Local distortion on lap ring flange

[quantrus]

I asked this question on another forum but have had no responses so far. It concerns the hydrotest on an ASME pressure vessel. A vessel recently built to Section VIII, Div 1 has heads attached to the shell with flanges. There is a fixed flange on the shell and a loose flange on the head that sits behind a welded lap ring. The assembled vessel was inspected, hydrotested, certified, installed at site (hydrotested a second time on site) and placed in service. During a turnaround some months later it was opened for cleaning. It was observed that the lap rings on both heads were somewhat distorted (presumably during the hydrotest). Both lap rings were rotated such that a dial guage reads the outer diameter to be higher than the inner diameter on the face (from 1/32" to as much as 1/16" across the 1 1/2" face). Three questions: 1) Does the lap ring distortion on hydro effect the certification? 2) Must the lap rings be remachined (neither has leaked)? 3) if lap rings are remachined will another hydrotest be required?

 

[SnTMan]

quantrus, don't take this as definitive, but:

1) No
2) No
3) Probably not, but some means to prove the work will likely be needed.

As always, you will want to consult your AI.

Regards,

Mike

 

[quantrus]

Thanks for your comments.