Well slow down there partner. Isn't the code as it stands today about right
on for what we know? Travis points out a big surprise, to me anyway. What,
he had a 100 psi difference in the demands pressure. That ain't fly... in
these part. Even if DW is academically more pure what does it matter if HW
is 90 or 110 psi differences. That is still significant. And we know HW is
based on a certain density of liquid and temperature. -30 and anti-freeze
ain't it. DW is a fairly easy tool today. Sure in 1950 perhaps it was a
bit more cumbersome thus the development of HW and the '60 where it entered
the code.
The 40 gallons was the annex section on a should keep them below for
maintenance reasons. Who cares where it comes from really it's a made up
code number at this point. Like 52,000 sq.ft. or 12" down. Nothing magical
just a made up limit based on judgment. And we know judgment is loosely
defined in our field.
Seems to me until there is testing that actually shows what is happening at
-30 and how fast the anti-freeze clears given testing volumes in the path of
travel we should leave it as is. If you want to go big (over the arbitrary
40 gallons) here's the penalty. It's just like the 500 and 750 gallon
limits to dry system. None of us are old enough to recall if these are
tested number but I bet they are nice round places to cut some things off
based on judgment.
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 Roland
Huggins
Sent: Friday, September 19, 2008 2:09 PM
To: [email protected]
Subject: Re: viscosities
I have also challenged using 40 gal as the trigger point. The
substantiation said that value was piked because it was where special
calculation were required (remember this was for changing the 07 where
there were NO other calculations thus that was BS). The old 40 gal
was a trigger for ECONOMICAL considerations between AF and dry pipe
which was no longer valid so deleted. We need to see at what point it
takes too long before the AF is discharged and we are getting just
water out in making the decision on what size requires the DW. 40 gal
is just too bloody small.
We shall see. Any one smell tar in the air?
Roland
On Sep 19, 2008, at 11:43 AM, Travis Mack, SET wrote:
>
> I think that I will just use this diagram in the future until there
> is more
> clarification on the issue from NFPA 13 officials. This will really
> impact
> those of you in the northern part of the country with respect to AF
> systems40 gallons. The viscosities get way out of hand real quick at
> those lower
> temps.
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