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Fuel oil density 

Fuel oil density is the absolute relationship between mass and volume at a stated temperature . the s.i unit is kg/m3 at a reference temperature typically 15c.

Knowledge of density is required for quantity calculations.the value also needs to be known in order to select the optimum size of gravity disc for the centrifuge.in addition to density gives an indication of other fuel characteristics including specific energy and ignition quality*(ccai).

Specific gravity of a substance is a ratio of the mass of a given volume to the mass of equal volume of water at the same temperature as it is ratio there are no units.

Relative density of a substance is the ratio of the mass of a given volume at a temperature t1 to the mass of given volumeof pure water at temperature t2 at specific gravity RD is a ratio and hence no units.for example RD at 20/4c.since 1m 3 of pure water at 4c has a mass of 1000kg,the density of a substance at t1c is equivalent to the relative density at t1/4c.

In the u.s.a and other countries the density of petroleum products is defined in terms of API gravity.this is an arbitrary scale adopted by the American petroleum institute for expressing the relative density of oils.

The terms density in vacuo or density in air are sometimes used on fuel delivery or bunker receipt notes.as density is the absolute relationship between mass and volume and not its weight to volume by definition is in vacuo.although often used,the term density in air is incorrect and should be referred as a weight factor.this is because a substance weighed in air is supported to a small extent by the buoyancy of the air acting on it.thus the weight of the liquid in air is slightly less than the weight in vacuo.there is no simple relationship between density and weight factor. But for bunker fuels the difference approximates to 1.1kg/m3.to convert density at 15c to the weight factor at 15c 1.1kg/m3 should be detected.