Demolition Method To Spare Embedded Conduit In Concrete

Do you know where the conduit is located?

All in a trench?

Helter skelter?

Don't have a clue?

to answer your questions in order:

Yes, approximately, we think. We will be having a ground penetrating radar company come out to survey the site to verify what our old manual, undimensioned drawings are showing.

Some, we think (the drawings really aren't all that terribly clear on this point.) but not all.

Somewhat... The MCC room feeding about a third of the mill is directly behind the piece of equipment we need to replace and the conduits are running pretty much all over that end of the mill in multiple directions. At this point finding a spot to do a core drill for a soil compaction study that won't risk cutting a conduit is going to be a fun exercise in of itself.

Without knowing what the conduit's materials are, it is impossible to offer anything other than a WAG. Some fluids will attack certain materials and some won't.

• When the concrete is reinstated, consider using cableways and traywork as part of the design and not installing conduits.
• What is wrong with running temporary bypass cables outside the foundation so as to keep whatever equipment needs to be sustained running while the existing foundation is destroyed?
• What is wrong with running the final replacement cables outside the foundations altogether?

Good Civils design can save the Electrical designer a lot of heartache; both disciplines need to work together during the detailed design phase of any project.

while I do not know this for certain, most of the conduits I've found out there so far have been rigid metallic conduit. If I had my 'druthers, I'd run the stuff in the overhead with drops going where it needs to go but the stuff originates in the MCC room and it all exits through the foundation so there would have to be a huge cableway intersecting the cable trench and taking it into the overhead. major undertaking and the powers that be will likely nuke that idea. The mill will be shut down while we make our upgrades (it will be done during a scheduled mill upgrade outage) so we don't have to jury rig a temporary bypass to stuff.

Okay you sure the conduit is in the concrete and not ran under it? That's how we always ran it. It was buried in the soil under the pad.

If it is in the concrete. Locate it. Use wet saw to isolated it from the rest of the surface of the pad that you are replacing to make the foundation for the new machine. Just pour around it.

Ultrasonic was first in my mind, but not to be.

You might look at these:

Hydrodemolition Company, IVS Hydro of West Virginia - IVS Group

RockFrac rock splitting mortar for no vibration non explosive ...

Two comments, neither one what you are actually asking for.

1) To locate conduits I wonder if you could use a speaker to inject sound or a vibrator to inject vibrations into/onto the conduit and hire a plumbing Leak Doctor to use their equipment to find the pipes (conduit)? Your GPR idea is probably better but this might be a Plan B to keep in your back pocket.

2) Is "demolish and replace the machine foundation" the only option? I assume a pad on top of the floor is not a good enough option. If the conduit is all beyond a certain depth (say 6") then could you make multiple cuts down to 6", break out this upper 6" level, insert lots of steel (probably welded together) and add a 6" pour?

I know #2 has the word "if" in it a lot. Since it seems like you might not be able to do what you want to do then it is worth considering what you don't want to do.

As a side note it would be interesting if you took pictures of the GPR tests and posted them with some comments. I have seen ground penetrating radar on TV but I don't know what capabilities are available or what the costs are. I would also love to know what frequency and power level they use.

I was going to suggest a plumber for doing tracing, don't know what the conduit material is .... or the size of it. I just had to do it an one of the plants where I work. Fortunately it was not heavily populated with under ground conduit.

But I would suggest that the OP start doing some planning on keeping the other equipment(s) running or down time, as well as contingency to mitigate the unexpected..... sounds like he'll be pretty busy.

It's kind of hard to envision conduit run through a massive foundation. I'll just relate this anecdotal experience. We had a fairly massive (roughly 10' x 10' x 10') foundation for a turbine and recip compressor that needed to be removed for new equipment. Hired an explosives contractor who drilled and blasted with C4 - in stages. I remember the re-bar being left clean and straight enough that it could have been re-used. This was done near an operating petrochem unit. If you could blast it, it might leave your conduit in place.

Maybe water-abrasive cut?

This is not an answer to removing the concrete, but might help to locate the conduits. IR cameras would be able to see the added heat from the power cables. Any conduit that does not have power running through it could have hot air blown through it to add heat. Plumbers that do underground leak detection have different methods to locate PVC pipe underground. Hope this helps some.

One crude but effective method is to get a mechanic's stethoscope and a pneumatic ball vibrator. Clamp/bolt/firmly secure the vibrator to the piece of conduit you want to locate. Starting with a low frequency operate the vibrator and listen to the pad with the stethoscope for the loudest locations of the vibrations, taking distance from the vibrator into consideration. The loudest points forming a line is the conduit location. Increase the rate of vibrations if necessary.

This can also be done with a screwdriver and a thumb on the top of the handle instead of the stethoscope. Put the handle-thumb end up to your ear with a little force against the ear and put the blade on the concrete pad. Same thing, listen to the loudest points.

This is the same way (without the vibrator) you can listen for bad bearings, broken teeth on a gear, lack of lubrication, broken or going broken pumps. etc It can also be used to find underground sprinkler PVC and Poly plastic piping that is buried. Put the sprinkler on and listen to the water flow.

Drill holes in the appropriate locations and use the expanding mortar materials previously mentioned to break up the concrete. Very little or no damaged conduit. If any is broken it was probably not installed correctly or was old and not very strong.

Good Luck, Old Salt

Is it reasonable that underfloor conduits would loop up under machinery pads?

Here is another link to a chemical concrete cracker:

http://www.dexpan.com/dexpan-how-to-use-dexpan-non-explosive-controlled-demolition-agent-breaking.aspx

That stuff looks awesome.

Hi Rorshach,

There are several companies with water jet systems that makes water jet cutting gear that supposedly can be set to cut or not cut embedded steel (see below) This is one I pulled off of Google for a basic concept.

Good Luck in whatever you have to use,

Expat 007

Concrete Demolition

With 20 years experience in industrial cleaning Hydrojet Systems are capable of tailoring solutions to unique applications.

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• Hydro DemolitionHydrojet Systems use high pressure water jets to demolish and remove concrete while not damaging the rebar. Our method is mainly used to remove concrete from sensitive structures, such as dams, tunnels, turbine linings, bridges, parking decks, harbours and docks for repairs. The variable parameters of the technique, water pressure, jet size and speed of application, make it possible to remove concrete in a very precise and controlled way.

I imagine the conduits installed before the machine base was poured would have been below floor level. Thus the block can be sliced off at floor level without harm to conduits below the floor. Only the conduits feeding the machine will protrude up into the block - and does it matter much if they get damaged when the block is removed.

I like HiTec's idea for splitting the concrete.

It sounds like you're already committed to spending a lot of money to solve the problem. How about dozens of low-wage laborers with PPE, hammers and cold chisels?

Can you just pull the wires out, mark them, destroy everything, and pull them through new conduit before the new pour?

I also think there might be a chance that you will spend more money trying to protect the old stuff, as it would cost to just tear it all out and put in new.

Just to clarify a bit, some of the existing foundation is just a slab, but other parts (the machine bases) go some ways down, and all have coolant trenches in them. (this is a pipe mill). our drawing is pretty clear on where the stub ups are, but no data I've seen on depth of conduit or whether they are in trenches or ducts or below the slab, or embedded in the slab. prior work has found other runs IN the concrete, so we cannot discount that possibility. GPR will give us some guidance on that I expect as well as fairly precise locations of the routing. (all we have now are approximate routings.) I'm not sure about hydraulic fracking/blasting sparing conduit. I can see it sparing rebar since solid bar is just that, solid, and not likely to collapse. Conduit, being thin wall and hollow probably would collapse I would expect.

You are correct about the conduit.The proper way is to bite the bullet($) and do it

properly,with temporary service to the equipment while the new concrete and conduit

is installed.

Even if the conduit did not collapse,it could pinch the insulation internally,causing a

delayed failure.This could come back and bite you in the arse later with liability

issues.

I do not believe the local Authority Having Jurisdiction would approve of re-using the

conduit anyway.

This may be off topic,because you asked how to do it, not if you should do it or not.

Hi Rorshach,

Did you ever do the upgrade, and what method and success/ failures did you have when you did it.

To cop a phrase.... Enquiring minds want to know-- It might help some of us in the future when faced with a similar problem.

Best regards,

Expat07