Simple Question

Simple answer= insurance.

Doesn't ANYONE know how to search????????????????

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• The "R" Stamp is required for all welding repairs performed on pressure vessels and, in addition, federal DOT law requires a holder of an "R" Stamp perform all welding repairs involving the shell of a DOT/MC specification tank. A "pressure vessel" is defined as any tank or vessel designed for operation above 15 p.s.i.g.
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• What's an "R" Stamp? Guthrie Heli-Arc

In laymen terms (and the way I understand it)

- with R-stamp the item has been repaired

- without R-stamp it is in its original conditions!

An R stamp allows for field repairs of pressure vessels, versus the lesser U stamp that applies to shop fabrication.

If the OP is outside of ASME jurisdiction, this may be moot.

thanks all for the valuable comments,, but I am from outside US and Canada. Is it still still required ? I know that National Board is only in US. Is that right?

Well, what did the Enginer/Surveyor from the company that supplies burst/leak indemnity insurance cover on the vessel say in response to the telephone call?

An "R" Stamp is a triennial endorsement on loan from The National Board of Boiler and Pressure Vessel Inspectors which allows us to perform repairs and alterations to a variety of non-fired pressure tanks and vessels.

And the main difference between them:

U stamp is for fabrication of pressure vessels and the R stamp is for repair and alteration of pressure vessels. These are stamped on finished work signifying complete compliance with the code requirements.