The needed answer depends on what is the underlying or driving question in why you ask.
The value of the definition is that it EXCLUDES the possible pressure created by surges and/or fire department connections. SO when you are defining the required rating of the system components, you have definitive variables to address. Why even look at one head flowing, just say pump churn plus max possible static supply (seasonal considerations included, tank full, etc) . On systems with a steep curve, it hurts to have to size your pump for the sprinkler design at the lowest pressure level of the tank or seasonal supply at system flow but your limiting pressure exposure at churn is with the highest available pressure. Roland Huggins, PE - VP Engineering American Fire Sprinkler Assn. --- Fire Sprinklers Saves Lives Dallas, TX http://www.firesprinkler.org <http://www.firesprinkler.org/> > On Mar 10, 2015, at 11:03 AM, Vince Sabolik <[email protected]> wrote: > > NFPA Definition: > > "3.3.23 System Working Pressure. The maximum anticipated > static (nonflowing) or flowing pressure applied to sprinkler > system components exclusive of surge pressures and exclusive > of pressure from the fire department connection." > > > The pump's gonna start with one head and it will be very close to a > churn pressure - say in excess of 175 psi. So what would apply? > Operating pressure with "X" amount of heads flowing or the one head that > started the fire pump? > > > O _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
