Bending old AL cable

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engtim

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A concern was brought up on a project where we were looking to splice into existing feeders to extend the runs. The existing are AL and 20+ yr old Tray Cable with about a 2.5' radius. We were going to straighten the cable, 'butt-splice' and continue the run.

The concern was that bending AL cable that has been 'cured' to it's position for such a time could cause fracturing, thereby compromising the integrity of the cable.

Is there any documentation out there that would substantiate this concern? I spoke with a cable rep that sounded more concerned about the jacket than the aluminum itself with regard to cracking or fracturing.

Thanks.
 
Me thinks the documentation should read as follows:
1) Megger before straightening. If it fails the megger it must be replaced anyway.
2) If it passes, remove cable, wash cable using hot water/steam setting at a self-help car wash, to make both cable & insulation more malleable before straightening.
3) Dry, install, & Megger test again.
 
There is no problem with the methods by which I would be performing the installation.

There are a couple of seasoned engineers who believe this may be a problem. So, I guess I was wondering if anybody else ever heard of such concerns? If so, are there any studies to substantiate the concern?

BTW, I've tried the carwash thing before but all the insulation was skinned of the cable by the time I got there from dragging it behind my truck.
 
LarryFine said:
Agreed, and simply removing the curve would only lose under four feet.
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I agree also. However, if we splice before the bend we will be outside of the building. Since we're splicing in the tray, I would prefer to be inside.

As an update:
I contacted a well known cable manufacturer whose metallurgist says unbending the cable would not be a problem as long as the inside of the cable is dry and there is no corrosion. From their view, it sounds like I should be more concerned with the insulation being brittle.
Since the portion of cable we are moving is inside, and out of UV exposure, I don't see much threat from the insulation. Moreover, we rutinely change motors (bending and unbending 4/0+ size cable) and have never had a problem with brittle insulation or conductors. I mention this because these conductors were installed around the same time as the feeders.
We will probably extend the existing aluminum feeders with more aluminum to ease cost and avoid AL/CU splicing (although I've done it, I just try to avoid it).

I realize this might sound like trivial, nit-picky stuff but in this instance, running all new copper will add $100k+ to the job.
 
Straighten the cable. If the insulation cracks, wrap it with the appropriate slicing tape to the specs of the original insulation. I can't see the concern here.
 
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