Clogged up conduits inside tank foundation
Clogged up conduits inside tank foundation
(OP)
Hi all. We have been tasked with replacement of old heating cables pulled through conduits embedded in the foundation of storage tanks (for preventing frost heave). However, these conduits (3/4") are ancient and in many places clogged up. Just pulling out those old cables has proven to be impossible. Anyone face something like this before? Any ideas on how to clear this mess up? Thanks in advance.
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
Tube material?
Tube ID
Length of Tube?
Cable OD
Type of insulation?
How old is "ancient"?
Might be better in the storage tank forum.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
Are you sure that the conduits are continuous?
Some installations may use direct burial heating cables with lengths of conduit on the ends for mechanical protection.
If continuous, try very high pressure water, left pressurized all day.
If removing the cables is impossible, abandon in place and use directional drilling to install new cables.
Consider perimeter cables installed down to below the frost line, and one or two cables under the tank.
The under tank cable does not have to be in contact with the tank.
If the conduits are electrically continuous, you may be able to use low voltage to drive a current through the conduits and use the conduits as heaters.
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Ohm's law
Not just a good idea;
It's the LAW!
RE: Clogged up conduits inside tank foundation
Is that where the job is?
I wasn't aware that freezing was an issue in Kuwait.
Are you sure that the cables are not cathodic protection?
Kuwait?
Not serious. I've been in Central America and have been reported as located in Virginia.
(I wonder if I am on the Company's radar .)(Common abbreviation of a Spanish translation)
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
RE: Clogged up conduits inside tank foundation
The cables are indeed heating cables pulled through continuous conduits. Yes I am based in ME and I have encountered this exact problem in two other sites in the region (current site being in Iraq). Pressurized water might be the way to go; we will give it a shot anyway.
RE: Clogged up conduits inside tank foundation
Any idea which direction they were installed? Going the same direction as installation might be a good idea.
Some sort of very light oil or maybe bentonite could be better.
But from your data you have a max annulus of 4mm? That's not a lot. But is there any sort of tubing you can find that can squeeze into the gap?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
Do both ends and then see?
Photos always help.
Of course if your foundation has cracked or settled a bit of you had frost heave in the middle of the slab then the tubes might be crushed or broken?
Kind of curios as to why you're replacing them if they haven't worked for a while? The damage has already been done?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
The last one I worked on did not even use heating cables.... just long lengths of 14AWG copper wire with XHHW insulation connected directly to the power source. In that one, the conduits did to straight across the pad to junction boxes on the outside of the pad at each side.
RE: Clogged up conduits inside tank foundation
Seal the ends to prevent the ingress of dirt.
I sometimes see small cavities plugged by insects building nests.
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
RE: Clogged up conduits inside tank foundation
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
Are they equally spaced across the tank so that some are shorter than others?
Start with the shortest and see what happens.
Then pull one to destruction / yield and then start flushing water / oil etc from the now broken end? At least it will be a lot easier to attach a pipe coupling to and then pull from the other side.
Or at least if you then drill it out some of the cable will be gone.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Clogged up conduits inside tank foundation
Dodger_Fan123 We had some difficulty but not a lot. The conduits in the one I worked on were 3/4" rigid conduit and where we could not pull the existing wire out, we were able to force a 1/4" spring steel fish tape through to open it up enough to flow water through. The water was to force out as much debris as possible before replacing the 14 AWG conductors. As I recall the diameter of the tank pad was about 80', but it was 30+ years ago.
RE: Clogged up conduits inside tank foundation
A couple of years ago, a long distance water main was installed alongside of the highway in front of our home.
They used horizontal drilling for distances of about 1/4 mile.
They are able to hit an access pit 1/4 mile away.
It was cheaper than trenching.
Explore this web-site:
https://www.directional.ca/
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
@littleinch
Rough pic attached (its a crude representation in ms paint, sorry!). The only places where we can actually see the cables are the pull boxes located on the foundation edges; rest of the conduits buried in the foundation. its a single run cable starting from jb 1 until the end.
@resqcapt19
We are putting forward to our clients this exact method! We will first try to run a fish wire and see if its gonna work; clear the conduits one by one. We will need tank shutdown so its a while away
@waross
Drilling on the foundation is a no-no since there is a chance to affect structural integrity.
RE: Clogged up conduits inside tank foundation
Then at least you could try pulling ot the yield force then relaxing and trying the other way, then relaxing and....
A bit of pull / push often works, especially if you can inject or force in some sort of lubricant - water, light oil, drilling fluid.
Clearly those middle runs are the worst but start on the short lines and see what happens.
Is each end a pull box and you can get to them or something else?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Clogged up conduits inside tank foundation
RE: Clogged up conduits inside tank foundation
Are there three separate cables or one multicore?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Clogged up conduits inside tank foundation