I see four possible calculation approaches for the sprinkler demand part of tank sizing:
1. Minimum Density x Tabular Design Area x Time 2. Minimum Density x Actual Design Area (developed using the 1.2 rule) x Time 3. Hydraulically Calculated Demand (Demand Calc) x Time 4. Hydraulically Calculated Demand (Supply Calc) x Time I intend to submit a Comment to clarify this. #1 is the easiest for everyone, the others require the sprinkler system to be fully designed before the tank size can be confirmed. It's also evident that all of the methods other than #4 will mean draining the tank in less than the required time duration. Then of course is how to decide whether to use 60 minutes or 90 minutes or something in between for OH. Bill Brooks William N. Brooks, P.E. Brooks Fire Protection Engineering Inc. 372 Wilett Drive Severna Park, MD 21146-1904 410-544-3620 410-544-3032 FAX 412-400-6528 Cell -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mark Sornsin Sent: Tuesday, August 09, 2011 7:32 PM To: [email protected] Subject: RE: Water storage/NFPA 13 Proposal I concur with Craig. It seems the proposal was written to clarify for AHJs that one needs NOT run a separate calculation for sprinklers closest to the source simply to identify maximum flows (and therefore maximum supply requirements). The remote area calculation(s) is 'good enough'. I do not think the proposal is suggesting you can calc a tank based merely on 'density x area x duration = volume'. The procedures "in Chapters 11 through 22 for the required duration as specified in Chapter 11, Chapter 12 and through Chapter 21" do not allow you to omit overages within the design area. Mark A. Sornsin, PE| Fire Protection Engineer Ulteig Engineers, Inc.| Fargo, ND [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, August 09, 2011 2:26 PM To: [email protected] Subject: RE: Water storage But we all know that a .15 gpm/sf over 1500 gpm doesn't calc out to exactly 225 gpm of flow and we know that most fires are controlled by 3 or less sprinklers. So if someone wants to cut it that close, go for it. Related to the question of whether to include hose stream or not, what's interesting is that in other areas of 13, it is clearly spelled out that the demand is to include both hose and sprinklers. But in the NFSA response it's talking about not considering the excess flow that is typical of sprinklers closer to the riser which are OUTSIDE of the remote area. It is NOT saying anything about factoring the imbalance or overage for the remote area sprinklers. Craig L. Prahl, CET Fire Protection CH2MHILL Lockwood Greene 1500 International Drive Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 CH2MHILL Extension 74102 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bill Brooks Sent: Tuesday, August 09, 2011 2:41 PM To: [email protected] Subject: RE: Water storage Well, I guess my point would be that you don't have to figure any hydraulic imbalance in your sprinkler water quantity. Just density x area x time. Perhaps Ken's approved proposal could be clarified to confirm. Bill Brooks William N. Brooks, P.E. Brooks Fire Protection Engineering Inc. 372 Wilett Drive Severna Park, MD 21146-1904 410-544-3620 410-544-3032 FAX 412-400-6528 Cell -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, August 09, 2011 2:10 PM To: [email protected] Subject: RE: Water storage OK? Craig L. Prahl, CET Fire Protection CH2MHILL Lockwood Greene 1500 International Drive Spartanburg, SC 29304-0491 Direct - 864.599.4102 Fax - 864.599.8439 CH2MHILL Extension 74102 [email protected] -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bill Brooks Sent: Tuesday, August 09, 2011 2:02 PM To: [email protected] Subject: RE: Water storage 13-494 Log #356 AUT-SSD Final Action: Accept (23.1.2) ________________________________________________________________ Submitter: Kenneth E. Isman, National Fire Sprinkler Association, Inc. Recommendation: Revise text to read as follows: 23.1.2 Capacity. Water supplies shall be capable of providing the required flow and pressure for the remote design area determined using the procedures in Chapters 11 through 22 for the required duration as specified in Chapter 11, Chapter 12 and through Chapter 21. Substantiation: The water supply only needs to provide the duration for the remote area, not the closer sprinklers in the system that will discharge more water. Also, all of the discharge chapters need to be specified, not just the basic storage Chapter 12. Committee Meeting Action: Accept Number Eligible to Vote: 25 Ballot Results: Affirmative: 22 Ballot Not Returned: 3 Brown, T., Hogan, A., McNamara, T. Bill Brooks William N. Brooks, P.E. Brooks Fire Protection Engineering Inc. 372 Wilett Drive Severna Park, MD 21146-1904 410-544-3620 410-544-3032 FAX 412-400-6528 Cell _______________________________________________ Sprinklerforum mailing list [email protected] http://fireball.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 [email protected] http://fireball.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)
