Answer
A Chief Engineer's bunker calculation must account for the specific operational profile of the vessel, including heavy auxiliary loads.
Step 1: Determine Daily Consumption Profile Establish the daily fuel consumption for the intended voyage speed and operational state:
Main Engine sea consumption (CME)
Auxiliary Engine consumption (CAE)
Note: On VLGCs and LPG carriers, ensure you factor in the massive electrical load of running the cargo reliquefaction plant during the voyage.
Boiler consumption (CBLR)
Step 2: Base Voyage Requirement Calculate the raw fuel needed for the 15-day passage:
Base Fuel = (C_{ME} + C_{AE} + C_{BLR}) X 15
Step 3: Add Safety Margins Apply a safe margin for adverse weather, currents, and routing deviations. The SMS or Charter Party usually dictates this (typically a 3 to 5-day reserve or a flat 10-15% addition).
Step 4: Account for Unpumpable / Dead Stock Add the known unpumpable volumes of all bunker tanks to ensure the calculated reserve is actually usable by the transfer pumps.
Step 5: Final Lifting Calculation
Total Required = Base Fuel + Safety Margin + Dead Stock
Bunker to Lift = Total Required – Expected ROB at the date of bunkering