It isn't always engineer ignorance driving the 20 fps. Air Force ETL 02-15 requires it for one.
Reed A. Roisum, C.E.T. | Karges-Faulconbridge, Inc. | Fire Protection Designer | Fargo, ND | direct: 701.552.9903 | mobile: 701.388.1352 | http://www.kfiengineers.com -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of Lamar Vaughn Sent: Tuesday, September 16, 2014 12:04 PM To: Sprinkler Forum Subject: Re: Water Velocity It would really be good if this thread could be shared with the engineering community at large. I STILL get specifications that require a maximum velocity of 20 fps. Very costly, especially when you have a good water supply. Lamar Vaughn, SET On Tue, Sep 16, 2014 at 12:03 PM, Roland Huggins <[email protected] > wrote: > actually the difference between the results for D-W and H-W does not > vary consistently (alas there is not a linear relationship). To > require using D-W at very high velocities is unnecessarily > conservative. At these velocities the pressure loss is so high that > it is self regulating so typically occurs only is limited sections of > the system. With all the averaging etc that our process entails, why > get anal on ONE piece of the puzzle? Having said that, one could > argue that one should account for the velocity pressure in the > discharge calc at high velocities BUT that is needed only when you > really have such velocities (like in a water spray > deluge) verses seeing an assigned value from our process. > > > Roland Huggins, PE - VP Engineering > American Fire Sprinkler Assn. --- Fire Sprinklers Saves Lives > Dallas, TX > http://www.firesprinkler.org > > > > > > On Sep 15, 2014, at 1:56 PM, Damien Shannon <[email protected]> wrote: > > > So purely along the lines of Andy Rooney's 'have you ever wondered why' > :) > > ... FM Datasheet 2-0, while not limiting the allowable velocity, > > does require that when velocity exceed 30ft/sec, that the > > calculation be performed via the Darcy-Weisbach Method rather than the > > Hazen-Williams. > > Entertainment value only, but would seem that the variance between > results > > in Hazen-Williams versus Darcy-Weisbach become more apparent with > > higher velocities. > > The 30ft/sec limitation (for application of Hazen-Williams > > calculations) > in > > FM 2-0 is strangely close to the 10m/sec (32.8ft/sec) limitation in > > EN > > 12845 Rules for Automatic Sprinkler Installations (previously BS 5306). > > > > > > _______________________________________________ > 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 ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com ______________________________________________________________________ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com ______________________________________________________________________ _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
