Which tank has a design pressure of 100-500 psi?

• A. DOT 406
• B. DOT 407
• C. MC331
• D. MC338

Answer: (C)

Understanding pressures on cargo tanks is key here. The design pressure is the maximum internal pressure a tank is built to safely handle. Tanks that carry liquefied gases under noticeable pressure are rated in a higher range, typically around 100 to 500 psi. That higher design pressure is what makes them suited for liquefied petroleum gases and similar service, where the gas is kept under pressure to stay in liquid form.

Among the tank types listed, the one designed for that 100–500 psi range is the LPG/propane-style cargo tank. It’s built to withstand the pressures generated by storing liquefied gases at ambient temperatures, which is why its design pressure sits in this higher band. The other tank types are designed for much lower pressures (or for non-pressurized service), so their design pressures do not fall in the 100–500 psi range. In practice, you’d confirm this by checking the tank’s nameplate, which lists the design pressure and the intended service.