Posthydro welding
Posthydro welding
(OP)
We have an ASME Code Vessel that has been completed through hydrotesting. The question has now been asked if we can move the nameplate bracket to a new location. My understanding has always been that if we weld on it again we will have to rehydro it. I have seen an answer in another thread that if the welding is for an external attachment (IE; Nameplate bracket) we don't have to rehydro it. Is this correct? Where in the Code does it specify this?





RE: Posthydro welding
Put yourself in the position of the AI. Let's suppose we decide to fillet weld brackets to a pressure vessel and let's suppose something went wrong and introduced a crack. Now you have a potential problem with a new vessel. I agree, the above scenario is remote if proper weld practices are followed. Codes are conservative.
If this were a boiler, Section I does permit some flexibility for post hydro weld repairs to P-No 1 base materials. However, it is up to the AI for these types of weld repairs as final acceptance.
RE: Posthydro welding
Not in code under NBIC repairs.
RE: Posthydro welding
Yes, it is "welding", but why would you consider that enough heat to material affect metal properties?
RE: Posthydro welding
It makes no difference what you or I think regarding the above. It is a Code requirement regarding no fabrication welding after hydrotesting.
If you need to re-attach the nameplate do it after the vessel is commissioned under the NBIC.
RE: Posthydro welding
Unfortunately, very small welds can easily create cracks in the pressure part HAZ depending on chemistry and cooling rate and weld filler metal selection. Will they grow under the loading conditions - maybe not, maybe so.
RE: Posthydro welding
RE: Posthydro welding
Often a nameplate would be placed near a manway. Often manways have structural connections near them such as manway davits or platform clips. Welding to these should not be an issue if such a location would be acceptable.
jt
RE: Posthydro welding
No.
The rules for alternative exmination and laternative testing methods are very clear - NDT or pressure test.
RE: Posthydro welding
They simply rivetted it to the plate pack.
They avoided the welding, and avoided redoing the hydrostatic test, but for some reason, it still leaked.
How I wish this wasn't a true story.
Regards,
SNORGY.