In the "old days" heads were staggered to help even out the flow as well as
hasten the acttivation.
David Bohannon
Fire Sprinkler Plan Review City of Atlanta
Department of Planning and Community Development
Office of Buildings
55 Trinity Avenue
Suite 3900
Atlanta, GA 30303
e-mail: dbohan...@atlantaga.gov
phone: 404-330-6193
fax: 404-739-4172
----- Original Message -----
From: "Mark Sornsin" <mark.sorn...@ulteig.com>
To: sprinklerforum@firesprinkler.org
Sent: Wednesday, April 25, 2012 4:18:18 PM
Subject: RE: Rounding off {Squaring off?}
I think it ultimately goes to the fact that they needed a simple way to space
sprinklers and square is much easier to work with than round.
As to the safety factor, Bruce pretty much hit it: it works. What is implied is
that whatever the safety factor is it must be enough. The problem is, if you
try to analyze the actual factor of safety you have to first ignore several
other potential influences on that factor. Accuracy of the water supply
information; actual pressure at the sprinkler; choice in design area (which may
be affecting the actual pressure on the sprinklers); effect on calculations of
including hose allowances and/or domestic allowances; effect on calculations of
using assumed (vs actual) friction coefficients for the pipes; etc. When some
people make the point that sprinkler calculations have 'so much' safety factor
built into them they are essentially correct. But why do people make those
assertions? Usually it is to justify lack of conformity to standards; and the
problem with going down that road is that none of these above influences can be
precisely measured in terms of additional safety factor they may or may not be
providing. True, some jurisdictions will waive hose allowances in calculations
under limited circumstances if it means saving the added cost of a pump and/or
tank. Certainly the knowledge of the remaining potential factors of safety is a
reason for doing this (on a limited basis). But you don't want to push it any
farther than disregarding one fairly measurable variable because uncertainty
raises exponentially with each added variable.
So the bottom line in my view is that one could certainly do a mathematical
exercise where they calculate the safety factor of all of the overlap in
sprinkler sprays; but first they would have to make assumptions about those
other influences. By the time they are done doing that, the exercise is nearly
worthless, except as a bit of intrigue for those of us in the business.
BTW - you can go to some manufacturer's web sites and view sprinkler spray
patters. If you look at the Viking M 1/2 in. upright, you'll see that at 7psi,
the spray from about 8 ft. above the floor reaches just over 9 ft. from the
centerline of the sprinkler. In a Light Hazard Occupancy, that overlaps the
7'-6" maximum distance, but does not reach the maximum diagonal distance of
10.6 ft. At 30 psi, you get closer to the 10.6 ft. Obviously, at smaller
spacing, the overlap increases (another variable to consider).
Mark A. Sornsin, PE| Fire Protection Engineer
Ulteig Engineers, Inc.| Fargo, ND
mark.sorn...@ulteig.com
-----Original Message-----
From: sprinklerforum-boun...@firesprinkler.org
[mailto:sprinklerforum-boun...@firesprinkler.org] On Behalf Of Bruce Verhei
Sent: Tuesday, April 24, 2012 12:51 PM
To: sprinklerforum@firesprinkler.org
Subject: Re: Rounding off {Squaring off?}
I've read in the past that this fell in the not well understood effect category
when engineers have desired to model how sprinklers actually work. This seems
to be difficult. They say something that ends with but sprinklers installed
and maintained to standards have a remarkable record of controlling fires in
buildings.
I want to buy one of the square heads. Are the threads square too?
Bruce
Sent from my Motorola ATRIX™ 4G on AT&T
-----Original message-----
From: Thomas Watt <firesprinklerssaveli...@gmail.com>
To: sprinklerforum@firesprinkler.org
Sent: Tue, Apr 24, 2012 13:05:01 GMT+00:00
Subject: Rounding off {Squaring off?}
I had a brain-fart and came up with this question for the forum. Especially the
engineers. Since sprinklers, in general, throw in a circular pattern, and we
calc the sprinklers as squares, there is always overlap so we are by default
miscalculating a percentage of the density. Has anyone ever calculated the
safety factor effect by ignoring the arcs outside the square???
Thomas
A+ fitter/Foreman
No work in Orlando, FL area
Willing to relocate
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