Christopher,

I can respect the choices made by the designer.  I'm sure whomever will be 
reviewing the final sprinkler layout will verify compliance with the code and 
related engineering documents.  


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: Monday, March 12, 2018 10:03 AM
To: sprinklerforum@lists.firesprinkler.org
Subject: Re: Protection Area of Coverage for Sprinkler [EXTERNAL]

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)
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