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Copper for boiler construction

How to identify grade

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Paul M14/04/2019 22:41:48
42 forum posts

Many years ago I purchased all the copper for constructing a boiler for a 31/2” locomotive. I recently began work on my loco after some years. Recent discussion with fellow model engineers raised the issue of boiler regulations and having to have certified the grade of copper. I don’t have any receipts to prove the grade. All the copper is formed, drilled and virtually ready for soldering. Am I going to have to scrap the copper and re purchase? Is it possible or viable to get the copper tested?

Paul Kemp14/04/2019 23:33:21
514 forum posts
18 photos


There was recent mention of this in another thread. Always best to consult with the tester that you propose to use for your boiler (they will likely want to see it during the stages of construction anyway if they are following the code precisely) but I think it unlikely they will want to see certs for the copper. If they do you could ask how many ME suppliers of materials provide these for copper as a matter of course! It's only really relevant for copper if you are TIG welding it to determine the arsenic content. Steel is a different matter.


IanT14/04/2019 23:36:46
1547 forum posts
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Assuming you are a member of an Association, Club or Society Paul - go and talk to your Boiler Inspector and take your materials with you. I'm sure a sensible solution can be found.



IanT15/04/2019 00:04:40
1547 forum posts
144 photos

Paul M - I believe this is the relevant part of the current 'Orange' Book (Vol1)

7.4 The Inspector shall satisfy himself:

a. That the materials used are of adequate thickness and the correct specification.

b. That, where required by the build procedure, the relevant material certificates are provided.

c. That the boiler is constructed in accordance with the design drawings.

d. That the requirements of Paragraphs 5.1 to 5.4 have been met. e. That all joining procedures have been satisfactorily undertaken and that the joints are sound. Particular attention should be paid to the penetration of silver solder and the adequacy of any welds.

For a conventional silver-soldered copper boiler being built to an accepted (e.g. known) design - personally I would want to check that the material was of suitable thickness and that the builder understood current boiler construction & test requirements. Provided I received assurance that the materials had been sourced from a reputable supplier - then I personally would be happy to agree the next build stage and schedule further inspection & tests. However, another Boiler Inspector may take a very different view and my opinion might not be held by others. Interpretation of the codes can vary.

The best advice is always to go and talk to your Inspector and seek his advice and guidance.



Hopper15/04/2019 00:40:01
4650 forum posts
101 photos

Probably easier to make new receipts than new boiler parts. wink

CuP Alloys 115/04/2019 08:39:05
240 forum posts

Hi All,

Get your brazing torch too near to some of the cheaper grades of copper and it will crack. This is caused by oxygen in the grain boundaries of the copper being converted to steam. It cannot escape and the copper fails.

It is referred to as "hydrogen embrittlement".

Avoid the risk.


Alternatively you can always blame the flux, the torch, the gas or even the silver solder!



Former Member15/04/2019 08:58:19

[This posting has been removed]

Paul M15/04/2019 09:05:53
42 forum posts

Thanks for the advice provided. Seems I might be ok or not depending on individual boiler inspector.

I am confident the copper is ok as it was purchased from A J Reeves be it before they changed ownership. Unfortunately I don't have a receipt. I will have to hold my breath and hope.

Would an older loco built prior to the tightening of regulations satisfy current testing procedures. I would expect there are plenty of them about with no proof of copper grade used?

Former Member15/04/2019 09:32:21

[This posting has been removed]

Phil H115/04/2019 09:52:16
290 forum posts
28 photos


I don't believe that you will have a problem if you go and speak to your local club inspector. You sound like you have done the best you can to control the materials etc. I suspect he will be more interested in the bush materials and the silver soldering stages. Also, please check your drawing. Many of the old drawings use threads in the plates for longitudinal stays instead of bushes. These features might catch you out.

If we start with material certification, we are heading for a minefield that you simply won't get out of e.g., most ME suppliers won't have proper QA, most self builders live at home, with a home workshop and no QA department?? Even if you had certificates, there is no guarantee that the parts are made from the same stuff. The QA issues go on and on and on and never end.

Phil H

Baz15/04/2019 10:44:18
409 forum posts

Paul M, a receipt only proves that you paid for it, a Certificate of Conformity states what material and what spec it is. My understanding of boiler regs is that you do not need certificates of conformity for any copper boiler only for steel boilers, a few boiler inspectors go over and above the regulations, which is wrong, we have a book of rules and they should be strictly adhered to. Totally agree with Phil H, it will be a minefield for our suppliers providing traceability of materials, imagine purchasing a large sheet of copper, it arrives from supplier with a c of c, you have to uniquely identify the material and link it to that c of c and every time you cut a piece off for a customer you have to provide a photocopy of the original c of c to the customer - you, and you would then have to do the same in your workshop, no good just chucking that bit of copper in the corner with all the other bits, it would need identifying and linking to its certificate, a bl**dy nightmare.

Baz15/04/2019 10:59:21
409 forum posts

Forgot to say that the good thing about c of c is full traceability right back to the foundry that made the material so it can be tracked to a large stockholder who sold some on to a smaller stockholder who sold it to the bloke you buy it from, traceability provides countless jobs across various industries and is essential fo medical and aerospace companies, but not for model engineers!

duncan webster15/04/2019 11:11:50
2650 forum posts
36 photos

And then if you unknowingly buy some material off an unscrupulous source the same cert can be photocopied endlessly. I've known this more than once in my working life

IanT15/04/2019 13:32:48
1547 forum posts
144 photos


Personally I would be very happy to view copper purchased from AJ Reeves as being from a "reputable supplier" - and I'm sure that there must be many engines still in service that have boilers built from materials supplied by Reeves at that time. I currently own four boilers, two built/tested & two unfinished - but I didn't purchase any of the original copper material for them - so I do not know what grade of copper was used and frankly I'm not going to worry too much about it either - at least as far as existing boilers are concerned.

Showing my ignorance perhaps - but I was not aware of the 'Oxygen-free' issue before reading Keith's post. I don't think I've seen this mentioned anywhere in any of the usual texts on the subject. Nor did it come up at the SF Boiler Inspectors Seminar that I attended a year or so ago (at least as far as I can recall - there's certainly nothing in the design notes provided).

However, if I were to purchase copper for a boiler in the future, it would now be something I'd certainly ask about. Whether Oxygen-Free is a real problem in actual model boiler practice, I'm not qualified to say. Nor do I know if there are cost implications in specifying O-F copper. Copper isn't exactly cheap whatever you buy.

However, we can speculate endlessly here about the suitability of your materials. Go talk to your Boiler Inspector and see what he (she?) thinks - then the two of you can agree the best way forward.



SillyOldDuffer15/04/2019 14:42:46
5925 forum posts
1281 photos

Posted by IanT on 15/04/2019 13:32:48:


Showing my ignorance perhaps - but I was not aware of the 'Oxygen-free' issue before reading Keith's post. I don't think I've seen this mentioned anywhere in any of the usual texts on the subject. Nor did it come up at the SF Boiler Inspectors Seminar that I attended a year or so ago (at least as far as I can recall - there's certainly nothing in the design notes provided).



It's mentioned in my copy of Wagner's 'A Manual of Chemical Technology', which the 1892 translation of the 13th Edition. It's a treasure trove of facts about Victorian industry.

The book describes 3 processes for refining copper. The Dry Process involves much use of heat and it produces copper that's not very pure, for example 'Mansfield Black Copper' was only about 94% Copper.

But by 1892 most copper was being made by Wet Processes, where Copper was dissolved in Ferric Chloride or Sulphuric Acid, and then precipitated out by adding scrap iron to the liquor. Wet processes produce purer copper than dry and also improve recovery of other valuable metals present in copper ore like Zinc, Lead, Arsenic, Silver, Nickel and Cobalt.

However, both wet and dry processes leave a lot of Copper(I) Oxide in the metal, and 'If this Oxide is present to the extent of 1.1% the metal is so deficient in tenacity and malleability that it cannot be forged at common temperatures without splitting at the edges`. Not unknown back then for commercial copper to contain more than 1.5% oxide, when it was described as 'short' or 'overdone'. A process called 'poling' could reduce the amount of oxide, but it was imperfect, expensive and liable to make the copper brittle due to 'over-poling'.

Impure copper was a serious problem for the electrical industry because tiny impurities cause the resistance of copper to rise by 20% or more. The book describes a new third process in which copper is purified by electricity. As electrolysis is highly effective at removing impurities and recovering valuable trace elements, and it's cheaper, it is - I believe - the only method of refining copper used today.

It must have taken several decades before the last old-fashioned smelter shut down and the last stocks of impure copper were gone. But since about 1940 I think, the memory that commercial copper once had multiple quality issues has pretty much faded.

I suppose it's possible that some recycled copper might be high oxide, but all the copper I've seen sold today is either low oxide or oxygen free.

I think anyone not using antique copper can be confident the material is suitable. No doubt someone will know I'm wrong!


Former Member15/04/2019 14:58:34

[This posting has been removed]

JasonB15/04/2019 15:16:09
18309 forum posts
2024 photos
1 articles
Posted by SillyOldDuffer on 15/04/2019 14:42:46:

I suppose it's possible that some recycled copper might be high oxide, but all the copper I've seen sold today is either low oxide or oxygen free.

I think anyone not using antique copper can be confident the material is suitable. No doubt someone will know I'm wrong!


Dave, its easy enough to buy C101 copper even from some of the common ME supplieres often mentioned here and that can suffer when heated at elevated temps that you may get when brazing for example even though it is said to be "low oxygen" rather than de-oxidised. Even "oxygen free" C103 can suffer from embrittlement though not as much as C101

Having said that it's interesting to see what grades of copper are used on commercial boilers, anyone looked on their paperwork lately?



Edited By JasonB on 15/04/2019 15:30:50

Brian H15/04/2019 15:29:05
1675 forum posts
109 photos

I've always believed that C101 was only a possible problem with oxy-acet, and then only if overheated.


JasonB15/04/2019 15:32:55
18309 forum posts
2024 photos
1 articles

Yes you have got to get it quiet hot which Oxy-Acet will do or propane may get a thin section to similar temps. I know of people who have melted the ends of firetubes with propane so it can be "overheated" with just that gas.

very hard to buy copper sections in C106 so that is why C101 is often used for stays and foundation rings.

Edited By JasonB on 15/04/2019 15:36:27

Former Member16/04/2019 08:57:45

[This posting has been removed]

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