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strongest joint copper ?

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strongest joint copper ?

Unread postAuthor: maggotman » Wed Jan 07, 2009 7:18 pm

in the very near future i will be making a hi pressur copper coaxel

i have 2 choices solder the fittings or braise them
i would Imagen the brazed joint would be stronger but would the heating process weaken the mettle i am using 28mm pipe chamber and 15mm barrel and up to 1000psi

what removable joint could i use to access the piston i don't trust compression fittings with this pressure
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Unread postAuthor: sputnick » Wed Jan 07, 2009 7:57 pm

I think just soldering would be sufficient, I would be worried about maybe accidentally melting the pipe with brazing or worse, thinning it without your knowledge only to be discovered upon pressurizing :shock: , after all it IS the same material that you are getting hot enough to melt, Have you heard of people brazing copper pipe before? because I have never heard such a thing.

I would just stick with soldering, its easy and it is very strong, probably the joint will be stronger than the pipe is anyways.

As for accessing the piston, what about connecting a male thread adapter to the copper, then using a threaded galvanized reducer as a cap? then adding all of your fill valves and trigger to that.

EDIT: I researched brazing copper pipe, and it is real and stronger than soldering, but I do not know if it is really needed in this case... solder has done well so far, I would look into if copper can even hold 1000 psi.
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Unread postAuthor: inonickname » Wed Jan 07, 2009 9:09 pm

Brazing is stronger, but you're going to hurt yourself taking copper to 1000 psi. I haven't found any copper pipe which will even nearly safely hold that pressure.
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Unread postAuthor: Gippeto » Wed Jan 07, 2009 10:40 pm

A brazed joint is actually stronger.


BUT;

The temps required for brazing will anneal the copper tube, and actually lower the maximum working pressure.

95/5 tin/antimony would seem to be a better choice.

According to the copper tube handbook, 3/4" Type M has a rated working pressure of 701psi @ 100F, and a burst pressure of 4715psi.

3/4" Type L has a rated working pressre of 1002psi, and a burst pressure of 5900psi.

Get yours here; :) It's free.

http://www.copper.org/publications/pub_ ... ndbook.pdf
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Unread postAuthor: iemand » Thu Jan 08, 2009 10:58 am

I asked someone in the shop where I buy my copper stuff, and he told me those removeable ones are the strongest, although he wasn't 100% sure :roll:
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Unread postAuthor: GalFisk » Sat Jan 10, 2009 6:56 am

Removable as in compression fittings? Those should not be used in cannons at all, they slip. I know of at least one accident with those (no injury fortunately).
I've used a female adapter with a screw plug to access the piston in my copper pneumatics.
The copper tube handbook is a great resource. You can also find the rating of different kinds of solder joints there. Personally I'd go with steel when dealing with these kinds of pressures though.
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