Marine Pumps are used to deliver various kinds of liquid on board such as sea water, fresh water, bilge water, ballast water, lube oil, fuel oil… According to a survey, each sea-going ship may have 36~50 marine pumps using about 5%~15% of the total energy consumed on ships.
Marine pumps may be applied on board and have different functions.
1. Pumps for the main propulsion systems. They are main seawater pumps, jacket cooling water pump, lube oil pump, fuel oil pump etc. These pumps ensure the proper working of the main engine.
2. Pumps for auxiliary system. For example, seawater pumps and fresh pumps for auxiliary engines, fule oil pump and boiler water feed pump for boiler, cooling water pumps for the refrigeratin systems, seawater pumps and condense pumps for distilling pump, and hydraulic pump for the steering gear and other hydraulic systems.
3. Pumps for safety and domestic system. There are ballast pump, fire fighting pumps, domestic fresh water pumps and so on.
4. Pump for special purpose. For example, cargo oil pumps on tanker, pumps for the delivery mud and so on.
According to the theory of hydrodynamics, the mechanical energy of liquid includes position potential energy, kinetic energy and pressure energy, and three kinds of energy can be converted into each other. Liquids can not flow freely from one position to another where the mechanical enerfy is higher due to the energy loss overcoming the flow resistance. Therefore, the function of pump is to increase the mechanical energy of liquid and deliver liquids to the places where needed.
