We use the 4" pumper connections for flow tests all the time. In Phoenix we have to calculate the 4,000 gpm fire flow onto the site and out of the private hydrants and I don't like doing hydraulic calc's out to 4,000 gpm using a graph from a 1,300 gpm flow test. The city water supply tends to compensate for greater demands by opening PRV's. The standard 1.85 curve we use is not accurate beyond the actual flow point (my opinion) from the test so we request flow tests with two or three 4" pumpers running. It's the desert so we have lots of free water?
Had an interesting comment from an FPE with Phoenix the other day about the 25% minimum between the static and residual. The Fire Dept. wasn't going to accept a flow test taken by the city water dept. because it didn't comply with the 25% pressure drop. The gpm from flow test was greater than our system demand. The problem seems to have gone away. Maybe the FPE hit his forehead with the palm of his hand and the light came on. I have never paid any attention to the 25% requirement. When calculating system demand only I always try to get a flow test with a flow that is above the system + hose demand. No surprises then. Ron F -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Travis Mack Sent: Tuesday, May 13, 2014 2:12 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 2508 E Lodgepole Drive Gilbert, AZ 85298 480-505-9271 fax: 866-430-6107 email:[email protected] On 5/13/2014 1:47 PM, Sean Lockyer wrote: > Here is an interesting question: In the event that you do not have an > adequate amount of water flow (in terms of GPM) is it acceptable to flow the > 4-1/2" pumper connection in lieu of the standard 2-1/2" connection on the > side ? I know that in NFPA 291 it is recommended to only blow off the 2-1/2" > outlet but when you blow off the pumper connection there is a formula used to > reduce it. However, even after the formula reduction you still have a far > higher amount of water (once again, in terms of GPM). My question is this, > can you use that GPM in your hydraulic calculations ? I would have to think > that most AHJ's would be hesitant to allow this to be used since you are > artificially inflating the water supply. > > What does everyone else think ? > > Sean Lockyer > Project Designer 4617 Parkbreeze > Court > Cell 386-279-1197 Orlando, > Florida 32808 > [email protected] Phone: > 407-816-9101 > www.AITLifeSafety.com Fax: > 407-816-9104 > > > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > er.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
