Craig, Thank you for the reply. I appreciate your frequent contributions to the forum, and I agree with your interpretation of the spacing rules. With respect to the head spacing on different lines, I am not going to second guess the designer. This is a large industrial type project with a significant amount of utilities, piping, cable trays, etc., as well as interior partitions. As he is employed directly by the sprinkler contractor that is installing this system, I am confident that he chose the most economical arrangement to satisfy the many constraints of this installation.
At the sprinkler contractor’s request, I did send a virtually identical question as an informal interpretation through NFPA last Friday. I will share that response when I receive it. Have a great (and profitable) day! Sent from my iPad Christopher H. Born, P.E. Director, Fire Protection Engineering|Principal Clark Nexsen 4525 Main Street, Suite 1400 Virginia Beach, VA 23462 (757) 455-5800 (757) 961-7933 (direct) (757) 644-8581(mobile) > On Mar 12, 2018, at 8:30 AM, Prahl, Craig/GVL <craig.pr...@ch2m.com> wrote: > > When a perpendicular obstruction becomes deep enough that the sprinkler > discharge is cannot throw under it based on the obstruction rules set forth > in NFPA 13, then you treat it the same as if it was a wall and space the > branch lines accordingly. If I have a steel framed building with 20 ft bays > and at the column lines there are 36" deep beams > > It's really very simple. Look at the distance of the deflector below the > deck and the distance above the bottom of the obstruction as well as the > distance off the edge of the obstruction in Chapter 8 of NFPA 13. > > Also, why would your designer add additional sprinklers to a branch line? > Where is the justification or direction for this coming from? > > If you have an obstruction, you just space the branch lines differently to > accomplish a uniform spacing arrangement in the bay or area where the > obstruction occurs. > > > Craig L. Prahl > Fire Protection Group Lead/SME > Direct - 864.920.7540 > Fax - 864.920.7129 > Direct Extension 77540 > CH2M is now Jacobs. > 200 Verdae Blvd. > Greenville, SC 29607 > craig.pr...@ch2m.com > http://www.jacobs.com > > -----Original Message----- > From: Sprinklerforum [mailto:sprinklerforum-boun...@lists.firesprinkler.org] > On Behalf Of Chris Born > Sent: Thursday, March 08, 2018 11:54 PM > To: sprinklerforum@lists.firesprinkler.org > Subject: Protection Area of Coverage for Sprinkler [EXTERNAL] > > 8.5.2.1.1 of the 2016 edition of NFPA 13 covers how to determine the area > covered by a sprinkler. This seems to be pretty straightforward, but I’ve > noticed some strange wording. Consider a building with exposed structure and > some beams that are deep enough to be obstructions, 36” as an one example. > > For spacing between branch lines, the standard says “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) ...” I understand the > reference to last branch line when referring to a wall, but not with respect > to an obstruction. Similar language exists for spacing along the line. > > Is this just poor wording, or is it really the intent not to allow > measurement to an obstruction if not the end line or sprinkler? I have a case > where a deep beam requires an additional line. The designer has spaced heads > closer together on the line that is further from the beam, so calculating > head spacing times twice the distance to the beam results in an area of less > than 100 sq ft (this is extra hazard). However, if the intent is to use the > distance to the next line (and ignore the beam) then the area is over 100 sq > ft. I think the layout meets the intent, but am interested in other opinions. > > Sent from my iPad > > Christopher H. Born, P.E. > Director, Fire Protection Engineering|Principal Clark Nexsen > 4525 Main Street, Suite 1400 > Virginia Beach, VA 23462 > (757) 455-5800 > (757) 961-7933 (direct) > (757) 644-8581(mobile) > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.firesprinkler.org/private.cgi/sprinklerforum-firesprinkler.org/attachments/20180308/c689782f/attachment.html> > _______________________________________________ > Sprinklerforum mailing list > Sprinklerforum@lists.firesprinkler.org > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > _______________________________________________ > Sprinklerforum mailing list > Sprinklerforum@lists.firesprinkler.org > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.firesprinkler.org/private.cgi/sprinklerforum-firesprinkler.org/attachments/20180312/aa0b8d4f/attachment.html> _______________________________________________ Sprinklerforum mailing list Sprinklerforum@lists.firesprinkler.org http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
