🔍 Key Concepts

• Purpose of pressure-vacuum (P/V) valves on tank vessel cargo tanks • What happens to a closed tank when pressure rises or drops too much • How tank structure and fittings respond to overpressure or vacuum situations

💭 Think About

• Think about why a tank needs both pressure and vacuum protection instead of just one or the other. • Consider what could physically happen to the tank shell and deck if vapors could not vent when cargo is loaded, discharged, or heated. • Ask yourself: which choice describes a consequence to the tank itself rather than to the atmosphere or deck area around it?

✅ Before You Answer

• Identify which options describe external effects (outside the tank) versus structural effects on the tank boundaries. • Recall that P/V valves are designed to keep pressure and vacuum within safe limits, not to act as fire barriers or spill containments. • Verify which choice best matches preventing deformation or failure of the tank structure when internal pressure gets too high or too low.