Which of the following pressures represents the normal pressure setting of a pressure-vacuum relief valve as normally found on tank vessels?

Correct Answer: Option D — 16.7 psia - 14.2 psia

Standard atmospheric pressure is 14.7 psia. P/V valves are calibrated to maintain tank integrity; a setting of 16.7 psia represents a 2 psi overpressure limit, while 14.2 psia represents a slight vacuum limit. These values ensure the tank structure is not compromised by pressure fluctuations during cargo operations.