Using direct burial instead of duct bank for some industrial areas

[alex321]

I would like your opinion on using direct burial cable instead of pvc for some industrial applications. The idea is that we can plow in the cable and save on installation and pvc costs. Obviously this will not work running several circuits, but how about just one or two circuits?

Can you think of any application where this would be acceptable?
Also, does anyone have any experience with a tiling machine that could do this, how many cables can be buried at once? And what sizes are typically buried?

The main idea behind this is we often have long lighting runs throughout the site, and it takes up too much time to trench, lay, and backfill with pvc. Plowing would save time and material.

I understand there may be some reliability and replacement issues, but let me know if you think the savings is worth the risk.

Just understand we are only considering this is certain areas. Most of the site will still be duct bank.

 

[davidbeach]

Why not plow in the PVC conduit?

 

[alex321]

The idea is to save time. PVC still has to be prepped. With a tiling machine it would take the wires directly off the spools and bury them quickly.

 

[davidbeach]

Right. You can also buy reels of light weight conduit and plow it in. Yes, you have the additional step of pulling the wire, but you then have the ability to pull it out again later. But you still skip all the hassle of open trench.

 

[desrod]

Hydro-Quebec Distribution used direct buried cables that came with a flexible conduit around it allowing cable replacement eventually.

It was 5-6 years ago when they started using it. Might be interesting to find out if they had to replace a cable and were able to do it.

 

[dpc]

As mentioned, cable-in-conduit shipped on a reel is available. It can't get much simpler than that.

C-L-X type armored cable is another option. It can be direct buried, but will more costly.

David Castor

http://www.cvoes.com

 

[alex321]

All is good information. Thanks. Now what locations would it be safe to use these methods, and what sizes are typically used? I am referring to industrial processing plants, so all the critical runs and high traffic areas will be in duct bank.

Lets say i wanted to direct bury a set of #10's or #12's to reach some lights in remote areas. What are some do's and dont's of direct burial. I realize PVC and innerduct would be a better choice but I am just speculating right now.

The wires can be anything from #12 to 500, what problems can occur from direct burial? and what areas of a plant would it be safe to direct bury?

 

[7anoter4]

Usually under pavement [pedestrian route] 2-3 ft below the surface will be safety. You may run parallel power cable of any conductor cross section and any number keeping a certain distance between and using a suitable derating factor following -for instance- NEC recommendation. Ampacity calculation could be a problem as the ground drying around the cable could increase the soil resistance. IEC 60287-3 may assist you to solve this problem also.

 

[wayne440]

The time saved for installation will be more than consumed when the direct buried conductor has to be repaired, and it will. When you plow in cable, you have exactly zero control over the quality of "fill" earth in contact with your cable, unless you use something other than the common vibratory plow. The plow blade can split a rock, and drop the cable right between the halves. Or it can ingest a sharp rock into the chute and damage the cable for many feet before the rock passes thru or someone notices.