Tankerman · Cargo Calculations — Trim Correction
When a vessel has stern trim, an ullage taken at a tank's reference gauge point that is not at the tank's center must be corrected because:
- ATrim tilts the liquid surface, so the gauge reads differently than the true average level — a trim correction from the tank tables is applied✓ Correct
- BTrim changes the cargo's density
- CTrim has no effect on gauging
- DTrim only matters for ballast
Explanation
With trim (or list), the liquid surface is no longer level relative to the tank top, so a gauge point off the tank's centroid reads high or low. The vessel's capacity tables provide trim/list corrections to convert the observed ullage to the equivalent even-keel value before entering the volume table.
Authority: API MPMS Ch. 3; vessel capacity (ullage) tables
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