Fuels supplied to a ship must be treated on board before use in order to remove solid as well as liquid contaminants. The solid contaminants in the fuel are mainly rust, sand, dust and refinery catalysts. Liquid contaminants are mainly fresh or salt water. The settling tank is the first step in fuel treatment process. Water and sediments can be separated by gravity and drained off at the bottom of the tank. Effective cleaning of residual fuels can only be ensured by centrifuges: a clarifier to separate particles and/or a purifier to separate water. In order to remove any solid particles not separated by centrifuging, fine filters are placed directly after the centrifuge, or in the supply line to the engine.
