Thermite type cutting rods

I have a diver/marine constructor friend that was going
diving to cut a propeller shaft from a tugboat. He said it
was a 10" shaft.
I have seen him cut thick metal before with what he
calls thermite rods. The rod consists of three different
diameter metal tubes that fit inside the other, they are
about twenty inches long.
From what I understand he connects a welder
and an oxygen tank to the rod. The welder starts the rods
on fire and the oxygen is fed down the center of the rod
to keep the metal burning.
My question, is the metal magnesium or some mixture of?
Are all three pieces the same?
Just curious, Mike
Reply to
amdx
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Sounds like a thermic lance to me; steel or iron rods inside a steel or iron tube fed with O2, once the iron is burning in an O2 rich atmosphere it produces colossal heat output which can melt its way through concrete, steel, you name it. I know of someone who (legitimately) cut the hinges off a bank vault door with one (or several). Martin
Reply to
Martin Whybrow
I don't believe the rod are steel or iron the are not heavy enough. I think aluminum or magnesium, but seem a little hard for those materials. Mike
Reply to
amdx
I teach welding at a commercial diving school. The rods you are talking about are properly called Exothermic cutting rods. The classic is the Broco rod.
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The rod is simply a tube of steel with a bunch of steel wires wedged inside so there is a air path down the center.
They don't actually need a welding power source. You can ignite one with a car battery. The oxygen is fed down the tube at around 125 psi. Once the end is used to strike and arc, with the oxygen feeding through the tube, the oxidation reaction of the steel is self sustaining. You end up with a blast of super heated molten steel and gasses. It will cut pretty much anything. The rods come in 18", 24" and 36" lengths.
The rods are protected on the outside by a layer of electrical tape. There are fancier rods with magnesium wires inside, but basic steel rods work fine. Some use wires and others are either nested tubes or a jelly roll structure. All work the same way.
If you do use a welding power source and are cutting steel, they will cut even faster if you run them at around 300 amps of DCEN.
We burn through about 240 lbs of Broco rod every month on our welding barge.
There is another variation of this process called a Kerry Cable. This is a long steel cable wrapped in a plastic case with an air path down the center of the cable. It works the same way as a Broco rod, but can be 100 ft long, so you just keep feeding it out as it burns back. Kerry Cable is much more popular in Europe, and at some big marine scrapping operations. It is almost never used in the Gulf of Mexico or pretty much anywhere else in the US. No real reason why, just tradition.
Arcair makes a version of Broco rod for use out of the water. They call it a Slice torch. They sell them to fire departments. I own one. I once made rods for mine by taking 1/4" steel hydraulic tube and stuffing it with gas welding wire. They worked great.
Broco also makes a tactical unit for use my military or SWAT teams. Handy for removing window cages and steel door hinges in a jiffy.
Reply to
Ernie Leimkuhler
I've made them with 3/8" black pipe with a piece of 3/8" cable hammered down the center. This also worked well. Interestingly, old ratty cable worked better than new.
John > > Broco also makes a tactical unit for use my military or SWAT teams. > Handy for removing window cages and steel door hinges in a jiffy.
Reply to
JohnM
This seems to be the correct link:
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Reply to
Curt Welch
I saw one a couple of weeks ago cutting a gear into thirds. A crane was used to pick up the gear and drop it from 40' to break apart the slag that held two parts together. Oh - the gear - it was about 8' in diameter and 4' wide. It was a cut tooth Helical type but had a flaw that was found in the cutting and it was scrap. That sucker burnt steel!
Martin Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
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Mart>> I have a diver/marine constructor friend that was going
Reply to
Martin H. Eastburn
How did they release a 8' (feet?) gear from a hook so that it could drop?
i
Reply to
Ignoramus27805
"Ignoramus27805" wrote in message news:CsGdnbsZKvAnf03bnZ2dnUVZ snipped-for-privacy@giganews.com...
Helical
scrap.
If it's a scrapping operation, they probably used a magnetic lifter
AWEM
Reply to
Andrew Mawson
Not a hook. In metal scrap yards, Electro-magnets are used.
The cutting tool was hooked to a 'propane delivery truck sized' bottle of O2. They had an on-site generator that kept the tank full of liquid ox. It likely cost a mint to get set up, but consider the pipeline of trucks needed when going through a semi-trailer of castings and other big steel.
They had Plasma for the small stuff. Used it on big stuff.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.
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Ignoramus27805 wrote:
Reply to
Martin H. Eastburn
Ernie, are there any UW welding and related texts available anywhere on the 'Net for download that you know of?
Thanks,
Pete C.
Reply to
Pete C.
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Reply to
Pete C.
Besides the sales brochures from Broco and Thermal Arc, there is only the Navy Welding manual.
The Navy Welding manual is a bit dated, but does cover UW welding and burning.
You can download it here
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Reply to
Ernie Leimkuhler
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Reply to
Martin Whybrow

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