Who said they wouldn't obstruct heat flow? Because they are more than 7.5 ft apart it can be considered to be "unobstructed" construction. But of course they are obstructions.
With unobstructed construction the deflector distance has to be 1" to 12" below the ceiling. You can't space the lines as if the beams don't exist. That is why the spacing is across the width of the bays. Since the lines are spaced 1/2 L off either side of them, you have sprinklers on either side of them as per 8.6.5.1.2 (2). Therefore you don't have to worry about the "Beam Rule (Table 8.6.5.1.2, and Figure 8.6.5.1.2(a)). All I'm saying is that you can space to the beams, bay per bay. You can be 5 ft off in the 20 ft bay and 7.5 ft off in the 30 ft bay and under those conditions it doesn't matter whether the sprinklers can spray under the beams or not. Larry -----Original Message----- From: Sprinklerforum [mailto:[email protected]] On Behalf Of [email protected] Sent: December-21-17 8:16 PM To: [email protected] Subject: Re: S & L Rule But Larry, if the beams are not an obstruction to heat flow OR spray pattern, it's like they don't exist, no? Brad. Quoting Larry Keeping <[email protected]>: > You don't need to do anything special with the deflector distance. > As per 8.5.2.1.1 (2), the line spacing is to a wall or obstruction: > > (2) Between branch lines as follows: > (a) Determine perpendicular distance to the sprinkler on the adjacent > branch line (or to a wall or obstruction in the case of the last > branch line) on each side of the branch line on which the subject > sprinkler is positioned > (b) Choose the larger of either twice the distance to the wall or > obstruction or the distance to the next sprinkler > (c) Define dimension as L > > The is no argument that the beams that delineate the bays are > obstructions. Even if the spray can throw under it, that doesn't > change that consideration. > > Larry Keeping > > > -----Original Message----- > From: Sprinklerforum > [mailto:[email protected]] On Behalf Of > [email protected] > Sent: December-21-17 5:53 PM > To: [email protected] > Subject: Re: S & L Rule > > I recently learned that the beam only acts like a wall if you can't > throw under it, so get those deflectors way up there! > (Crow and Thunderbird rocks) > > Merry Christmas Forum, > > Brad. > > Quoting Bob <[email protected]>: > >> The beam is an obstruction that acts like a wall. You’re covering >> floor space, so as long as each sprinkler covers the correct area (30 >> sf), then the spacing that you are describing sounds in compliance >> with NFPA 13 spacing rules. >> >> >> >> Thank you, >> >> >> >> Bob Knight, CET III >> >> 208-318-3057 >> >> >> >> From: Sprinklerforum >> [mailto:[email protected]] >> On Behalf Of James Crawford >> Sent: Thursday, December 21, 2017 3:00 PM >> To: [email protected] >> Subject: S & L Rule >> >> >> >> We have been having a discussion in the office about the S&L rule for >> spacing of sprinkler heads. We received a sprinkler drawing with some >> spacing that we do not agree with, see below, but can find no >> specific direction in NFPA #13 (2013) that says it is wrong. >> >> >> >> Basic situation we have a small building with a 20’ bay and a 30’ bay. >> Ordinary hazard spacing. >> >> >> >> For the 20’ wide bay, we have2 lines spaced at 10’ apart , so we have 5’ >> off the wall then 10’ between the next line and 5’ to the beam line, >> the heads are spaced at 13’ along these lines. >> >> >> >> Then we have a 30’ bay where we have 2 lines spaced 15’ apart, 7’6 >> off the beam then 15’ between the heads then 7’6 to the wall, heads >> are spaced at 8’ >> along the line >> >> >> >> So our discussion is the sprinkler lines along the beam line which >> would be 5’-0” plus 7’-6” for 12’-6” between the line. The sprinkler >> heads in the 20’ >> bay are spaced at 13’-0”, so if we use the S&L rule these heads are >> spaced at 12’-6” x 13’-0” or 162.6 ft². Is this correct? >> >> >> >> And yes I know we could space the 30’ bay with 3 lines at 10’ apart >> and that is what I would do but it is not our design. >> >> >> >> Comments >> >> >> >> Thank you >> >> >> >> >> >> James Crawford >> >> Phaser Fire Protection Ltd. >> >> Phone 604-888-0318 >> >> Fax 604-888-4732 >> >> Cel 604-790-0938 >> >> Email [email protected] >> >> Web www.phaserfire.ca > > > > _______________________________________________ > 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-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
