couldn't deliver enough water to provide a full stream - it was hollow. We recorded the highest reading we could get nearest the center of the opening. We then flow-tested a 2 1/2" port. When graphed, the two sets of data were a Venus/Mars thing. So we tossed the pumper data and used the data from the 2-1/2" port. Ed Kramer Lawrence, KS -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Mark A. Sornsin, P.E. Sent: Wednesday, May 14, 2014 8:34 AM To: [email protected] Subject: RE: Can a hydrant flow from the pumper connection be used for the hydraulic calculations ? Steve - you seem to be off on a tangent and did not understand the question. Its o.k. - that happens at your age. I agree with Travis. I have done several water flow tests using the 4-1/2" port. Apply the proper coefficients and life is good. Of course, flowing that port can have logistical problems due to the large amount of water and/or damage cause by the discharge - so be careful, plan accordingly, or find an alternative approach if necessary. But he raises another peeve of mine. Further to Ron's comments, why do we have to reduce residual pressure to the point of being at least 25% lower than the static? If my sprinkler design anticipates 700 gpm for sprinklers and hose combines, and I run a flow test that produces 1,000 gpm with only a 1 psi drop in pressure, why would I attempt to open more ports or hydrants? In this example we have a flat curve. We're going to need to flow a huge amount of water relative to my design demand to achieve the prescribed 25% drop. To what benefit would we do such a thing? The only reason I can imagine is "because our contract/AHJ says so" - which a crappy reason, but may be legit, sadly. My personal belief is that 291 requires a certain drop in pressure because they want better accuracy for when they extrapolate to a residual pressure of 20 psi. I.e., the flow test is for fire departments to evaluate available firefighting water for their purposes - not necessarily for sprinkler design purposes. Will this method give more accurate result for sprinkler design as well? Yes - but too often it is a level of accuracy not needed (as in my example above) and is not worth the effort expended. Mark A. Sornsin, P.E. | Karges-Faulconbridge, Inc. | Fire Protection Engineer | Fargo, ND | direct: 701.552.9905 | mobile: 701.371.5759 | http://www.kfiengineers.com -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Travis Mack Sent: Tuesday, May 13, 2014 4:12 PM To: [email protected] Subject: Re: Can a hydrant flow from the pumper connection be used for the hydraulic calculations ? Are you asking if you can do a flow test from the pumper connection? If so, then sure you can. You just need to modify the coefficient based on your pitot. How are you inflating the gpm? If you measure 1200 gpm from the 2½" and you measure 2000 gpm from the 4.5", how is that inflating flow? You should typically have a lower residual pressure when flowing the pumper connection than the 2½" connection. If you are looking to 291 for direction, are you getting the required 25% drop in static and residual from your 2½" flow? If not, what do you do? You are required to open up additional hydrants to get the flow. So, to get additional flow, you can also flow from the pumper connection. Maybe I am misunderstanding your question. Travis Mack, SET MFP Design, LLC _______________________________________________ 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
