GRINDING INSIDE PRESSURE VESSEL AFTER Hydrotest

[Andrea.Abbo]

Good morning,
due to an excess of penetration in the weld of a nozzle connection, is not possible to insert the floating part of the level switch inside the vessel. The vessel was hydrotested and certified by third party for PED certification. Can I grind the excess of penetration without compromising the certification of the equipment? I already asked the instrument manufacturer to provide a float with different shape, but they already provided the smaller one they have in their catalog.

 

[gtaw]

Interesting question. The grinding may reveal a leak path that was a factor during the original hydrotest. This would be more of a concern if the vessel was only subject to a visual examination prior to and during hydro.

The short response would be to rehydro the vessel after the grinding was performed. If the vessel was subject to additional NDE, then I would expect the vessel would have to be retested exactly the same way it had been tested prior to the "rework or repair."

Best regards - Al

 

[Andrea.Abbo]

Dear Gtaw,

thanks for your reply. I also asked a NoBo in charge to release PED certification and I would like to share with you its feedback. First of all is the Manufacturer of the Vessel that shall authorize such activity. Once I will receive the OK to proceed I can grind the excess of penetration, having care just to reduce it and do not go under the thickness of base material. After that a VT and LP inspection shall be carried out. I will report all the above action in a report to be attached into the Vessel documentation and that's it. Grinding is a simple operation which does not change the structure of base metal. Hydrotest after "repair" is not required in this case.

Ciao

 

[XL83NL]

You mention PED, so it's good to consult the NoBo, (or better) let the MFR take full charge and responsibility for the work involved and have him contact the NoBo; after all, it's hiw responsibility to provide the CE-mark.
If this were a vessel constructed to ASME VIII-1, UG-99(a)(1) may have provided you a waive to perform grinding after hydro, without having the need to rehydro;

UG-99 STANDARD HYDROSTATIC TEST
(a) A hydrostatic test shall be conducted on all vessels
after

(1) all fabrication has been completed, except for operations
that could not be performed prior to the test,
such as weld end preparation [see U-1(e)(1)(-a)], and cosmetic
grinding on the base material that does not reduce
the actual thickness below the design thickness; and
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