140.Bunker calculation / Density correction formula

The basic formula used for calculating the bunker quantity in weight is:

Mass = Volume x Density

• After receiving the bunker, take sounding/ullage of all the bunker tanks using sounding tape and note down the tank temperature. Use sounding paste in the tape while measuring distillate fuel such as MDO for easy reading.
• The ship always does not float with an even keel so the floating conditions of the ship such as trim and list should be well noted while taking the sounding of bunker tanks.
• Every ship is provided with a tank capacity table in which each tank capacity in volume is marked against the successive levels of sounding/ullage with correction factors under various trim and heel conditions of the ship. The volume of fuel oil at tank temperature for the corresponding tank sounding is thus measured using tank capacity table, which gives the actually sounded volume.
• The density of fuel oil (in kg/m3) at a standard reference temperature of 15⁰C is always provided by the supplier in Bunker Delivery Note. With this, the density of fuel oil at tank temperature can be determined using ASTM table or using software most commonly installed on all ship’s computer.

The formula used to calculate the Temperature Corrected Density is:

= (Density of Fuel Oil @ 15⁰C) x [1- {(T-15) x 0.00064}]

Where:
T = temperature of oil in bunker tanks in degree Celsius,
0.00064 = Correction factor

Since the bunker oil is normally supplied to the vessel at a temperature higher than 15⁰C, the formula used for calculating the bunker quantity in weight will be:

Metric Tonnes =  (Actual Sounder Volume) X (Temperature Corrected Density)

 The corresponding values of each tank are tabulated for easy reading and the total weight of bunker quantity is calculated.