Inco 600 weld crack

[Mous1747]

The weld below was done back in march, this is the heat shield of a catalyst converter in a nitric acid plant. this heat shield is made out of Inco 600. this has been in service since march and it was all new back then. The temperature inside the converter reaches about 1100 F. I am told the weld wire is 82

During a startup two days ago after a routine catalyst change, these cracks developed (not sure if these are new cracks or maybe there was something there before but not visible)

What may have caused these cracks? is it bad weld to begin with? or maybe there was a large temperature swing during startup that propagated a crack that was already there? or something else?

 

[EdStainless]

You need to cut a sample out for careful examination.
This could be related to the original fit or penetration of the weld.
I would be looking at the WPS and the actual weld data also.

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P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

That crack has opened up quite significantly, which indicates stored stresses in your structure. Perhaps due to the shrinkage of the circumferential weld that meets at that corner.

 

[Tmoose]

is that a crack in the weld running circumferentially ?

 

[Compositepro]

The crack appears to me to be perpendicular to a circumferential weld.

 

[0707]

What may have caused these cracks? is it bad weld to begin with? or maybe there was a large temperature swing during startup that propagated a crack that was already there? or something else?

According to your quote this is usual in internals of catalyst vessels, during sturt ups and shutdwons when the rise and set of temperature is not smooth controled abrupt thermal expansions can lead to crack welds wich are the more stressed points of the round baffles.

What Ed said is also advisable

 

[Tmoose]

Is that a crack in the weld running circumferentially ?