There has been very, very little testing with sloped roofs. The problem
with your idea is that simply flowing water from a sprinkler and seeing
if it hits an adjacent one doesn't answer the skipping question. It has
to be done under actual fire conditions. It is the combination of the
fire plume and discharge (and the resulting cooling at adjacent
sprinklers) that determines if skipping will occur. (the 6 ft
distance has not been determined to work. it was chosen years ago more
or less arbitrarily. In fact, in actual fire tests, severe skipping has
occurred many times with spacing greater than 6 ft, and baffles were of
little help in those situations.)
The dilemma with this application is not skipping due to discharge from
adjacent sprinklers, but getting sprinklers to operate . Any approach
that does not include a line of sprinklers at the roof peak is very
unlikely to be effective.
Sometimes you have to just accept that NFPA 13 doesn't address all
situations you're going to see in the field and you have to kick it back
to the architect/engineer to decide what they want.
Joe
Todd Williams - FPDC wrote:
I had another thought. How much testing has been done on pitched
roofs? There has to be a point where sprinklers impact each other when
the deflectors are not parallel and it is probably a function of angle
and distance. When the deflectors area parallel, the 6 ft distance has
been determined as an acceptable minimum. As the angle between
deflectors increases and the spray starts to point towards adjacent
heads, would the acceptable distance likewise increase? You have spray
that is pointing at adjacent sprinklers and at some angle,
interference is going to occur. This would occur with both
arrangements in 8.6.4.1.3.1. Any thoughts?
At 10:09 PM 5/23/2008, you wrote:
Todd,
Nothing, to my knowledge, is approved for such a steep slope. I
suggested the attic sprinklers in response to the suggestion for
sidewall sprinklers at the peak. My only intent was to suggest that,
if you're going to go beyond the defined limits of a type of
sprinkler, you should at least start with a type that at least is
intended to work in a similar application. I can't say that the attic
sprinklers will work, but if they won't, sidewall sprinklers at the
peak certainly won't work either.
Joe
Todd Williams - FPDC wrote:
Joe, Attic sprinklers aren't approved for slopes greater then 12:12
and I have about 28:12. Also, I didn't think you could use attic
sprinklers in occupied spaces.
This is an occupied space (church sanctuary) not a concealed one.
Also, this is a historic building (c. 1859) and is very
architecturally sensitive. The pipe is exposed and soffits and
baffles are not an option.
At 02:27 PM 5/23/2008, you wrote:
Could you use Attic sprinklers at the peak? They accomplish the
same intent as sidewalls at the peak, and have actually been tested
in that configuration.
Joe
Todd Williams - FPDC wrote:
I am working on a historic church sanctuary with a pitch of
approximately 28/12. The arrangement calls for branch lines to be
symmetrical on each side, similar to NFPA 13 (2002) figure
8.6.4.1.3.1(b). I can meet the requirements for the steeply
pitched roof section 8.6.4.1.3.3 and my "S" distance over the peak
is good, but my straight line distance between sprinklers would be
less than 6 ft and the deflectors would be effectively pointing
the discharge towards the sprinkler on the opposite side. I think
I have a problem here, but I am not sure how to address it. Any
thoughts?
Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
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Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
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