Ralphy, Correct. As with any equation that has variables that have been simplified for ease of use the actual accuracy diminishes. Pipe schedule systems are nothing more than calculated systems that have been reduced to a simplified schedule that is overly conservative. That's why the mostly tend to calc out (of course there's exceptions and we don't necessarily need fifteen emails that challenge the rule) and why we can usually build a more economical system if we calc it--the degree of accuracy in a calced system is just more precise. I can't even get absolute precision in many static mathematical systems, pi would be an example, so a formulae that ignores many insignificant factors like Hazen/Williams does, and is broadly applied over a spectrum of physical conditions, and compensates for the variations conservatively will by nature have a degree of "safety" built-in.
On Thu, Sep 24, 2009 at 10:26 AM, Ralphy Henderson <[email protected]> wrote: > I believe I read that in Mark Brommans' book but I could be wrong. From what > I understand the Hazen-Williams formula is not the most accurate in the world > and actually produces results which are more demanding than the actual > situation. If such is the case, and given a few of the other factors that I > mentioned, I don't see the reason to hem and haw over 5 psi in a LH or OH > situation. > > > --- On Thu, 9/24/09, [email protected] <[email protected]> wrote: > > > From: [email protected] <[email protected]> > Subject: RE: Inadequate Water > To: [email protected] > Date: Thursday, September 24, 2009, 4:16 PM > > > Ralphy, > Please enumerate where the safety margins are in Hazen-Williams in terms of > water supply. In fact, what are all of the safety margins and > conservatives that Hazen-Williams provides? > > Thank You > > Rahe Loftin, P.E. > Region 7 - GSA > Office - 817-978-7299 > Fax - 817-978-8644 > Cell - 817-371-3102 > > > > > > Ralphy Henderson > <ralphbuccan...@y To > ahoo.com> [email protected] > Sent by: cc > sprinklerforum-bo > un...@firesprinkl Subject > er.org RE: Inadequate Water > > > 09/24/2009 11:10 > AM > > > Please respond to > sprinklerfo...@fi > resprinkler.org > > > > > > > Isn't an issue of 5 psi really a non issue? I mean, you generally have an > AHJ mandated safety factor (or should) of 5-10%, a hose allowance that may > or may not be used, plus calculations that are based upon Hazen-Williams > which in itself is not as accurate as other methods and provides an > additional safety margin. > Not only that but there are usually design options as well. Perhaps the > remote area could be re-evaluated - maybe there's that head in the closet > that really doesn't need to be included in the calcs, maybe looping a few > of the branchlines in the most demanding area would solve things, changing > BFP to a more friendly friction loss model, did the hydraulics program use > the modified equivalent lengths based upon NFPA #13 or were these > considerably rounded up by default (I've seen that)? Could changing > sprinklers to larger / smaller orifice help, sliding up and down the design > density curve to meet actual calculated sq. ft'g (if no reductions are > taken) etc.. > Even without consideration of the above it would seem that 5 psi is not > lawsuit material - at least to me. As long as this is not storage or extra > hazard I don't see what the big deal is. > -Ralphy > > > > > > _______________________________________________ > 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) > > > > > _______________________________________________ > 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) > -- Ron Greenman Instructor Fire Protection Engineering Bates Technical College Tacoma, WA Member: SFPE, ASCET, NFPA, AFSA, NFSA AFAA, WSAFM _______________________________________________ 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)
