Brazing of threaded joints 2

[fpnut]

How common/safe is it to braze a threaded joint?

Not looking to do it, just curious since I came across a really old piping manifold (30+ years old) that was still in use. Seemed to me like an threaded valve brazed onto a block.
I'm just wondering how common it is, or any pros and cons of doing it. Just seemed to be a good way to create a permanent, leak free joint... until you need to replace the valve of course.

 

[TugboatEng]

I see no issue. The clearance might be a bit tight to get meaningful capillary action with a silver alloy but silicon bronze can be used to build a nice cap. Seal welding is a procedure in some jurisdictions but brazing is easier, especially in the field, when temperatures allow.

 

[Artisi]

May have been brazed to stop leakage.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[CWB1]

It’s commonly called an “emergency fitting,” and is done all day every day by plumbers and hvac techs. They’ll braze them onto all manner of valves, manifolds, and tubing to make uncommon connections.

 

[MJCronin]

Is it just me, or wouldn't such a threaded/brazed joint be inherently weaker than a joint designed specifically just for brazing ?

Yes, yes... I am aware that it is probably done all of the time in the field and yes, we are dealing with low pressure systems.

But, my question is ... wouldn't a brazed seal-welded joint be weaker than a real seal-welded joint ???

MJCronin
Sr. Process Engineer

 

[EdStainless]

In most of these systems seal welding isn't really an option.
We used to do it to high purity gas lines where needed absolutes seal, most joints were socket brazed but some were threaded and brazed due to availability of fittings.

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P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

it is unnecessary to to tap a hole then braze it. fitting to hole, tack in place then braze it.
drilling and tapping holes for braze is wasting time and labor.

 

[TugboatEng]

Fabricating special socket fittings when threaded options are available is a waste of time and labor. Ed's statement is true. Different industries have different requirements and this is especially the for systems that don't see mass production.

 

[moltenmetal]

"molten metal" is the thread sealant of choice above about 400 F, if straight threaded fittings with metallic gaskets are not an option.