Am I missing something here? 8.15.2.5.3.4 states: 'Tie-in drains
SHALL be provided for multiple adjacent trapped branch lines.....'.
Shall is just a grammatically correct way of saying y'gotta. If you
have the multiple adjacent trapped branch lines, they have to be
connected with a tie-in drain. Section 14.4.4.5 says not to include
them in hydraulic calculations. To me, that's a pretty open and shut
deal. Does it create a gridded dry system, technically yes, but to
me, this section says that this arrangement is allowed. Keep in mind
that the cross sectional area of 1" pipe is roughly 1/4 of the CSA of
2" and 1/16th of 4". That creates a very different scenario than say
4" and 3" where the ratio is 9/16. It would be interesting to check
trip times of a system with the tie-in drains attached and one where
they are plugged off.
At 01:02 PM 6/28/2007, you wrote:
There is a flaw in your reasoning. IF 14.4.4.5 was a connection from
different pipes to the drain without any interconnection, how could
it impact the hydraulic calculation since the flow would only be out
of the system to the drain?
The tie-in drain is used only 8.15.2.5.2.4 and 8.15.2.5.3.4 (which
provides the basic definition of interconnection branch lines). Then
chap 14 tells use tie-ins are not to be part of the hydraulic
calculation which is conservative since only a gain (small as it
might be) would be seen.
It is intended to minimize their use IF POSSIBLE but the explicit
text in the drain section trumps the general text on forbidding grids
in dry pipe systems.
Roland
On Jun 28, 2007, at 8:59 AM, [EMAIL PROTECTED] wrote:
Easy. 8.15.2.5.3.4 specifically addresses multiple adjacent
trapped branch
pipes and 14.4.4.5 does not. 14.4.4.5 is general and is not
addressing the
connecting of the ends of branch lines. 14.4.4.5 is addressing a
drain
that connects to a pipe in the system and drains to an outlet without
connection to other piping in the system.
Thank You
Rahe Loftin, P.E.
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Todd G. Williams, PE
Fire Protection Design/Consulting
Stonington, Connecticut
860-535-2080
www.fpdc.com
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