Composite sample

A container with a lid is dipped into the barges oil tank and when it is 1/6 of the way down the lid is removed and a sample taken, it is then taken up and poured into a container. This is repeated in the middle and at the bottom of the tank, the three samples are then thoroughly mixed and divided up to be delivered to the vessel and barge. See BS 3195: Part 1, Sampling Petroleum Products