Convert observed bunker volume to contractual mass by correcting density from the delivery temperature to 15 °C.
Formula
$$ \rho_T = \rho_{15} - \alpha (T - 15) $$
$$ m = \rho_T \cdot V_\text{obs} \cdot 10^{-3} $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\rho_T$ | Density at delivery temperature | kg / m³ | result |
| $\rho_{15}$ | Certified density at 15 °C | kg / m³ | BDN certificate |
| $T$ | Observed bunker temperature | °C | delivery-manifold sensor |
| $\alpha$ | Volumetric expansion coefficient - 0.64 (residual) / 0.70 (distillate) | kg / m³ / °C | ISO 91-1 Table A |
| $V_\text{obs}$ | Observed bunker volume | m³ | meter / ullage |
| $m$ | Delivered mass | t | result |
| $10^{-3}$ | Kilograms → tonnes | - | constant |
Volume figures on a bunker meter are always at observed temperature, not 15 °C. If the ship invoices on mass and the meter only records volume, this correction is the only step between the two numbers.
Sources
- ISO 91-1 - Petroleum measurement tables.
- ISO 8217 - Marine fuels specification.