Which tank car has only one fitting on the top?

• A. Non-pressure
• B. Pressure
• C. Cryogenic Liquid
• D. Tank with Top Multiple Fittings

Answer: (B)

When identifying tank cars by top fittings, the number of fittings on the top tells you what type of car it is. A tank car designed for pressurized cargo normally has a single top fitting—the dome on top houses the valve assembly, and only one top outlet/valve is needed to load, control pressure, and vent the contents. This single top fitting minimizes potential leak points and suits the requirements of handling compressed gases.

Cryogenic liquid tank cars, on the other hand, require multiple top fittings for loading, venting, relief, and vapor return because of the extremely low temperatures and the need to manage boil-off safely. Non-pressure and “top with multiple fittings” designs imply more than one top connection for various functions, which doesn’t match the single top fitting configuration of a pressure car.

So, the car with only one fitting on the top is the pressure tank car.