PVC 90Deg. 25foot radious

[Szavala]

I need to pull new set of feeder wires (5)-750 kcmil in one 6" PVC underground but we found the conduit have at the end 2-90? elbows 5' radious and in the middle have 4-90?elbows 25' radious, the distance of point A to point B is 365'.
those 90?25' radious is considering drag resistance on a wire pull ?

 

[iwire]

Code wise it is 360 degrees max between pull points regardless of radius.

 

[PetrosA]

... the conduit have at the end 2-90? elbows 5' radious and in the middle have 4-90?elbows 25' radious...

I can't imagine that you got those angles right. Two 90 sweeps (one at each end) for stub ups, then four 90 elbows would not make a 25 foot radius - mathematically impossible unless the conduit runs around back onto itself, in which case you wouldn't have a circle, but a square. Are you sure they aren't some lesser angle? Only a 22.5 degree bend x 4 would give you a measurable radius for a 90 degree arc or 45 degree x 4 for a 180 degree arc. Which is it?

 

[Volta]

I can't imagine that you got those angles right.....

well, what if it's a 4-point saddle underground?

 

[PetrosA]

well, what if it's a 4-point saddle underground?

How would a 4 point saddle underground give you a 25 foot radius?

 

[Volta]

I read the OP to imply that the horizontal bends are simply placed in a curved trench. If four 10' lengths were joined and bent into a trench that had a 25' radius completing 90 degrees it would about work.

Now, 6" is pretty stout...

 

[kingpb]

If you know the actual conduit configuration (not guess) then model it and do a pulling tension and sidewall pressure calc.

The NEC means nothing in this regard if calc can show that the cable can be pulled without damage. This is an area where having a registered PE do the calc could be beneficial.

 

[K8MHZ]

As I read the OP, there are 6 90's total. One on each end and four in the middle.

 

[augie47]

Thankfully, POLY-WATER is available in a 55 gal drum.
(5) 750 for 365 ft with ANY bends.. hard for some of us to comprehend.

In CU one run would be 2 tons of wire

D-DRUM

55-gal drum (208 l)

 

[iwire]

The NEC means nothing in this regard if calc can show that the cable can be pulled without damage. This is an area where having a registered PE do the calc could be beneficial.

I do not follow you, regardless of the pulling tension calculations there are no exceptions to the 360 degree rules. PE or not.

 

[kingpb]

I can't imagine that you got those angles right. Two 90 sweeps (one at each end) for stub ups, then four 90 elbows would not make a 25 foot radius - mathematically impossible unless the conduit runs around back onto itself, in which case you wouldn't have a circle, but a square. Are you sure they aren't some lesser angle? Only a 22.5 degree bend x 4 would give you a measurable radius for a 90 degree arc or 45 degree x 4 for a 180 degree arc. Which is it?

How does a 90 deg bend equate to a radius? I can make a 90 deg angle/bend with a 100' radius. They are independent of each other.

 

[kwired]

I can't imagine that you got those angles right. Two 90 sweeps (one at each end) for stub ups, then four 90 elbows would not make a 25 foot radius - mathematically impossible unless the conduit runs around back onto itself, in which case you wouldn't have a circle, but a square. Are you sure they aren't some lesser angle? Only a 22.5 degree bend x 4 would give you a measurable radius for a 90 degree arc or 45 degree x 4 for a 180 degree arc. Which is it?

Any bend could have any radius, as others have pointed out. As an example OP may have something like a line starting out running east, first bend turns to the north second bend back to the east third bend could turn to north or south, and 4th bend could turn east or west, and the run never came back to itself just went around obstacles that would have been in the preferred path. That said there is still too much deflection if there are additional bends at each end.

 

[kingpb]

I do not follow you, regardless of the pulling tension calculations there are no exceptions to the 360 degree rules. PE or not.

This is an area of the NEC where it oversteps its bounds and has nothing to do with safety. 4-90 degree bends is misleading and can easily be shown by calc that a 2 bend pull will damage cable, but hey 4 is allowed so pull away, WRONG.

Done it before; use 90.1 (C), 90.2 (B), or (C) or 90.4, show the inspector a professional looking calc with my PE seal on it, meet with him to go over the calc in detail, and typically case closed.

But in this particular case, the OP did not even mention what the cable run is for, you have assumed the NEC applies, I assume it does not.

 

[kwired]

This is an area of the NEC where it oversteps its bounds and has nothing to do with safety. 4-90 degree bends is misleading and can easily be shown by calc that a 2 bend pull will damage cable, but hey 4 is allowed so pull away, WRONG.

Done it before; use 90.1 (C), 90.2 (B), or (C) or 90.4, show the inspector a professional looking calc with my PE seal on it, meet with him to go over the calc in detail, and typically case closed.

But in this particular case, the OP did not even mention what the cable run is for, you have assumed the NEC applies, I assume it does not.

Conductors potentially damaged during the install is not a valid concern for NEC?

I don't doubt you can show a run with two bends that need more pulling force or otherwise cause damage than another run with four bends.

Why you assume NEC doesn't apply?

You want to help with the pull?

 

[kingpb]

Conductors potentially damaged during the install is not a valid concern for NEC?

Nope, not when the damage is based on poor installation practices or engineering design; and the install is unverifiable by observation regardless of what stage of construction. The 4-90 limit does not guarantee undamaged cable. You can damage cable installing it in a straight run only 3' long.

The NEC wants to make a blanket statement that only 4-90's are allowed, but doesn't require a calc to show that even works. It doesn't matter what size the cable or pipe is either it can still be an issue. This code requirement is useless and in some respects creates a danger due to false sense of security.

Why you assume NEC doesn't apply?

I am assuming since the OP did not say what it was for, it is a utility distribution feeder within a power generating facility.

That assumption is just as valid as someone else assuming it is to feed a commercial power center.

 

[kwired]

I am assuming since the OP did not say what it was for, it is a utility distribution feeder within a power generating facility.

That assumption is just as valid as someone else assuming it is to feed a commercial power center.

Well maybe he just has a bunch of 6" pipe and 750 KCMIL laying around and has nothing better to do with it, and doesn't even intend to ever energize it

Wish I could afford a hobby like that

 

[PetrosA]

How does a 90 deg bend equate to a radius? I can make a 90 deg angle/bend with a 100' radius. They are independent of each other.

Right, but the OP stated that there were 4 90s with a 25' radius. This is kind of confusing. If there are four bends making an arc of 90 degrees with an approximate 25' radius, they can't be 90 degree bends. If there are four 90 degree bends each with a 25' arc, you'd have 40' of pipe on each arc which is very different from a pulling POV than a 5 foot sweep since you probably have about as much resistance from gravity at that point as you do from the bend in the conduit.

Any bend could have any radius, as others have pointed out. As an example OP may have something like a line starting out running east, first bend turns to the north second bend back to the east third bend could turn to north or south, and 4th bend could turn east or west, and the run never came back to itself just went around obstacles that would have been in the preferred path. That said there is still too much deflection if there are additional bends at each end.

Understood. I'm still just trying to understand what exactly he means by four 90 elbows with a 25 foot radius. Either each elbow is made out of a 40' length of PVC or he has one "elbow" or site-made sweep with a 25' radius made up of four premade bends, ex. 22.5 degrees. Your example doesn't explain how any of the 90s have a 25' radius.

Edit to add: Now that I checked some things online, it's also possible to get 11.25 degree sweeps in 6" sch 40, 80 and DB60 or 120. There's not really enough info to calculate the exact radius, but it looks like a 90 turn made up of 11.25 degree sweeps could be close to a 25' radius.

 

[hurk27]

All bends are based upon a radius of a curve

draw a 50' diameter circle now bend a pipe to fit between the 12:00 and 3:00 positions or from the 0? to the 90? points and you will have a 90? bend with a 25' radius you can buy 90? sweeps to make pulling easier, all you have to have is the room to install them, pulling through a 25'r sweep will be much easier then pulling through a 5'r or 10'r sweep.

to add a little to this, if the diameter is 50' then we can use 3.14 to find how much pipe is needed to make this 25'r sweep:

50'*3.14=157/4=39.25' or 39' 3" of pipe or 4 10' sticks with 9" cut off one of them

I agree with Bob, it still does not get around that the NEC will not allow over 360? of bends with out adding a pull box, just because you might be able to doesn't mean you should.:happysad: the requirement does not have any exception to allow an engineer to over ride this requirement like it does in other articles, so P.E. or not, its not allowed.:happysad:

 

[hurk27]

I need to pull new set of feeder wires (5)-750 kcmil in one 6" PVC underground but we found the conduit have at the end 2-90? elbows 5' radious and in the middle have 4-90?elbows 25' radious, the distance of point A to point B is 365'.
those 90?25' radious is considering drag resistance on a wire pull ?

personally I would if possible to install a pull box or vault in the middle of the 4 25' r sweeps this will give you 4 90? bends in each run and put another pull point in the middle, would still be a hard pull and you better hope the pipe has no sand in it, even a little will grab the insulation of the wire and bring the pull to a halt, but even clean it's not going to be an easy pull.

 

[Fulthrotl]

I need to pull new set of feeder wires (5)-750 kcmil in one 6" PVC underground but we found the conduit have at the end 2-90? elbows 5' radious and in the middle have 4-90?elbows 25' radious, the distance of point A to point B is 365'.
those 90?25' radious is considering drag resistance on a wire pull ?

assuming 25' radius is pipe swooped in ditch.

also assuming you are pulling aluminum.
i'm doing underground in november, one run of which
is 4", having four 750 mcm's, with a ground, 650' long.
in aluminum, that pull at current pricing is $8,200 for
the wire, so i'm suspecting you aren't pulling copper.

there will be three 36" sweeps, one on each end, one at
about 450' and a number of swoops in the run, count on
it.

wire will be simpull, pulled dry. it'll be pulled with a 2,500#
mule tape, with a maxis 3000# tugger for the first part,
and a 12,000 lb greenlee pull rope for the last half of the
pull.

i doubt i'll see 2,000# on the strain gauge.

if you pull with simpull, what you are pulling should
be effortless.

i've yet to see an inspector count a schwoop as a 90.