Copper for boilers

[Barneydog]

Hi Guys,

I am just ordering copper for my new boiler.
Which should I use and why?
The choice is expensive C106 grade or cheaper C101 grade?
I am told that C106 grade is only used by the professional boiler making companies But that the difference is minimal.

Thanks

Julian

[Jo]

Quote from SandyC 

For copper boilers which are silver soldered/brazed the copper grade most specified and acceptable to the boiler inspectors is: -

C106 Copper

Phosphorus deoxidised copper is the grade of copper where oxygen is removed by the controlled addition of phosphorus during the melting cycle. A slight excess of phosphorus ensures complete removal of oxide. The residual phosphorus remains alloyed with the copper within the specified range 0.013-0.050%. The copper content is 99.85% minimum and the grade conforms to the compositional requirements of British Standard alloy designation C106.
C106 is superior to the electrolytic tough pitch copper electrical grade (C101) and should be specified for all non-electrical applications, especially those involving assembly by welding or brazing. Phosphorus deoxidised copper is not susceptible to hydrogen embrittlement which is a serious risk with non-deoxidised grades.

Related Specifications

BS2871.
Cu-DHP.
DIN 1787.

You want the C106.

But most model engineering suppliers only supply C101 

Jo

[Bluechip]

M-Machine do C106 . 

And a belated Happy New Year to All ... 

Dave

[AOG]

What about C122?  C106 is almost unobtanium around here.

Thanks

Tony

[SandCam]

What about C122?  C106 is almost unobtanium around here.

Thanks

Tony

Hi Guy's and Gal's and A Happy New Year to you all.

Tony,

C122 has almost identical characteristics and is also Phosphorous deoxidised... it is therefore is a perfectly suitable alternative to C106.

Whatever you do... don't use, or accept, C101 or C103... they are not oxygen free, despite what some suppliers say, they are both actually a Low Oxygen grade... the exact quantity not being specifically controlled during manufacture.

You may need to obtain 'certificates of conformance/authenticity' for all the materials you use in your boiler construction nowadays, depending on your country of origin, this is certainly the case for the UK, especially for boilers over 2litres capacity which fall into groups I -IV of the PER (Pressure Equipment Regulations) regulations.

Note... Commercially built boilers which fall into the above groups MUST be CE marked... However, I have, so far, been unable to establish whether this now also applies to Home built boilers after they have obtained test certification... most sources are a bit vague on this requirement.
The Green Book suggests that they should not.

Small boilers of under 2litres capacity, regardless of working pressure, fall under the S.E.P (Sound Engineering Practice) group of the PER and should not be CE marked, commercial or otherwise.

Check with your boiler inspector before doing or purchasing anything. The latest UK test code (Green Book) now requires a Written Scheme of Examination for each and every boiler being tested, regardless of size/capacity, and this will list the certificate serial numbers and materials used.
Failure to provide this information could prevent you getting your boiler tested.

Other countries will have their own rules, so these check first.

I hope this helps.

Best regards.

Sandy.



 

[Jasonb]

Macc Models is another source of C106, Noggin End and GLR Kennions do C106 tube too

[Barneydog]

All the tube is not an issue as it is all C106. It is just the plate which was C101. He has now found some C106 plate big enough for me. He will issue a receipt stating it is C106 which should be ok with the inspector. Sandy C sent me a very direct email today stating that C101 must never be used. Many thanks Sandy for the guidance.

This now gives another question. I have several good lengths of copper tube in my workshop from various sources designated for several future projects.....Don't we all!!!??? Without certification/receipts how can we tell the grade of the copper?


Happy new year

Julian

[tangler]

I think the worms are wriggling out of the can here.  It seems to me that, in the UK, for a home constructed copper boiler made using silver soldered joints, a boiler inspector will not expect to see material certification.  This therefore implies that any nominally pure copper is adequate for the purpose, as has been demonstrated by every amateur boiler maker since records began.  The requirements for welded copper boilers are entirely different since the construction method involves melting the copper with a consequent drastic change to the metallurgy.  I suspect there is confusion between the 2 requirements.  I may be entirely wrong but until some body can show me chapter and verse I shall continue to offer boilers constructed from copper bought, without tracability, from  the ME trade, to my club inspector.

Cheers,

Rod

[michaelr]

Rod. Your view on building copper boilers and the material used is the most common sense and practical approach to the subject that I have read for some time, and also in my opinion and I agree is all that is needed.

Mike

[SandCam]

I think the worms are wriggling out of the can here.  It seems to me that, in the UK, for a home constructed copper boiler made using silver soldered joints, a boiler inspector will not expect to see material certification.  This therefore implies that any nominally pure copper is adequate for the purpose, as has been demonstrated by every amateur boiler maker since records began.  The requirements for welded copper boilers are entirely different since the construction method involves melting the copper with a consequent drastic change to the metallurgy.  I suspect there is confusion between the 2 requirements.  I may be entirely wrong but until some body can show me chapter and verse I shall continue to offer boilers constructed from copper bought, without tracability, from  the ME trade, to my club inspector.

Cheers,

Rod

Hi Rod,

See paragraph 7a and 7b of the Green Book...AKA

The
EXAMINATION & TESTING
of
MINIATURE STEAM BOILERS
(Revised Edition 2012)

quote...

"The inspector shall satisfy himself:-

7a.  That the materials used are of the correct thickness and
specification. 

7b.  That, where required by the build procedure, the relevant
material certificates are provided."

A lot of this has come about by changes to the PER regulations since 2002 and the inspector would be perfectly within his rights to ask for such certification in order to approve a home built design.

Even if the boiler was being built to a published design, he would still be within his rights to ask for these in order to verify that the materials used are as specified on the design drawings. 

He MAY also request viewing of same even for a commercial boiler.

Using unknown, or incorrect, grades of Copper for boiler work can lead to early joint failure, or worse, often due to using Copper containing Oxygen which can quickly lead to cracking caused by Hydrogen embrittlement.
Not a safe situation for a steam pressure vessel.

Best regards.

Sandy.
Retired manufacturer of Model steam boilers and engines.

[Jasonb]

Even if the boiler was being built to a published design, he would still be within his rights to ask for these in order to verify that the materials used are as specified on the design drawings. 
Sandy.

Problem is how often do you see the grade of copper specified on an ME drawing?

[Tennessee Whiskey]

If you have to have a boiler inspected you can expect to satisfy the inspector; plain and simple. The specs and regs are written to cover the safety and well being of all, and to be honest, the insurance companies. As with any law, rule, regulation, or specification ever written, there is room for "interpretation" , however, common sense will virtually never enter into that interpritation. You can spend hours and dollars arguing an "interpretation" , or, if you want the "stamp" painlessly, give them exactly what they ask for, or even upgrade( however that could bring on more explanation and then more interpretation  ). In regards to Jason's last post: if you are taking as much time as it takes to construct a nice boiler, take the time to confer with the inspector. Show him the drawings, discuss materials( I.e. grade not specified) , and genuinely inquire of what he expects. Now, so y'all don't think old Cletus has lost it; I'll sign this post the way I would have when I had a real job.

H. Eric Douglas
Boiler Inspector/ Welding Engineer
BE&K Construction
Birmingham, Al

[Firebird]

Hi

To pick up on my mate Julians question, is there a way of telling the difference between C101 and C106. Over the years I have picked up various bits of copper tube from steam fairs and model engineering shows which I hope will become boilers to power mostly stationary engines. I understand that copper tube is always C106??? I have a very nice piece of 4" tube 12swg that is obviously old. It was actually donated by our old friend John Bogstandard but I have no paperwork to say what it is. I have a few pieces of copper plate that I have picked up here and there but none of it is marked. Is C106 marked??? How can we be sure that even if the vendor says it is C106 that is actually what we get???

Cheers

Rich

[10KPete]

I'll re-ask part of Rods post: reworded: Is silver brazing going to result in an oxygen problem the same as welding would??? Brazing doesn't melt the base metal....

Pete

[tangler]

Folks,

I think the "Green Book" that Sandy refers to is this: http://www.nameng.org.uk/images/Boiler_Testing_Documents/2012_Test_Code_V12a.pdf

This document is the one that the insurers of our clubs use to guide the "amateur" club members who have taken on the responsibility of certifying boilers as safe to use.  It really is pretty vague and my interpretation of that is that here in the UK we have a successful self regulation system for model locomotive boilers outside of the regulations that apply to commercial and professional use and everybody is happy to keep it that way.

"1.2    Legal   requirements,   such   as   the   Pressure   Systems   Safety
Regulations  2000  (PSSR),  do  not  normally  apply  to  persons
operating  pressure  equipment  as  a  hobby  activity.  However  the
Health and Safety Executive considers it good practice for persons
using  such  equipment  to  provide  the  same  level  of  health  and
safety protection as they would if they were duty holders under the
Regulations. To aid this process the principles (my italics) of PSSR have been
followed in drafting this document..."

The Written Scheme of Examination is not prescriptive, all it says is that the procedure that is used to examine the boiler is written down and lodged as part of the certification.

The only mention of material certification is :

"7. b.That, where required by the build procedure  (my italics), the relevant material certificates are provided."

I interpret this to refer to welded boilers, not those that are silver soldered.

My boiler inspector has visually examined the quality of my silver soldering so far and is happy that it looks right.  He will want to examine the quality of the silver soldering on the crown stays before the boiler is closed and will then have a look at the complete thing before doing an hydraulic test.  He seems to be happy that the boiler is made of copper (unspecified), has bronze (not brass) bushes, is constructed with a variety of silver solders and is to an established design.

The interpretation of the Boiler Testing document is perhaps coloured by whether one is looking at it from the commercial viewpoint of a professional boiler maker where traceability is required or from the the amateur maker following successful procedures that have been used by followers of the hobby for over 50 years.  Perhaps this why Sandy and I differ in our views.

Best wishes to all,

Rod


Rod






 

[tangler]

I'll re-ask part of Rods post: reworded: Is silver brazing going to result in an oxygen problem the same as welding would??? Brazing doesn't melt the base metal....

Pete

I'm no expert on copper alloys.  This may be of help: https://www.copper.org/publications/pub_list/pdf/a1050.pdf.  An excerpt from page 7 is appended:

Rod

[10KPete]

Thanks for that, Rod!!

I've done a ton of welding and been exposed to a ton a metalurgy and everything I've learned says that for the feared embrittlement to  occur the temperature must be at or very near melting. But I'm no expert so I always seek the advice of those more learned than I.

I will continue to silver braze with no fear of compromising the material, what ever the alloy!!!!!

Pete

[SandCam]

Hi Pete,

I would suggest you review this excerpt from the same publication.


"Page 38

Brazing Copper

Oxygen-bearing coppers are susceptible to oxide migration and Hydrogen embrittlement at elevated temperatures. These Coppers should be furnace brazed in an inert atmosphere or torch brazed with a neutral or slightly oxidising flame."

If you can't provide the correct atmospheric conditions then you could well be in trouble.
Best bet is to use de-oxidised Copper and not worry about it.



Rod,
As for the regulations and the Green Book etc... I don't propose to get into a heated discussion on this other than to say that whilst a lot of the PSSR 2000 stuff is not applicable a great deal of the PER regulations are and have been since 2002... with amendements in 2013.

The argument that things have been done a certain way for the last 50 years has led to a huge number of different interpretations of the rules with many clubs and organisations doing their own thing so to speak, which just resulted in a great deal of confusion and the whole purpose of the Green Book was, in conjunction with the HSE, the various model engineering organisations and the insurers of our models, to establish a common testing and certification method, based on the salient points from both official regulations, which satisfied all concerned, be they commercial builder or amateurs.

I don't think people/clubs etc should put their own interpretations on it's content... to do so just creates unnecessary confusion.

Rich and Julian,

There is no foolproof way that I know of, other than a full metallurgical analysis test, to distinguish between different grades of copper such as C101 or C106.
Any supplier worth his salt will provide a traceable certificate of authenticity, not just a piece of paper with his say so on it... if he can't or won't then go elsewhere... Providing a customer with a Phoney one could lead to his prosecution.

Keep Happy guy's and gal's

Best regards.

Sandy.

[Jasonb]

Hi Pete,

I would suggest you review this excerpt from the same publication.


"Page 38

Brazing Copper

Oxygen-bearing coppers are susceptible to oxide migration and Hydrogen embrittlement at elevated temperatures. These Coppers should be furnace brazed in an inert atmosphere or torch brazed with a neutral or slightly oxidising flame."

Sandy By Braze are they talking of the higher temp brazing as we know it in the UK where the Oxy-acc torch will be getting the copper very close to melting point, the description of the flame type suggests oxy-acc not propane.  Or do they include the lower temperature silver soldering?


Best Advice to Rich and Julian is to talk to whoever will be inspecting the boiler as it is there interpretation of the rules that will ultimately be the deciding factor if their boilers get passed or not.

J

Edit, answered it myself and it does include silver solder as a brazing material.

[10KPete]

This is where I have always received my definitions:

"Brazing - The American Welding Society (AWS ), defines brazing as a group of joining processes that produce coalescence of materials by heating them to the brazing temperature and by using a filler metal (solder) having a liquidus above 840°F (450°C), and below the solidus of the base metals."

"The basic difference between soldering and brazing is the temperature necessary to melt the filler metal. That temperature is defined to be 842ºF/450ºC by the American Welding Society (AWS) but is often rounded to 840ºF. If the filler metal melts below 840ºF the process being performed is soldering."

I don't know how the rest of the world defines these things but I suspect it is similar.

Just trying to clarify....

Pete

[steamer]

This is where I have always received my definitions:

"Brazing - The American Welding Society (AWS ), defines brazing as a group of joining processes that produce coalescence of materials by heating them to the brazing temperature and by using a filler metal (solder) having a liquidus above 840°F (450°C), and below the solidus of the base metals."

"The basic difference between soldering and brazing is the temperature necessary to melt the filler metal. That temperature is defined to be 842ºF/450ºC by the American Welding Society (AWS) but is often rounded to 840ºF. If the filler metal melts below 840ºF the process being performed is soldering."

I don't know how the rest of the world defines these things but I suspect it is similar.

Just trying to clarify....

Pete

Yes this has been a debate for as long as I can remember, I'm sure a better definition can be found by specifying the "spelter" liquidius point on the boiler documentation...but then again....I'm not digging that one up.....

Dave

[SandCam]

This is where I have always received my definitions:

"Brazing - The American Welding Society (AWS ), defines brazing as a group of joining processes that produce coalescence of materials by heating them to the brazing temperature and by using a filler metal (solder) having a liquidus above 840°F (450°C), and below the solidus of the base metals."

"The basic difference between soldering and brazing is the temperature necessary to melt the filler metal. That temperature is defined to be 842ºF/450ºC by the American Welding Society (AWS) but is often rounded to 840ºF. If the filler metal melts below 840ºF the process being performed is soldering."

I don't know how the rest of the world defines these things but I suspect it is similar.

Just trying to clarify....

Pete

Hi Pete,

As Dave states below, this has been a frequently debated topic for many years with no real resolution.

To help clarify things regarding the temperature ranges involved when using Silver Solders (the correct term being Silver Brazing) on Copper boilers... the 2 most generally used alloy types here in the UK  for boiler work are: -

Johnson and Matthey 'Silver-flo 452' which contains 45% Silver and has a liquidus range between 640 - 680deg C. (This replaced the older Easyflo and Easyflo 2 grades which contained Cadmium)

and their 'Silver-flo 252'  which contains 25% Silver and has a liquidus range between 680 - 760deg C.

These latest alloys are both Cadmium free.

The USA and other countries have direct, or very close, equivalents for these grades which will have much the same liquidus temperatures.

So these fall well above the minimum 450deg C specified by the AWS as Brazing Temperatures.

There are some high temperature Silver loaded soft solders which are often used by the Plumbing/heating trade but these generally have a melting point around 300deg C... 'Comsol' being one of these.

A quite common problem being seen more frequently is that a beginner mistakenly uses this type for his/her boiler construction as it is often sold, and described, only as Silver Solder... unfortunately it is not an easy solution to remedy, since you cannot use the correct Silver Braze material without first totally removing the soft type first.

Jason,

Oxy- Acetylene is not the only gas mix which can melt Copper... MAP and/or Propane torches are just as capable of doing so.
There is always the Oxy-Propane variety as well, which can almost equal oxy-acetylene and is becoming more popular now since the annual costs of hiring oxy-acetylene bottles has risen very sharply, both here in the UK and also in the USA, so a lot of users are making the change over.
There are now places where you can buy an Oxygen tank and a Propane tank for a one of fee and you then just exchange them for new ones when empty, just paying for the gasses... there is no annual hire fee since you own the bottles.
All of these types of torch are very capable of producing a non-neutral flame, the straight gas types are more likely to produce a carburising one rather than Neutral, let alone an oxidising one and a long way from an inert atmosphere... they are therefore very likely to provide the means for producing Hydrogen Embrittlement in Silver Brazed joints in Copper containing Oxygen.

And Yes I agree that having a talk with your local boiler inspector is the best way to go since he/she will, or should, be able to advise the appropriate construction materials where these are not specified... generally the inspector will also wish to examine progress at several stages of the construction process and well before testing time comes.

I trust this helps.

Best regards.

Sandy.

[10KPete]

The debate issue is why I posted the AWS definitions. If you read the definitions, by AWS and other authorities, there is no debate!! Brazing is brazing and soldering is soldering.

The confusion is primarily in Model Engineering!! Primarily in Britian it seems where silver brazing is almost always referred to a silver soldering. Both the process and the products!! Until I looked in to Model Engineering I never found contradictory terms.

Having observed the issue for some decades now it is obvious that the issue is so well entrenched among the 'established set' in ME that a change will be difficult. But I also believe that correct usage by those so willing can seriously reduce the usage error and perhaps even cause some new to ME to take up the proper terms. I include the periodical literature.

By the way, "spelter" is a term for brass used as filler in brazing and does not apply to silver alloys.

Pete

[Jo]

Any metal alloy designed to melt and join metal together is called a "solder,".

You can blame Holtzaffel for the term silver soldering, he was caught using it back in 1846 

Jo

[10KPete]

That's right, Jo. And when it melts above 840*F it's then a braze. So 60% silver alloy is silver brazing alloy.

Warm up the Time Machine, boys. And bring the pitchforks and ropes.   

Pete @ off to slibber slobber some oxy-Cu with some oxy-acet in my 1/2" superheater.

[Johno]

Hi to you all,

It’s been some time since I have posted, due to other distractions.

I have been following his thread with some interest as I am looking to obtain a small boiler to run my Stuart Engines. Do I buy an off-the-self one at some cost, but with limited satisfaction or do I construct one, less cost, but greater satisfaction?

If I choose the self-build route, I not only need to decide upon a design, I also need to obtain suitable materials, hence the relevance to me of this thread.

It would appear that some would say that the precise grade of copper (either C101 or C106) is not that important given that the joining method is ‘Silver soldering’.

Others are adamant that using the correct grade (C106) is crucial in order to avoid the very real possibility of hydrogen embrittlement.
Then there is the question of is it;  ‘silver soldering, silver brazing or just brazing? I see this is more of a question of common usage, I vacuum the carpets but my good lady ‘hoovers’ them, although we have a Dyson!

To add to the debate, I refer to references I found following a web search.

One is from the relevant data sheets with respect to grades of copper from a UK Material Company: Holme Dodworth Ltd. http://www.holmedodsworth.com/materials/copper/copper-specifications
 
“C101 / CW004A is the normal grade for general electrical use as busbar, motor and transformer components, windings and many other current carrying applications. It is also very popular with architects for applications where the corrosion resistance is required for building applications. Over time the C101 will also develop the weathered copper, green patina, appearance that offers additional corrosion resistance and a desirable look. The use of this alloy in elevated temperature environments can be limited due to oxygen being present in the form a serious risk with non-deoxidised grades. Oxygen being present in the form of CU O. This can cause the alloy to be susceptible to hydrogen embrittlement in reducing gasses or when welding or brazing using an oxy-fuel gas flame.”

“The copper content of C106 is 99.85% minimum. This is the preferred grade for non-electrical purposes such as fasteners, roofing sheet, plumbing tube and other general engineering and constructional applications. The alloy comes into its own where the manufacture of the component or plant involves welding or brazing. This grade of copper is not susceptible to hydrogen embrittlement which can be serious risk with non-deoxidised grades. “

And the other from: CuP Alloys Ltd a supplier of Silver solder/brazing materials
http://www.cupalloys.co.uk/best-practice/: -

“Copper is available in many grades. Tough pitch copper should be avoided. It contains dissolved oxygen. If the reducing (blue zone) of the flame heats the copper, the oxygen is converted into steam. This steam penetrates the grain boundaries of the copper causing cracks to form. This phenomenon is called "hydrogen embrittlement". Catastrophic failure can occur without significant deformation or obvious deterioration of the component.
Use oxygen free copper C101 and C106.”

At the moment still very confused and sitting on the fence, although currently my legs are daggling on Sandy's (SanyCams) side.  There must be a definitive answer to this one, or least some clear guidance depending on specific circumstances.

Cheers
Ian

[crueby]

Another question in all this - does it matter if the boiler is going to be coal-fired or butane fired when complete? I have seen some references in the past to additional issues with alloys on coal-fired boilers.

Hope this does not generate another round of historically different standards/opinions based on different countries rules and regulations, but it probably will...   

 

[Johno]

Hi,

I agree, although i would suggest that it's not an issue of local regulations, more of engineering principles, engineering is a based physics after all.

In full size practice the method of combustion, or more importantly the products of combustion that it produces has great bearing on the modes of deterioration of the various boiler components. When boilers were converted from coal to oil, then to gas, whole teams of engineers would spend many hours exploring the consequences.

the same may be true in model engineering field.

Cheers

Ian

[10KPete]

 
 


Pete

[Jasonb]

Another question in all this - does it matter if the boiler is going to be coal-fired or butane fired when complete? I have seen some references in the past to additional issues with alloys on coal-fired boiler

The sulphur in the coal gasses will attack filler alloys containing phosphor

[///]

Excellent thread, so to summarise so far (for my future project)
Cadmium free,
Oxygen free,
Phosphorus free,
Got it 

[Jo]

And make sure you use bronze for all the bushes.

This picture was taken about 10 seconds after when what was supposed to be a bronze bush (that was actually brass) failed on the back head of a boiler. Luckily no one was within 10ft of it when it broke. If anyone had been shovelling coal in the fire box at the time 

Jo

[10KPete]

  

That's scary!!

Just what are the preferred grades of bronze for brazing into boilers???   

Pete

[tangler]

Excellent thread, so to summarise so far (for my future project)
Cadmium free,
Oxygen free,
Phosphorus free,
Got it 

Don't forget the Zinc!

Rod

[Barneydog]

For the sakes of replacing some of what was lost in the recent migration here is what I have done.
I have bought all the copper I need for my simplex boiler. It is all C106 and all has a letter of conformity from my supplier. All the stays and bushes will be made from phosphor bronze.
Once I have shown it all to my boiler inspector and have his ok I will start. When I do start in the next few weeks I will start a new topic.

Regards

Julian

[Barneydog]

Hi Guys,

I realise it is a while since a post was added to this topic but I felt that a new post is appropriate.

We have contacted several commercial metal suppliers and they all say the same. Tube is C106 but nobody stocks or supplies C106 sheet. Almost all sheet is C101.
Reeves and GLR kennions only supply C101 with their boiler kits.

I appears that embrilltement is only an issue if the copper is melted which in our case only applies if it is welded. Silver soldering does not melt the copper.
I have spoken to my boiler inspector and he has said the same. He also said he only needs to know the copper is of decent quality and condition with the supply of certificates and receipts. He has no requirement to know the grade. We have fairly well cleared out our local copper supplier of all the C106 he had in stock so should be ok for the next couple of engines then it is on to C101 sheet.

Regards

Julian

[Jasonb]

Macc do sheet in C106

https://maccmodels.co.uk/materials-metal/copper-sections/copper-sheet/25mm-copper-sheet-300mm-x-300mm.html

C106 is also easier to flange