Some tanks are designed to have an internal pressure which is higher or lower than ambient pressure? This reduces what in the tank

• A. Higher vaporization
• B. Lower vaporization
• C. Increased vapor pressure
• D. Reduced fuel flow

Answer: (A)

Vaporization in a tank is driven by the pressure in the gas space above the liquid. If the headspace pressure is kept higher than ambient, that backpressure suppresses the liquid’s tendency to turn into vapor. In practice, designing tanks to have internal pressure different from ambient reduces the amount of vapor that would form under normal conditions. So the design aims to limit vapor generation when conditions would otherwise cause higher vaporization. The other choices don’t fit this mechanism: increasing vapor pressure isn’t the direct effect, and reduced fuel flow isn’t the consequence of headspace pressure control.