Which statement best describes an identifying feature of a lifter roof tank (covered floating roof)?

• A. Lifter roof tanks use a single solid cover.
• B. Two roofs: Tank cover and floating roof.
• C. A vapor dome on top.
• D. A built-in spill containment pan.

Answer: (B)

A lifter roof tank is a covered floating roof storage tank, meaning it has two roofs: a fixed outer tank cover and a floating roof inside that sits on the liquid surface. The fixed outer roof provides weather protection and helps seal against rain, while the floating roof rises and falls with the liquid level to minimize vapor space and emissions. This dual-roof setup is the identifying feature, distinguishing it from tanks with only a single solid cover or from bare floating-roof tanks. Features like a vapor dome or a spill containment pan can appear in various designs, but they’re not what defines this type.