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Defining Code Stamps

Defining Code Stamps

Defining Code Stamps

A conversation with a "CODE" shop the other day raised the question of U versus R stamps.  The code shop insisted that a "U" stamp is acceptable for repairs instead of an "R" stamp.  I disagree but others in my group do not.  What is the concensus of the forum?

Secondly,  Can a 3/4" thread-o-let be installed on U stamped pressure vessel without a code shop?  I say no but some in my group do not.  They say there is an exemption in the code but I haven't seen it yet.

Thanks in advance.

RE: Defining Code Stamps

1. See the Forward of ASME SecVIII Div.1 Second paragraph.
Rules for "NEW" construction. "U"
2.NBIC-RA-2110(a) "repair or alteration". "R"

Most jurisdictions will require an "R" for repairs.

Is the "thread-o-let" a pressure retaining part attached directly to the pressure vessel? If so,you need a Code Stamp to attach it,"R"or"U". Depending if the vessel is used or new.

Check with the National Board or the Local Jurisdiction.

RE: Defining Code Stamps


I think that it is important to understand that the ASME Boiler and Pressure Vessel (B&PV) Code is a standard for new construction ONLY.  Section VIII of the B&PV Code has defined rules for the use of the "U" Stamp (and others) on new pressure vessels.

The Standard (and Code) for repair is ANSI/NB-23 "the National Board Inspection Code", which is the responsibility of the National Board of Boiler and Pressure Vessel Inspectors.  NB-23 has defined rules for the use of the "R" Stamp (and others) on in-service pressure vessels.

Not all states, commonwealths and provinces require compliance with these Standards so you should always check with the juridiction in which the equipment is installed (registered) to be sure of the requirements.

Regards, John.

RE: Defining Code Stamps

Any repair or alteration to ASME stamped pressure vessel can be performed with the use of a "U" stamp providing the P/V has not been put in service. Once the P/V has been put in service the repair organization must be a holder of a "R" stamp and the Codes of use are API 510 and or NBIC and any rules for construction not covered in these codes will refer back to ASME BPVC Section VIII the original code of construction.

RE: Defining Code Stamps

LAMAN75-I do not entirely agree with your statement. What if the vessel is shipped elsewhere and needs an extra fitting prior to being used? I believe this would require a "R" and not a "U". The way I read the Code is that after the final pressure test and stamping the vessel is complete and then falls under the NBIC. There are some provisions for some touch-up work and openings.

So now you say,what if we just finished a vessel and discovered we forgot to install a small coupling "R" or simple rework in the place of manufacture. This could be addressed by your QC System by giving the AI authority until the vessel is shipped and writing a procedure for rework and further testing. Or you may state it is not complete until the Data Report is signed. That is something you need to discuss with your AIA. It may be possiable to not to require an "R" in this instance.

I would also not be happy with the use of API 510 for the alteration or repair of a "U" stamped vessel.

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