How to calculate fuel oil consumption

Basic Fundamentals

• Fuel is always measured in tonnes because mass  is constant(weight does not change with temperature)
• Whereas  volume changes with temperature(volume of bunker increase with temperature (and vice-versa)
• Fuel consumption is calculated over a specific period of time, generally over a 24 hour period

Basic Formula for Mass=Volume*Density

units are mass tonnes,

volume is m3,

density is tonne/m3

Step1-Volume- Reading of common fuel flow meter counters should be taken at a specific interval of time say 24hour.

Formula for volume=(Present counter- Previous counter)*0.001 

where Flowmeter counter measures the flow in lit/h

The correctional factor is used to convert litre/hr to m3/hr                                                                      1litre/hr=0.001 cubic metre/hr

Step 2-Density -BDN provides density  at 15deg cel
(Which poses a problem as fuel is flowing at a temperature higher than 15deg
Therefore, we need to consider temperature corrected density at tonne/m3)

Formula 
Temperature corrected factor=Density at 15deg* { 1-{(T-15)*0.00065}}
                                                             

where T is the temperature of the oil

Density@15 is tonne/m3

0.00065 is the Correction factor

                                                                                             
Finally, Step 3
Fuel consumption =Volume*Temperature corrected factor(TCF)
                                                               

Where volume is in m3

TCF is in tonne/m3

Fuel consumption is measured tonnes specified over a period of time generally 24hrs