🔍 Key Concepts

• Fuel oil system venting requirements in 46 CFR • Purpose of a service tank vent line on fuel systems • How minimum nominal pipe size is chosen to safely relieve pressure

💭 Think About

• Which regulation part in 46 CFR covers fuel oil tanks and vent piping? Check that first, then look specifically for service tanks. • Think about why vents must be large enough: what happens during filling, thermal expansion, or fire exposure if the vent is undersized? • Compare the listed sizes with what you’d expect for a vent that must handle worst‑case pressure without exceeding tank design limits.

✅ Before You Answer

• Verify in 46 CFR (Subchapter F or relevant subchapter for your vessel type) the exact table or paragraph for fuel oil service tank vent sizes. • Confirm the regulation is talking about service tank vent lines, not overflow lines or other tank types. • Make sure you’re looking at nominal pipe size, not inside diameter or area equivalence.