Re-rating of U-Tube exchanger

[imransaeed1804]

A brand new exchanger (U-Stamped + National board registration) was not stored properly and tubes are corroded internally (30% max). Now as per calcs, still there is enough thickness. What I don't understand/know is that how shall we proceed with the documentation?
1- Do a rerating calcs and get another u-stamp or
2- do another inspection as per NBIC and redo calcs to get another NC reg?

3- if its decided to re-tube the exchanger, R-Stamp is needed?

Please comment.

 

[metengr]

If you still have sufficient wall thickness that does not require a de-rate, you document the inspection results, and place the Hx into service.

De-rating a pressure vessel is not under the NBIC, it is discussed with the local regulatory body to ensure proper pressure relieving devices have been replaced and documented. Re-rating a pressure vessel to a higher design pressure is an alteration by definition in the NBIC.

If re-tubing is decided, this work should be performed under the NBIC, and documented with a Form R1.

Nothing changes with the U- stamp nor with application of the NBIC.

 

[imransaeed1804]

Thanks for your reply metengr. What would be the "local regulatory body" in this case? I thought NB is the locale regulatory authority in US?

 

[metengr]

imransaeed1804
In the US, the local regulatory body are either cities (if large enough) or state agencies. You can visit the National Board web site and look up the various Jurisdictions and contacts.