UG-99(a)(1), cosmetic grinding after hydrostatic test 2

[hcjulien]

Hi,

according to you, can we grind flush longitudinal and circumferential butt weld after hydrostatic test according to UG-99(a)? Please take note that grinding will be done without affecting the required thickness of the shell.

If yes, what are your references (standard, books, etc.)?

Regards,

Hcjulien

 

[metengr]

Why don't you check ASME B&PV Code, Section VIII, Div 1? This is the obvious reference I would use.

 

[hcjulien]

Metengr,

thank you for your quit reply. UG-99(a)(1) only mention ''base material''. Is that include weld?

Regards,

hcjulien

 

[metengr]

Yes, this would be applicable to weld cap reinforcement.

 

[hcjulien]

metengr,

because it's not 100% clear in the ASME Section VIII div. 1 UG-99(a) paragraphs, do you have a reference book, interpretation, etc. with a clear mention that weld cap reinforcement are included in the ''base material'' mentionned in UG-99(a)(1)?

Thank in advance,

hcjulien

 

[doct9960]

hcjulien,

can we grind flush longitudinal and circumferential butt weld after hydrostatic test according to UG-99(a)?

In my opinion, grinding flush the weld is not considered "cosmetic". Was it possible to perform the grinding prior to hydrostatic test? If your answer is YES, then you have violated the Code. UG-99(a)(1) is very clear on that.

You can still grind flush the weld, but you need to re-hydrotest. Check with your AI.

 

[metengr]

The reply by doct9960 forced me into re-thinking about this scenario. Cosmetic grinding is really a subjective call. The Code is silent on describing what "cosmetic" is and my interpretation is allowing for the mechanical removal of metal without affecting the pressure boundary. There is nothing that describes how much to remove regarding surface area, so in my opinion you can cosmetically grind several square feet or several square inches of base metal as long as the pressure boundary thickness is not impacted. The code is silent on flat topping butt and seam welds. Yes, the Code is specific regarding base metal because welds can have reinforcement and local grinding to prepare the surface for NDT is permitted. I consider this cosmetic, as well

Now, the key words are "after fabrication is completed". If the vessel was hydrotested and stamped prior to flat topping welds, in my opinion you have met all of the necessary code requirments. Flat topping welds for purposes of installation or to enhance field examination for TOFD or conventional UT no longer falls under the ASME B&PV Code. An in-service repair code like API or the NBIC takes precedence. Once the vessel has been hydro tested and stamped it is completed.

If the vessel was hydrotested and not stamped because flat topping was performed before stamping, I would have to agree with doct9960 that fabrication was not completed and you must re-hydrotest before stamping.