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In reading your original post carefully, into lengths of efforts being performed, and verses the results..

I'd say good chance 70 year old conduit run installed underneath building slab, would assume probably GRC raceway for entire length, and 70 year old raceway, being probably unusable.

Personally by now, I'd being exploring the other option.

In mapping out another path in routing, for replacing w/new raceway.

Just my two cents.. Have safe day @ the office..
 

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Hackenschmidt
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The problem with this kind of problem is if you spend 2 days trying to free the wires and then give up, who's eating the time? Customer says you should have just started on the replacement.
I think you have to present this to the customer as what it is, a gamble, early and often.

If you told the customer this is going to take a day or two at a cost of $XXXX and you'd guess it's less than 50-50 odds of success, but it might save $YYYYY on conduit, they can decide how they like the odds.

I am guessing a school doesn't like to gamble with their budget money and their worst fear is explaining $XXXX for nothing.

Lots of business owners I deal with don't mind gambling, they'd say take a day and see what you see then fall back to the sure thing.
 

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Years ago on old gas station runs across the yard, full of petroleum piping and tanks and where the general contractor didn't want to saw up the paving and remove it, due to the costs and possible damage involved.

We would fill the run with water and then blow it out with compressed air for a first rinse. If that didn't work, refill with water and run a bare fish tape in from both ends to break up and stir the rust.

If that didn't loosen it, then we filled the run with muriatic acid and let it soak for a day or two. Once the wires were out, we would swab the run out with rags tied securely to a fish tape.

Several rinses with water and blow the run out each time till the water came out clean at the opposite end.

The blow out only worked if you had a big enough compressor to blow the liquid out in one complete whole slug. If you used a small portable, it would only blow out enough liquid to leave an air passage on the top of the conduit, and the rest of the liquid would remain in the bottom half of the conduit.

It may take a few treatments, depending on conditions, but it always got the conduit usable again, without cutting and digging up the paved yard.
 

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Fill the conduit with water, or polywater and water combination whatever.

Then you need to "hammer" the conductors out. All together as one, wrap the tugger a few turns and percussively alternate between full force pull and 0 tension in rapid blasts. You need to find that "sweet spot" This should sound something like the police are knocking on your door. Each percussive pull will release some of the stuck until most of it is defeated and what's left isn't enough to keep the conductors in place and it just slides out like goose crap through a tin horn. It will not appear to be working until it lets go, so don't give up after a few tries.

When this works I get 25% of the rabbit.
 

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I knew one guy that would use transmission fluid to free up old stuck wires at gas stations. He claimed it worked, I never tried it.
 

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Tool Fetish
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Customer called on a Monday morning a few years ago. 150 amp 480v main breaker for the office (located 500' away) was off or tripped, they couldn't tell. MEG cables; all shorted. Tried to pull from feed end in shop area. Used a chain fall and broke a 1/2" Samson rope. Couldn't pull through this. They had re-paved the machinery parking lot over the weekend and put all of the machines back on the lot. I questioned why they repaved the lot. Oh, there was a big puddle in the middle so we milled it down and regraded before repaving. I guess it had been cut down before, the 3" rigid with four 4/0s was only about 6" down from the surface.
157441
157442
 

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Discussion Starter · #29 ·
Update for today:

We temped in some groundwater pumps that were fed from this pool feeder from a nearby rooftop panel. We also ran our locator over the feeder wiring path, it's mostly straight, we could not find any j-boxes, handholes, etc.

We put a shop vac on it again and attempted to suck a bag and string through just to see if it would slip by the wiring and help us proof the conduit, made it about 50' before it would stop, which puts us under the gym floor. String and bag came out rust colored and wet.

Looked into running a new conduit. I think boring is out. Running overhead, is not good. We'd have to penetrate the roof and then cross a curved roof for half the run, then transition to the side of the building with all sorts of trim, flashing, and delta rib siding creating issues with finding a spot to secure the conduit.

I also put some thought into using some of your guys ideas. Pouring Polywater Cablefree down the pipe and blowing it through with a trailer air compressor. Then fabricating an A-frame support with a chain hoist to keep constant tension on it.

I proposed both ideas to the school district as well as the costs and they opted for trying the Polywater and constant tension over running new conduit. At least for now. They said they are talking about demo'ing part of the building for a future remodel where the new overhead conduit would have to run, and didn't like the idea of having to do it over again.

So as it sits, the A frame is being built by a local fabricator tomorrow, Polywater should be here tomorrow or Friday, 4 gallons of it. I asked the fabricator to make the A frame stout because I'm going to be using a 5 ton chain hoist. He said no problem. We are planning for Mon or Tues. I'll try not pull wires in half this time....

Just for the record, we've had a representative from the school district on site the whole time we have been there investigating. All of this work up to this point has been done with their approval. Honestly, their guy on site has been right there helping us get this figured out.

I figure if we can get this thing set up with tension on it, the school district can check the tension periodically themselves and then, if we are lucky, call us and tell us it has broken loose one day. We have some time until school starts, so we can let the Polywater do it's thing without being in a rush.

So we'll see how it goes.
 

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Update for today:

We temped in some groundwater pumps that were fed from this pool feeder from a nearby rooftop panel. We also ran our locator over the feeder wiring path, it's mostly straight, we could not find any j-boxes, handholes, etc.

We put a shop vac on it again and attempted to suck a bag and string through just to see if it would slip by the wiring and help us proof the conduit, made it about 50' before it would stop, which puts us under the gym floor. String and bag came out rust colored and wet.

Looked into running a new conduit. I think boring is out. Running overhead, is not good. We'd have to penetrate the roof and then cross a curved roof for half the run, then transition to the side of the building with all sorts of trim, flashing, and delta rib siding creating issues with finding a spot to secure the conduit.

I also put some thought into using some of your guys ideas. Pouring Polywater Cablefree down the pipe and blowing it through with a trailer air compressor. Then fabricating an A-frame support with a chain hoist to keep constant tension on it.

I proposed both ideas to the school district as well as the costs and they opted for trying the Polywater and constant tension over running new conduit. At least for now. They said they are talking about demo'ing part of the building for a future remodel where the new overhead conduit would have to run, and didn't like the idea of having to do it over again.

So as it sits, the A frame is being built by a local fabricator tomorrow, Polywater should be here tomorrow or Friday, 4 gallons of it. I asked the fabricator to make the A frame stout because I'm going to be using a 5 ton chain hoist. He said no problem. We are planning for Mon or Tues. I'll try not pull wires in half this time....

Just for the record, we've had a representative from the school district on site the whole time we have been there investigating. All of this work up to this point has been done with their approval. Honestly, their guy on site has been right there helping us get this figured out.

I figure if we can get this thing set up with tension on it, the school district can check the tension periodically themselves and then, if we are lucky, call us and tell us it has broken loose one day. We have some time until school starts, so we can let the Polywater do it's thing without being in a rush.

So we'll see how it goes.
Nevermind constant tension. It's hammertime.
 

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Assuming you free the wires, and clear the conduit with compressed air and maybe some sort of pig, would using tray cable or the fabled Teck be an option? We know that the inside of the conduit will be rough at best from rust and a hard fault to ground. The TC, or Teck would provide additional protection from wire rattle in rough places in the conduit.

The idea of using a thumper may work used in conjunction with the A frame hoist.

Hopefully the A frame can be knocked down for ease of transport, and can be widened to straddle a pickup to load things in the shop when you are done with it at the school. With some iron casters, you may be surprised how often you'll be able to use it at other job sites picking up gear and rolling it around.
 

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Discussion Starter · #32 ·
Assuming you free the wires, and clear the conduit with compressed air and maybe some sort of pig, would using tray cable or the fabled Teck be an option? We know that the inside of the conduit will be rough at best from rust and a hard fault to ground. The TC, or Teck would provide additional protection from wire rattle in rough places in the conduit.

The idea of using a thumper may work used in conjunction with the A frame hoist.

Hopefully the A frame can be knocked down for ease of transport, and can be widened to straddle a pickup to load things in the shop when you are done with it at the school. With some iron casters, you may be surprised how often you'll be able to use it at other job sites picking up gear and rolling it around.
I had the same thought. I need to try and use a cable/wire with DB insulation, whether it's USE, pvc coated MC, tray cable, etc. Verifying with a megger after installation will also be done.

The A frame is being built specific for this job, it's only going to be about 7' tall, may never get used again. Just tall enough to fit a chain hoist and some wiring under it. I mentioned to the fabricator I'm not trying to hoist items to great heights, I just need to move some wire 6" to know I've got it loose. So he's fabbing something up quick and simple.
 

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Assuming you free the wires, and clear the conduit with compressed air and maybe some sort of pig, would using tray cable or the fabled Teck be an option? We know that the inside of the conduit will be rough at best from rust and a hard fault to ground. The TC, or Teck would provide additional protection from wire rattle in rough places in the conduit.
Armoured Teck90 would not be pleasant to pull through any 90s.
 

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The A frame is being built specific for this job, it's only going to be about 7' tall, may never get used again. Just tall enough to fit a chain hoist and some wiring under it. I mentioned to the fabricator I'm not trying to hoist items to great heights, I just need to move some wire 6" to know I've got it loose. So he's fabbing something up quick and simple.
Pictures please. .... Pretty Please! :)
 

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Armoured Teck90 would not be pleasant to pull through any 90s.
Is it doable with a tugger? Until I joined here I had never heard of it. I honestly wish I had it available to me as r-mix plants, especially old ones, would be a great place to use it.
 

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There have been lots of great ideas to get the wire out.
However I wonder if I would use a conduit that has so much damage done to it?
Short of re-honing the length of the conduit. How are you going to be sure that when you pull in the new wire you will not damage it? OR worse 13 months down the rode when there is a big load on the cables. An inspection camera would go a long way for peace of mind.
Might be time to consider the new relining of pipes like they are doing for sewers here.

I understand your situation, I would not even consider using the conduit. This is a school and your good will in the area.
 

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Tool Fetish
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We only pull USE-2 conductors underground, never THHN or THWN. USE-2 is a tough insulation. It's a b--ch to skin in winter but we deal with it. I just purchased the new Dewalt potato peeler, will try it out on the next project.
 

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Is it doable with a tugger? Until I joined here I had never heard of it. I honestly wish I had it available to me as r-mix plants, especially old ones, would be a great place to use it.
Maybe, but you risk ruining the cable if the pulling gets too tight. If the armour comes apart it might damage the cable.

Since it is supposedly a relatively straight run, if I were able to get the old conductors out, I would maybe dig down wherever I could on either end and eliminate the 90's if possible, even if it meant a new route from the edge of the building to the equipment. Actually, if the conductors don't come out I might still dig at either end as a last ditch effort to get them out.

If that's doable, then you don't even need teck, ACWU would be much cheaper.

I would camera it before I tried pulling anything though. AND pull something the same size as the cable through first, just to make sure.
 
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