Pressure Vessel Alteration Requirement?

[TiCl4]

I have been exploring addition of cooling baffle plates inside an existing pressure vessel. The addition of these plates would require new brackets to be welded to the sidewall of the vessel. We plan to do this in two parts - first, to weld the brackets on and put the vessel temporarily back into service while the rest of the installation is being prepared, and second, to weld in the baffle plates and associated cooling piping in the tank. Since welding the brackets to the vessel is touching the pressure boundary of the tank, I contacted an inspector to determine what would be needed for approval of the alteration. While I expected the required NDT for the bracket welds, what I did not expect was the inspector's assertion that ALL welds that then attach to those brackets then are also subject to the same requirement for inspection and approval. He seems to believe that anything attached to these brackets would now constitute a pressure boundary modification and would thus require inspection.

Where would he be getting this requirement? If I welded these brackets on and, say, later on welded on a vertical bracket riser on one of the already-installed brackets, how would that affect the pressure boundary of the vessel? The failure of that connection weld would not result in loss of containment.

Any guidance on what requirements are for this in ASME VIII? Any pointers on which subsections have definitions of the pressure boundary of the vessel and which sections cover alterations to existing vessels?

 

[TGS4]

What is the original Code of Construction of this vessel? Where is it physically located? If you are in North America - it is likely to be less an issue of the original Code of Construction, and more an issue with the NBIC/jurisdiction.

 

[TiCl4]

ASME Section VIII Div 1. NB Stamped - North America. Pressure vessel was built in circa 1973. Jurisdiction isn't an issue; this pressure vessel is located in one of the few states where there are no laws concerning pressure vessels. It is completely legal to create, modify, and run a pressure vessel at pressures >15 psig with no code stamp.

So it's not a jurisdiction thing. I was wondering how the inspector got that internal additions to a pressure vessel also became part of the pressure-retaining boundary, and what Section VIII Div 1 had to say about modifications or inspection requirements there. I've glanced through a few sections in the code but haven't found anything yet.

 

[david339933]

The inspector should be able to point to the Code and show you where they are getting this information. NBIC would classify this as a repair or alteration based on the loading of the clips. See NBIC Part 3 - 3.3.3 and 3.4.4.
May also want to see U-1(e)(2) and endnote 3 of Sec. VIII Div. 1

 

[r6155]

ASME VIII is for a new equipment.
Good information in API 510, API 579 and ASME PCC-2.
Be careful, your equipment is in service since 1973!!

Regards

 

[TiCl4]

R6155,

Thanks for the warning. The recent fit-for-service review has showed no material loss over time of the vessel walls; the vessels are also run atmospherically, with the pressure rating only required during upset conditions.

Thanks for the input, all - I'll take a look to see what some of these resources say.