If you would like a good answer, run the calcs based on actual installation. You will find some interesting results based on 10 psi. or 10% as is the case. Designers must learn through teaching or experience to recognize tight installations and allow for more room hydraulically. Tight installations, are there other kinds?. Cecil, it would be nice if this would be addressed in class. Knowing you, it probably already is. On Jun 14, 2014 4:59 PM, "Cahill, Christopher" <[email protected]> wrote:
> "in order to establish consistent enforcement." That has to be the > funniest thing I've heard recently. > > This is a highly localized issue with regards to the available water > supply. IMHO the safety should be 0 but we need more guidance on a > procedure to establish the test. Once you get the right test there are > plenty of other safety margins buried in the calcs and number of heads > calc'ed. I know places where 2 am is the lowest expected pressures static > wise but little flow so the residuals are typically higher. But then when > after the tanks are full in the day statics are high but usage is also high > for low residuals. Which curve? What about seasonal changes? We're you > (rhetorical) in Oklahoma City a few years ago when you check in to hotel > they have a big sign saying you may not have water for a shower in the > morning due to the drought? But 10 years in City of St. Paul there was > absolutely NO reason to have a safety. Very stable. > > And before the Standard gets involved be sure we have a problem. Best I > can tell we don't. > > "consistent enforcement." Good one. > > Chris Cahill, PE* > Associate Fire Protection Engineer > Burns & McDonnell > Phone: 952.656.3652 > Fax: 952.229.2923 > [email protected] > www.burnsmcd.com > *Registered in: MN > > > Proud to be #14 on FORTUNE's 2014 List of 100 Best Companies to Work For > > > > > -----Original Message----- > From: Sprinklerforum [mailto: > [email protected]] On Behalf Of Sprinkler > Academy - C Bilbo > Sent: Friday, June 13, 2014 5:15 PM > To: [email protected] > Subject: RE: Calculation Safety Factor > > Ron, > Stay tuned...... the NFPA 13 Committee is dicussing this very item.. It > appears that we would like to set the "buffer" or "safety factor" in order > to establish consistent enforcement. > We meet for the next two weeks to discuss this and much more.... > I'm going to create an Academy blog that will be a streaming feed of how > votes go in the Committee's discussions. Votes in Committee meetings are > only a good indicator because there has to yet be an official ballot made. > The meeting only requires a 50% voice vote to move a change to the ballot. > But the balllot requires an affirmation of two-thirds. > > It should be recognized that the above is my opinion as a member of the > NFPA, and has not been processed as a formal interpretation in accordance > with the NFPA Regulations Governing Committee Projects and should therefore > not be considered, nor relied upon, as the official position of the the > NFPA, nor any of their technical committees. > > Sincerely, > > > Cecil Bilbo > Academy of Fire Sprinkler Technology > Champaign, IL > 217.607.0325 > www.sprinkleracademy.com > > [email protected] > > > > OUR STUDENTS SAVE LIVES!! > > > > > Date: Fri, 13 Jun 2014 13:01:36 -0700 > > Subject: Re: Calculation Safety Factor > > From: [email protected] > > To: [email protected] > > > > The first interpretation but not for mere fluctuations. More that it's > > for mathematically degrading systems due to higher anticipated demand > > (new communities), or deterioration of the entire municipal system due > > to age (older, established communities). And my understanding is it > > originated with IRI and was to be applied to the water supply > > (downgrading the supply by 10%), not the FP systems individually. As > > is often the case, when the fire service gets married to an idea (like > > a single head in a kitchen being a system) it perpetuates itself into > > the lore and the origins, and concurrently, the rationale, are lost to > > the dim times of pre-history-don't you get it? it's turtles all the > > way down. Since municipal raters and underwriters could impose such a > > rule on a municipality, but the fire service couldn't, the fire > > service shifted the burden to calculations of the individual systems. > > Although the math for either method is a wash, how does derating the > > system address the water supply itself? If the purveyor derates > > voluntarily then the further derating of the system is overkill and > > expensive, and if he doesn't the system derating is valueless. I think > > this may be why NFPA never even mentions "safety margins" or > > "factors." I realize I'm pretty much alone in this interpretation, and > > I'm not even 100% sure of the origin of the "rule," but 10% > > degradation of the system hydraulics, particularly with 5 year internal > inspection intervals, just makes no sense to me. > > > > > > On Fri, Jun 13, 2014 at 12:22 PM, Rahe Loftin - 7PMC > > <[email protected]> > > wrote: > > > > > I have always been under the impression that the safety factor > > > indicated in specifications for hydraulic calculations was for water > > > supply fluctuations in sprinkler systems connected to public water > > > supplies. This is also indicated in the commentary in the NFPA 13 > Handbook. > > > > > > However, recently a sprinkler contractor was contending that it was > > > to allow for field piping changes. > > > > > > Any opinions? > > > > > > *Thanks* > > > > > > *Rahe Loftin, PE * > > > _______________________________________________ > > > Sprinklerforum mailing list > > > [email protected] > > > > > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprin > > > kler.org > > > > > > > > > > > -- > > Ron Greenman > > Instructor > > Fire Protection Engineering Technology Bates Technical College > > 1101 So. Yakima Ave. > > Tacoma, WA 98405 > > > > [email protected] > > > > http://www.bates.ctc.edu/fireprotection/ > > > > 253.680.7346 > > 253.576.9700 (cell) > > > > Member: > > ASEE, SFPE, ASCET, NFPA, AFSA, NFSA, AFAA, NIBS, WSAFM, WFC, WFSC > > > > They are happy men whose natures sort with their vocations. -Francis > > Bacon, essayist, philosopher, and statesman (1561-1626) > > > > A problem well stated is a problem half solved. -Charles F. Kettering, > > inventor and engineer (1876-1958) > > _______________________________________________ > > Sprinklerforum mailing list > > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkl > > er.org > > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
