Thoughts And Perspectives From The Team

Pressure Vessel Certification Requirements

AUTHOR T Bailey, Inc.


PUBLISHED Mar 13, 2021

Pressure vessels are robust storage containers that hold products under pressures ranging from 15 PSI all the way up to a whopping 3,000 PSI. While vessels can be built to hold higher pressures, the certification requirements for these are increasingly stringent.

The most common types of pressure vessels are process vessels, heat exchangers, and storage vessels. These can be found in most industrial and commercial environments.

Because these vessels operate at such extreme pressures, a poorly built pressure vessel is a massive workplace hazard. strict standards are in place to ensure they are fabricated correctly.

What Is Pressure Vessel Certification?


pressure vessel stamps

There are a variety of pressure vessel certification requirements that must be met when fabricating new vessels or when making repairs or alterations to existing vessels.

These pressure vessel codes ensure that vessels and boilers are safely built and that future engineers have a solid record of a vessel’s entire history, including fabrication and all the repairs and alterations made to the vessel.

What Are the Different Pressure Vessel Stamps?

There are many but two common pressure vessel code stamps in the USA are an ASME code “U-Stamp” and the NBIC certification “R-Stamp.”

The U-Stamp (ASME Pressure Vessel Code)

The ASME Certification for Unfired Pressure Vessels (U-Stamp) comes from Section VIII Divisions 1-3 of the ASME Boiler and Pressure Vessel Code — a set of regulations and safety requirements accepted by over 100 countries.

U-stamp ASME standards govern everything related to construction, design, and engineering of unfired pressure vessels including:

  • Pressure vessel thickness
  • Material
  • Design of penetrations and connections
  • The way the vessel is joined
  • And much more

There are three different U-Stamps, each one related to Divisions 1-3 of the Code.

R-Stamp (NBBI Authorization)

The NBBI Certificate of Authorization (R-Stamp) comes from the National Board of Boiler and Pressure Vessel Inspectors. This stamp governs repairs and alterations.

Both pressure vessels and fire vessels (like boilers) fall under the purview of the R-Stamp.

How To Determine Which Pressure Vessel Certifications Are Required?

Which stamp you use depends on the sort of work you’re doing. If you’re doing repairs or alterations to an existing vessel, then you’ll need to use the R-Stamp. If you’re fabricating a new pressure vessel or boiler, then you’ll use one of the three U-Stamps, as these regulate new construction.

To help you figure out which stamp to use for new vessels, here are brief descriptions of the three different types of U-Stamp:

  • Division 1 U-Stamp. Governs the fabrication of design-by-rule vessels. Is best used for small-scale, standard, specific designs.
  • Division 2 U-Stamp. Regulates the construction of design-by-analysis vessels. Is often used for orders with multiple identical vessels as it allows you to fabricate using thinner materials, thus improving efficiency. As a result of allowances like thinner materials, Division 2 has stricter testing requirements.
  • Division 3 U-Stamp. Governs the design and fabrication of high-pressure vessels that have an internal or external operating pressure of over 10,000 PSI.
As for coatings, the intended service conditions will determine the type of coatings a vessel receives (if any). Coatings are governed by customer and design engineer requirements.

Can a Pressure Vessel Have Multiple U-Stamps?

No. Once a vessel or boiler has been built and given a U-Stamp, all further alterations and repairs are R-Stamped.

Can a Boiler or Pressure Vessel Acquire Multiple R-Stamps?

Yes. Anytime a pressure vessel is repaired or altered in any way, an R-Stamp plate must be affixed to the vessel. Or, if a stamp plate already exists, it must be updated with the date of repair and paperwork must be filled out recording what was done to the vessel. This paperwork must be filed for future reference in accordance with the requirements of the governing jurisdiction.

Quality Control Systems in Place for Pressure Vessel Certification

The testing and quality control measures required for new pressure vessels depends on the U-Stamp used. For example, Division 1 vessels can be exempted from NDE testing via increased design factor, while Division 2 vessels have more stringent NDE requirements.

Here at T BAILEY INC., we perform a wide range of robust testing on our pressure vessels, including:

  • Radiographic Testing (RT)
  • Ultrasonic Testing (UT)
  • Impact Testing
  • Hydrostatic Testing
  • And much more

A Quality Pressure Vessel Fabricator Near You

Since 2011, T BAILEY INC. has been fabricating some of the best pressure vessels in the Northwest. Our dedication to stringent quality control and extensive testing procedures ensure that our vessels are built to a superior standard of quality.

From fabrication to coatings and delivery, we are a one-stop-shop for all your pressure vessel needs. To request a custom bid for your project, please contact our office today.

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