🔍 Key Concepts

• Cargo tank pressure control on gas carriers during discharge • Role of shore vapor return systems vs. ship’s vaporizing equipment • Safety considerations when introducing gas from outside sources into cargo tanks

💭 Think About

• When cargo volume in the tank decreases, what happens to the vapor space and why does pressure drop? • In normal discharge operations for liquefied gas cargo, where can replacement vapor safely come from? Only from ashore, only from the ship, or potentially both? • Think about standard gas carrier practice and regulations: is there usually a single required method, or are multiple acceptable methods depending on the terminal and ship’s equipment?

✅ Before You Answer

• Verify how vapor balance is typically maintained between ship and shore during discharge of liquefied gas cargoes • Consider whether shipboard vaporizers are designed for supplying vapor back to the cargo tanks, to shore, or both • Check which options would be considered standard and safe operational practices on modern gas carriers under typical terminal agreements