TIG welded copper boilers

Again this concerns a 5" gauge locomotive.

How do TIG welded copper boilers compare with traditional silver soldered boilers? What are the advantages and disadvantages?

JA

As an ex coded welder and boiler maker I have made a few with tig. The main advantage is that there is no phlanging required. Its a lot easier to set up and a lot cheaper to build. There are no downsides other than they look different. On the other hand the welder is very expensive - think minimum 500 amp water cooled industrial - nothing that you can buy at machine mart! You also know that every joint has the penetration you have put into it.

Cost mainly. Silver solder is expensive so a professionally made boiler TIG welded is cheaper in materials.

Here is the firebox of my 5" King

regards Martin

Fizzy -

I believe the copper has to be a "de-oxidised" grade for welding, could you confirm / explain / correct. please?

Hi Nigel,

You are right about using oxygen free copper for welding, more info here.

Thor

Most copper sheet/tube on sale to model engineers will be C106, which is claimed to be OK for welding

Hi Nigel, I've yet to come across a piece of copper I couldn’t weld. Most copper nowadays is suitable for welding, and I have never had any issues (if the copper contains enough oxygen you'll get porosity in the weld so you’ll pick it up very quickly). I’ve even done some minor cosmetic repairs to my copper castings using TIG.

I have a normal DC welder (200Amps) and have never had power input issues with the boilers I’ve welded. Interpass and preheat temperature should be kept to above 400DegC, and as with silver solder you need to insulate the boiler to prevent excessive heat loss. My humble opinion: if you can build a fine model, TIG welding copper is easy…

Cool

What's the best way to preheat a big copper boiler without oxidising it as a gas torch would ? An oven?

I just use a gas torch, so does heavy industry. Shouldn't really be moving a chunk of copper at that temperature; not much mechanical strength for moving. It doesn't seem to be an issue with CuO reducing relatively easy. Interestingly if you watch copper melt in a furnace it melts like ice, where brass or LG tends to leave a shell which needs to be skimmed.

By that I assume you don't back purge by filling the barrel with gas?

I design the joints so that back purging isn't necessary.

Not wishing to stir up a hornet's nest, but I think anyone contemplating welding their own copper boiler should speak to their club's boiler inspector first. The SFED rules on testing say

An Inspector acting as a competent person who carries out an examination under the Written Scheme of Examination shall have such sound practical and theoretical knowledge and actual experience of the type of system which is to be examined as will enable defects or weaknesses to be detected which is the purpose of the examination to discover and their importance in relation to the integrity and safety of the system to be assessed

which implies that the inspector should know about copper welding and possible defects. Not all will. Don't get me wrong, welded boilers are fine as long as stuck together by someone who knows what he is doing.

I would encourage all model builders to constantly try new manufacturing methods and techniques to improve the hobby and hone their skills! The boiler inspectors should follow suit, and if needs be, up skill...

Many thanks for the replies.

I am not intending to make the boiler myself but to get it made commercially. So far I have found four firms that can make it, two using TIG welding and two silver soldering. The head of boiler inspection at my local club said that TIG welding is considered too new a process by some.

I have yet to make any decisions.

JA

I am not a welder but I agree that It is about time we moved forwards on TIG. Just a quick google says that TIG has been around since the 1940s. So it might be new to the Victorians who first built steam locomotives but it is not a new process.

Phil H

Agreed, if you turn up with a commercially built boiler and a proper welder cert for the bloke who built it there should be no problem, time for some SFED guidance. If it's commercially built then whatever has replaced CE mark will require welder certs, so there should be no issue. It only costs pennies to photocopy the cert. Problem comes with home built.

The big railways used to weld repair copper fireboxes with oxy acetylene. That must have been heroic. I believe they had one bloke inside and another outside to get a balanced setup. Bags I be the outside man!

Not SFED but MELG guidance, otherwise we'd run the risk of one Federation's boiler-admirers saying the opposite to another's.

However, since commercially-made copper boilers have been advertised in ME for quite some while now, and obviously made to the CE / new UK version rules, there should be no problem with any UK MES' boilder inspector accepting one of those.

It would be home-built boilers that might be awkward because a club boiler-inspector may understandably consider him or herself not sufficiently experienced in examining such construction, so decline to inspect it. Not necessarily anyhting wrong with the metalwork, just amateur boiler-inspectors recognising their own limitations.

It is an area that should be examined, not put aside as "not invented 'ere, Guv '! " .

'

Incidentally the original EU Directive that gave rise to all this hoo-ha, actually mentions only two materials, of unspecified grades, for any type or pressure-vessel: stainless-steel and aluminium! As far as safety goes it waffles on about qualified welders and the like but says of the design little more than that "it has in fact to be safe".

It did not say that anyone need complicate the paperwork as confusingly as we've only gone and done. The only physical things new compared to our hobby's former, simpler system are tighter rules on steel boilers, rules for the garden-gauge scales, more sensible test-pressure factors and test-intervals, and the WSE - notionally straightforward but buried in a right swarf-bucket of paperwork and handbook!

I have very little respect for certifications and markings. Exceptional designers and builders very seldom make good bureaucrats and I have yet to meet a bureaucrat that can do anything other than talk.

We had a CE UK professionally built Romulus boiler that one of our members imported with all the necessary paperwork. I had a look at it and wasn’t impressed with the welds; as a general rule you don’t TIG weld hot rolled boiler plate without the correct prep-work. It lasted a few runs and failed (quite badly) in the firebox. The supplier was of course very distresses, sorry and would fix it free of charge as long as shipping was covered by the buyer, and another two years waiting; the normal BS (bureaucrats speech). I made the comment that if they couldn’t do it with clean plate there was no chance of them fixing a steamed boiler. He eventually decided to have one of our builder’s fix it and it’s been running ever since (think it cost a good bottle of something nice!).

Lucky for us our boiler inspector is a qualified engineer who has designed and built a few boilers and between him and the other members (who have built locos) any new members are guided through the design and construction of their boiler. In the end each boiler has walked a careful path and the data book is kept with the boiler inspector with the welding samples etc.

My understanding is the UK code [The Boiler Test Code. 2018. Volume 1- Boilers 3 bar litres to 1100 bar litres.] does not require the welder to be qualified but samples do need to be submitted to the boiler inspector to check competency, as it should be. The Australian code [AMBSC Code Part 4 Duplex steel boilers] does require a rather stringent welder qualification (AS1796 with a minimum of two years’ experience) but even there an amateur can weld his own boiler under instruction from a qualified person.

I think the O/P questioned Tig welded COPPER boilers so Hot rolled boiler plate hardly qualifies. Fizzy has given the simple answer as although Ex, at least he was coded and advised that Mickey Mouse welders and welding equipment is a no no. No doubt the O/P will be checking on the qualifications of the supplier? and yes, horror stories abound of some suppliers disasters. A mate ordered a Simplex boiler from a noted supplier in OZ and was surprised to find water coming out as fast as he could put it into it DESPITE the test certificate stating it had been pressure tested to 150psi. Although taking a bit longer and costing a bit more due to overseas postage, the company set up by a young lady in the UK supplied the excellent new one.

Regards Ian