Design Guidance for Pipe Expansion Joints?

3/10/2020

I'm working on a project with a very extensive horizontal standpipe; it is about 2000 feet long and in a loop, so almost 5,000 linear feet when all said and done.

Where can I find guidance on providing expansion joints?

Due to the system being so long, we're worried about providing some flexibility in the instance of extreme temperature swings (Virginia). Would seismic flexible joints be appropriate?

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4 Comments

Dan Wilder

3/10/2020 08:22:50 am

Depending on the coupling style you are utilizing (flex or rigid) and referencing Victaulic specifically.

Understand the available expansion of a rigid or flex based coupling:
-4" 005H is 0.16"
-4" 009N is 0.17 but you need to account for the gasket thickness within the pipe
-4" 75 is 0.13" (but these expand more than that in my experience but I can't find that number)

You may need to account for the pipe growth as well.

Calculating Thermal Growth:
https://www.victaulic.com/assets/uploads/literature/26.02.pdf

You can use the Style 150 "Mover" or 155 Expansion Joint (these are ordered to be in contraction, expansion, or neutral based on the expected movement) instead of a full seismic loop like a Metraflex (which is supposed to be installed in a "neutral position" anyway, so when the system is pressurized it would not be in this position) or the NFPA version Section A.9.3.3(a) of the 16' Ed.

The NFPA seismic approach would be my option just due to the fact that even if it flex's, it is still within listings and it's not there to provide a seismic solution (it's also cheaper).

You will notice the expansion on any laterals, especially so where those pipe pass through walls, you may see some damage on pressurization. 4-Way brace these locations to lock in that position and use the expansion options between as needed.

Banna

3/24/2020 10:22:57 am

I do agree with Dan on using flexible couplings to accommodate thermal movement. Rigid couplings are supposed to provide full rigidity in terms of movement, so I don't recommend using it. Victaulic style 177N, 77 or 75 are considered an expansion joint of its own. I tend to use style 177N giving the max pipe end separation (4.6 mm of movement for 4" coupling). Style 155 movers are a great solution as well for combined expansion/ contraction applications.
It actually depends on so many parameters, maybe what best fits you is a combination of rigid & flexible couplings. You can reach out Victaulic VDC team and they can run the calculations for your piping system & they may also suggest the best practice or solution

Paul Pinigis

3/10/2020 10:05:52 am

You may want to consider MetraFlex segments in the system.

Ken Thackery link

3/10/2020 12:30:35 pm

Is the standpipe system exposed to freezing? Metraflexes are not required unless you're crossing a seismic joint. An expansion joint is not a seismic joint. Metraflexes are UL/FM approved and the calcs are reasonable depending on the movement value. If you feel the need to use them based on structural requirements then use Metraflex.

I have used these extensively on SeaTac- Seattle airport projects in direct collaboration with the structural engineer. At a seismic joint, movement values increase as height increases. I understand Virginia is does not have seismic requirements.

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