<b>Pumps</b> There are a number of different pumps on board of ships to convey the most varied of media: cooling water, oil in the lubricant circuit, service water, extinguishing water, ballast water, etc. Depending on the area of application and task, different pump systems are used. The task of pumps is to convey liquids from a lower to a higher level or from a space of low pressure in a space of higher pressure ( e.g. the bilge) or a container from which the liquid is taken. The higher level is determined by the liquid level of an elevated tank (e.g. side ballast water tank, cargo tank) or by the pressure line (e.g. fire extinguishing line) into which the pump delivers. Pumps are divided into two main groups according to their functional principle: positive displacement pumps and flow pumps. These groups are further subdivided according to the type of construction; The centrifugal, gear and piston pumps are predominantly used in shipbuilding.