What is the minimum design pressure for ASME Section VIII?

• A. MAWP
• B. 15 psig
• C. 1.25 × MAWP
• D. Zero

Answer: (D)

In ASME Section VIII, design pressure is the pressure the vessel is designed to withstand, which is the maximum allowable working pressure (MAWP). The minimum design pressure is effectively zero because, for internal pressure design, the vessel must be able to tolerate at least atmospheric pressure inside. The code does not require a positive minimum design pressure beyond this; if there’s a possibility of vacuum or external pressure, those conditions are handled separately with dedicated design provisions rather than as a positive minimum internal design pressure. So the lowest pressure the vessel is designed to withstand from inside is zero gauge pressure, i.e., atmospheric pressure.