Fittings for connecting DI and HDPE pipe?

Question

Fittings for connecting DI and HDPE pipe?

kfeng (Civil/Environmental)

(OP)

21 Jun 02 16:42

I'm designing a 30" HDPE pipe force main which will be connected to an existing 30" Ductile Iron pipe force main.
The question is what kind of fittings are necessary? Will there be any special requirement because we have two different types of pipes here. Thanks very much for your time and any input.

sow (Mechanical) · Answer 1 · 2002-06-25 14:10:51

Viking Johnson, amongst others, make pipe couplings suitable for your requirements. Probably better off in the piping forum with this.

Cheers.

dicksewerrat (Civil/Environmental) · Answer 2 · 2002-07-29 22:12:54

YOU CAN GET AN HDPE FLANGE FROM YOUR PIPE SUPPLIER. THIS CAN BE WELDED TO THE PIPE WHEN IT IS IN PLACE. THE FLANGE WILL FIT ALL DI FLANGES. JUST USE A MECHANICAL TO FLANGED COUPLING. DON'T FORGET TO WELD AAT LEAST TWO TIE-BACK RODS TO THE HDPE TO ATTACH TO THE DI FLANGE.

Ag93 (Mechanical) · Answer 3 · 2003-01-03 19:16:41

Sorry for the late reply, new member here.  A few more comments regarding connecting HDPE to DI (or PVC, etc).

Joint restraints, in-line anchors, or a combination of both may be required when non-PE pipe and components are connected to a piping system that does not have restrained joints.

Due to the Poisson Effect, when internal pressure is applied to the HDPE pipe, it will expand slightly in the radial direction and contract away from the connection.

Therefore, it is necessary to have a fully restrained connection between the HDPE and DI pipe such as a flange or MJ Adapter (allows you to tie directly to the DI).  Since the force exerted by the HPDE due to the Poisson Effect can be significant, one restrained connection may not be enough.  ie...The second DI joint may pull apart.

Therefore it will be necessary to either install a thrust anchor on the HDPE pipe to take out the thrust.  Or restrain several joints of the DI down stream to avoid the potential pull out.

HDPE pipe manufactures discuss this phenomena in their engineering manuals.  check out www.performancepipe.com      ;

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Fittings for connecting DI and HDPE pipe?