Flex Couplings for Non-Seismic Expansion Joints?

4/7/2022

Under the "Protection of piping against damage where subject to earthquakes" NFPA 13 requires "listed flexible pipe couplings" to be installed where pipe passes over seismic joints or building expansion joints.

Is there any similar requirement when the building is not subject to earthquakes?

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8 Comments

Pete H

4/7/2022 06:40:24 am

Not seeing anything in NFPA 13 (2016) outside of Section 9.3, which is protection of piping against damage where subject to earthquakes.

Best stab in the dark I can offer is any building that is going to be subject to intense vibration (so over a concert stage, anything near a large speaker that is going to be all about that bass) would be 'best practice' to aim for listed flexible couplings over rigid couplings for joining grooved pipe 2-1/2" and larger.

Glenn Berger

4/7/2022 08:05:52 am

Flex couplings are required at seismic expansion joints. Flex couplings can be used in all locations.

Franck

4/7/2022 09:13:33 am

I have seen such practice, when buildings were possibly subject to settlement (soft soil).
It is the case, for example, for fire pumps on the suction pipe side between the tank and the pump, when they are on different settlement (to allow some possible movement over time between the 2 buildings).

Alex

4/7/2022 11:39:54 am

Hi,

I have seen the same as Frank mentioned. If the building is subject to settling or moving, the last thing you want is the FP pipe to be the most ridged!

Alex

Jack G

4/7/2022 10:21:12 am

Nfpa allows less space around pipes where they cross thru floors, fire walls, masonry walls, where the couplings on either side within a certain distance are flexible couplings.
Thermal expansion should be another consideration, where foam water systems, antifreeze are used. Roofs that generate heat to sprinkler systems installed within a foot , ( where dissolved air will cause increased pressure) is another place to involve flexible couplings.
Tall structures with powerful lighting, will generate a lot of heat that will be aspbsorbed by the system piping.

Dave

4/7/2022 10:59:04 am

I see, you are pointing out that since 9.3 states “Where Subject to Earthquakes” (Moved into its own Chapter 18 in the 2019 edition) that the subsection on flexible couplings only applies in areas subject to earthquakes. (Because it is always important to understand the hierarchy of the numbering). I have never designed in areas NOT subject to earthquakes so I have never considered that. (Conversely, I have reviewed plans from freelance designers in non-seismic zones who are not familiar with the requirements nor efficient bracing design). In the handbook edited by Matt Klaus, he states “the AHJ and the system designers should come to an agreement early on in the project to determine whether or not protection against seismic damage…will be required. The determination is typically driven by the building code and hinges on the location of the project and the nature of the occupancy of the building.” The handbook states NFPA 13 does not address the issue of where earthquake protection is to be provided, however SEI/ASCE 7 is adopted by reference in current model building codes. Interesting question.

Respectfully, the allowance for decreased annular clearance by use of flexible couplings on each sides applies to walls (and frangible construction and successive studs or joists), but not to other assemblies such as floor penetrations.

Dave

6/15/2022 02:25:59 pm

Actually, my last statement that the clearance allowance does not apply to floor penetrations is refuted by the way NFPA #13 refers back to the floor flex coup requirement. For example, in the 2016 edition, 9.3.4.5 refers back to 9.3.2.3.1(2)

Max

4/7/2022 05:18:54 pm

Flex coupling could be used to follow the slope of the roof in some cases.

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Flex Couplings for Non-Seismic Expansion Joints?

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