Topping-off Loading Rate
Reduced rate for the final 10 % / slack-ullage stage to allow tank-level alarms to respond and avoid overfill.
Topping-off rate
2,000m³/h
Time for final stage
24.0min
Formula, assumptions, and limits
$$Q_\text{top} = Q_\text{bulk} \cdot (1 - r)$$
Typical reduction 50–70 % in the last 5 % of ullage on modern tankers. Too fast → overfill alarm fails to act; too slow → berth occupancy cost. Initial loading also reduced until liquid covers the inlet (≤ 1 m/s to avoid static).
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $Q_\text{bulk}$ | Main-stage loading rate | m³/h | terminal agreement |
| $r$ | Topping-off reduction | fraction | procedure |
| $Q_\text{top}$ | Reduced loading rate | m³/h | result |
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