Cabling underground

[ppabel1]

HI,

can anyone tell me how to go about running fibre from one building to another, a distance of about 50M.

what kind of trunking is used?

cheers

Paul

 

[RSKing]

Paul,

Can you give us any more detail?

1. Is there conduit currently between buildings?
2. If there is conduit, is room available for another cable?
3. Is there an existing aerial path?
4. What service type will you use the fiber for(Voice/Data/Video/Fire Alarm)?
5. Is the light source LED,Laser, etc.?
6. Is there a path between the building entrance points and the termination closets (if not the same)?

Thanks,

Richard S. King, RCDD/LAN/OSP
TKG Consulting Engineers, Inc.

 

[ppabel1]

hi mate,

that wasmy main question. there is no conduit. I was after a sugeestion for conduit under the ground

 

[skip555]

use interduct the nice thing is you will be able to get it in one peice rather than having to connect it .

1" interduct is around .50 a foot.

 

[ppabel1]

where can i purchase interduct in the uk?

cheers

Paul

 

[mikeydidit]

http://www.innerduct.com/

Paul contact these people and see if they can help you.

Mike Jones
LSUHSC

 

[AvayaNovice]

Innerduct is not rated for underground use neccesarily. Normally... you'd run conduit, and then run innerduct through the conduit... or you'd run "poly pipe" which has a million different ratings, and that also comes in one piece.

While the link that mikeydidit provided does appear to have several types that are UG rated, make sure to check. Otherwise it will crack and become useless after a few years.

Poly pipe which is what we use for direct boring, is certainly rated as such.

We usually always run innderduct inside of our conduit as a second layer of protection, and also allows pulling of new cable in the same conduit with little to no contact.

If you're running 50 meters, I would suppose that 2" should be plenty.

 

[3rc]

On a little short run like that it is a good idea to run a tracer wire for locating in the future.

 

[JRichardT]

Another possible underground rated 'conduit' you could use is sprinkler line. It comes in various sizes and lengths, and is readily available.

 

[AvayaNovice]

That's true, although conduit has a much more smooth surface on the inside, and is less prone to damaging cable as its pulled (hence innerduct) but this isn't to say that I've pulled cable through a variety of things... including sprinkler pipe. Anything should do, it just depends on the application that you're implementing it for. If I was implementing a fiber link for two telephone switches for a large business... I wouldn't mess around. Too important.

 

[ppabel1]

it looks like you can only get innerduct in the us not the uk

cheers

Paul

 

[mikeydidit]

Paul while they do make direct buried type fiber cables, be sure to put it in some sort of conduit. For the most part, we have our cables placed by using a directional boring machine and pull conduit back through. If you intend to trench this, have them go at least 24” to 36” deep. Place a small wire in the conduit with your fiber (most fiber cables do not have steel strength members anymore) so you can locate it again. Have the people that are doing the trenching place a marker tape in the last 1 foot of backfill. The theory here is if someone does digging before you can locate your fiber, they will dig up the tape before they get to your conduit. This will give you something to use that is protected the best you can. Here in Louisiana the odds of having a cable cut or damaged can be expected every 3 years, regardless of what you do. Hope this goes well for you.

Mike Jones
LSUHSC

 

[SparksLondon]

I am an electrical contractor, I have never pulled fibre undergound but have done a lot of conduit work. Here are some points:
1.This sounds like a critical communications cable so you should assume that it will get dug up or damaged and therefore run two pipes different routes as far apart as possible.
2.Assume that the pipe will fill with water and use the appropriate cable, many underground duct systems are porous and do not have any method of draining off leaks or condensation within the pipe.
3.To limit water ingress avoid,if possible, access/pulling points outside the protection of the buildings.
4.Many ducting systems are corrugated, do not use them as they increase drag on the cable.
5.Do not have any bends undergound except a gradual rise to floor level within the building, any 90 deg bends will cause problems.
6.50m does not seem very long but it will if you have any problems pulling cables in so take more precautions than you think are necessary. It may make sense to tape your fibre to a draw wire or rope along its entire length this will avoid stretching the fibre.
7.don't plan on being able to pull a second cable in over the top of your original,if you need several cables pull them together or install several pipes in the trench as the cables will probably be damaged sliding over each other.
8.As an alternative use a catenary wire and hang the fibre on it, this will need careful consideration of the weight,sag, tensile strength, fixing brackets and cable type(affected by UV,range of temperatures, ice etc).

Regards John Burger

 

[daronwilson]

Were this my installation, I would place a minimum of 2" PVC conduit in the ground. There is no problem I am aware of using sweep 90's, they are generally available with radii varying from 12" to 48". We only use the 48" sweeps for fiber runs.

I would pull innerduct inside the conduit, we routinely use a 1" PVC corregated innerduct in the pipe, then pull the fiber in the innerduct. If you do choose to add more cables or fiber, pull in another inner duct or pull the wire outside the innerduct inside the conduit.

When pulling the fiber in, follow the manufacturers requirements. Use only outdoor rated fiber, since there may be moisture in the conduits and ducts when done. You will either be pulling on just the kevlar strength member of the fiber, or depending on the manufacturer you may be using a kellums type grip on the jacket.

Good Luck!

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[AvayaNovice]

Corregated innerduct actually reduces the amount of friction and makes it easier to pull... if you get the right kind, and lubricate as specified.

I would do the same as DW, place 2" PVC, run 1" innerduct... and be done with it, I might possibly put in 3" or 4" if I knew that there was a chance of more cable going in later... as 1" innerduct crowds a 2" conduit pretty much.

 

[Jtodd]

We've started specificing a product to replace innerduct called Maxcell. Its a fabric innerduct. In a 4" PVC you can get 9 cells as apposed to 4 using standard innerduct. It's sold buy TVC Communications (

http://www.tvcinc.com).

Very cool stuff. There are a couple new competetors on the block now, but this one was the only one available when we first started looking.

Justin T. Clausen
Physical Layer Implementation
California State University, Monterey Bay

 

[AvayaNovice]

TVC is a good company, but do they take forever to get things shipped out. They have a good amount of products though.

Never tried fabric innerduct. We're experimenting with aerial innerduct right now, instead of just over highways and what not, we're thinking about putting most of our fiber plant in it. We'll see. Mostly overlashed, some if it isn't even lashed yet actually, pretty sketchy.