Fillet Welded Patches with Reinforcing Plug Welds

[mechengr12]

I was hoping someone could provide some additional guidance on fillet weld patch plates in pressure vessels with plug welds. I know this is in ASME PCC-2 and provides some minor details, but I was having some difficulties understanding the requirements. I am looking to put a 304SS 30”x20” plate with plug welds. How large and how many plug welds are required? In comparing the Circumferential force equation is the diameter at mid-wall the diameter of the vessel to the middle of the thickness of the wall from center of vessel? When comparing the allowable load on perimeter fillet weld what is the allowable base metal stress for 308 weld material? (I have run the calculation but my circumferential seems to be much higher since the diameter of the vessel is 13’). Please ask me for additional details if you need some more information to help answer my question.

 

[GenB]

You can look into dimpling vessels for guidance. Plugwelds are governed by pitch. You didn't give thickness who ch) s needed to calculate. T of patch and t of base metal.

 

[Duwe6]

For strength calc's, use the value for your 304 basemetal. 308 is stronger than 304 - hence all good PQR coupons break at basemetal or HAZ. Can't take credit for anything higher than basemetal, so 20.0 kips at 200°F / 18.3 kips at 400°F.

 

[PMCap]

Please note that repair of pressure vessels using Fillet Welded Patches with Reinforcing Plug Welds is prohibited by the NBIC.


Perhaps the below may be of some help in resolving your issue:

Restoration by encapsulation without removal of the degraded area is not prohibited by the NBIC per Interpretation 04-01

This method of restoration can be very cost effective as the degraded area does not have to be removed thus saving fit-up, welding, and examination installation time and avoiding entry of foreign matter into the vessel.

The Encapsulation component attachment weld is typically classified as an ASME Category D weld that would not require volumetric examinations.

The AI has the authority to waive the hydrostatic pressure test.

Typically, a liquid penetrant or magnetic particle examination is performed on the root and final pass of the full penetration encapsulation to shell attachment weld. See NBIC Interpretations 98-33 and 98-38.

Alternatively, the encapsulation component can be supplied with a pressure port for local pressure testing – see NBIC Interpretation 01-15

I suggest you search the internet using the keywords such as asme - vessel - restoration by encapsulation, etc.

Let me now if you need any further help on this method of restoration for which I am extremely familiar

 

[dhengr]

Smaustin12:
I don’t know the ASME codes the way you guys do or should, but a pressure vessel patched with a plate, fillet welded all around, and then tied in with plug welds, sounds like an inferior repair to me. Plug welds are surprisingly difficult to size, space and do well, so each one of them becomes several inches of potential weld defects, which are difficult to inspect. I would assume that you must repair the defect in the original shell first and then your new pl. is primarily a reinforcement.

 

[Duwe6]

sidenote: if you are getting defects in the wrap-around fillet welds on plugwelds the welder needs to be fired/retrained and the foreman immediatly demoted.