Pulling Calculation - tray cable through underground conduit?

TwoBlocked

TwoBlocked

Senior Member
Location
Bradford County, PA
Occupation
Industrial Electrician
Haven't done much underground conduit work and am wanting to know just how much pulling force will need to be exerted. The pulling app I usually use just lists wire, not cable. Is there a pulling app you fine folks know of that gives calculations for tray cable in conduit?

The three conduit runs are 200 feet of 2" PVC with 2" rigid 6ft stub ups. There's two 90's in the PVC and another two 90's in the rigid. The pull is expected to be one 3 conductor #8 tray cable and one 16 conductor #16 tray cable. Yeah, going for large radius 90's, even if I gotta make them myself, and ordering a 5,000 gallon tanker of lube. ;)
 
That does not sound like a difficult pull...I would not even try to do a pulling calculation.

As far as the long radius 90s, none of the pulling calculations I have used show that they have any effect on the pulling tension. You only need them when the pulling tension is high to reduce the sidewall pressure on the insulation, as the pressure is a function of the pulling tension and the radius of the bend.
 
TwoBlocked said:
Then for me, it does sound like a difficult pull ... ain't got a tugger. That's why I'm wondering how much the pull will actually be.
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With billing rates approaching $3 per minute, I have to use equipment to reduce the labor costs.

For calculation purposes, I would just use a single conductor cables that has approximately the same ODs, and at least as much weight per foot.
 
TwoBlocked said:
Haven't done much underground conduit work and am wanting to know just how much pulling force will need to be exerted. The pulling app I usually use just lists wire, not cable. Is there a pulling app you fine folks know of that gives calculations for tray cable in conduit?

The three conduit runs are 200 feet of 2" PVC with 2" rigid 6ft stub ups. There's two 90's in the PVC and another two 90's in the rigid. The pull is expected to be one 3 conductor #8 tray cable and one 16 conductor #16 tray cable. Yeah, going for large radius 90's, even if I gotta make them myself, and ordering a 5,000 gallon tanker of lube. ;)
Click to expand...
Are you saying there is (4) 90° on each of the 3 runs?
 
don_resqcapt19 said:
With billing rates approaching $3 per minute, I have to use equipment to reduce the labor costs.

For calculation purposes, I would just use a single conductor cables that has approximately the same ODs, and at least as much weight per foot.
Click to expand...
Yeah, that's what I did. Came out to about 225 lbs. Am thinking we'll get one of those $1,000 tuggers that run off a portable drill. They're good for 600 lbs continuous. I figure that's one man-day, well worth it in this situation.
 
rambojoe said:
Are you saying there is (4) 90° on each of the 3 runs?
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Yes, and little can be done about it. It's at a gas pad. the trenching is actually for gas piping, with the conduit above it. At one end we leave stub-ups. At the other end it goes to a vault that will be covered until the drilling and fracking are finished. Hoping we can leave that 90 go until the vault is uncovered, but can't plan on it. Can't ask for an additional vault somewhere. There will be equipment and driveways all over the place. A possibility is to wait to install the 90 in the vault until the cables are pulled, and then put the 90 and stub-up onto the run where the rigid meets the PVC. (Shhh, don't tell the NEC folks )

Oh, and before anyone mentions it, yes, we're using female adapters and bell end conduit.
 
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