Copper Boiler Making

[Blue HeelerParticipant @blueheeler]

I read often searching posts in regards to making a copper boiler, to never use brass fittings.

Can someone enlarge on this advice?

[Paul KempParticipant @paulkemp46892]

Brass is copper and zinc, the zinc in the mix is leached out by the water at elevated temperature leaving a spongy porous mass of copper, which is weak.  It is common for brass fittings that have been in service for some time to fail!  Bronze however is a mixture of copper and tin, tin is not affected in the same way as zinc.  All boiler bushes and fittings should be made of bronze.  If you want to silver solder them then best not to use a leaded bronze or aluminium bronze.

Paul.

[Blue HeelerParticipant @blueheeler]

 

All boiler bushes and fittings should be made of bronze.

Hi Paul, but what about blowdown fittings, sight glass fittings, safety valves, check valves etc….they are all made from brass?

[JasonBModerator @jasonb]

They probably are on your “toy” size engines as even the boilers of things like a Mamod are brass. Note Paul said elevated temperatures which you are less likely to see on your relatively low pressure boilers with small burners.

All the fittings on my 2″ traction engine that will come into contact with the boiling water are bronze or gun metal, those that just see steam are part or fully brass.

If you look at this clack or check valve that is designed to screw into a bush on a boiler you can see that the horizontal part is a different colour to the rest. The reason is that part will see the hot water so is a bronze, the rest will only see cold feed water so is done in easier to machine brass. Same with this blowdown the gland nuts and outlet pipe are brass but body is PB. Similar from other makers. So not “ALL” made from brass.

Safety valves should only see steam, the odd bit of priming when they will come into contact with boiler water is unlikely to do much harm so brass would be OK

To complicate things you can get DZP brass which is often used in things like plumbing fittings which is not affected as DZP is ” Dezincification Proof”

[Blue HeelerParticipant @blueheeler]

G’day Jason, always nice to read a reply from you mate.

I have a well made 4″ copper boiler with these fitting –

 

Copy of 4161 Blanking Nut 3/16 x 40

 

4188 Angle Water Check Valve

 

4259 Boiler Sight Glass Assembly

 

I would like to make a bespoke upright coal fired boiler out heavy walled copper tube and just working out the list of items to purchase.

[Paul LousickParticipant @paullousick59116]

If you are building a copper boiler in Australia you should get a copy of the AMBSC Code Part 1 which states that all fittings silver soldered or brazed to the boiler cannot be brass because it may be subject to dezincification and fail. Replacing them would be difficult and the boiler would have to be re inspected. Screwed in valves, etc can easily be replaces if they leak or fail. Your purchased sight glass and valve should be OK. My sight glass is brass and a purchase item and is still good after 7 years.

[noel shelleyParticipant @noelshelley55608]

Following a NEW advert in ME offering to produce TIG welded copper boilers, what are the requirements in the context of paperwork, eg codeing Etc to get a certificate on this type of construction. Since most designs are for silver soldered construction, that the boiler will be TIG welded and the original design need to be altered to be so made, will it be accepted as “to a published design” or will calculations have to be provided as a NEW Design ?

I ask this question as having seen TIG welding in both Stainless steel and aluminium where the work LOOKS beautiful but lacks penetration or depth, therefore mechanical strength and fails. I could see such welds soon failing as the boiler is cycled and stress cracking occurs. Noel.

[duncan webster 1Participant @duncanwebster1]

Assy code allows leaded bronze in boilers, and both sae660 and Colphos claim to be OK for brazing. Both contain lead

[JasonBModerator @jasonb]

Noel, see this Facebook post and replies

Catagories explained on their web site.

[Blue HeelerParticipant @blueheeler]

This is the literature from my current 4″ boiler –

“Miniature Steam”, boilers are built to the highest quality standards.
They comply. where appropriate, with the following design, construction and testing requirements of:
– Australian Standard AS 4343 Level E
– Australian Miniature Boiler Safety Committee, (AMBSC) code part 3 Issue 1.0 – 2006 Sub-Miniature Boilers and AMBSC code part I . Issue 7 – 2001 
– UK Boiler Test Code 2018 – Volume 2″

[Paul KempParticipant @paulkemp46892]

Your question was why you see a lot of advice not to use brass fittings in steam boilers, which I answered in a simple form, you didn’t ask what the various codes require, that’s a different question!

Yes many / most commercial boiler fittings do seem to be brass, why?  I don’t know!  Probably because brass is slightly cheaper.  Having seen the result of dezincification on some of these, I don’t buy them but make my own.  I have just finished a 3 cock gauge frame for my half size traction engine.  I could have bought one for around £300 with no certainty on material or I could make my own.  Material I had mainly in stock cost unknown now as purchased a long while ago but it’s all boxed up and marked so I know what it is.  The stainless I was short of for the cocks was £8.  My labour was effectively free but if charged certainly not economic as including plugs and copper washers there are about 20 separate parts in the assembly discounting the glass and seals so it took me about 24hrs to make.  However it’s quite a satisfying thing to make and I know it’s not going to rot away any time soon!

The blow down valve I am also making from bronze and at 1/2” BSP with 120 psi behind it would be a fearsome lump of shrapnel if it parted company from the boiler.

As Jason says, pressure and temperature (and size) play a part in the decision on material.  I am sure on your boiler, brass will probably see you out if you are not steaming it half the weekends in the year.  But as to why brass is not the ideal choice, you have your answer.

Paul.

[JasonBModerator @jasonb]

I suppose it also comes down to the fact an screw in fitting is easier and less costly to replace than say a bush that is soldered as part of a boiler.

Although he did not say what grade of brass, I enquired of Miniature Steam

“All of our boilers are made to Australian boiler Code AMBSC.

The boiler is made of the following

Boiler    Copper

Boiler Bush    Bronze

Boiler cast fittings    Bronze

Bolt on eg taps water gauge bush etc made from brass

Kind regards

John”

[Blue HeelerParticipant @blueheeler]

Thanks all, appreciate the replies to the thread.

I’m going to be probably asking a lot of questions if this project gets off the ground, I have a lot of boilers but have always coveted a coal fired one.

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