Ron,
I should never have used the term "density" in describing the discharge
from an ESFR as it gives the false impression that density is a direct
measure of sprinkler performance, which it most certainly is not. I
should have said that you can't design K14 ESFRs with an operating
pressure less than roughly 25 psi.and expect an effective discharge
pattern. It may be fine if the fire starts directly under a sprinkler,
but not if the fire starts right in the middle between two sprinklers.
You are assuming that there is a direct relationship between discharge
density and area of operation in a fire. For many fires (flammable
liquids, shielded combustibles etc), that is not a valid assumption.
The best example I can give is a test run several years age with 4 ft.
wide solid shelf racks 12 ft.high protected by K11.2 sprinklers
operating at 50 psi.(80 gpm per sprinkler) The fire spread to the ends
of the test array and jumped a 4 ft. aisle. A lot more than 12
sprinklers operated.
The real message here is that mixing suppression and control concepts to
come up with a conclusion that something "should work" is dangerous.
It's easy to "solve" a problem if you start with the answer you want and
then work backwards by selecting the data that supports it. The problem
is that you can change the answer, and "prove" that one, too.
Joe
Fletcher, Ron wrote:
Is the .8 based on 64 sqft, 80sqft, or 100 sqft? Or is it 80 gpm
minimum? Seems like .8 x 1500 (1200 gpm) should be able to control most
OH Grp II hazards even if the discharge patter is a little weak.
Ron
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Joe
Hankins
Sent: Tuesday, December 19, 2006 11:59 AM
To: [email protected]
Subject: Re: ESFR in production areas
You can't calculate and ESFR for a density less than about 0.80 because
they will not develop an effective distribution patern at those low
pressures. That's why Tyco reacted to your suggestion the way they did.
Joe
Fletcher, Ron wrote:
We have run into the problem of ESFR's in production areas many times
but mostly due to the obstruction rules. I haven't had an AHJ try to
apply area/density criteria to ESFR's.
Offer to calc a full RA at "X" density to prove the system exceeds that
prescribed for the hazard. There is no precedence for treating ESFR's
as area/density but if the AHJ wants a full size remote "area" then
they should be willing to allow a "density" calc in lieu of the ESFR
discharge criteria. (In for a penny in for a pound.)
The Tyco guys once asked me if I had any ideas for new products. I
suggested they cross list ESFR's for area/density. They looked at me
like I had two heads so I wouldn't look for any changes from the OEM.
Ron Fletcher
Aero Automatic
Phoenix, AZ
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of John
Powell
Sent: Monday, December 18, 2006 3:25 PM
To: [email protected]
Subject: ESFR in production areas
We have an issue with ESFR in a rack storage area interspersed with
componant assembly. The assembly process does not involve flamable
liquids or hydraulic equipment. There are no shielded hazards and the
storage complies with the ESFR listing. Our AHJ requires that the
limited assembly/process hazard be listed for QR sprinklers, which it
is, and the number of ESFR sprinklers calculated for the usual OH area
of operation discharging at the listed pressure for the storage and
building height involved. Seems excessive to me. Have the forum
members had any similar ruling?
John Powell - New Zealand
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