Marine engineer must know the procedure of bunker calculations. Otherwise leads to oil spillage and shortage of bunker during bunkering operations. Trainee Marine Engineer has duty to take sounding and calculate daily consumption to provide it in Noon report. Many people do not how to calculate bunker. In this article , i will explain step by step procedure to calculate correct bunker and consumptions. I will also provide trick so that you do not forget.
I have already told you significance calculating bunker. For this you required A data sheet which is available in the engine room.
Bunker calculations
Bunker also calculate for knowing how much daily consumptions of engine.
Fuel consumptions or bunker taken is always in Metric Tonne (MT ) on ship. Actually Fuel Consumptions Is How Much fuel is consumed and it is calculated in MT not in Kilograms (KG ).
Why We take Bunker in Metric Tonne ?
It is taken in Metric tonne because Volume of the fuel used on ship changes with change in temperature. And It is not possible to measure the weight of fuel used physically. That’s why we used metric tonne for fuel oil.
Bunkering calculations Formula
Actually, we are measuring its weight. so, basic formula we know is, Mass (kg ) = Volume (m^3 ) / Density ( Kg/m^3 )
so, Mass = Volume / Density
Unit for Mass= kg, volume + m^3 and density = kg/m^3
As i have already told you why we take bunker in MT. So, formula for calculations is, Mass ( in MT ) = Volume ( in m^3 ) / Density ( tonne/ m^3 )
Mass = Volume / density (v/d).
Units are, Mass in metric tonne, volume in m^3 and density in Mt/m^3
Note :- Density used for fuel is called corrected density. As we know the density of fuel change with change of temperature. so, density is at that temperature.
Corrected density :- It is density of fuel oil at the temperature of tank or barge.
Note :- unit of density is kg/m^3 and MT = 1000 kg.
with formula mass volume * density in kilogram and when it is divided we get it in Metric Tonne ( MT ).
how to convert MT into m^3
Volume (m^3 ) = Mass (MT ) / Density
Use the above formula to convert MT into M^3.
Corrected Density
What is corrected density ?
Corrected density of fuel oil at the temperature of tank or barge.
What is the formula of corrected density ?
Corrected Density at t1 temperature = Density of fuel oil at 15 Degree celcius * [ 1- { t1-15)*0.00064}]
Density of fuel oil at 15 degree celcius is mention in bunker delivery notes (BDN ).
T stands for the temp. of oil in the bunker tank in the degree celcius.
0.00064 in the formula is bunker correction factor.
volume of oil inn m^3 .
How to calculate the volume (m^3 )
Volume of fuel oil kept in a tank is calculated by a book called sounding Book which is available in Engine room.
In sounding book , volume of fuel is mention according to height from bottom . To find Height ( CM )we take sounding of tank with the help of sounding tape. So, we get the volume of fuel oil.
For a particular tank, a sounding table is provided Calculate the volume by Including trim.
In sounding table, at particular sounding depth in cm volume of fuel oil is mention even keel ,trim by ahead and trim by astern.
In sounding table there is depth gap of 5 cms and you get the sounding in between the two depth, then to calculate sounding use unitary meythods.
Bunker calculations procedure step by step
Let us take a example in term of fuel oil consumptions so that you can easily calculate bunker.
I am providing a figure of sounding table below.
Assume i take a sounding of heavy fuel oil with the help of sounding table or get a height on sounding tape 894 cms and your ship is trim by 0.5 meters by astern at temperature of 50 degree celcius.
See the figure, you get a density of fuel in 294.35 cubic meters at ship 0.5 trim by astern.
Now, we have volume of fuel oil = 294.35 cm^3
Density of fuel at 50 degree celius = corrected density of fuel at 50 degree ?
use the formula for of corrected density.
corrected density = Density of fuel oil at 15 Degree celcius * [ 1- { t1-15)*0.00064}]
Density at 15 degree celcius is mention in bunker delivery notes. let us,
Density at 15 degree celcius = 0.9909
Temeperature of fuel = 50 degree celcius
Now, Corrected density of fuel at 50 degree celcius = 0.9909 [ 1-0.00064(50-15)}
=0.9909[1-0.00064(50-15)]
=0.9682
Mass = volume * density
=294.35*0.9682
=284.98967 kg
= 284.98967/1000 = 0.28498967 MT
This is details explains of bunker calculations.
Bunker calculations another example.
Consider we have to take 285 MT of Diesel Oil in a tank 1. Capacity of tank is 400 m^3 at trim of 0.50 m. Tank is fully empty.
Now we get density of Diesel oil at 15 degree celcius from bunker delivery notes. let us assume , density of diesel oil at 15 degree celcius = 0.9909.
Temperature of diesel moil at the time of pumping =n 50 degree celcius.
Now, Corrected Density at 50 degree celcius = D at 15 degree [ 1 – 0.000645 ( T-15)]
Putting all the information, you will get,
=0.9682 kg/ m^3
Volume = mass / corrected density
=285 / 0.9682
=294.35 m^3
as mentioned above , volume of tank = 400 m^3.
As i have to take 285 MT of diesel oil and their volume we get = 294.35 m^3 and capacity of tank is 400 m^3. so, we can take in the tank.
Note :- If the Tank there is some fuel assume 100 m^3. As we know fuel in the tank filled upto 85 % of capacity. In this conditions, we fill not fill the all diesel in one tank. When tank get filled 85 % then we have to open the filling valve of another tank.
85 % of 400 m^3 = 340 m^3
Them 340 m^3 – 294.35 m^3 = 45.65 m^3 of fuel need to transfer in another tank. For another tank we have to follow the same procedure to find volume of fuel.
Summary of Bunker Calculations
1.Find volume of fuel oil by using sounding table in m^3
2.Calculate Corrected density at Particular Temperature. Unit of Density is Kg / M^3.
3.Calculate Mass by using formula mass = density * volume.
Note :- You will get this mass in kg. Divide it by 1000, you will get in Metric Tonne (MT )
This is about calculating Quantity of fuel in metric available in tank.
