Sinooutput marine pump

Marine pumps refer to the marine machines used on ships to increase the pressure or potential of liquids and liquid materials to make them flow. Pumps are generally necessary to transport liquids to places with higher locations, farther distances, and higher pressures. Pumps can also be used to generate high-pressure liquid for hydraulic transmission. The pump is driven by an electric motor or other prime mover.

The characteristics of marine pumps are: the pump is required to avoid cavitation due to fluctuations in the suction liquid level when the ship is rocking and tilting; in order to reduce the pump's occupied area and facilitate maintenance, a vertical structure is generally adopted; the flow-through parts are made of bronze, the raw materials such as brass or stainless steel to minimize corrosion. Marine pumps are widely used on modern ships.

Generally speaking, a diesel-powered cargo ship requires 36 to 50 pumps of various types, accounting for 20% to 30% of the total ship machinery and equipment.

A, Marine pumps are widely used on modern ships. According to their different uses, they can be divided into:

• Pumps for ship power units. 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 devices, cooling water pumps for refrigeration devices, seawater pumps and condensate pumps for seawater desalination devices, etc.
• General ship pump. There are bilge water pumps, ballast water pumps, fire pumps, daily fresh water pumps, daily seawater pumps, and hot water circulation pumps; there are also general-purpose pumps that are used as ballast, fire-fighting, and bilge water pumps.
• Special pumps for special ships. Some special purpose ships are also equipped with special pumps for their special operating requirements, such as cargo oil pumps on oil tankers, mud pumps on dredgers, salvage pumps on salvage ships, and water jet propulsion pumps on water jet propulsion ships. Fishing pumps on netless fishing boats, etc.

B, According to the different working principles of the pump, marine pumps mainly fall into the following categories: 

(1) Positive displacement pumps Positive displacement pumps rely on the movement of working parts to cause periodic changes in the working volume to absorb and discharge liquid. When the working volume increases, When the pressure decreases, the liquid is sucked in, and when the working volume decreases and the pressure increases, the liquid is discharged, and the pressure of the liquid is directly increased by squeezing. According to the different movement modes of moving parts, it can be divided into two categories: reciprocating pumps and rotary pumps. The former includes piston pumps and plunger pumps; the latter includes gear pumps, screw pumps, vane pumps, etc.

(2) Impeller pump The impeller pump relies on the impeller to drive the liquid to rotate at high speed, continuously produces suction and discharge effects, transfers mechanical energy to the transported liquid, increases the pressure of the liquid, and achieves the purpose of transporting the liquid. According to the different structural characteristics of the impeller and flow channel of the pump, it can be divided into centrifugal pumps and vortex pumps.

(3) Jet pump The jet pump relies on the working fluid with a certain pressure to generate a high-speed jet in the nozzle to inject the fluid, and then increases the energy of the injected fluid through momentum exchange. According to the different working fluids used, they can be divided into water jet pumps, steam jet pumps and air jet pumps. In addition to being classified according to different working principles, pumps can also be divided into vertical pumps and horizontal pumps according to the position of the pump shaft; single-suction pumps and double-suction pumps according to the number of suction ports; and electric pumps according to the prime mover that drives the pump. , steam pumps and diesel engine pumps. Generally, pumps on ships are named according to their functions, such as main engine seawater cooling pump, main engine lubricating oil pump, etc.

Marine pumps performance parameters:

In order to indicate the performance of the pump, the following performance parameters are usually given on the pump nameplate and instructions to facilitate selection and comparison.

1. Displacement, also called flow. It refers to the amount of liquid that the pump can transport per unit time. What is expressed by volume is called volumetric flow, often expressed as Q, and the unit is m3/s, or m3/h. What is expressed in terms of mass is called mass flow, often expressed as G, and the unit is kg/s, or t/h. The displacement marked on the nameplate is the displacement of the pump under rated working conditions, which is called the theoretical displacement. In practice, the amount of fluid displaced by the pump is always less than the theoretical displacement.
2. Pressure head, also known as head. It refers to the energy transferred by the pump to the liquid per unit weight, usually expressed as H, and the unit is meters. If all the lift is used to increase the potential energy of the liquid, and assuming there is no pipeline resistance loss, the lift is the height that the pump can make the liquid rise.

3．Power refers to the amount of work done per unit time, and the unit is watts. The power of the pump is divided into output power and input power. The output power (effective power) of the pump refers to the energy actually transferred to the liquid by the pump per unit time. The input power of the pump, also called shaft power, refers to the power transmitted by the prime mover to the pump, represented by P. The power indicated on the pump nameplate refers to the input power of the pump. Since there are various energy losses in the actual operation of the pump, the effective power of the pump is always less than the shaft power.

4. Efficiency refers to the ratio of the effective power of the pump to the shaft power, expressed as a percentage.
5. Speed refers to the rated number of revolutions per minute of the pump shaft. It is commonly expressed as n, and the unit is rpm. The speed of a reciprocating pump is often expressed as the number of double strokes of the piston per minute, and the unit is times/minute. Most pumps are directly driven by the prime mover, and the two rotate at the same speed. However, electric reciprocating pumps generally need to be decelerated, so the speed of the pump shaft is lower than that of the prime mover.

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