Agree w/ Travis. Couple comments as a 20 yr. firefighter. Assuming a
modern fire department with ability to conduct interior operation (offensive
attack) and master stream (both defensive or offensive) ability to conduct
roof operations.
I'm going to grossly generalize here: If the fire isn't controlled by the
sprinklers by the time the FD is ready to conduct offensive operations at
the fire it's probably a total loss - save the foundation fire. This time
starts when the fire starts not when the FD learns about it. Fire starts at
time 0, FD learns about it 5-10 minutes later, response of 5 minutes (maybe
30-60 minutes in rural areas) 5-20 minutes on scene to actually get the
nozzle to the fire. So ball park 15 minute on the quick side 35 minutes on
the long side. If it's still raging and growing 15 minutes into the fire
the FD really can't be expecting to be conducting offensive attacks with a
quick extinguishment (1 or 2 lines). The master streams and many lines are
going up and it's surround and drown. The 900 gpm for an EHII system is
nothing compared to what the FD will need to bring the situation under
control at this point. I've been to many a fire where the outcome was set
as soon as the call comes in. Some of them were set with a positive outcome
(no matter how bad we did it was a 1 line fire not much damage). Others were
all we did was burn it down slower by even trying.
With this I have always thought the time requirement of 13 were a bit long.
Granted I generalized but do the minor variations and few exceptions warrant
the cost of the times prescribed? I'm sure some say yes and some say no
thus they are what they are and not less or more. You propose 1, I propose
3 the code is 2, got to love it.
Now on the water supply for hydrants in the fire code. Not much different.
The time it takes to effectively set up those high flows in a way makes them
pointless. Even in metropolitan areas it might take an hour to get 6000 gpm
flowing. We've had discussions on this forum where there are places that
there is no way to get even a couple thousand.
Would you have accomplished the same if you just let it burn? Or do we often
(sometimes?) put on a show for the public to justify the expense of the FD?
My only real point is Fire Protection Engineering often forgets the FD
component and reality and adds many costs to things that can't really happen
or serve little purpose. Other times we should do more. So if you are
really "E"ngineering a project some variation could be warranted with
appropriate consideration and safety factors.
I know SFPE started a project a few times to explore these issues related to
local FD capabilities. I seem to recall it stalled. Perhaps SFPE can be of
assistance.
Chris Cahill, P.E.
Fire Protection Engineer
Sentry Fire Protection, Inc.
763-658-4483
763-658-4921 fax
Email: [EMAIL PROTECTED]
Mail: P.O. Box 69
Waverly, MN 55390
Location: 4439 Hwy 12 SW
Waverly, MN 55390
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Travis Mack
Sent: Tuesday, September 25, 2007 11:43 AM
To: [email protected]
Subject: RE: How much Water Supply Duration is Important?
In today's litigous society, I would not think of intentionally doing less
than the minimums of the prescriptives codes / standards.
T
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Reza Esmaeili
Sent: Tuesday, September 25, 2007 7:52 AM
To: [email protected]
Subject: How much Water Supply Duration is Important?
Hi,
I know it is very important to take care of water supply duration, but how
much important?
Imagine fire brigade is very close to the factory and will come to
extinguish fire in less than 5 minutes.
If for an extra hazard occupancy which I need at least 90 minutes of water
supply for my wet pipe sprinkler system demand, I reduce it to 45 minutes,
then what will happen?
If I don't care about my required pressure and flow, then the entire
system will fail, but if I reduce water supply duration, then system will
work properly but only for 45 minutes, so if the fire brigade can come in 5
minutes, there wouldn't be a serious problem, Imagine that no one is going
to approve the system (No insurance, ...). I just want to analyze fire
behaviour in this case, it is not a real project.
Thanks,
Reza
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