Marine pumps refer to a variety of pumps for ships that meet the requirements of ship codes and marine technical conditions. They are often used on ships to transport various liquids such as seawater, freshwater, sewage, oil and fuel.
Marine pump refers to the machinery on the ship used to increase the pressure or potential of liquids and liquid materials to make it flow. Generally, a pump must be used to convey liquid to a higher position, a longer distance, and a higher pressure. The pump can also be used to generate high-pressure liquid for hydraulic transmission. The pump is driven by a motor or other prime mover. The characteristics of marine pumps are: it is required that when the pump is swaying and tilting, cavitation cannot occur due to the fluctuation of the suction liquid level; in order to reduce the area occupied by the pump and facilitate maintenance, vertical structures are generally used; Made of materials such as brass or stainless steel to minimize corrosion.
Marine pumps have a wide range of applications on modern ships. Generally speaking, a diesel-powered cargo ship requires 36 to 50 sets of various types of pumps, the number of which accounts for 20% to 30% of the total ship machinery and equipment.
I. Marine pumps have a wide range of applications on modern ships. According to their uses, they can be divided into: (1) Pumps for marine power plants. There are fuel pumps, lubricating oil pumps, seawater pumps, fresh water pumps, hydraulic pumps for steering gears or other deck machinery, feed water pumps for boiler units, cooling water pumps for refrigeration units, seawater pumps and condensate pumps for desalination units, etc.
(2) General-purpose pumps for ships. There are bilge pumps, ballast water pumps, fire pumps, daily freshwater pumps, daily seawater pumps, hot water circulation pumps; and general-purpose pumps that also serve as ballast, firefighting, and bilge pumps.
(3) Pumps for special ships. Some special purpose ships also have special pumps set up for their special operating requirements, such as cargo pumps for oil tankers, mud pumps for dredgers, salvage pumps on salvaging vessels, water jet propulsion pumps on water jet propulsion vessels, Fishing pumps on netless fishing vessels, etc.
2. According to the working principle of the pump, there are mainly the following types of marine pumps: (1) Positive displacement pump Positive displacement pump sucks and discharges liquid by periodically changing the working volume caused by the movement of working parts. It sucks in liquid when the working volume increases and pressure decreases, and discharges liquid when the working volume decreases and pressure increases. Pressure directly increases the pressure energy of the liquid. According to the movement of the moving parts, it can be divided into two types: reciprocating pump and rotary pump. The former includes piston pump and plunger pump; the latter includes gear pump, screw pump, vane pump and so on.
(2) Impeller pump The impeller pump relies on the impeller to drive the liquid to perform high-speed rotary motion, which continuously generates suction and discharge effects. It transfers mechanical energy to the liquid being conveyed, so that the pressure of the liquid can be increased, and the purpose of conveying the liquid is achieved. Centrifugal pumps and vortex pumps can be divided according to the structural characteristics of the impeller and the flow channel of the pump.
(3) Jet pump Jet pumps rely on a working fluid with a certain pressure to generate a high-speed jet in the nozzle to eject the fluid, and then increase the energy of the ejected fluid through momentum exchange. According to the working fluid used, it can be divided into water jet pump, steam jet pump and air jet pump. In addition to the classification of pumps according to different working principles, they can also be divided into vertical pumps and horizontal pumps according to the position of the pump shaft; divided into single suction pumps and double suction pumps according to the number of suction ports; and electric pumps according to the prime mover of the driving pump , Steam and diesel pumps. Generally on the ship, the pumps are named according to the function of the pump, such as the main engine seawater cooling pump and the main engine oil pump.