🔍 Key Concepts

• Cargo grade definitions (Grades A, B, C, D, E) under 46 CFR for flammable and combustible liquids • Differences between open gooseneck vents with flame screens and pressure-vacuum (PV) valves • Which cargo grades are considered most hazardous and therefore require more restrictive venting arrangements

💭 Think About

• First, mentally rank cargo grades A through E from most hazardous (highest vapor pressure/lowest flash point) to least hazardous. Which grades are allowed the simplest venting system? • Ask yourself: Would the highest-hazard cargoes be allowed on a tank with only a gooseneck and flame screen, or would they require more sophisticated venting and protection? • Look at which grades are typically allowed in cargo tanks with open vents versus those that must have PV valves and other safeguards.

✅ Before You Answer

• Verify in the regulations which grades are defined as flammable liquids with very low flash points and high vapor pressures—these usually need tighter controls than just a gooseneck and screen. • Confirm which cargo grades are expressly allowed to use open vents with flame screens rather than PV valves in 46 CFR Subchapter D (Tank Vessels). • Before choosing, eliminate any option that includes grades you know are classified as requiring closed or controlled venting systems because of their high vapor pressure.