Chris,
There are almost 2 questions here; the first being about this case
and the second about what to do in general. In this situation, since
you have a 15 psi cushion, I would think that high velocities on the
existing mains in this situation would be tolerable. Personally, I
like to keep velocities below 30 fps. You didn't say if this was a
wet or dry system. I would be very skeptical about a dry system
because the high velocities cold potentially break off any existing
scale build up and create a problem. Just my opinion.
Todd
At 10:46 AM 6/2/2008, you wrote:
A question for where there is healthy pressures. Around
here 60 is considered high. I know places with 28 static.
Got a OHII system that needs to be changed to EXII.
That's not negotiable. It's a 40 yo pipe schedule
system. That appears to be in good shape. The BL need to
be replaced for 100 sq.ft. but the main even the last 12'
of 2.5", 25' of 3" and 36' of 3.5" can fly without being
replaced. The openings are where I need them. There is a
FP with about 140 psi at the 900gpm demand. The "problem"
is the velocities in one segment of pipe are just about 40
(last piece of 3") and about 30 in the 3.5". I quote
problem because I know 13 has no limit, this is not FM.
There is still better than 15 psi safety.
So the question is where you have pressure do you
typically burn it up with small pipe size at the cost of
velocities getting high or do you leave a lot of safety?
Again not FM and OK per 13.
Any thoughts on why this is a bad idea? It's easy to say
just pull the offending pipe. In reality though you all
know the competitive market and spending owners money.
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
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
www.fpdc.com
860.535.2080
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