🔍 Key Concepts

• Overflow and vent sizing requirements for double bottom tanks in 46 CFR (protecting against overpressure during filling) • Relationship between fill line area vs. total vent/overflow area • Purpose of vents vs. overflows in tank protection

💭 Think About

• When you pump into a confined tank, what happens if the incoming flow cannot escape as air or liquid fast enough? • Should the vent/overflow capacity be less than, equal to, or greater than the fill line capacity to safely relieve pressure? • Think about whether regulations usually require a single vent to match the line, or a total combined area to exceed it.

✅ Before You Answer

• Verify in 46 CFR that the rule speaks about total area of all vents and/or overflows compared to the fill line area • Check whether the regulation specifies a percentage greater than 100% of the fill line area for safety margin • Confirm whether the requirement allows vents, overflows, or both combined to satisfy the area requirement, instead of requiring overflows only.