"In order to form a more perfect thirteen" we play like walls are not
there even when they are, and rated no less-- density/area method--
and we play like walls are there when they are not-- as in this and
the recent 'saw-tooth type' ceiling discussions.
TC members have always kept it Conservative though so it's all good.
.
Quoting "MFP Design, LLC" <[email protected]>:
Larry:
I think the original question is asking what is the area of coverage
of this setup. You have two lines that are 10' apart with
sprinklers 13' on center on the lines. Call these lines A and B.
Then in the adjacent bay, you have lines 15' on center with
sprinklers 8' on center. Call these lines C and D.
The question is the sprinklers on branchline B. They are 13' on
center going down the line. The next adjacent line C is 12'-6"
away. So, basically, are the sprinklers on branch line B spaced at
13' x 10' (5' from the beam), or 13' x 12'6" (12'6 is the distance
between the lines). If this dividing point was a full height wall,
then there would be no question. But, the floor area is
unobstructed as the sprinklers may or may not throw under this beam.
What if the beam is 24" deep. With SSU's and being 5' from the
beam with a 12" deflector, I can easily throw under that beam and
get all floor area protected. Of course with the distance of 7'6
from the beam, I can cover all of the floor as well.
I have always used and always been taught to space them in the bay,
end of story. I recall one job that had an AHJ that was asking for
everything you can think of. This particular issue was one of them.
We ended up agreeing to change what would have been the spacing on
Branch line "B" in this example to have the sprinklers 10' on
center. That way, using his 12'6" between sprinklers, being 10' on
center kept things less than 130 sq ft.
So, in this example, the spacing along the branch line would be
Line A = 13' on center for sprinklers
Line B = 10' on center for sprinklers
Line C & D = 8' on center for sprinklers
Again, this goes against how I was taught to space the sprinklers
and how I have always done it. I just see the reasoning behind the
question. Does the answer change if you have a girder instead of a
beam? Why or why not?
Merry Christmas to all and to all a good night!
Travis Mack, SET
MFP Design, LLC
3356 E Vallejo Ct
Gilbert, AZ 85298
480-505-9271
fax: 866-430-6107
email:[email protected]
http://www.mfpdesign.com
https://www.facebook.com/pages/MFP-Design-LLC/92218417692
Send large files to us via: https://www.hightail.com/u/MFPDesign
LinkedIn: https://www.linkedin.com/in/travismack
“The bitterness of poor quality remains long after the sweetness of
low price is forgotten.”
-----Original Message-----
From: Sprinklerforum
[mailto:[email protected]] On Behalf Of
Larry Keeping
Sent: Thursday, December 21, 2017 8:04 PM
To: [email protected]
Subject: RE: S & L Rule
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
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