Thawing frozen conduit techniques

[JayCee]

I was wondering if anyone had any recommendations for techniques to thaws out conduit that has filled with water and frozen shut? I'm looking for options that would be usable with various conduit sizes and types in temperatures as cold as -50°F.

 

[infinity]

There is professional pipe thawing equipment. I've heard of guys using a stick welder to unfreeze pipes.

 

[don_resqcapt19]

If you have a metal conduit without a lot of parallel paths, you can set up a continuous duty welder with the leads connected to each end of the conduit. If there are parallel paths because the frozen conduit it in contact with other conduits or other metal piping that creates a parallel path, you can't flow enough current through the frozen conduit. The one time we did it, it took a few hours for each conduit, but it was no where near -50°F.

Probably Rob's suggestion of professional pipe thawing equipment is best. One type uses a small flexible tube that you would insert into the conduit and pump heated fluid through the tube. Sometimes this is water but as the water comes back out of the end where you inserted the tube you have a frozen mess. Some systems use a propylene glycol antifreeze solution. This is the environmentally safe antifreeze and you will even find it as an ingredient in low budget ice cream.

 

[tom baker]

I have thawed a frozen water line with a small plastic tube, connected to hot water source, pushed in to the water line. It’s was slow going but worked. Pipe thawing would be faster. Some have thawed frozen water lines by making a tent and using heater in tent.

 

[augie47]

In that environment I think I would be looking at pressurizing my conduits once the water was removed

 

[don_resqcapt19]

In that environment I think I would be looking at pressurizing my conduits once the water was removed

If they are rigid or IMC, you really can't do that....our straight thread couplings won't hold pressure. You could get the ice melted and run air through them to keep blowing out the water, or you could fill them with an antifreeze solution.

One issue is the potential damage to the conductors after they are installed and the conduit fills with water and freezes again.
I worked on a couple of parking lots with rigid conduit and a 2' burial depth...the conductors had to be replaced every few years and I am pretty sure they were being damaged by the crushing force when the water in the raceway froze.

Also had to replace a length of fiber for the same reason. The fiber was not under a paved surface, so we drilled some drain holes in the 90s to keep the water from filling the conduit. It seemed to have worked as we did not have any more issues with the fiber in the raceway. Could not do that in the parking lot because of the paved surface.

 

[TwoBlocked]

I once thawed out a frozen drain pipe with a compressed air hose.

 

[don_resqcapt19]

I once thawed out a frozen drain pipe with a compressed air hose.

Yes the heat of compression could be enough to melt the ice in a conduit.