🔍 Key Concepts

• Understand how flammability and vapor pressure of grades D and E liquids affect venting needs • Know the basic function of tank venting systems on barges (removing vapors safely, preventing over/under pressure) • Differences between simple open vents, pressure‑vacuum devices, and mechanical ventilation

💭 Think About

• For relatively low‑hazard petroleum products (like grades D and E), do you usually need complex mechanical systems, or simpler passive systems? • Which option best prevents both over‑pressure and vacuum in the cargo tank during loading/unloading and temperature changes? • Which venting arrangement is commonly used on tank barges specifically, not just on any cargo tank?

✅ Before You Answer

• Check which choice actually responds automatically to BOTH pressure increase and vacuum (not just one or neither). • Verify which system is passive (no moving parts like fans/blowers needed for normal operation). • Eliminate any choice that is mainly about distribution of vapors (piping layout) rather than the primary safety venting device on the tank itself.