The history of shipbuilding goes back to ancient times - the first mention of swimming facilities appeared more than five thousand years ago. Then people traveled along rivers and seas on ships powered by rowers. Since then, shipbuilding has made a tremendous breakthrough, and today this industrial sector occupies a leading position in the economic and political sector of the country's development.
Today, the generally accepted terminology is according to which a sea vessel is a large-sized floating facility intended for marine fishing, transportation of goods or transportation of passengers. A sea ship is a military watercraft. For the normal operation of any of these types of ships, reliable operation of all elements and systems is required. First of all, it is required to ensure the optimal operation of ship pumps, because the movement of various liquids through the ship's pipelines is constant.
Why are pumps needed on board?
Initially, pumps were created exclusively for lifting water. The first model of a marine hydraulic device designed to pump water from holds was a hand piston pump. Now it is widely known as pump-action. The introduction of steam power plants on ships provided the emergence of steam-driven reciprocating pumps.
Other, more modern types of hydraulic mechanisms began to spread in shipbuilding along with the development of technology. The emergence of electric motors played a huge role in the development of new pumps. Their implementation has provided an increase in the frequency of rotation of the working body of the device and the power of the pump.
Today, pumps are widely used in all sectors of the economy. The shipbuilding area was no exception. Currently, all existing types of such devices are actively used in marine shipbuilding.
What is a pump?
A pump is a device designed to move fluid from a lower level to an upper level. Sometimes, using this mechanism, fluid is transported to give it a certain amount of energy or increase pressure. In the main systems of a marine vessel, pumps are used almost everywhere: they are located in power plant systems, hydraulic drives, crew life support systems, etc.
The principle of the pump
Converting the energy of the engine of a ship's pump into the energy of a moving fluid, these devices make it move in the right direction (rise up, move horizontally or circulate inside a closed system). Creating the necessary transportation of a certain working fluid, such hydraulic devices are in any case part of the pumping system, the circuit diagram of which is suitable for the conditions of water supply or sanitation.
Schematic diagram of any ship pumping station
As a drive mechanism in this circuit, an electric motor connected to the mains is used. The intake of working fluid comes from the lower basin and moves along the pressure line to the upper level due to energy conversion. The energy of the working fluid passing through the pump is always greater than the energy in front of the pump.
The pressure of the outgoing fluid depends on the supply, power and efficiency of the device. It represents the increment of the specific energy of the fluid being moved from the point of entry into the pump to its exit. Expressed in meters, it determines the height of the lift or the distance of movement of the working agent.
The main characteristics of the hydraulic device
The fluid supply is characterized by its volume per unit time. The optimum pump power is needed to create the required pressure and overcome all types of losses that are inevitable when the fluid moves through the pipeline. The pump power, expressed in kW, determines the power of the drive motor and the installed power of the entire pump station.
The efficiency of the pump determines the appropriateness of its use when changing the basic parameters of the pumping station.
How ship pumps are divided
All types of pumps installed on a ship are classified according to the following criteria:
- By the location of the drive shaft (horizontal or vertical).
- By type of drive (electric drive, turbine drive or drive from a piston mechanism). The drive gear of the pump can be connected directly to the drive shaft or through a gearbox. It can work autonomously or autonomously. Autonomous pumps can operate independently of other installations, while non-autonomous (mounted) pumps are driven by the mechanism they serve.
- By the force of the created pressure (low-pressure, medium-pressure or high-pressure).
- There is also a classification of ship pumps for their intended purpose . They can be special, general ship or designed to service certain components and mechanisms of a swimming facility or ship’s power plant.
Special pumps can be used to transfer water to roll or trim tanks of a floating vehicle, to transport liquid cargo or to remove their residues from cargo compartments. With their help, hot water can be supplied to the washing devices of these compartments. Rescue vessels can be equipped with powerful dewatering pumps, and fire vessels with huge performance fire pumps.
The pumps used to equip the main and auxiliary components of the vessel are used for the smooth and efficient operation of these elements. Usually they are introduced in machine-boiler compartments and power plants. These include: fuel-pumping, fuel, oil, nutrient, condensate, water and other types of devices.
Marine pumps and their characteristics
Depending on the principle of operation, there are volumetric pumps - vane, gear, screw. Pumps can be centrifugal or jet. They can be classified by purpose and type of use. So, for example, there are ballast pumps, bilge pumps, feed pumps (used to supply oil or water to the cooling system), fire pumps, discharge pumps and others. The essence of the operation of volumetric pumps is the periodic supply of a separate amount of working fluid from the suction chamber to the compression chamber.
The simplest volumetric hydraulic mechanisms are rotary piston pumps. Piston pumps are usually used in general ship systems, hydraulic deck-mounted devices and mechanisms, the main engine system and steering machinery maintenance.
Centrifugal pumps are hydrodynamic devices. The main working body in them is a rotating wheel, on which there are blades or blades. They transmit the necessary energy to the fluid and direct the flow. These devices provide a continuous stream of fluid, i.e. feed evenly. The size of the impeller and the frequency of its rotation affects the supply of the working agent (pump capacity). Large impeller diameters at high speeds provide greater hydraulic performance.
Centrifugal pumps are characterized by a continuous stream of liquid and, therefore, uniformity of flow. The supply (productivity) of the pump depends on the dimensions of the impeller and its speed: the larger the diameter and frequency of rotation of the impeller, the higher the pump performance. Very often, to increase the fluid supply, centrifugal pumps are multi-wheeled.
By the type of direction of the working agent, vane pumps are divided into centrifugal and axial (sometimes called propeller). This also includes vortex hydraulic devices. In centrifugal and vortex pumps, the working fluid can move radially, and in axial (propeller) - along the axis of the shaft.
In jet pumps, energy is supplied along with the flow of the working agent (liquid or steam). The potential energy of the flow in the nozzle of the pump is converted into kinetic. Due to the high-speed flow of the working stream into the suction chamber, the working agent itself entrains liquid or gas from this chamber. The mixed stream moves through the discharge pipe through the diffuser. The ability to dry suction and create a deep vacuum can provide the pump under water. However, the low efficiency and autonomy of this type of pumps are their drawback.
A jet pump designed to pump a working fluid, i.e., to increase its pressure, is called an injector. Injection pumps are often used to power the steam generators of small vessels. Injectors are called jet pumps that provide suction of the working fluid. They are used to remove air or condensate from any rooms or units.
Kinds
A very common type of hydraulic device is a gear pump (NS). The feed element is a pair of gears located in a hermetically sealed housing. When the wheels begin to rotate, the teeth that are not in contact create an increase in volume and fluid is sucked through the lower inlet pipe. Portion quantities of the incoming liquid gradually accumulate in the space between the wheels and are pressed to their outer side. So the working agent enters the compression chamber and passes into the outlet pipe. This type of marine pump is used when pumping viscous fluids with good lubricating characteristics, such as fuel or oil.
Screw pumps on ships are also volumetric. Depending on how many working elements a pump has, one, two, three or multi-screw devices are distinguished.
When the drive shaft rotates, the screw makes a complex rotational movement, in which the working fluid coming from the suction pipe enters the inter-screw space. When the screw is rotated through a certain angle, the working agent in the screw chamber is locked, as it were. The operation of the screws leads to the injection of the working agent into the pressure pipe. If too much fluid accumulates and pressure increases, a special safety valve opens in the compression chamber - excess fluid is dumped back into the inlet chamber.
The principle of operation of a ship’s vertical centrifugal pump is based on a continuous supply of working fluid. The working body of the pump is a rotor with special blades mounted on a rotating drive shaft. The drive is carried out by an electric motor. During the operation of a centrifugal pump, engine energy is transmitted to the fluid by the rotating blades. At the same time, they create the necessary pressure, under the action of which the movement of the working agent from entrance to exit is ensured.
Vertical multistage centrifugal pumps are used almost everywhere in all power plants. Multistage marine pumps are used where it is necessary to create high pressure media. The principle of operation of such devices is that the liquid, having reached the required pressure in one stage, flows to the outlet pipe through the next stage, where its pressure rises again.
Depending on the power, the pumps can have a different design. The huge capacity of the injection pumps of large tankers can reach about tens of thousands of tons of liquid per hour.
Pump assignment on board
Pumps on ships are needed for pumping seawater or using them in various basic systems of a swimming facility. Usually these are general ship systems such as:
- Fire fighting.
- Drainage.
- Cooling
- Sanitary.
- Drainage.
- Ballast
The most important floating systems where various types of pumps are used
To ensure fire safety, each ship must have a ship's fire pump on board. Usually these units are compact and lightweight. In order to effectively respond to a fire and quickly localize the source, the pump must start quickly. In this case, the fire pump must provide the necessary pressure and flow to provide a powerful stream of water.
In the case of filling the holds with sea water, a dewatering ship pump is used. According to safety requirements, there must be at least two drainage pumps on fishing or transport vessels. For passenger liners, three such pumps are required. Moreover, one of them should produce only drainage, and the other two can be used for other purposes, but they must be included in the general drainage system.
Cooling or heating systems are needed to heat or lower the temperature of the working environments of ship installations. So, for example, before supplying fuel to an internal combustion engine, it must be cleaned and heated. But lubricating oil must, on the contrary, cool. The movement of the working fluid is ensured thanks to the operation of special pumps.
To ensure a comfortable crew stay, the ship's sanitary system is needed. The operation of such a system is provided by sanitary pumps. With their help, drinking water or intake water is supplied to the bathrooms.
The ballast system is used to drain and fill the ship’s ballast tanks with sea water.