Sounds like we have an NFPA 13 conundrum. What about adding check valves?
At 05:36 PM 6/29/2007, you wrote:
The problem is the, by tying the ends of the branch lines together,
you now have to get all of the air in the entire system out of the
system before you get uninterrupted water flow. In a dry tree, you
only need to get the air out of the cross-main and one branch line,
leaving the remaining air trapped at the end of the non-flowing
branch lines. I suspect that a system with tie in drains would
sputter and spit intermittently for quite some time. Bottom line,
tie in drains on a dry system turn it into a dry grid (and not just
as a technicality), which is unacceptable.
Joe
Ken Holsopple wrote:
To all,
Now that the water is clearing up on this one, let me muddy up again. I
agree that the drain does not need to be included in the hydraulic
calculations, however what happens to this configuration for a water
delivery calculation. I would think the tie-in would need to be included
because of the (minimal)added volume, but more so because the effect a
tie-in drain may have on the side of the system that is opposite your
calculated sprinklers and how it affects the compression of the air in other
areas of the system. I think this would definitely affect water delivery in
a low pressure system.
I have done water delivery calculations, but I haven't attempted anything
other than side feed trees. In the calculations I have done, I have found it
amazing what some small things can affect a calculation where seconds are
precious. At this point, I don't not believe that the water delivery
software would accept this. And when I have some free time, I'll attempt it.
Does anybody have any thoughts on this one? I don't see anything in NFPA '13
'02 other than the delivery requirements.
Can of worms anyone?
Best Regards,
Ken Holsopple
Design Manager Rowe Sprinkler Systems, Inc.
570-837-7647
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
860-535-2080
www.fpdc.com
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