Obstruction in 3" pvc feeder

[cjownby]

Anyone have any ideas for clearing concrete out of a 3" pvc conduit? We've tried muuratic acid but it evaporated after a few days and the obstruction is still there. To make matters worse..these guys pulled a rope through with a rag attached to it and it snapped...so now the obstruction which i believe is concrete, is now accompanied by a 1" rope with a knot in it and a hand towel. This pipe is part of a parallel run to an emergency backup generator and is encased in a duct bank.

 

[Geordie Spark]

Anyone have any ideas for clearing concrete out of a 3" pvc conduit? We've tried muuratic acid but it evaporated after a few days and the obstruction is still there. To make matters worse..these guys pulled a rope through with a rag attached to it and it snapped...so now the obstruction which i believe is concrete, is now accompanied by a 1" rope with a knot in it and a hand towel. This pipe is part of a parallel run to an emergency backup generator and is encased in a duct bank.

Is there any chance of battering it out with a scaffolding pole?

assuming it's a straight run of course.

 

[cjownby]

Its right after the 90. So we cant directly hit the obstruction. We can bend a peice of 3/8 threaded rod and get in down there but its not heavy enough to actually break it.

 

[Knobhead]

Time to set to with the windy pick then.

If you could have caught it in time sugar will stop the cement setting. Then it can be washed out.

I’ve got to ask, how did you get cement in it?

 

[cjownby]

The windy pick? Haha whats that?

To be honest I think it may have been sabatoge. We fired a guy who was on drugs about a week before and we already had a string in the pipe. So I think it was clear until maybe a few days after trying to pull the wire in. The rope snapped when we attempted the wire pull. Then they thought they could clear it out by pulling the rope through with a rag on it. So now thats stuck as well. Im open to any and all suggestions. Has anyone ever heard of using blasting caps? I know its a pvc pipe but it is encased in concrete. Ive seen people use it on rigid conduits but never on pvc. Im just running out of options and it needs to be done yesterday.

 

[trev]

The windy pick? Haha whats that?

Pneumatic drill

 

[cjownby]

Gotcha. Im gonna look into that now.

 

[davesparks]

I’ve got to ask, how did you get cement in it?

I believe the normal method is to wind up the groundworkers responsible for burying the ducts, a surprisingly easy thing to accomplish.

Personally I have never had a problem as I always make a point of making friends with them all but I have seen it far too many times where people go in with a chip on their shoulder and a 'i'm better than some poxy groundworker' attitude.

 

[cjownby]

Well in the states, atleast in florida. The electricians who do the groundwork also work on the rest of the project. However on this project, most of the guys who were here for the underground portion of the job have moved on or been fired. This is the worst underground electrical job I have ever encountered. Nearly 50% of the underground conduits are clogged, broken or in the wrong spot. This is a huge 2 year long project in sarasota, fl.

 

[mhar]

Ultrasound (as in used to shatter kidney stones)?
High pressure water jet?

 

[Geordie Spark]

Its right after the 90. So we cant directly hit the obstruction. We can bend a peice of 3/8 threaded rod and get in down there but its not heavy enough to actually break it.

Then unless you can find a rat with very sharp teeth you're ducked.

I'm wondering though if such a thing as a core drill with a flexible shaft exists ....

I used to make core drills and the rigs to drive them almost 40 years ago and flexible shafts were something that was discussed but that was as afar as it got. Maybe things have changed now?

 

[cjownby]

That sounds like what we need. Just not sure if that's a thing. Im gonna get with one of the plumbers here later and maybe they can do us a favor.

 

[jaypp]

Can you put a camera down first to see what you're up against?

 

[Marvo]

Plumbers have a rotating drain clearing attachment they can use to break up loose bricks and concrete that gets stuck in drains. Not sure if it would work on a solid plug of concrete though.

The other option is chemical, spirit of salts will dissolve concrete of any MPA rating but it's not environmentally friendly and you need gloves, apron, mask etc if you work with it. You'd also need to flush out any other chemicals you've thrown in there first as well to prevent any unwanted reactions.

 

[Slowhand]

years ago I worked on the Butlins refurb in Bognor. The groundworkers had put the brick chamber in the ground with ducts leading off from it to each kiosk in the skyline pavilion and the usual blue 6mm rope to pull the cable through. lovely job all finished with patterned blockwork and fancy coloured tarmac on top of it.
Problem was when we tried to pull the cables through we found out the ducting in the chamber and the ducting at the kiosks were only a couple of metres long. There was no ducting at all between them. Big Oops!!
The groundworkers had been paid and were long gone.
It all had to be dug up and re-done.
There was some choice language that day

 

[edexlab]

Might be a long shot but what about a mole ...not a well trained rodent but the type used for running cables/pipes ......
You never know until you try...
it might be possible to break up the concrete or even just move it to the other end where digging down might be an option

 

[cjownby]

Thanks for all the ideas and responses. Ill let you know what actually works.

 

[Darkwood]

Push some cheese down one side and seal the end temp' then at night the rats will go down the other side and chew through the concrete to get to the cheese..... ps use a smelly cheese for faster solution.

Don't say I didn't help yer

 

[Engineer54]

I too have to ask how a plug of concrete got into the pipe too?? This sounds like a joint has partly parted during the pouring of the concrete, which means that no PVC adhesive was used when the duct was being erected. In all the years i've been responsible for the laying of underground cable ducts, i can only recall one such instance where the adhesive was overlooked on one joint after a measuring mock up was conducted, prior to being installed permanently....

As far as i can see, it's all down to spades and jack hammers, but then i've never used chemicals, and quite honestly be very reluctant to use them as residues will remain in the ducts no matter how much flushing is carried out, .....that's if flushing out is even an option!!!

 

[cjownby]

It could have gotten into the pipe when the walls were being poured. In the states, when erecting erecting exterior block walls, cells of the block walls with steel rebar are filled with concrete. If the cover on the end of the pipe wasn't strong enough or had come off due to weather or anything else, the concrete could fill the pipe. The crews here that do the concrete pouring are usually immigrants that dont speak English and dont understand the consequences or dont care.