Is it Nfpa 13 code for dry systems that the couplings have a flush type gasket?
In the 2010 edition it states the coupling and gasket shall be listed but I can not find anything stating the type of gasket to be used.
You are back a few editions.
Can you give the section you are looking at.
My answer would be the fitting, to include the gasket, is tested as one assembly. So if the coupling itself is listed for fire protection use, that would also include the gasket.
18.104.22.168 in the 2010
I'm looking for the reference in the 2019 edition now.
2019 edition it is 22.214.171.124.
I don't like to see standard gaskets used on dry pipe systems as it traps water in the gasket allowing corrosion to prematurely rot out the pipe ends. But I can't seam to find any where stating that the gap seal type are required.
The "gap" is part of the design of the coupling and gasket that creates a seal. If the gap wasn't there the gasket would not seal properly. There are gaskets such as those on the Victaulic 005 that have the ridge inside but these aren't meant to seal the ends of the pipe together, just provide installation assistance. That being said, grooved end fittings are certainly a weak point on dry systems.
Same wording has not changed in nine years.
Like I said the entire assembly should be tested and listed as an assembly, to include the gasket.
Will post another answer with links, may take a day or two to show up
Why are gaskets used in dry pipe systems required to be listed?
Gaskets on grooved couplings have a limited degree of fire endurance when used on dry pipe systems. Therefore, the listing requirements of some grooved couplings include an evaluation of the coupling’s performance in dry pipe sprinkler applications. In addition, dry systems typically are exposed to extreme temperatures. Couplings for dry systems have their gaskets evaluated for their resistance to air leakage at the minimum temperatures referenced in the listing.
If it is listed than NFPA 13 allows it
Such as::: https://s3.amazonaws.com/s3.anvilintl.com/resources/submittals/FP-SUB-74FP_Gruv-190305.pdf#page=1
I agree with Dave Welch. However, I am seeing a problem currently with dry system thin wall pipe. These systems are failing faster than anticipated. I have seen systems no more than 10 years old, with the groove coupling removed and the pipe ends (at the pipe belly) show severe corrosion, The problem doesn't appear to be the couplings, it seems the thin wall pipe is creating the issues. Just my thought.
Yes, let me clarify - the grooved end on lightwall pipe - not the coupling itself. The groove in the pipe along with the way the couplings are designed promotes puddling which in turn speeds up the decay process of the pipe. Thinner pipe will fail before thicker pipe obviously and it's become almost a cottage industry unto itself replacing dry systems with lightwall pipe with heavier pipe and/or a nitrogen system.
My 2 cents to the discussion-agree with all comments. Roll grooving the thinwall pipe also creates a "hump" inside the pipe wall which encourages puddling of the system water and a place for "bugs" to multiply and corrode the pipe. The recent changes to pipe pitch of all dry/preaction systems-not just ones in areas subject to freezing-was in part to address the water "puddling" situation. The best case scenario(this year!) is to use Black steel(!), cut grooved, schedule 40 pipe, and a means to avoid moisture and dry the system piping interior out as much as possible. (Hence the trend to using nitrogen generators for supervisory pressure in lieu of using compressed air.) However-the contractors and owners may cry foul-as this will increase system design and installation costs.
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