The 'U' stamp indicates which type of vessel?

• A. Fired pressure vessel per Section VIII Div.1
• B. Unfired pressure vessel per Section VIII Div.1
• C. Unfired pressure vessel per Section VIII Div.2
• D. Pressure vessel components

Answer: (B)

The U stamp is the mark for unfired pressure vessels. It signifies that the vessel was manufactured under the rules for unfired pressure vessels in ASME Section VIII, Division 1. If a vessel is designed to Division 2 rules, it would carry the U2 stamp instead of U. So the correct interpretation is an unfired pressure vessel per Section VIII, Division 1.