These barges are like floating petrol stations. They fill the ship's fuel tanks with diesel fuel and bunker oil. Exchanging fuel between the bunker barge and ship must be done so that not even a drop of oil escapes.
The fuel hoses that are used are specially sealed with valves so that no oil can leak from them. The hoses are hoisted onto the ship and locked onto the ship's fuel pipe.
The locking device is checked to make sure it is secure. Once locked on, the valve opens. Fuel can then be pumped from the barge into the ship's fuel tanks.
Even the smallest spill is immediately reported. Spilt oil on water spreads very quickly. The sooner the oil can be contained, the easier it will be to do the cleanup. There is no hiding even a small oil spill in a port and it is not difficult to find who is responsible. The offending ship will be prosecuted in court and may have to pay a very costly fine.