I'm with Ron.
See NFPA 13-2016
23.4.4.6.2.
Brad.
Quoting Ron Greenman <[email protected]>:
I'll agree the sprinkler knows nothing, but that is irrelevant. We are
working with a mathematical model that will, if all the rules are followed,
give us a reasonable degree of confidence that it will perform to the
design intended, which is, in this case, to keep a fire contained within
the most demanding design area (or any other similar, but less demanding
area) for a specified duration. So for OH I can space my sprinklers along
the ceiling at a MAXIMUM of 15 ft apart, in any direction perpendicular to
the walls, which is a maximum square footage per sprinkler of 225 square
feet, and a MINIMUM of six feet between them for a total square footage of
36. So given Mike's layout, he is well within the parameters of this rule.
Now though we run into another rule which states we cannot EXCEED 130
square feet of floor area per sprinkler in OH so if we run our sprinklers
at 15' apart on the line we can have a MAXIMUM distance between lines a
fraction over 8.5 feet. Since the sawtooth creates a "compartment," so to
speak, because of the obstructive nature of the "wall" the "compartment"
distances are 8x15 per sprinkler so he is well within the spacing rules
regarding "throw," and since his horizontal space coverage area at the
floor is less than 130 sqft per sprinkler he is within the area limitation
for OH. His density will be a minimum of 0.15 gallons/min/sqft and
presuming he has enough pressure to push that quantity of water through the
system to the 13 (before adjustments to the design area, if any) design
sprinklers the system will p[erform as desired. Back to the ignorant
sprinkler. Will it adjust to the 1.0'x7.5'x7.0'x7.5' layout and deliver
exactly 0.15 gpm to each square foot per minute? Of course not. What will
happen though is the system will supply enough water to up to 13 sprinklers
anywhere in the system to meet the design parameter (containment of the
fire to no more than 1500sqft). We can feel confident about this since
sprinkler systems have been doing so for over a hundred years both in pipe
schedule and hydraulically designed configurations. In every system, there
is a prize and that is containment or suppression of a fire. There are
several design methods to obtain the prize and 13 is merely a prescriptive
set of rules to get us there. As long as we follow the rules we'll be
alright. If we want to play mathematician or fluid dynamicist then we'll
cease to be layout technicians and we'll get distracted and our eyes will
stray from the prize.
On Thu, Nov 30, 2017 at 9:33 AM, Nick Maneen <[email protected]> wrote:
You are correct. The sprinkler does not know it needs to throw water in
mainly one direction. It will be 15x14
*Nick Maneen, SET *
*c* 704.791.7789 <(704)%20791-7789>
*From:* Sprinklerforum [mailto:[email protected].
org] *On Behalf Of *Michael Hill
*Sent:* Thursday, November 30, 2017 12:30 PM
*To:* [email protected]
*Subject:* RE: Saw-Tooth Ceilings
Yes, the actual floor area is about 120ft² per sprinkler. Each sprinkler
has to spray 7’-0” towards the next line. The next sprinkler is within
1’-0” of the vertical portion of the ceiling (which I am considering an
obstruction) and will not spray any further in that direction. The water
will hit the obstruction and fall straight down. I know the sprinklers can
cover that 7’-0” spray, but I need to make sure it does so at the correct
density. So for hydraulic purposes is the spacing considered 120ft² or is
it 210ft².
My take is that the sprinkler is 7’-0” form a wall or obstruction, as the
sprinkler has to spray 7’-0” to cover to the low portion of the saw-toothed
ceiling. L=14 and S=15. So hydraulically that sprinkler has to cover
210ft². I would like to say it is covering 120ft² but I need to see where
in NFPA-13 that it says I can do so.
Mike Hill
*From:* Sprinklerforum [mailto:[email protected].
org <[email protected]>] *On Behalf Of *Ron
Greenman
*Sent:* Thursday, November 30, 2017 12:09 PM
*To:* [email protected]
*Subject:* Re: Saw-Tooth Ceilings
If I'm understanding your description and question properly you are
covering about 116-117 sqft of floor area if one considers the 1'8" rise at
the tip of the tooth an obstruction, which I would, and your "throw
distance" along the slope is at 0-360 degrees=7.5'/90 degrees=7.0'/180
degrees=7.5 degrees/270 degrees=1.0'. That puts you within coverage rules
for OH, and throw range rules for SS sprinklers.
On Thu, Nov 30, 2017 at 8:33 AM, Michael Hill <[email protected]> wrote:
I am working on a firing range that is going to have a saw-tooth type
ceiling installed. I have a question about determining maximum protection
area per sprinkler.
The vertical portion is 1’-8” tall with the distance from the high point
to the low point being 8’-0”, measured along the slope. Sprinklers need to
be spaced close to the vertical portion of the ceiling, to protect them
from stray projectiles. The sprinkler will end up being about 7’-0” from
the low point of the ceiling, measured along the slope. The sprinklers are
about 8’-0” apart, but with a 1’-8” vertical portion of the ceiling between
them. Sprinklers are spaced 15’-0” apart along the branchline. See attached
sketch (if it came through).
Would the spacing be 15’ x 8’ or would it be 15’ x 14’?
I feel it should be 15’ x 14’ as any individual sprinkler needs to cover
7’-0” in one direction, measured along the slope. I feel the vertical
portion of the ceiling is an obstruction and can almost been interpreted as
a wall that extends to the floor. I also thought I needed to increase my
design area for sloped ceiling for this situation, but have since been
shown the commentary in the handbook that explains why it is not required
for saw-toothed ceilings. Maybe I am wrong about the spacing as well.
Mike Hill
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Ron Greenman
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253.576.9700 <(253)%20576-9700>
The Universe is monstrously indifferent to the presence of man. -Werner
Herzog, screenwriter, film director, author, actor and opera
director (1942-)
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Ron Greenman
[email protected]
253.576.9700
The Universe is monstrously indifferent to the presence of man. -Werner
Herzog, screenwriter, film director, author, actor and opera
director (1942-)
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