Seeking info

[Weldsol]

hello guys, just had a dabble TIG welding some copper, the pieces were bright but not prepared, DCEN, the tip was a 2.4 thoriated, No5 ceramic, 20cfm Argon, max 90 amps. the filler was a piece shaved of the parent strip. The first two pix are a lap joint of 1.5mm thick the second two are a lap joint 0.9mm. front and back. the blow hole is me trying some silicon bronze but not sure of the rods cus i've had em that long the label has faded.
probably get better results with a pristine set up.

Best regards sutty

You seem to have a lot of pores in the welds you need to know what type of copper you have.
1. Oxygen free copper (CDA C10200 ) = good for welding no oxygen content
2. Tough pitch copper (CDA C11000) = bad for welding as it can contain up to 500 ppm oxygen

Paul

 

[sutty]

Cheers Paul, I have no idea what type, just some off cuts we had lying about.
I didn't know if it was because the torch set up was dirty, left the job dirty too. Just looked at the place I get my metals from, no spec stated. I'll ask next time I go.
we're sticking to silver solder for this project.
Thanks for the advice , always welcome.

Best regards sutty

 

[sutty]

Hello guys , finally got started, Eddie made the boiler top and bottom caps under close supervision, we didn't use the hammer form method we pressed them out, another trip to the metal shop tomorrow for the copper for the firebox top. Still waiting for the material for the firebox.
regards sutty

 

[Steamchick]

 

[sutty]

Hello guys, the material for the firebox turned up so got that sorted, had a bit of luck with the holes for the cross tubes, I had along series centre drill that was the exact size of the cross tubes. some pix of the set up below, also some pix of the fire box, Ive left the cross tubes a little long and plan to skim them off after silver soldering

Regards sutty

 

[Steamchick]

Hi Sutty. Don't trim them except as necessary to prevent them being choked by the outer tube. The copper actually conducts heat through to outside the main firebox, so aids heat transfer, and you sold really have about 1/8" 3mm min. projecting for a fillet of silver solder to strengthen the joints.
Looks really good though!
Is there 0.002" to 0.004" clearance to form a capillary gap for the silver solder?
K2

 

[sutty]

Ken, ok will do, we’ll just take the corners off the out side ones, I might even get Edd to make some longer ones for the middle tubes, never thought about the extra length and the heat transfer.
they’re a good fit so should be ok. Got the bronze for the bushes so they’ll be some repetition turning for Edd in the morning, we might even get the outer shell drilled .

best regards. Sutty

 

[Steamchick]

Hi Sutty, if you have an auto-centre-pop, you can easily distort the edge of holes 3 or 4 times around the circumference of the holes, which can be used to locate tubes and bushes centrally so there is just a couple of thou gap all round for the capillary action of silver solder to penetrate through the joint. If you have some feeler gauges, you can check this with the thinnest 0.002in. feeler, which should be so flexible you can bend it to fit the curve of the small pipes. I haven't used a feeler, but you can try...
K2

 

[Weldsol]

Looking at your pictures the wall thickness of your copper looks a lot on the thick side or is it an optical effect ?
Paul

 

[sutty]

Hello Paul, the thickness of the bits were suggested by steamchick as I had no idea about the stresses involved or the regs around boiler construction. The firebox shell is 2' x 10g the end caps are 3mm, they do look pretty meaty in the pix.

Regards sutty

 

[Weldsol]

Hello Paul, the thickness of the bits were suggested by steamchick as I had no idea about the stresses involved or the regs around boiler construction. The firebox shell is 2' x 10g the end caps are 3mm, they do look pretty meaty in the pix.

Regards sutty

It must be the picture as it looks a lot bigger than 10g .
My Allchin traction engine boiler (published design) was 10g for the front & rear firebox plates and 13g for the rest.
the barrel was 13g and the fire tubes 22g working pressure 100 psi -200 psi hydraulic test and 120 psi steam test
My Burrell 3" scale was shown as 10g firebox and barrel ( again published design ) I ended up making a steel one as I could get hold of all the correct grades of material complete with all the cert's for just beer money and I did the same for my Shay 71/4" gauge loco
Re pickle I have always used citric acid crystals at home as it is safer although a bit slower (but that depends on how much crystal to water ratio you use.)
Paul

 

[sutty]

Hello Paul, I'm on a steep learning curve here, but the best skill I have ever learnt is patience. I got some citric acid crystals and I like the way they work.
we done a bit more today, got the boiler bushes to knock up tomorrow and might even get some soldering done, Ive got some plans for a small water feed pump so might make that the weekend, not sure yet where it should enter, I presume it's below the water line.
I think all the bits inside the shell are done , I'll check them all before we start soldering.
Regards sutty

 

[Steamchick]

Hi Weldsol,
Simply: As an international standard I use AMSE design rules, as explained by Koso Hiraoka in Live steam and outdoor railroading: Nov/Dec 2006.
I recommend you buy a back copy (copyright prohibits me from copying it to this forum).
Also, I have researched the Compressive strength of tubes, and hoop stress calculations, and found the weakness in many books and boilers is the failure mode of tubes with boiler/steam pressure on the outside: Particularly where the tube is penetrated for bushes, cross-tubes, etc. - For this I understand ASME use a "blanket" stress concentration factor of 3.3. (I had previously used a determined SCF using diameters and thicknesses from empirical tables and generally had an SCF of 2.5).
I guess that many who have designed boilers "back in the day" - decades ago - didn't have the research from the Web and modern safety standards to work with, so many old boilers do not meet my calculated stresses or the ASME limits.
I simply believe that when advising others in public (like this forum) I must recommend the best I know.... to the best of my knowledge. Hence my recommendation for the thicknesses of tubes for Sully has followed that principle.
I would query your boiler designer - if he is still able to explain his choices of thickness? (I have found many designs from the 1920s to 1970s that would fail today's ASME requirements).
If any experts can advise better, then that would be very good. (I am NOT an ex-spert, just a "spurt" that has been "under Pressure"!).
K2

 

[Weldsol]

Hi Weldsol,
Simply: As an international standard I use AMSE design rules, as explained by Koso Hiraoka in Live steam and outdoor railroading: Nov/Dec 2006.
I recommend you buy a back copy (copyright prohibits me from copying it to this forum).
Also, I have researched the Compressive strength of tubes, and hoop stress calculations, and found the weakness in many books and boilers is the failure mode of tubes with boiler/steam pressure on the outside: Particularly where the tube is penetrated for bushes, cross-tubes, etc. - For this I understand ASME use a "blanket" stress concentration factor of 3.3. (I had previously used a determined SCF using diameters and thicknesses from empirical tables and generally had an SCF of 2.5).
I guess that many who have designed boilers "back in the day" - decades ago - didn't have the research from the Web and modern safety standards to work with, so many old boilers do not meet my calculated stresses or the ASME limits.
I simply believe that when advising others in public (like this forum) I must recommend the best I know.... to the best of my knowledge. Hence my recommendation for the thicknesses of tubes for Sully has followed that principle.
I would query your boiler designer - if he is still able to explain his choices of thickness? (I have found many designs from the 1920s to 1970s that would fail today's ASME requirements).
If any experts can advise better, then that would be very good. (I am NOT an ex-spert, just a "spurt" that has been "under Pressure"!).
K2

 

[Weldsol]

I was not querying your calculations ! just the photo made the material look like 6mm thick.
And I have a copy of the ASME boiler code and the EU PED
I think you read things in my quote that weren't there
Paul

 

[sutty]

Guys, Like I said we're on a learning curve, Paul you're right, these are just phone pix, can't be arsed to dig out a proper camera.
Edd already knows and understands there's a difference in the stresses a copper tube can stand under heat and pressure, and now he knows how much heat copper sucks up. we started to solder in the cross tubes in the fire box, we started with a No 1 nozzle on the O/A mainly because I didn't want him to linger in one spot and melt the tubes but it was nowhere near hot enough, needn't have worried though he took to it like a duck to water. we had to go up to a no7 nozzle to get the heat in then back to No5 for better control, a bit too much on one side because he was moving the torch too slow but the other side was a lot better, the flue into the firebox impressed me.
I set it up on a lazy susan from Axminster tools so he could spin the job while he heated the job.

Best regards sutty

 

[Steamchick]

No problem Weldsol. I was simply saying where I was coming from..... because I am not 100% confident that I am doing it right. If anyone knows better, I want to learn. If some of what I am doing is right, then it is good to get feedback to that effect, and where I am wrong, I need to be corrected.
So I welcome your comments.
Cheers,
K2

 

[Lloyd-ss]

Hi everyone, I am really late to the party on this one and have to admit that I know nothing about boilers except that the potential energy contained inside one is something that must be understood, and treated with great respect.
I am very curious about copper as the material choice. Cost and strength are a couple of negatives. Aesthetics, heat transfer, and maybe authenticity are a couple of pluses. I know that if I hunted around in previous threads I might find the answer, but it seems like there are some seasoned veterans right here, and I am hoping to learn. And sutty, with your extensive welding background, you could have been working with a material you had lots of experience with, so there must be so good motivation for using copper. There is definitely some good advice in this thread, and I am not at all questioning the material choice, I am just curious.

I have done unofficial destructive testing of high pressure (3,000 psi plus) air tubes for air rifles and I have found that all materials met or exceeded their spec, so the same should be true with your material choice. But sometimes the failure point isn't where you might intuitively think it is going to be, but when you do the calculations, you find out that yup, that is right where it was supposed to fail.
Just my 2 cents.
Lloyd
P.S., I have YouTube videos of some of those tests.

 

[sutty]

Hello Lloyd, we decided, my grandson and I, to build a model of an old mill steam engine. Mainly to get him away from anything with a screen. I have no experience of steam , boilers or engines or working with copper.
I had no idea about the properties of copper or the regulations around boilers but a couple of post on the net and soon help was at hand. The knowledge that's available at your finger tip is amazing, Steamchick had a look at what we were proposing to build and explained what we needed to change and why and advice from Jens, and Weldsol helped. It's coming along now and I think my apprentice is enjoying it.

Best regards sutty

 

[Lloyd-ss]

Sutty, thank you for taking the time with your grandson. He will remember this project ... and you... forever.
I will sometimes take my grand daughters on "a nature walk" thru our woods. And for the same reason you do it with your grandson. I tell their mom that I am going to take them on a "forced march", LOL. She understands the humor. They grumble at first, but so long as I don't push too hard and take the fun out of it, they enjoy it, and learn a lot, too.
Lloyd
P.S. I appreciate the "art" of good welding, although few elevate it to that level. I never could.