# Copper Boiler Fabrication



## sunworksco (Jan 30, 2011)

I'm getting ready to build a 7.5" diameter x 4.5" height all-copper boiler.
The wall thickness will be 1/8" and the working steam pressure of 150psi.
Will I need any stays? ???
I'm going to roll copper plate to form the tank shell and copper rivet the seam together then silver solder the overlapping seam.
Thanks,
Giovanni


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## tel (Jan 30, 2011)

Stays will depend on the number and layout of your tubes. Generally speaking any area over about 3/4" x 3/4" will need staying, especially at 150 psi, which is above the general pressure for models. When you overlap the seam, make sure you put in some centre pop dimples to hold the plate/s far enough apart for complete penetration.


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## sunworksco (Jan 30, 2011)

Tel,
Can you please post a drawing of that?
I am planning to flatten the rivets on the inside of the boiler, before soldering.
I am using rivets in the plates, as well.
I will use silver solder paste in between the plate seams.
Regards,
Giovanni


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## Jasonb (Jan 31, 2011)

You may find it easier to to butt the ends of the ring together and then fit a "butt strip" behind, this will give you an easier job when it comes to fitting the flanged end plates as there will be no gap where the ring overlaps. The strip is kept short of the ends.

Basically if there is nothing supporting the end plates they will bulge so you need to fit stays, if you look at this pic of my Traction Engine boiler you will see the stays are spaced on 7/8" centres.







The act as stays on teh front tube plate but you can also see above the tubes on teh flat area there are 4 stays which run front to back.

Assuming you have done the calculations to arrive at your 1/8" thickness calculating the stays required should not be a problem.







Solder paste is not ideal as you may not get enough solder into the joint best to do as tell says and let it flow into the gap from one side.

J


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## tel (Jan 31, 2011)

Jason (and his pics) have pretty much said it all, and better than I could.

Beautiful work on that boiler Jason - that could be used as a good example anywhere!


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## Jasonb (Jan 31, 2011)

Can't take the credit for that one its made by Helen Verrall of Western steam

The brass bummy throatplate, manhole, washouts and door are the only bits I've done

J


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## sunworksco (Jan 31, 2011)

Jason,
A beautiful textbook example!
Is that a stationary boiler?
Will I need any stays since I am filling the entire plate areas with 1/8" copper tubes?
Thanks,
Giovanni


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## compspecial (Jan 31, 2011)

Giovanni, As I'm sure you know, Stanley boilers used a steel barrel reinforced by wrapping it with piano wire, but as there were so many tubes expanded into the end plates they acted as stays. I don't know if the same would hold true for a model copper boiler, but when the Stanley boilers were tested to destruction (at well over 1,000 psi) it was due to the tubes being flattened by the pressure! 
                       Stew


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## GWRdriver (Jan 31, 2011)

giovanni  said:
			
		

> Will I need any stays since I am filling the entire plate areas with 1/8" copper tubes?


Wait! 1/8" tubes are FAR too small - they will severely restrict gass flow. Using an long-accepted formula for sizing flues [ID² = L/65] the optimum diameter for a flue of this length is approximately 0.260" so your flues could be .250" inside diameter but should not be less for optimized balance between free gas flow and heat absorption.

Have a look at the front end of Jason's boiler. Notice the proportion of flue diameter to barrel diameter. Now visualize what the proportion of 1/8" tubes to 7" diameter would be - far too small. If you are firing with coal you can use a slightly larger flue and accomodate slight changes in ID and increased resistance due to sooting. If you are gas firing this won't be a consideration. If you fill the flue sheets of your boiler with flues, similar to the way the bottom half of Jason's boiler has been "fillled" with flues, you will not need any longitudinal staying. It is also important to leave some distance between the flues for water circulation, in fact too many flues too close together can significantly impact the amount ot water and steam space a boiler needs. There are a couple of formulae for this space but generallay I use 1/8" minimum between nearest flue surfaces on small boilers, or boilers with small flues.


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## Jasonb (Jan 31, 2011)

Without seeing the drawings I would not like to commit myself but if the whole surface of the two ends is being filled with tubes like the lower half of my boiler then probably not. Do you mean 1/8" wall as bore is a bit tight

No its only going to be stationary until I finish the rest, this was the state of play about 6mths ago.






J


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## Jasonb (Jan 31, 2011)

If your boiler is going to have this many tubes then you won't have room for stays anyway 






more pics here


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## sunworksco (Jan 31, 2011)

Thanks, Guys!
I have learned a lot listening to you experts here.
I will use 1/4" ID copper tubes and keep them 1/8" distance from the walls.
Can I use Type-M copper tube?
I just got 3D CAD drawings for the Flying Tea Kettle body and chassis.
I can now make the wooden bucks to form the aluminum body sections.
Thanks again,
Giovanni


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## arnoldb (Feb 1, 2011)

Hi Geovanni

Type M might be a bit too thin-walled for flue tubes; I'd strongly suggest you use type K.

I had a couple of questions on the calculations for flue tubes here and received excellent feedback; it might really be worth you while to go through that thread and do the calculations; there's also links to the copper.org site with some really great data sheets.

Jason, interesting post on that last image; I see they TIG those boilers!

Regards, Arnold


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## sunworksco (Feb 1, 2011)

The laser programmer can set up the design for the tubing size and clearances with quick results.
Thanks,
Giovanni


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## xo18thfa (Feb 10, 2011)

1/8" wall thickness for a 7.5" diameter shell at 150 PSI is way too thin. It needs to be 3/16" thickness. I site two references:

1. Kozo Hiaroka's "Building the New Shay" has an appendix on copper boilers. According to the chart on page 297, 1/8" wall is only good to about 100 PSI.

2. K.N. Harris. See excerpt below. The wall thickness should be .180" Max pressure on 1/8" wall is 104 PSI.







Also, I have heard, but never saw in writing, that the max pressure on any copper boiler is 110 PSI. The reason is that under pressure, water boiler boils at higher temperatures. At 150 PSI water boils at 366 degrees F, not 212F as it does at room temp. Copper looses strength quickly with elevated temps. A boiler may pressure test fine with cold water, things may be different when its hot.

If you are going to TIG weld, consider doing it in steel with copper flues.


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## sunworksco (Feb 10, 2011)

Thanks!
Very good info.
I will keep the boiler at 100psi and use a 115psi pressure relief valve.
This amount of pressure should be fine in a 7.5" diameter x 4.5" height steaming a two-cylinder engine with 1-1/8" bores.
I will be using Anton gas/steam pressure regulators. 
Is it possible to cast a copper shell?
I was considering rolling an 1/8" copper plate into a shell with tapered ends where the seam mates up and then silver solder.
I will be wrapping 316L stainless steel wire around the boiler shell similar to the full-scale Stanley boiler shell.
This method nearly doubles the strength of the boiler shell.
Thanks,
Giovanni


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## xo18thfa (Feb 10, 2011)

Here is a link to K.N. Harris' book on model boiler building. The info is still relevant. 

http://www.fastonline.org/CD3WD_40/JF/424/19-422.pdf

Rolling a copper barrel by tapering the ends is fine. That's one form of a coppersmith's joint. Strapping the joint is another method. 

The dimensions you mentioned sounded like a Stanley Steamer boiler. The properties of steam and functioning of boilers sometimes don't scale down very well. The flues in model boilers need to be larger in diameter then just scaled down from an original. If the flues are too small, the fire won't draft through. It will just snuff out in the firebox. Don't ask me how I know that. Harris talks about flue size. He gives a range. Use the larger end of the range.

Harris also talks about heating surface, boiler efficiency and how much steam a boiler will produce.  He also talks about how much steam a motor requires to operate at pressure and speed.


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## GWRdriver (Feb 10, 2011)

Generally speaking 125psi is an absolute maximum for model boilers. As Bob's examples point out, in addition to the tensile strength of copper falling on a predictable curve as operating temperatures rise, the safe pressure capacity of a model copper boiler barrel is relative to it's diameter. My understanding of the behavior of copper is that once you go above 125psi the tensile strength curve drops off to such an extent that very quickly you come to a point where adding more wall thickness does not produce more pressure capacity. Now what, one might ask, is what about the many instances where British builders of full size locomotive boilers used copper plates for fireboxes? Many of those engines certainly ran at above 125psi. That's a question I've not seen asked and I don't know the answer.


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## sunworksco (Feb 10, 2011)

I'm hoping that the wire wrap will help.
A 125psi rating would be great!
Thanks for the KNH book!
It is very nice. :bow:


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## sunworksco (Feb 10, 2011)

Does anyone have info or experience with the Anton gas burner regulator valve???? ???
I'm very impressed with their products but not sure which design to use.


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## Jasonb (Feb 11, 2011)

> I will keep the boiler at 100psi and use a 115psi pressure relief valve.



You need to rate the safety valve at the working pressure of the boiler not above it and size it so that the pressure won't keep rising with a full fire.

I also see that you said you were getting the flue holes lazer cut, I would not form them until the endplates have been flanges as you are likely to distort the ones around the edge and may end up with elongated holes that the solder won't fill the gaps.

J


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## Dan Rowe (Feb 11, 2011)

Giovanni,

I think you said in another thread that your location is near Sacramento CA. The pressure limit in the CA boiler code for uninspected boilers is 100 psi. That is the ASME pressure limit for miniature boilers which is used in a lot of states for small boiler code exemptions.

I would set the max. working pressure at 100 psi for this reason in the US and use a 100 psi safety valve.

As Jason mentioned the size of the safety valve should be checked by firing the boiler at full rate with all the outlet valves closed. The numbers I have read state the boiler should not go above between 6 to 10 percent above the working pressure so for a 100 psi boiler the safety valve should keep the pressure below 106 to 110 psi.

There are a two references in my model boiler stack that covers sizing safety valves. Kozo covers the topic in the "Building the New Shay" and the AMBSC Code Part 1 Copper Boilers covers the topic.

Dan

Edit: The Maryland Model Boiler Code states 106% of the max working pressure for the safety valve and I just read that the Pennsylvania Live Steamers also test the safety valves to 106% so I will use that for the limit when I test any boiler I build.


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## xo18thfa (Feb 11, 2011)

Dang it Dan!! I keep forgetting to order that AMBSC Code.


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## sunworksco (Feb 11, 2011)

Jasonb  said:
			
		

> You need to rate the safety valve at the working pressure of the boiler not above it and size it so that the pressure won't keep rising with a full fire.
> 
> I also see that you said you were getting the flue holes lazer cut, I would not form them until the endplates have been flanges as you are likely to distort the ones around the edge and may end up with elongated holes that the solder won't fill the gaps.
> 
> J




J,
You are right in your comment. I will set the pressure gauge at 106psi.
I'm not forming the end-plates. They will be machined out of 3/8" copper plate.
I'm sure that the wire-wound boiler shell and the machined copper end-plates will handle up to 150psi, but too much liability!
You steamheads will guide me down the correct path. Thank you for helping me design this! :bow:
They will look like the full-scale end-plates.The end-plate to shell surface will provide a 90* silver solder joint.
I will post the build here with the hydro-test pressure rating, too.


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## Jasonb (Feb 12, 2011)

giovanni  said:
			
		

> J,
> You are right in your comment. I will set the pressure gauge at 106psi.



*NO* you set it at 100psi for a 100psi working pressure and the pressure is not allowed to read more than 106psi when its given a steam test. If you set it at 106psi then your working pressure will be 106 and should not rise above 112.36psi .

J


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## steamer (Feb 12, 2011)

Thats how I understood it too Jason.

Dave


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## doubletop (Feb 14, 2011)

xo18thfa  said:
			
		

> .................... I site two references:
> 
> 1. Kozo Hiaroka's "Building the New Shay" has an appendix on copper boilers. According to the chart on page 297, 1/8" wall is only good to about 100 PSI.
> 
> 2. K.N. Harris. See excerpt below. The wall thickness should be .180" Max pressure on 1/8" wall is 104 PSI.



This has been quoted here before and is probably the same as the Shay Appendix but get hold of a copy of Live Steam and outdoor Railroading LS Vol. 40 No. 6 Nov-Dec 2006 with Kozo's article "Safety of copper boilers". Its a really good read along with The KN Harris book gets you a long way to understanding all this. The article has a good section on stays and their spacing.

Get it here https://secure.villagepress.com/store/items/list/group/285

They'll ship worldwide

Pete


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## sunworksco (Feb 15, 2011)

Thank you,
Giovanni


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## Dan Rowe (Feb 26, 2011)

Giovanni,
Did you download the Harris boiler book Bob linked in reply #16?

It has all the formulas for the calculations you need to make. This includes a a method to decide how much heating surface will be required for any engine bore and stroke and design RPM. The engine stuff is Chapter 1 and I have read it far more times than any other section of the book.

Now take a look at design No 5 in the appendix. This a small version of the boiler you are attempting to design. The text actually mentions that the Stanly steam car had a very large version of the boiler.

If you get stuck with Harris ask questions several of us have worked this through a few times. 

Dan


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## sunworksco (Feb 26, 2011)

Thank you.


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## steamin (Mar 2, 2011)

Gentlemen, thank you for this thread. I have sat here for the past 45 minutes reading about the development of this boiler. Great stuff for sure. I have down loaded Harris's book to my laptop. I hope to get to it soon. I did go to Amozon.com to see if they had copies for sale. They do have some and they are very expensive. So I appreciate the link. :bow:


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## Roy h Biggs (Mar 8, 2019)

steamin said:


> Gentlemen, thank you for this thread. I have sat here for the past 45 minutes reading about the development of this boiler. Great stuff for sure. I have down loaded Harris's book to my laptop. I hope to get to it soon. I did go to Amozon.com to see if they had copies for sale. They do have some and they are very expensive. So I appreciate the link. :bow:


Just bought one from ebay for $24.


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## bentprop (Mar 9, 2019)

I don't know how big a boiler you want to make,but if you can find an old copper fire extinguisher,they make very nice boiler barrels.From my memory,the one i made was 2" diam.x6" long,and I think about 1/8 thickness. the extinguisher also provided material for the end caps.Simply cut the leftover pice lengthways,and flatten,then peen over on a mould.In my case ,just a scrap of wood shaped to suit.I used copper brake pipe for the tubes.


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## John Antliff (Mar 14, 2019)

If this is any help - I made a 6 inch vertical boiler last year with 83 flues from 1/4 inch O/D copper refrigeration pipe 5 inches long with a 1.25 inch O/D superheater tube in the middle.  It did not require any stays and was designed to run at 100 psi.  I have a Youtube video of the building of it and the final use I put it to for it's first steaming.  I designed it primarily for gas but it may be used with coal later on for a 7 1/4 in gauge De Winter locomotive.  The photo is of the grate I made for steaming it on coal and consists of 207 x 6.2 mm dia. holes in a 5 & 3/8ths diameter 10mm thick steel boiler plate disc.


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