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Using welder to thaw conduit #61679 01/31/06 08:13 PM
Joined: Apr 2001
Posts: 507
golf junkie Offline OP
Using a welder to thaw ice in a conduit was somehting that I've read about but never acutally done. Today I had a chance to do it.

The conduits are 3/4" GRC buried in the slab of an Anhydrous Ammonia tank. The conduits carry heat trace lines that are supposed to keep the ground from heaving and destroying the slab. The job was to replace a majority of the heat trace.

Almost all of the conduits were plugged with ice. The Anhydrous stays at -20°F so even during warm weather the slab is frozen.

We attached the welder at each side of the tank and ran 400A through the conduit for about 20 minutes. That would loosen up the ice enough that we could pull out the old trace.

Also learned today that an engine driven scroll compressor will pump enough air at 100psi that you can blow heat trace out of a conduit. Make sure no one is in front of the gun barrel!


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Re: Using welder to thaw conduit #61680 02/01/06 09:42 PM
Joined: Dec 2004
Posts: 94
tkb Offline
I thawed out an 1-1/4" RGS at an asphault plant for a truck wash shack about 10 yrs ago.
After we thawed it we hooked up our blower to it and blew it clear.
There was a lot of ice chunks flying around.
Pretty cool.

Re: Using welder to thaw conduit #61681 02/01/06 11:28 PM
Joined: Aug 2005
Posts: 44
AllClear Offline
Did You Pull new Heat trace in or did You Just leave the welder hooked up!

I Have Dumped Heet down conduits to thaw them, Then used compressed air to blow them clear. We Use compressed air to Blow mice and pull strings thru conduits. it is alot easier and quicker than a vac.
Just don't forget to remind the guy on the other end to stand clear or he'll get Soaked!

It's Not The Fall That Kills You...
It's That Sudden Stop At The End
Re: Using welder to thaw conduit #61682 02/02/06 12:10 AM
Joined: Feb 2003
Posts: 939
frenchelectrican Offline

that one trick i like to use but most area it is banned pratice for safety reason in case stray current get to somewhere else and do wonderfull damage. few years ago i ran 350 amp thru the frozen pipe and a bit of stray current went to next building and got the ground rod over heated almost point to start to burn the wood off.

air commpressor do pretty good trick once you get the air flow thru my most common trick is used my truck exhaust it is hot engough to thaw out the pipes and alot of gunk fly out on oppostion end.

honestly i try to rember what link or source saying about welder on frozen pipe is big no-no.

merci , Marc

Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

Re: Using welder to thaw conduit #61683 02/02/06 06:01 AM
Joined: Jul 2002
Posts: 680
walrus Offline
HEre's another discussion about welders and thawing pipes.

Re: Using welder to thaw conduit #61684 02/02/06 07:28 AM
Joined: Nov 2000
Posts: 2,148
resqcapt19 Offline
Golf Junkie,
What was used for the heat trace? The last ammnonia tank that I worked on, we just used #14 XHHW. About a 1000' per 30 amp circuit. One end connected to the breaker and the other end connected to the neutral.

Re: Using welder to thaw conduit #61685 02/02/06 10:15 AM
Joined: Jan 2005
Posts: 5,316
renosteinke Offline
Cat Servant
That always seems to be a clever trick, until something unexpected happens.

Electricity will travel in all directions- not just toward the ground wire. Damage happens in unexpected places...someone three doors down get zapped- bad- because of a loose fitting. Several sub-panels get fried- often starting a fire in the process.

This "handyman trick" is something to be avoided.

Re: Using welder to thaw conduit #61686 02/02/06 06:05 PM
Joined: Jul 2002
Posts: 680
walrus Offline
What handyman trick??

Re: Using welder to thaw conduit #61687 02/02/06 10:53 PM
Joined: Apr 2001
Posts: 507
golf junkie Offline OP
"This "handyman trick" is something to be avoided"

So how would you solve the problem?

Re: Using welder to thaw conduit #61688 02/02/06 11:01 PM
Joined: Apr 2001
Posts: 507
golf junkie Offline OP
"What was used for the heat trace? "

It was a type of trace I hadn't used before. It used a very fine heating element wound around two insulated conductors. It's rated @ 8w/ft. Expensive stuff though at $5/ft.

There were 56 conduits beneath the tank divided into 4 480v circuits.


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