🔍 Key Concepts

• Ullage is the empty space in a tank above the liquid cargo • Ullage is measured vertically from a fixed reference point down to the surface of the liquid • On tankers, reference points for measurements must be permanent, repeatable datums

💭 Think About

• Which option describes a fixed, standard reference point that will not change when the tank structure or liquid level changes? • Think about what point a measuring tape or ullage tape is actually hooked to or passed through when taking a reading on deck. • Which choices describe parts that might vary slightly with construction or wear, versus a clear, designed measuring reference?

✅ Before You Answer

• Identify which option is a measurement datum rather than just a physical feature of the trunk or port • Confirm that the reference point is accessible from deck for routine ullage tape use • Eliminate any options that depend on the exact internal geometry at the bottom of a fitting rather than a defined top reference.