underground fiber optic conduit

[tntech_fiber]

Hello there. This is my first post so this may not be in the correct forum, but here goes:

I'm project manager for a 2500' fiber optic cable install, and we are trying to piggyback on top of a nitrogen line install along the same route. Can we (legally, to code, etc.) bore these two within the same sleeve? The nitrogen gas is contained in 4" stainless steel and the fiber will be inside innerduct inside a 2" conduit, most likely schedule 40 PVC. I have spent the last few days studying the NEC, NESC, and the Tennessee Code Annotated.

Is there any other literature to consult? I know Article 300.8 says electrical code cannot be in the same cable tray as gas pipe, and Article 770.133 says fiber can be in the same cable tray as electrical, but there is nothing about fiber and gas pipe being together. Seems like it could since fiber is a nonconductive material, but I need some verification of this in writing.

 

[hbiss]

Re: underground fiber optic conduit

I'm going to assume here that this is on private property and you are not a utility installing this along a public right of way.

The NEC would then apply however I am not aware of any part that addresses different services in an underground trench (or boring). Gas, electric and communications are installed in the same trench on a regular basis.

In your situation you have a nitrogen line which is not natural gas and a FO cable which has no voltage on it. I can't see where the hazard would be. I think this is a design issue as to whether it is advisable to run the PVC conduit next to the nitrogen line, (I'm assuming it isn't liquid nitrogen and won't be cold) but there isn't any code that would prohibit it.

-Hal

 

[tntech_fiber]

Re: underground fiber optic conduit

You're assumptions are correct. I had assumed that the trench or bore would be the equivalent of a cable tray or raceway.

As long as the fiber is dielectric (no metal parts), I don't see a problem with it. I would just like some verification. Do you think it could be treated as a neutral (the NESC makes reference to this) and if so, is there a section of the NEC about running gas pipe and a neutral together?

 

[hbiss]

Re: underground fiber optic conduit

It would not be common (matter of fact it's prohibited) to run a neutral by itself.

The NESC may say something about this because that may be something a utility may do, not us.

-Hal

[ June 20, 2005, 04:51 PM: Message edited by: hbiss ]