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Dry Pipe System Subdivision per NFPA 13 2010 and 2013 editions

Dry Pipe System Subdivision per NFPA 13 2010 and 2013 editions

Dry Pipe System Subdivision per NFPA 13 2010 and 2013 editions

(OP)
NFPA 13 2010 revised the 2002 edition to allow subdivision of Dry Pipe Systems (which is relevant for us for the purpose of remaining below 750 gallon capacity to avoid trip test time concerns).

The standard (2010&2013) states:
7.2.3.9 Unless installed in a heated enclosure, check valves shall not be used to subdivide the dry pipe systems.

NFPA 13 2013 edition clarified this new wording with the additional sections:

7.2.3.9.1 When check valves are used to subdivide dry pipe systems in accordance with 7.2.3.9, a hole 1⁄8 in. (3 mm) in diameter shall be drilled in the clapper of each check valve to permit equalization of air pressure among the various parts of the system.

7.2.3.9.2 Where auxiliary drains are not provided for each subdivided section, an approved indicating drain valve supervised in the closed position in accordance with 8.16.1.1.2, connected to a bypass around each check valve, shall be provided as a means for draining the system.

My question is if I have a dry pipe system (no combined preaction or anything else), what is an appropriate layout of check valves to subdivide the system?

For example, can you have two check valves above the dry valve (each with a 1/8 in. diameter hole drilled in the clapper) with no other devices such as control valves?
The section concerning subdividing preaction systems or combined dry/preaction systems has this figure/arrangement for subdivision which is too costly and defeats the purpose of avoiding two dry valves in the first place. I am concerned that this is how you have to do it.

Figure:



The way I'm doing it (which I'm hoping isn't wrong) this picture has a butterfly valve at the bottom, a dry valve on top of that, a tee with a check valve (drilled hole) above it, and on the bull head of the tee leading to an elbow and another check valve (drilled hole) which effectively subdivides the system in two for the purpose of trip time tests. Is it right?

RE: Dry Pipe System Subdivision per NFPA 13 2010 and 2013 editions

sounds like your thinking is correct


Prior to the 2010 edition, 7.2.3.9 conflicted with the requirement in 7.4.4.1 that combined dry pipe and preaction systems be subdivided as well as contradictory to the requirement in 7.9.2.8.4(5) for separate indicating control valves and check valves for ceiling and in-rack preaction systems, as illustrated in Figure 7.9.2.8.4. If subdivision is necessary for those systems, there is no reason that it should not be acceptable for dry pipe systems, which operate in similar fashion.


do you see anything that kicks you back to 7.9.2.8.4(5) ? and the control valve requirement??

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