Todd, I wish my boss thought the same way.....:) -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Todd Williams Sent: Tuesday, March 29, 2011 5:38 AM To: [email protected] Subject: Re: Cloud Calculations
Let's think about this for a moment. We have all basically agreed that heat collectors do not work. There we are mostly thinking about the 1' x 1' or 18" x 18" variety. However, I think we could all pretty much agree that if the heat collector was 100' x 100' and the sprinkler was in the middle, then it would probably activate. So that means that the effectiveness of any heat collection device is one of scale and design. We are looking at clouds, as well as ducts and cutting tables over 4 ft wide as not only obstructions, but also as heat collectors. In some situations the sprinklers may activate, sometimes they may not. We don't know. Three things can happen in a fire situation: only sprinklers below the cloud open, only sprinklers at the ceiling open or a combination of the two. The first situation is unlikely and then only if conditions are perfect. This would require a sprinkler under the cloud to activate and cool the jet so insufficient heat makes it to the upper level to activate additional sprinklers. The second scenario would be that if none of the sprinklers below the clouds opened and only those at the ceiling. This means you would effectively have a shielded fire, developing away from sprinkler protection. If you look in NFPA 13, shielded fires are classified under Extra Hazard Group II. The third being a combination of ceiling and cloud sprinklers. This would be the best case (short of no fire at all). Sprinkler below would attack the fire at its origin and the ceiling would prevent it from spreading. However, this would have a greater water demand. Since we don't know which of the three scenarios are going to occur, what would be the best course of action in design? If we calculate using all sprinklers in the RA, then we have scenario 1 covered easily, scenario #2 would give more water at the ceiling to address the shielded fire issue and the design is based on scenario #3 so that is covered. Just my thought process. Todd G. Williams, PE Fire Protection Design/Consulting Stonington, CT 860.535.2080 www.fpdc.com _______________________________________________ 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)
