This is not an issue that is intended to be caught by the hydraulic calculations for the system demand. It is purely and simply a deficiency in the pump design (as already indicated by Matt). The original design was fine but when someone changed the water supply, THEY were responsible for ensuring the pump curve was still acceptable.
This is also a problem for new systems when water supply modifiers are applied. You have to size the pump for both the sprinkler demand based on the lowest available supply pressure AND the churn limits based on the highest supply pressure. Roland Roland Huggins, PE - Senior VP Engineering American Fire Sprinkler Assn. Dallas, TX http://www.firesprinkler.org <http://www.firesprinkler.org/> Fire Sprinklers Saves Lives > On Jun 27, 2018, at 8:21 AM, Prahl, Craig/GVL <[email protected]> wrote: > > I have a system that was originally designed with a fire pump taking suction > from an elevated municipal water tank. At some point in time the system > source was changed from the tank to a municipal water supply. This change > has resulted in the system pressures being well over 200-250 psi. So far > nothing has blown out, yet but numerous buildings and underground were built > based on standard pressure rated components. > > The thought for the day is this, when you run a calculation, the output will > show the minimum required pressure at the hydraulically most remote sprinkler > that is required to provide the design flow rate. The calculations also show > the deviation between Required and Available system pressures. So, when the > fire pump kicks on, what the system ACTUALLY sees is the rated pressure of > the pump being introduced into the system, not the minimum required pressure > that is shown in the calculations, Agreed? > > If it is stated that in the calculations that the pressure at the sprinklers > on an upper floor will be less than 175 psi but those on the lower floor will > be greater is it safe to assume based on the ACTUAL pressures coming out of > the pump that the entire system will likely see pressures exceeding 175 psi? > > Looking for some thoughts. > > Craig Prahl | Jacobs | Group Lead – Fire Protection | 864.676.5252 | > [email protected] <mailto:[email protected]> | www.jacobs.com > <http://www.jacobs.com/> > > ________________________________________________________________________________________ > > NOTICE - This communication may contain confidential and privileged > information that is for the sole use of the intended recipient. Any viewing, > copying or distribution of, or reliance on this message by unintended > recipients is strictly prohibited. If you have received this message in > error, please notify us immediately by replying to the message and deleting > it from your computer. > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > <mailto:[email protected]> > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > <http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org>
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