Submerged Cables 1

[sparkybrewer]

I need to determine the best solution to replace failing class 1E safety-related 4160V feeder cables that are routed in buried conduit, which is full of water. I will need to consider the following options.

1. New alternate route above ground. Cost - approx 5M.
2. Use of inner conduit. Cost - approx 800K.
3. Use of armored cable. Cost - approx 800K.

Options 2 & 3 are the most viable and economical solutions.

Any suggestions for manufactures or OE. Thanks for your help.

 

[7anoter4]

Did you mean the actual 4.16 kV cable runs through cable duct banks and manholes?
This path -namely the manholes-it is almost always full of water. So what is it the problem? Corrosion?
You may seal the ducts if you could first to empty the water somehow.
But cable jacket [pvc, chlorosulphonated polyethylene [hypalon] and other has to be resistant to water penetration -even against sea water.

 

[dpc]

Pulling new armored (MC?) cable through existing conduits could be a problem. If you are in North America, I'd contact Okonite regarding their C-L-X metal-clad cable. It would be a good solution if it can be installed.

Why not just replace with like cable? Is it the water that is concerning you?

David Castor

http://www.cvoes.com

 

[davidbeach]

Everything underground should be assumed to be full of water at all times anyway. Only equipment and conductors suitable for submerged used can be installed below ground.

 

[sparkybrewer]

The cable runs through 400 feet of conduit that is buried under the building slab. The cables are very important and are required for safe shutdown of the plant. The plant is expected to run an additional 20 years. We have looked into using Okonite, however their cables are not submersable, only water resistant. We are looking for a solution that is very dependable and would not require replacement during the life of the plant.

 

[Laplacian]

What type of cables are you presently experiencing failures with? Cross linked polyethylene notorious for water ingress? Are these shielded cables?

There should not be any issues using cable rated for underground conduit or direct bury service if it was not mechanically damaged during installation.

If you had cables fail in the underground conduit, are you sure the conduit is still mechanically sound (not collapsed or sheared), or that the cable didn't weld a slug onto the ID of the conduit when it failed?

All the major cable manufacturers offer equally reliable cable, if applied and installed correctly.

 

[dpc]

"Submersible" implies operating at some depth underwater. That is not the situation you have when a conduit is full of water. This is a very common situation, and generally, good quality cable should have a long life in this situation. The CLX cable has a PVC jacket on top of a continuous extruded aluminum sheath which is on top of the normal EPR cable.

You can look into standard submarine cable used for underwater applications. But it probably won't fit into your existing conduit. Why not just run a new cable outside along a wall?

David Castor

http://www.cvoes.com