HDPE conduit and cable thermal expansion issues

[tomecki]

I'm looking at an application where some power and fiber optic cables are installed in HDPE conduit. Total length and ambient temperature fluctuation is such that the conduit will expand and contract by up to +/- 5m (15 ft). The cables inside will expand and contract at a much lower rate.

I'm looking for some references/advice on how this can be handled. The obvious thing to do is to leave some slack so that the cables can get pulled in and out of the conduit as the length changes. Some other issues arise though. The power cable has a splice which won't be able to handle as much tension as the rest of the cable. I'm not sure how to determine the tension in the cable when the conduit expands. The fiber will see compressive loads when the temperature drops possibly kinking it inside the conduit etc.

Has anyone done/seen anything like this done?

Any advice would be appreciated.

 

[Compositepro]

I would be more worried about the movement relative to the ground or anchor points. Once that is taken care of the cables will probably be okay. HDPE is not a stiff material so the restraining forces would not be high. Restraint in one direction will show as movement in the other directions (i.e, radial). The same conditions exist between copper conductors and wire insulation.