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Beading rolled copper tubes

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cnr6400:
Hi Bryan, I didn't do any beading on the boiler I built, just used the expander in my photos, and boiler worked fine. I had propane gas firing on that one, not sure if the tube beading is needed with coal firing or oil firing to help cope with the ash and or soot abrasion using those fuels, just in case you are not firing with gas.  :cheers:

Jasonb:
I don't know what regulations apply where you are but for anyone reading this in the UK at the end of the day any queries should be put to whoever is going to inspect and certify the boiler as they will have the final say.

SandCam:


Hi Guys,

Copper tubes in a mild steel plate will lead to Galvanic corrosion of the steel around the joint.
Steel being Anodic and Copper being Cathodic.

Not really the best combination and may not be permitted by your local regulations.

Just a warning.

Sandy... retired boiler maker.

Jasonb:
It's quite common on some of the 2" and 3" model traction engines, Haining's designs have been around for years and seem to get approval without problem.

Zephyrin:
years ago I had changed the flue tubes of a very old vertical steel boiler with copper tubes, expanded in their hole between 2 cone bits and a long threaded rod (no beading); it was successful, pressure tight up to 3 bar, and tested up to 8 bar after caulking with soft solder...
I agree that this fix wouldn't pass the boiler inspector test, but it allows steaming my engine once a year.

the galvanic corrosion occurs with see water, owing to its large amount of sodium chloride, with the low ionic content of the water the steam enthusiasts usually use, this kind of corrosion remains remote I guess !
 

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