radioactive cell and the conduit bends we have to work with

[Tulsa Electrician]

Would like to add a well planed out route with you amount of bends would be a good idea. Do some pulling calculations as you go.

 

[Tulsa Electrician]

There has been many times we pull right through the pull boxes etc as long as the run will not damage the conductors. I believe that is why Larry mentioned a C. Pull through and be compliant as well.

 

[winnie]

I've always wondered if there was a way to put bearings inside of a conduit system to reduce pulling tension.

However I think that the answers along the lines of 'do a careful calculation of pulling tension and if you can design/show a safe pull the AHJ should permit a variance' make the most sense.

The other side of a the coin is a reminder that pulling around bends is an exponential force multiplier. The equation has an e^k∙theta term in it, doubling theta results in far more than doubling pulling force.

-Jon

 

[Barbqranch]

I have never done this, nor needed to. But, I wonder if say you have a 200 foot pull w/ bends, if you could put 2 ropes in the conduit, and attach one of them at the end of the wire, and the other 100 feet back. Pull them both, keeping even pressure on them, and the second one should relieve stress on the end of the wire.

 

[ramsy]

Utilities relieve stress on aerial conductors by spiraling them around a messenger wire.

If this works with underground raceways, finding that method advertised on the internet is another matter.

 

[tom baker]

I have never done this, nor needed to. But, I wonder if say you have a 200 foot pull w/ bends, if you could put 2 ropes in the conduit, and attach one of them at the end of the wire, and the other 100 feet back. Pull them both, keeping even pressure on them, and the second one should relieve stress on the end of the wire.

Clever. Like distributed power on a freight train (engines in the middlle)

 

[LarryFine]

Clever. Like distributed power on a freight train (engines in the middlle)

That is smart. It can help when you're running out of puling space, too.

 

[winnie]

You would still have the full tension of the pull, but taken up by rope rather than by the conductors. As long as the conductors didn't get pinched under the rope I think it would do a great job of reducing the force on the wire. You would also be committing to leaving at least one rope in the conduit.

Taking this to the extreme, you could insert the wire into a suitable rope, say an 8 or 12 strand braid. If the rope material is low friction and low stretch (say HMPE), it would both reduce the pull tension and carry a large fraction of that tension.

-Jon