Weld Repair of ASME Nozzle 2

[Derek57]

Good afternoon all,

A LH2 pressure vessel that was manufactured about 20 years ago was recently opened and had an internal inspection performed. During the inspection, it was discovered that there was incomplete penetration on the nozzle weld, and after referring to the ASME Code, the nozzle did not have to have RT performed at the time of construction.

Does this weld need to be repaired according to NBIC standards or another national standard? What other options are available to ensure continued and safe operation?

Thank you very much

 

[metengr]

Yes, this weld should be repaired after a visual inspection of an in-service vessel. Regardless of what was done earlier during construction, incomplete penetration can result in fatigue crack propagation in service or other potential failure because this is a crevice. Remember, ASME Code only provides minimum requirements for long term safe operation.

You can try to evaluate if service loads or conditions can result in crack propagation. This requires engineering analysis to justify. It would be much easier to grind out and weld repair to ensure complete penetration.

 

[Derek57]

Thank you very much metengr! I'm still getting the hang of ASME and PV engineering so I very much appreciate the feedback.

 

[Vinch]

Derek,

If you are referring to incomplete joint penetration it may not be a defect as this nozzle weld could have been designed that way. Nozzle welded only from one side is allowed per ASME sect.8 under some conditions. It is not be the best practice but it is allowed.

You should look for the design criteria for that joint from manufacturer drawings and data reports. Liquid hydrogen being non-corrosive, I would not worry to much about having a crevice on the inside unless there is considerable load cycling.

If it was designed as a full penetration weld or fillet welded from both sides then it is a weld defect and repairs will be needed according to NBIC standard.