Copper Boiler Fabrication

[Jasonb]

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

 

[Dan Rowe]

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.

 

[xo18thfa]

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

 

[sunworksco]

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.

 

[Jasonb]

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

 

[steamer]

Thats how I understood it too Jason.

Dave

 

[doubletop]

.................... 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

 

[sunworksco]

Thank you,
Giovanni

 

[Dan Rowe]

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

 

[sunworksco]

Thank you.

 

[steamin]

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:

 

[Roy h Biggs]

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.

 

[bentprop]

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.

 

[John Antliff]

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.