Dears,
Is soldering prohibited under SecVIII-1? I cannot find anything against it.
The problem is that copper tubes have to be attached to a copper tubesheet, and the best perfomance we achieved is with solder of liquidus/solidus about 250C. It does not fall into UB, nor UW. So, there are no requirements, but no prohibition neither. Can this be used under U2(g)? Any experience anyone?

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Konrad Anikiel

Our experience is that a "soldered" vessel was rejected in Canada, because the manufacturer had made the wrong translations. The vessel was actually "Brazed", only the translation was wrong.

Sure it is soldering? not brazing?

UB says
Definition: The term brazing as used in Part UB is defined as a group of welding processes that produce coalescence of materials by heating them to the brazing temperature in the presence of a filler metal having liquidus above 840F (450C) and below the solidus of the material.

This is exactly as AWS A3.0 defines brazing. Soldering is defined in A3.0 the same way, only it's "not exceeding 450C".

Is French "brasage" both brasing and soldering? It's "lutowanie" in Polish, only with addition "miękkie" (soft) or "twarde" (hard).

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Konrad Anikiel

Konrad,

we have the same translation in German, LÖTEN means soldering and brazing. It is distinguished by the adjective soft and hard respectively.

However, this does not solve your problem. I would say what is not prohibeted is permitted, but would I accept it as Inspector?
Would I accept glueing? Certainly not!

Since paragraphs like UG-43 do not list brazing as an allowable method for the attachment of nozzles, or UG-55 for lugs, UG-116 does not specify a letter "S" on the nameplate, I would not accept it as an Inspector.

But I have an idea: Can you define the tubes and their soldered connection to be "not pressure retaining internals?" This works only when the shell of the exchanger has the same working pressure than the tube side, and when there is no soldered connection on the outside.
When the nameplate only gives the shell side pressure/temp, there is no problem.
Happy?

Dirk

Dirk,
You wouldn't accept glueing, clear. But I suppose you would accept riveting, wouldn't you? After all, there are still some quite nice rivets seen here and there. And what about thermal shrink connections? What about compression fittings? Even expanding tubes doesn't have that sort of requirements as welding has! And there's more one can enlist, that you use everyday, maybe even not knowing that your life depends on something that you wouldn't be that sure whether it could be acceptable in a pressure device. I think that suitability and acceptability of a method is quite well defined: "provided they give the same level of safety as other methods described"- or so (trying to recall this from the top of my head). The only question: is it possible to prove their level of safety and compare to the other ones? And I'm quite confident that soldering is quite easy to prove, using similar methods as those used to qualify brazing. Anyway, the most important requirement in brazing is that the joint has to show no lower strength than the base material- you can glue metals with this satisfied

PS There's more suitable workaround: solder the tubes, and then expand them. And treat the expansion as the strength method. Solder would be like a metallic gasket (acceptable, yes?). If they pass qualification from Appendix A- no more questions asked. How's that?
After all, these joints don't even have category nor type. SecIV even suggests to use oring seals only! What if such an oring is glued to prevent from loosing? What kind of glue might be acceptable then ? A chewing gum would do?

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Konrad Anikiel

Konrad,

The soldered and expanded connection is certainly acceptable, when qualified as you described. No problem.

DK