JP -
I think there are a couple of things to consider, with respect to
control mode density area sprinklers.
First, your density for ordinary temperature sprinklers for a class III
solid pile storage to 20' would be 0.285 gpm/sqft, from table 14.2.4.1
(2010 edition), and the maximum spacing would be 100 square feet each,
per Table 8.6.2.2.1(d), and you would need to flow at least 20
sprinklers to attain the 2,000 sqft minimum remote area.
You can reduce the density to 0.215 gpm/sqft by using high temperature
sprinklers, as noted in table 14.2.4.2. Doing so will also allow you to
increase the spacing of your sprinklers to 130 square feet each, based
again on Table 8.6.2.2.1(d). That would require at least 16 sprinklers
to attain the 2,000 sqft minimum remote area.
The k-factor of the sprinkler can be as low as 8.0, for either CMDA
temperature rating, as noted in section 12.6.2, as the density is
greater than 0.20 gpm/sqft but not more than 0.34 gpm/sqft.
I don't know the rationale behind the differences in the flows
required. Consider:
CMDA = 2,000 sqft x 0.215 gpm/sqft = 430 gpm + 500 hose = 930 gpm
CMSA = 15 AS @25 psi = 840 gpm + 500 hose = 1,340 gpm
ESFR = 12 AS @ 50 psi (14.0K) = 1,188 gpm + 250 hose = 1,438 gpm
It appears that not all sprinklers are the best solution for all situations.
PARSLEY CONSULTING
Ken Wagoner, SET
760.745.6181 voice
760.745.0537 fax
[email protected] <mailto:[email protected]>e-mail
www.ParsleyConsulting.com <http://www.ParsleyConsulting.com>website
On 12/20/2010 12:43 PM, J.P. Merlino/ Ing.L.Lagomarsino y Asoc. wrote:
We have doubts regarding criteria for protection of the following:
Class III, solid pile
Storage height: up to 20 ft
Máximum building height 30 ft
NFPA 13 2010 Edition
As we understand, the code gives two options which are:
1) Per 14.2.4, Control Mode Density Area:Figure 14.2.4.2 With ordinary
temperature, K=11,2 sprinkler we need 0,215 gpm/sq ft over 2000 sq ft. Flow
rate equals 430 gpm
2) If we go to 14.3, Control Mode Specific Application, Table 14.3.1, for same
conditions, we are required to have 15 sprinklers with K= 11,2 operating with
a minimum discharge pressure of 25 psi. Flow rate equals 840 gpm and density is
0,43 gpm/sq.ft.
Are both cases valid for the hazard we are protecting?
Why such a large difference in terms of flow and density?
Best regards and thanks in advance
J.P. Merlino
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