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TIG welding copper boilers.

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Andrew Tinsley06/08/2017 21:02:03
987 forum posts

Over the years I have made 7 or 8 copper boilers fom 3.5 " gauge to 7.25" NG beasts. All silver soldered and still running.

I have now got my old US built, professional TIG welder going, at long last. Browsing over some TIG welding topics I found that the process was now used to weld copper boilers (model variety). This set me thinking, I have more or less given up making larger size boilers as I can no longer readily take the intense heat given off in the process. A case of old age!

Now I realise that TIG welding copper will still be warm work, but nothing like a couple of big Sievert burners going full blast plus oxy-acetylene gear. It would have been a coke hearth and blower bellows, but coke isn't so easy to get these days!

So is TIG welding a copper boiler, as an amateur a going proposition, or is it limited to those with a current "ticket"?


Ady107/08/2017 00:05:20
3583 forum posts
514 photos

I would give it a go if I had the gear, nothing worthwhile is ever easy

I've been waiting years for a "newer" way of doing boilers to emerge, the standard system sounds like a nightmare

The downside is copperwork can be so expensive if it turns out to be not practicable

No doubt there will be somewhere on a US website trying to pioneer this kinda stuff, it sounds a very new approach

(Puts me in mind of the first micro diesel which came out of Switzerland in the 30's or 40s)

Edited By Ady1 on 07/08/2017 00:18:53

John Baguley07/08/2017 03:33:34
452 forum posts
48 photos

Your biggest problem will be getting it tested if you want to use the boiler in public. The average club boiler inspector won't be qualified to test a welded copper boiler and probably won't touch it with a barge pole, especially if it is welded by a non coded welder. You are going to be looking at having it tested by a relevant professional tester at possibly considerable expense.

Good luck if you do decide to go ahead though.


Edited By John Baguley on 07/08/2017 03:34:13

Circlip07/08/2017 10:08:02
1045 forum posts

Bottom line is always going to be insurance. One of the unfortunate results of disposable income and "cheap" machinery is that while SOME are capable of making a better fist of welding, others "glue" bits together and slap a coat of paint over it and it LOOKS fine.

Even with a small claim your friendly insurance company squirm when giving rather than taking. At least with a coded weld person carrying out the work you have a bit of paper certifying work integrity.

Regards Ian.

JasonB07/08/2017 10:18:17
17313 forum posts
1865 photos
1 articles

Really comes down to how good your welding is, as Fizzy on here has shown boilers can be tig welded at home and the welds commercially tested for a very modest sum and then if your club inspector is willing to accept these test certs then you should be OK.

In Fizzy's case he used to be a coded welder and did it with a steel boiler, copper being more of a challenge due to the current needed.

Nick Jarmany26/03/2019 10:15:42
1 forum posts

Guys, Interesting thread. You all seem to be talking about Tig WELDING boilers, but how about using the Tig process to braze? SifBronze type filler. Surely that would be no different from a construction/testing viewpoint as a gas silver soldered boiler?

Has anyone tried Tig brazing a copper boiler?

Regards, Nick

FMES26/03/2019 11:34:28
602 forum posts
2 photos

I've TIG Brazed a couple of copper boilers, but you need to put the same amount of background heat in as normal the TiG unit was used as I didn't have any Oxy-acetylene handy at the time.

The TiG arc is very localised and braze / silver solder won't run into a flange properly unless background heating is used as well, and its quite easy to melt the copper if you're not careful.


CuP Alloys 127/03/2019 09:36:28
226 forum posts

Brazing relies on capillary flow between two closeiy adjacent components.

That requires a temperature difference within the joint to promote it. Otherwise the filler metal will not penetrate.

The common result is that you succeed in partially blocking a hole, not filling the joint and leave a crack in the back of the joint.

If you want to weld then weld. Design your joints accordingly. Don't mix your apples and pears!

It's like trying to achieve the combination of performance and economy from an internal combustion engine by mixing diesel and petrol!

Good luck trying to braze and using a TIG torch.


Andrew Tinsley27/03/2019 10:56:11
987 forum posts


It was never my intention to braze or silver solder using TIG! I was interested in TIG welding a copper boiler. At my age I will probably buy a commercial boiler!


SillyOldDuffer27/03/2019 11:34:27
5365 forum posts
1090 photos

Just a thought, but if welding why Copper?

I think Copper is a very sensible choice for a model boiler because it's relatively straightforward to make and inspect a corrosion resistant pressure vessel adequate for the relatively low-pressures and temperatures involved. The skills and equipment are within amateur reach and the technology is well understood.

Grown-up boilers are never made of copper because they aren't strong enough. Instead, welded steel is used. Made and maintained properly steel boilers comfortably out-perform copper but they aren't easy to make 'properly', and in model sizes corrosion and difficulty inspecting the insides introduce a serious risk of failure. It's much harder to control the chemistry of small boilers run infrequently with indifferent feed-water plus problematic drying out and storage. I feel steel isn't a good choice for model boilers (mostly).

How about making a boiler from Titanium? Stronger than steel, corrosion resistant, and it can be TIG welded. I suspect the main problem would be proving the approach is safe in the absence of a well-established track-record.


Andrew Tinsley27/03/2019 12:45:48
987 forum posts


Take a look at the cost of Titanium, you might just change your mind.


JasonB27/03/2019 13:00:21
17313 forum posts
1865 photos
1 articles

Dave, some full size locos have copper boiler well at least the fireboxes are copper.

Also depends a lot on your Model, steel is the norm on traction engines 4" and above even some 2" ones and also quite common on things like the larger gauge NG locos

Edited By JasonB on 27/03/2019 13:14:46

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