What I'm trying to describe is like a restaurant where most of the building may be light hazard seating areas but then you have a kitchen area which is more demanding although it's about a 1/3 in size. I'll sometimes run two calcs (especially if water isn't all that great or if we're trying to keep on budget) - one to size the piping in the light hazard areas then a separate calc for the ordinary group I areas. The pipe sizing in the kitchen could be solid two inch all the way down the line but the seating areas could be smaller piping but both would have the supporting calcs to back it up. There's nothing in NFPA #13 that says you have to apply the ordinary group I calcs to the light hazard seating areas as long as you prove both hazards with supporting calculations. The same applies for what I was describing earlier. But let's say it's all light hazard. The most demanding area may consist of a bunch of tiny offices but it's only on one side of the building and the fact of a bunch of small offices is making this particular area the most demanding so you run your calc on it and determine this whole area needs 2" piping. But then you look at the rest of the project and think, "well, the rest of the project doesn't contain near as many compartments as this area" so you run a supplemental calc on the next most remote area and calcs indicate the rest of the building could be protected utilizing only 1 1/4" piping. You have calcs to prove the worse case and then you have the calcs to show the typical portions of the building need not be as stringent.
--- On Thu, 9/24/09, Ron Greenman <[email protected]> wrote: From: Ron Greenman <[email protected]> Subject: Re: Inadequate Water To: [email protected] Date: Thursday, September 24, 2009, 6:17 PM Ralphy, But we design to the worst cases expected. First we decide what type of fire we'll have-low, moderate, severe. and then chose hazard. From the we chose an area of acceptable loss, choose a density that will under normal conditions based on that first choice contain a fire to no more than that area, and then determine the hardest place(s) within the building for meeting the criterion we just established. These areas are the most demanding and we calculate systems to them. Fires elsewhere will be of the same nature but getting the water there will be less demanding. Or fires may be contained well before we've met maximum and they those will be less demanding no matter where they are. I love folks trying to create magnitudes of precision from variable s of reality. Kinda like the silk purse/sow's ear thing. On Thu, Sep 24, 2009 at 10:46 AM, Ralphy Henderson <[email protected]> wrote: > You're right but that's not the point. The point is maybe the particular > design area is not indicative of the whole building's situation. Maybe the > most demanding area could be looped at the branchlines then a supplemental > calc performed on the next most demanding area which would establish the norm > for the rest of the building. Since most of the time your most demanding area > is going to be the one, not neccessarily farthest from the riser but the one > with the most sprinklers in your design area or the higher occupancy > classification which may not be the case for the typical areas of the > building. A secondary calc could establish that but the primary could be > calc'd for it's specific characteristics. > > > --- On Thu, 9/24/09, Timothy W Goins <[email protected]> wrote: > > > From: Timothy W Goins <[email protected]> > Subject: RE: Inadequate Water > To: [email protected] > Date: Thursday, September 24, 2009, 4:26 PM > > > "maybe looping a few of the branchlines in the most demanding area would > solve things" I always thought that the remote area calcs and design set the > standard/minimum for the entire system. No one knows, but GOD and an > arsonist, where the actual remote area might be or fire may start/be. > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Ralphy > Henderson > Sent: Thursday, September 24, 2009 11:10 AM > To: [email protected] > Subject: RE: Inadequate Water > > > 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) _______________________________________________ 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)
