Which nameplate marking indicates a pressure vessel safety valve?

The marking on a pressure vessel that indicates it possesses a safety valve is represented by "UV." This designation is part of the ASME (American Society of Mechanical Engineers) Code, which governs the design and construction of pressure vessels. The "U" in the marking denotes that the vessel is constructed under the provisions of Section VIII of the ASME Code, specifically dealing with pressure vessels. The "V" indicates that the pressure vessel is provided with a safety valve, which is essential for ensuring the safe operation of the vessel by relieving excess pressure to prevent potential failures or accidents.

Understanding the context of the markings is crucial. While "V" marks a vessel associated specifically with pressure, and "NV" signifies a non-pressure vessel, neither clearly indicates the presence of a safety valve. "UM" refers to vessels designed for unfired pressure vessels under similar ASME guidelines but doesn’t specifically denote a safety valve. Thus, "UV" is the correct choice since it clearly communicates both compliance with safety standards and the inclusion of a safety valve feature within the pressure vessel.