Unfortunately there is no such data. The30% area penalty came from fire
loss data analysis done by FM of sprinklered losses that showed, on
average, that 30% more sprinklers operated in dry system fires than wet
system fires. The bad news is that the loss data and analysis are more
than 40 years old now, and do not reflect the growth in fire challenge.
I seriously doubt that there would be such a smooth, linear relation
between the water delivery time and the area of operation of sprinklers.
The more intense the fire, the larger the operating area. The extreme
example is ESFR sprinklers which can't tolerate a delay of more than a
few seconds. At the other extreme, with a very slow growing fire, a one
minute delay could make no difference.
The one think to take some comfort from is that there have been few
catastrophic dry system fires, and we all know that a majority of dry
systems depend on accelerators to meet the delivery requirement and that
the likelihood of an accelerator actually working is very low.
This is just another area where there is essentially no hard data behind
a common design practice.
(The one exception is the Quell system. There, the design requirements
were determined by actual testing)
Joe
[EMAIL PROTECTED] wrote:
Joe,
>From a system performance standpoint (not just what's stated in the
standard), can you define "acceptable water delivery time"? Has there
ever been a series of tests in LH or OH scenarios where "time to
inspector's test" is related to "design area increase"?
In other words, if you have a 30 second time can you reduce the design
area to a 15% penalty or whatever? Or, conversely, if you have a 90
second time can you double the design area and have comparable
performance? Has this concept ever been proposed?
If anyone knows these answers you'd be the one.
Bill Brooks
William N. Brooks, P.E.
Brooks Fire Protection Engineering Inc.
372 Wilett Drive
Severna Park, MD 21146
410-544-3620 Phone
410-544-3032 FAX
412-400-6528 Cell
-------- Original Message --------
Subject: Re: Gridded pre-action and dry
From: Joe Hankins <[EMAIL PROTECTED]>
Date: Sat, December 22, 2007 11:03 am
To: [email protected]
They found that they could reduce the trip time to almost zero and
exhaust from the end of the cross mains and still not get an acceptable
water delivery time.
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