Marine pump refers to a variety of pumps for ship use in accordance with the provisions of the ship’s code and the requirements of the ship’s technical conditions. On board they are often used to transport seawater, fresh water, sewage, slip oil and fuel oil and other liquids.

Brief description

Marine pump refers to the ship used to increase the pressure or position of the liquid and liquid materials can make the flow of machinery. Transportation of liquids to the location of higher, farther, higher pressure generally must be pumps, pumps can also be used to generate high-pressure liquid for hydraulic transmission. Pumps driven by electric motors or other prime movers. Marine pumps are characterized by: the requirements of the pump in the ship rocking and tilting, can not be due to fluctuations in the suction level and cavitation; to reduce the footprint of the pump and easy maintenance, generally using a vertical structure; flow-through parts made of bronze, brass or stainless steel and other materials, in order to reduce corrosion as much as possible.

Marine pumps in modern ships have a very wide range of applications, in general, a diesel-powered cargo ships, need 36 to 50 units of various types of pumps, the number of ship machinery and equipment accounted for 20% to 30% of the total.

Classification

1，marine pumps in modern ships have a very wide range of applications, according to its different uses, can be divided into:

(1) ship power plant pumps. There are fuel pumps, lubricating oil pumps, seawater pumps, fresh water pumps, rudder or other deck machinery hydraulic pumps, boiler unit feed pumps, refrigeration unit cooling water pumps, desalination unit seawater pumps and condensate pumps and so on.

(2) ship general pumps. There are bilge pumps, ballast water pumps, fire pumps, daily fresh water pumps, daily sea water pumps, hot water circulation pumps; there are also ballast, fire, bilge pumps with the general pump.

(3) special ship-specific pumps. Some special-purpose ships, but also for its special operational requirements and set up special pumps, such as oil tankers, cargo oil pumps, dredgers, mud pumps, salvage pumps on board salvage pumps, water jet propulsion pumps, water jet propulsion pumps, no-net fishing boats on the fishing pumps and so on.

2, according to the different working principles of the pump, marine pumps are mainly the following categories:

(1) volumetric pumps

Volumetric pump is relying on the movement of the working parts caused by the working volume of the periodic increase and decrease in changes in the suction and discharge of liquid, when the working volume increases and the pressure decreases when the liquid is inhaled, when the working volume decreases and the pressure rises when the liquid is discharged, and rely on the squeezing and the pressure of the liquid directly to the increase in pressure energy. According to the movement of the moving parts of different ways, it can be divided into reciprocating pumps and rotary pumps two categories. The former has piston pumps and plunger pumps; the latter has gear pumps, screw pumps, vane pumps and so on.

(2) Impeller pumps

Impeller pump is driven by the impeller of the liquid for high-speed rotary movement, continuously produce suction and discharge effect, the mechanical energy transferred to the conveyed liquid, so that the pressure of the liquid can increase, and to achieve the purpose of conveying liquid. According to the pump impeller and flow channel structure characteristics of different, and can be divided into centrifugal pumps and vortex pumps.

(3) Jet pumps

Jet pump is relying on a certain pressure of the working fluid in the nozzle to produce high-speed jet ejection fluid, and then through the momentum exchange and the ejected fluid energy increase. According to the different working fluids used, and can be divided into water jet pumps, steam jet pumps and air jet pumps.

Pumps in addition to different classification according to the working principle, but also according to the pump shaft position is divided into vertical pumps and horizontal pumps; according to the number of suction port is divided into single-suction pumps and double-suction pumps; according to drive the pump prime mover is divided into electric pumps, steam pumps and diesel pumps. Generally on board are in accordance with the function of the pump for the pump named, such as the host sea water cooling pump, the host skid oil pump, and so on.

Performance parameters

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

1. Displacement, also known as flow. Is the amount of liquid that can be transported by the pump in a unit of time.

Expressed in terms of volume is called volume flow, commonly used Q, the unit is m³/s, or m³/h.

Expressed in terms of mass, it is called mass flow rate, commonly used G, unit is kg/s, or t/h.

The displacement indicated on the nameplate is the displacement of the pump under rated conditions, called the theoretical displacement. In fact, the amount of fluid discharged by the pump is always less than the theoretical displacement.

2. Pressure head, also known as head. Refers to the pump to the unit weight of the energy of the liquid, often expressed in H, the unit is meters. If the head is used to raise all the liquid level energy, and assuming that there is no pipeline resistance losses, the head is the pump so that the height of the liquid can rise.

3. power, is the size of the work done per unit of time, the unit is watts. Pump power output power and input power points.

Pump output power (effective power) refers to the unit of time the pump actually passed to the liquid energy.

Pump input power, also known as shaft power, is the prime mover to the pump power, expressed in P. The power labeled on the pump nameplate refers to the input power of the pump. As the pump in practice there are a variety of energy losses, so the effective power of the pump is always less than the shaft power.

4. efficiency, is the effective power of the pump and the ratio of shaft power, expressed as a percentage.

5. Speed, is the rated number of revolutions per minute of the pump shaft. Commonly used n, the unit is rpm. Reciprocating pump speed is often the number of double strokes per minute to the piston to indicate that the unit is times / min. Most of the pump system by the prime mover direct drive, the two speed is the same. But the electric reciprocating pump generally need to be decelerated, so its pump shaft speed than the prime mover low.