🔍 Key Concepts

• How LNG (Liquefied Natural Gas) is kept cold (refrigerated) in cargo tanks • The purpose and use of an LNG heel during ballast voyages • Difference between pressure control and direct cooling of the tank structure

💭 Think About

• Ask yourself: during ballast (no cargo loaded), what source of cold medium is still available on board to absorb heat entering the tanks? • Consider how LNG tanks stay at cryogenic temperature: is it mainly by changing pressure, by removing gas, or by circulating cold liquid? • Which option actually cools the tank walls and internal structure, not just the vapor above the liquid?

✅ Before You Answer

• Identify which choice involves circulating or using cold liquid LNG rather than just handling vapor or pressure • Verify which methods would waste cargo or be unsafe/uneconomic in normal operations • Check which option is commonly used to maintain low temperature of tanks between loaded voyages using a small remaining cargo (heel)