Snaking of buried large diameter HDPE fused pipe

[jacky89]

For small diameter HDPE pipes, sometimes it is recommended to snake the pipe in the trench if installed in hot weather to avoid thermal expansion/contraction stresses. For large diameter hdpe pipes, is this also done and if so how do you snake a large diameter hdpe in the trench? Thanks.

 

[bimr]

Never heard of this. Where did you come up with this idea?

"Placing pipe that has been in direct sunlight in a cooler trench will result in thermal contraction of the pipe’s length. This contraction can generate force which could result in pull-out at mechanical couplings or other buried structures. Allow pipe to cool before making connections to an anchored joint, flange, or a fitting that requires protection against excessive pull-out forces. Covering the pipe with embedment will facilitate cooling."

http://www.plasticpipe.org/pdf/chapter07.pdf

 

[rconner]

I believe "snaking" plastic pipe has been recommended by many in the plastic pipe industries since at least as far back as the early to mid-1970's when I first saw same, and I think you will find is even also reflected in some current publications that are searchable online. While I think I have also seen varied explanations for such recommendations over the years, and/or this as a response to/cure or excuse for some past problems with welded or fused systems etc., I think all writeups or specifications I have seen basically had roots/or common thread in the very pronounced thermal expansion/contraction behavior (or very high thermal expansion coefficients) of plastic pipes as compared e.g. to common metal pipes.
Assuming there is sound technical or overriding reason for doing this e.g. with fused or welded plastic pipe systems, it sure would seem snaking the pipe wouldn't much help the hydraulics, uniform underlying soil support of piping in common trenches, future dependable locateability of the pipeline, nor necessarily the integrity of any lateral service/connections (as some folks are also now recommending bent plastic pipes should not be tapped for stress concentration/safety reasons). Also, I agree one might also wonder about the practicality of this approach in larger, stiffer pipelines in trenches, and also e.g. in HDD applications?

 

[cvg]

compacted backfill will restrain the pipe sufficiently to resist movement. However, if the pipe extends above the surface or is laying on the surface, you should expect movement due to expansion and contraction. Anchor blocks may be used to prevent pullout from fittings above ground. snaking the pipe for above ground applications with no restraint (such as commonly done in surface mining) is recommended

 

[jacky89]

Ic. Thanks guys.