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What the ASME U and R stamps mean for your pressure vessel

When a customer asks for a code vessel, the conversation quickly turns to stamps. Silverfox holds the ASME U Certificate of Authorization and the National Board R stamp, and understanding the difference helps you specify the right scope and budget.

The U stamp: new construction

The U stamp certifies that a pressure vessel was designed, fabricated, inspected and tested in accordance with ASME Section VIII, Division 1. That means calculations reviewed against the code, welders and procedures qualified to Section IX, non-destructive examination as required by the design, a hydrostatic or pneumatic test witnessed by an Authorized Inspector, and a Manufacturer’s Data Report (U-1) registered with the National Board. Owners, insurers and jurisdictions rely on that data report for the life of the vessel.

The R stamp: repairs and alterations

Vessels in service get corroded, re-rated or modified. The R stamp authorizes us to perform repairs and alterations on existing code vessels under the National Board Inspection Code (NBIC), with the same discipline: written procedures, an Authorized Inspector and an R-1 or R-2 form that keeps the vessel’s history complete.

Code or non-code?

Not every tank needs a stamp. Atmospheric storage, low-pressure process equipment and many skid-mounted vessels can be built as non-code, saving cost while still following good engineering practice. We help you make that call early, because adding a stamp after fabrication is rarely possible.

• Design pressure above 15 psig usually points to a U-stamped vessel.
• Jurisdictional requirements in Texas and neighboring states vary; we check them for you.
• Repairs to any stamped vessel should be done by an R-stamp holder to keep it insurable.

Planning a new vessel or a re-rate? Request a quote and we’ll review your drawings within one business day.