I think you have highlighted an issue where most flow testers may have a blind spot. There are plenty of water providers who use combinations of pumps and tanks. If fact I'd say every system with an elevated tank has to use a pump at some point, otherwise how would they fill the tank? Todd - Is your system solely dependent on pumps (i.e., no elevated tanks)?
Most of the time we really don't know how many pumps are pumping and how they are controlled when we open the hydrant and record our results. However, we always get out the 1.85 paper and plot the results as if we were looking at a pure gravity-fed system. This is one reason to always flow at least the sprinkler + hose demand just in case you're looking at a pump assisted water supply vs gravity only. In this case you could have something as simple as a controls issue where the new variable speed pump wasn't set up correctly. If the controls had been set up differently the flow test would have been run, results recorded, and another slow day would have occurred on the AFSA forum. So, in addition to being required to be an architect, an engineer, and a code official, the sprinkler designer has to be a municipal water supply designer as well. Bill Brooks William N. Brooks, P.E. Brooks Fire Protection Engineering Inc. 372 Wilett Drive Severna Park, MD 21146 410-544-3620 Phone 410-544-3032 FAX 412-400-6528 Cell -------- Original Message -------- Subject: Re: variable public water supply From: "Ron Greenman" <[EMAIL PROTECTED]> Date: Thu, November 27, 2008 1:16 pm To: [email protected] Ed, I think you're right about this but I think I'd take a "multiple design area" approach with the same design area. Maybe calc for the one or two heads that only open 98% of the time and then calc that to both the pump running and not (who knows what the demand on that pressure grid may be at any time and how your fire effects that?), and then maybe calc at five heads, then at ten heads, etc. until I've calc'd the entire design area(s). Of course I'm a glutton for punishment as well as turkey. And on this Thanksgiving I'm thankful for, among other things, the time forum members take to unselfishly help each other with their knowledge, opinions, insight and experience. On Wed, Nov 26, 2008 at 8:14 PM, Ed Kramer <[EMAIL PROTECTED]> wrote: > Todd, > > Had a similar situation several years ago. This particular building had > multiple design areas ranging from light to high piled storage. We decided > we had to design to the no-pump supply data. Using your example of a 650 > gpm sprinkler demand, what if only 75% of the design area sprinklers > activated? That's a sprinkler flow of approx 488 gpm. If you design to the > with-pump supply, you may or may not be getting the density you need. > Difficult to predict since the actual delivered density increases with fewer > sprinks activated. > > At best, I think you lose some of the hidden safety factors normally built > into the hydraulics. > > Now eat lots of turkey - THAT will put you to sleep! > > Ed Kramer > Littleton, CO > >> >> I did a flow test yesterday where the municipality had recently >> installed a new variable speed pump at a pumping station. The static >> pressure was 67 psi. We flowed the hydrant and the pressure dropped >> to about 45 psi (flow of about 500 gpm). Then the pump kicked in and >> boosted the pressure back up to 65 psi at a flow of about 750 gpm. >> The system I am designing is a 13R, so which curve to use is obvious. >> However, if the sprinkler system design required 650 gpm, should I >> use the curve without the pump or include the new pump as the water >> supply for the design? Prudence may dictate that you use the supply >> without the pump, but what if now a pump would be required to meet >> that demand? I know this is rhetorical, but I'm losing sleep...... >> >> Todd G. Williams, PE >> Fire Protection Design/Consulting >> Stonington, Connecticut >> www.fpdc.com >> 860.535.2080 > > _______________________________________________ > Sprinklerforum mailing list > http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum > For Technical Assistance, send an email to: [EMAIL PROTECTED] > > To Unsubscribe, send an email to:[EMAIL PROTECTED] > (Put the word unsubscribe in the subject field) > -- Ron Greenman at home.... _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [EMAIL PROTECTED] To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field) _______________________________________________ Sprinklerforum mailing list http://lists.firesprinkler.org/mailman/listinfo/sprinklerforum For Technical Assistance, send an email to: [EMAIL PROTECTED] To Unsubscribe, send an email to:[EMAIL PROTECTED] (Put the word unsubscribe in the subject field)
