Question 69 OSV02 - Mate - Offshore Supply Vessels

The Correct Answer is B ### Why Option B (4980) is Correct The question asks for the **net amount** of cargo loaded, given that the gross volume was 5,000 barrels at a loading temperature of $70^{\circ}\text{F}$. In the petroleum industry, the net volume (the actual quantity of oil received or shipped) is determined by correcting the observed volume (Gross Standard Volume, or GSV) back to a standard reference temperature, usually $60^{\circ}\text{F}$. This correction is necessary because petroleum expands when heated and contracts when cooled. The temperature difference ($\Delta T$) is: $$\Delta T = \text{Observed Temperature} - \text{Standard Temperature}$$ $$\Delta T = 70^{\circ}\text{F} - 60^{\circ}\text{F} = 10^{\circ}\text{F}$$ Since the loading temperature ($70^{\circ}\text{F}$) is higher than the standard temperature ($60^{\circ}\text{F}$), the oil is currently expanded. To find the net volume, we must calculate the volume correction factor (VCF) and apply it to the gross volume. The formula for the volume change (and the VCF calculation) depends on the coefficient of expansion ($\alpha$): $$\text{Volume Change} = \text{Gross Volume} \times \Delta T \times \alpha$$ **1. Calculate the Volume Change (Contraction):** $$\text{Volume Change} = 5,000 \text{ barrels} \times 10^{\circ}\text{F} \times 0.0004$$ $$\text{Volume Change} = 5,000 \times 0.004$$ $$\text{Volume Change} = 20 \text{ barrels}$$ **2. Calculate the Net Amount (Volume at $60^{\circ}\text{F}$):** Since the oil was measured at an expanded temperature, we subtract the calculated volume change from the gross volume to find the net volume: $$\text{Net Amount} = \text{Gross Volume} - \text{Volume Change}$$ $$\text{Net Amount} = 5,000 \text{ barrels} - 20 \text{ barrels}$$ $$\text{Net Amount} = 4,980 \text{ barrels}$$ The net amount of cargo loaded is 4,980 barrels, which corresponds to option B. *** ### Why Other Options Are Incorrect **A) 4800:** This option implies a much larger correction factor ($5000 - 4800 = 200$ barrels). This would require a temperature difference of $100^{\circ}\text{F}$ (if $5000 \times 100 \times 0.0004 = 200$) or a much higher coefficient of expansion, neither of which matches the given data. **C) 5020:** This option incorrectly adds the volume correction (20 barrels) to the gross volume ($5,000 + 20 = 5,020$). This calculation would only be correct if the oil was loaded at a temperature *below* the standard temperature ($60^{\circ}\text{F}$), meaning the oil was contracted and needed to be expanded (corrected upwards) to reach the standard volume. Since the loading temperature ($70^{\circ}\text{F}$) is higher than $60^{\circ}\text{F}$, the correction must be subtracted. **D) 5200:** This option implies an extremely large correction (200 barrels) that was incorrectly added to the gross volume. This represents a miscalculation of both the magnitude and the direction of the temperature correction.