Bunkering
Bunkering is the process of supplying fuel — bunkers — to a ship. Fuel is transferred from a bunker barge alongside, a road tanker or a shore pipeline into the fuel tanks of the ship. The operation involves agreeing the quantity and grade, connecting hoses, transferring the fuel, and measuring what was received.
Because bunkers are the largest single running cost of a ship and disputes over quantity and quality are common, bunkering is closely controlled: the quantity is checked by a bunker survey of tank soundings, a representative sample is taken and sealed, and the supplier issues a Bunker Delivery Note. It is also a high pollution-risk operation, tightly proceduralised to prevent spills.
Fuel is by far the biggest variable cost of running a ship, and bunkering is where quantity and quality disputes and pollution incidents happen. Tight measurement, sampling and documentation at every stem is what protects the operator from being short-delivered, sold off-spec fuel, or landed with a spill.
How is the quantity of bunkers received verified?
By a bunker survey — measuring tank soundings or ullages on the barge and the ship before and after transfer — and cross-checking against the Bunker Delivery Note. A sealed representative sample is also taken for quality.