On ships, it is often necessary to transport liquids such as water and oil.
For example: in order to ensure the safety and sanitation of the ship, the sewage accumulated in the bilge must be regularly discharged outboard; the fuel oil should be continuously delivered to the main engine and generator to ensure the continuous operation of the machine; the boiler should be supplied with water in time, In order to ensure that the boiler can continuously generate steam; to ensure the normal operation of the machine, lubricating oil and cooling circulating water must be continuously provided; in order to improve the stability of the ship during navigation, it must be completed by transferring ballast tank water; The transfer of cargo oil should also be completed on board. The delivery of these liquids is usually completed by special equipment – a “marine pump”. So the function of a certain marine pump is to deliver a certain liquid that is required. In this sense, a pump is a machine that transports liquids.
Fundamentals of pumping liquids
The machinery enables the flow and transport of liquids. In general, the liquid flows from high to low. In ships, outboard seawater can flow into the ballast tank through pipelines, but bilge sewage cannot flow outboard by itself; when the boiler blows down, open the blowdown valve, and the boiler water with pressure greater than the outside will flow out through the blowdown pipe, but less than the boiler water. The boiler make-up water with water pressure cannot flow into the furnace along the water supply pipe by itself. In order to improve the stability and safety requirements on ships, liquids such as fuel oil, lubricating oil, and fresh water are often stored in low-level cabins, and these liquids must be sent to high-level main engines, generators, and boilers at any time. Only by doing work can the liquid have a certain mechanical energy to achieve the purpose of transportation.
The mechanical energy of liquid consists of three forms: potential energy, pressure energy, and kinetic energy. According to the law of energy conservation and conversion, the three can be converted into each other.
(1) Potential energy – also known as potential energy, the higher the position of the liquid with the same pressure, the greater the energy
(2) Pressure energy – the water position in the pressure water tank in the engine room is low, but its internal pressure is large, so the water can flow higher through the pipeline. The higher the pressure, the higher the flow direction. The determined energy is called pressure energy.
(3) Kinetic energy – also known as velocity energy, the water flow velocity at the exit of the fire hydrant is relatively large so that the water can be rushed to the upper deck of the ship. The higher the speed, the higher the rush height.
