🔍 Key Concepts

• LFG (liquefied flammable gas) cargo tank design and what hazards pressure buildup creates • Difference between pressure/vacuum control devices and overpressure emergency relief devices • How vapors move in and out of a tank during loading, discharging, and temperature changes

💭 Think About

• When a closed cargo tank warms up or is filled, what happens to the vapor pressure inside, and what type of device is normally used to keep that pressure within safe operating limits? • Which option is designed mainly to stop flame propagation, which to stop sudden high flow, and which to automatically open and close for small pressure/vacuum changes? • Think about normal operations: Which device cycles frequently as the tank breathes, rather than only opening in a rare extreme emergency?

✅ Before You Answer

• Match each answer choice with its primary function (flame blocking, flow limiting, pressure/vacuum control, or emergency relief only). • Ask: which device is specifically described in regulations for routine control of both overpressure and vacuum in gas cargo tanks? • Verify which device is designed to protect the tank’s structural integrity during normal thermal and cargo-handling conditions, not just in a catastrophic failure.