Pressure-vacuum relief valves, as used on tank vessels, are usually set to operate between what two points?

Correct Answer: Option C — 14.2 psia and 2 psig

Pressure-vacuum relief valves protect cargo tanks from structural damage due to over-pressurization or vacuum collapse. Standard settings typically range from slightly below atmospheric pressure to approximately 2 psig, ensuring the tank remains within safe design limits during loading, discharging, and thermal expansion or contraction of the cargo vapors.