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Stability & CargoPage 2 of 12

Gross Standard Volume: free water out, then the temperature correction

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Gross Standard Volume: the free water comes out first, then the oil is brought to 15 °CLeft, the tank as gauged at 38 °C: Total Observed Volume 18420 m³, with 64 m³ of free water under the oil, found with the interface detector. Taking the water out leaves the Gross Observed Volume, 18420 − 64 = 18356 m³. Right, the same oil at the standard 15 °C, through the volume correction factor: 18356 × 0.9782 = 17955.8 m³, the Gross Standard Volume.AS GAUGED · 38 °CAT 15 °Cinterface detector① water outGOV 18356 m³② × VCF 0.9782oil shrinks 400.2 m³TOV 18420 m³free water 64 m³GSV17955.8 m³Level differences magnified, on one scale · tank height schematic

The rule

  • The tank table turns the corrected gauging into the Total Observed Volume (TOV): everything in the tank at the temperature it is now, water included.
  • Free water lies under the oil; the interface detector finds its level, and its volume comes off first: GOV = TOV − free water.
  • Oil swells when it is warm. The volume correction factor (VCF), read from the table for this cargo's density and temperature, brings the volume to the standard 15 °C: GSV = GOV × VCF.
  • Warmer than 15 °C, the VCF is below 1 and the GSV comes out smaller than the GOV; colder, it is above 1.

Formula

  • GOV = TOV − free water
  • GSV = GOV × VCF

Worked example

Total Observed Volume from the tank tables18420 m³
Free water found with the interface detector64 m³
Cargo temperature, average of the tank38 °C
Volume correction factor at that temperature0.9782
  1. GOV = 18420 − 64 = 18356 m³
  2. GSV = 18356 × 0.9782 = 17955.8 m³

Answer17955.8 m³

Common mistake

Multiplying the whole Total Observed Volume, free water and all, by the VCF: 18420 × 0.9782 = 18018.4 m³.

The factor describes how oil changes with temperature. The 64 m³ of water is not cargo and does not follow it, so it must be out of the figure before the factor is applied — left in, it adds 62.6 m³ of cargo that is not there.