Thermite Welding

The Junk Drawer is for those Off Topical discussions where we can ask questions of the community that we feel might have the ability to help out.

Moderators: Harold_V, websterz

redneckalbertan
Posts: 1275
Joined: Thu Nov 01, 2012 10:39 am
Location: South Central Alberta

Thermite Welding

Post by redneckalbertan » Sun Mar 30, 2014 3:41 pm

steamin10 wrote:I have a 3" high pressure gas main that runs on the North edge of my property line. Every 5 years or so, they come along with a testor, and eventually a guy digs little post holes and drops in a 16 inch bag with a copper wire, that is thermite welded to the gas main. Done. That is the protection for steel piping in the ground here.
I have been watching the railroads around here for the past few years in the hopes of seeing thermite welding done. Just wondering if anyone here has worked on a crew that has done thermite welding either on a railroad or other.

hammermill
Posts: 2938
Joined: Sun Jun 27, 2010 10:43 pm
Location: pendleton or

Re: Thermite Welding

Post by hammermill » Sun Mar 30, 2014 4:03 pm

common commercial application name is Cadwelding. IT I is used for making nonreversible electrical connections to things like tanks ground rods, fish ladders, pipelines. what the gas company is doing is attaching sacrificial anodes to steel pipeing

you can buy the ingrediants from a company named skylighter for doing things like dramatic distruction of hard drives hihi look under thermite

https://www.google.com/search?q=thermit ... d=0CDkQsAQ

redneckalbertan
Posts: 1275
Joined: Thu Nov 01, 2012 10:39 am
Location: South Central Alberta

Re: Thermite Welding

Post by redneckalbertan » Sun Mar 30, 2014 4:08 pm

hammermill wrote:you can buy the ingrediants from a company named skylighter for doing things like dramatic distruction of hard drives
I never thought of using this for hard drive destruction... I've always wrapped a ground cable around a hard drive a couple times and done a little bit of high amperage welding.

hammermill
Posts: 2938
Joined: Sun Jun 27, 2010 10:43 pm
Location: pendleton or

Re: Thermite Welding

Post by hammermill » Sun Mar 30, 2014 4:46 pm

well there you are, thermite, magnesium powder to start the burn, maybe a little mystery material to help get it going and no need to other data distruction methods.

User avatar
steamin10
Posts: 6712
Joined: Sun Jun 08, 2003 11:52 pm
Location: NW Indiana. Close to Lake Michigan S. tip

Re: Thermite Welding

Post by steamin10 » Sun Mar 30, 2014 6:15 pm

I have done thermite (cadweld is a brand name) welding. The material comes in a plastic case about the size of a 35 mm film can. You use a specially prepared copper cable that has a bronze slug on it, and clamp the mold onto whatever you are going to weld the cable to. We used it for grounding traffic light poles and street illumination lights. Some installations require it for lightning protection or simple grounding to a Earth ground copper clad rod. Much more secure than a clamp.

You fill the carbon block with the Aluminum powder, Iron powder, and something else, (I dunno) from the plastic can, and touch it off with a flint striker. It burns about 3-4 seconds, and the bronze is welded to whatever you put it on. Bump the slag with a wrench, it falls off, a good tug verifies it's on, and you're done. Takes longer to write this than doing the job.

About 3 of these duct taped to a half inch water pipe, and it will burn completely in two. (Ask me how I know). :)
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

J. Randall
Posts: 144
Joined: Fri Aug 17, 2007 6:34 am

Re: Thermite Welding

Post by J. Randall » Mon Mar 31, 2014 2:46 am

I have also used a Cadwelder quite a bit, welding magnesium anodes, and test leads to crude oil pipelines. Also took care of 17 impressed current rectifiers that protected several hundred miles of pipeline. Had no formal education in the subject, but learned quite a bit about it the hard way.
James

PeteH
Posts: 1065
Joined: Mon Jun 11, 2007 10:49 pm
Location: Northern New Jersey, USA

Re: Thermite Welding

Post by PeteH » Mon Mar 31, 2014 11:03 am

When I was a kid, the local "street-railway" (i.e. trolleycar) company used thermite to weld connections and make repairs to the rails. I saw it done a few times, but since this was better than a half-century ago, my memories of it may be foggy.

That said, IIRC they prepared the area to be welded -- not sure how they did that, but I think it involved some chisel work. Then they put a sand/clay mould around it, and over that mouldbox, they stood a thing like a tripod, with a thing like a flowerpot in it. The thermite powder went into the "flowerpot" and then some starting composition -- probably something like sparkler powder -- on top; and finally a piece of magnesium ribbon. They'd light the ribbon and "retire rapidly" because the flowerpot would shoot sparks a long distance; eventually the white-hot molten metal flowed out the bottom of the pot and into the mould.

I usually lost interest around then, so I never saw them breaking off the casing or cleaning up the weld.

I think I also saw them ignite the thermite with an oxy-acet torch, once.

BTW, a while back there was someone offering the components for thermite on FleaBay.
Pete in NJ

TomB
Posts: 446
Joined: Mon Jan 14, 2008 7:49 pm
Location: Southern VT

Re: Thermite Welding

Post by TomB » Mon Mar 31, 2014 2:37 pm

Never heard of protecting steel pipe this way. Its a good example of ignorance from somebody who should know better. I've mentioned in other posts that I have a ski mountain with several miles of steel snowmaking pipe, all of which is corroding. I've always blamed it on iron oxide that is native to the mountain gravel. (If I set a welding magnetic ground down in the sand/gravel it will have stuff stuck to it when I pick it up and I've always though that was iron oxide. Never kn ew the chemistry but assumed that iron oxide plus water leads to a slightly corrosive acid.) But this discussion of using a copper leg as a sacrificial material to slow steel corrosion makes me wonder it that is the case and also if it may be important to me to understand the cause and prevention.

Does anyone have one or more links to technical papers or background web pages on the topic? I will also plan to go and review the Cadwelder web pages.

Tom

hammermill
Posts: 2938
Joined: Sun Jun 27, 2010 10:43 pm
Location: pendleton or

Re: Thermite Welding

Post by hammermill » Mon Mar 31, 2014 4:06 pm

start with a look active cathodic protection. then look at passive systems

just about every tank farm, pipeline etc is protected by them and as one member pointed out they can spread out for miles

here is a start

http://en.wikipedia.org/wiki/Cathodic_protection



http://books.google.com/books?id=a_z_Z_ ... on&f=false

Mr Ron
Posts: 1873
Joined: Tue Dec 22, 2009 12:36 pm
Location: Vancleave, Mississippi

Re: Thermite Welding

Post by Mr Ron » Mon Mar 31, 2014 5:29 pm

63 years ago when I was 16, I messed around with thermite and actually welded a cast iron lathe spider that was broken in two. I wonder how many kids today could do that. Back then, kids did all kinds of things because we were curious. You can call it "self educated". Everything I learned, I learned by doing and making mistakes along the way. I'm sure there are a lot of old-timers out there who can agree with me. Many years later, I took some machining courses and discovered that I was doing it right all the time. That was a waste. My son is now following in my footsteps. Although he has a degree, he still realizes that the hands-on approach is the best. A smart person can learn everything he needs to know on his own in much less time than in a school.
Mr.Ron from South Mississippi

User avatar
steamin10
Posts: 6712
Joined: Sun Jun 08, 2003 11:52 pm
Location: NW Indiana. Close to Lake Michigan S. tip

Re: Thermite Welding

Post by steamin10 » Mon Mar 31, 2014 7:55 pm

On the gas pipeline that fed the house and hood here, I want it uderstood that the copper wire they welded to the iron pipe had a bag of zinc based chemicals that the wire came out of. This provided a sacrificial ground to the system, and when tests showed they no longer were of value another was placed there.

The system it supports dates from the late 40's, as far as I know.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

User avatar
mcostello
Posts: 836
Joined: Sat Jan 04, 2003 10:45 pm
Location: Lancaster, Ohio

Re: Thermite Welding

Post by mcostello » Mon Mar 31, 2014 9:03 pm

An Anode Test Station reader is what I am doing as a part time job. This month I have tested about 300-400 of them. Yearly checks of anode protection is a Federal rule.

Post Reply