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Кораблестроение, океанотехника и системотехника
объектов морской инфраструктуры» (только для профиля
океанотехника и системотехника объектов морской инфраструктуры)
Marine Engines
There are four main types of marine engines: the diesel engine, the steam
turbine, the gas turbine and the marine nuclear plant. Each type of the engines has
particular application.
The diesel engine is a form of internal combustion engine in which the
power is developed by the piston in the cylinder. But some power is lost due to
friction in the cylinder. Most large merchant vessels are powered by medium-speed
diesel engines; they are cheaper, smaller in size and weight.
In steam turbines high pressure steam is directed into blades of the shaft,
rotates the shaft; the rotary motion is transferred to the propeller shaft. Steam is
produced by boiling water in a boiler. Steam turbines are more often used in ships,
especially in container ships.
Gas turbines use gas to turn a shaft. A gas turbine engine is very light and
easily removed for maintenance. Gas turbines can be completely automated.
Nuclear power in ships is mainly used in icebreakers. A ship uses the energy
released by the decay of radioactive fuel to generate steam. The steam is used to
turn a shaft via a turbine.
Repair
Repair is fixing any sort of mechanical or electrical device if it has got out of
order or broken. It is performing the routine actions which keep the device in
working order or prevent trouble in maintenance. After repair the device must
perform the required function properly.
The repair actions include the combination of all technical, administrative
and supervision actions, tests, measurements, replacements, adjustments and
inspection. It means that any machinery is repaired up to such condition that it may
be continuously used.
In marine practice it is very often necessary to repair some machinery on
board ship. But very complicated machinery, lack of necessary spare parts, absence
of highly-qualified specialists makes repair difficult for ship’s engineers; besides
most types of repairs are very costly.
Examples of repairs which can be carried out on board ship are main engine
piston, crankcase bearing overhauls, pump and auxiliary machinery overhauls. But
all the parameters must be checked to prevent any possible breakdowns after
repair. Tests and trials should be carried out to check the quality of work, newly
installed equipment, materials and systems.
Cooling System
Cooling is a method of heat removal from components. Cooling of the diesel
engine is very important and necessary due to high temperatures and friction
between moving parts of the engine. The main function of the cooling system is to
carry away the hat, to reduce wear, and thermal deformation. The engine parts that
require cooling are the cylinder, the piston, the exhaust manifold, fuel valves,
crosshead guides, etc.
The cooling medium can be fresh water, sea water, oil and air. The most
often used cooling system is enclosed fresh water system. In this case the engine
room is almost free from corrosive and dirty sea water. Fresh water does not form
scale but it is very costly.
Sea water is free of charge and may be discharged into the sea. But it
contains a lot of minerals, forms deposits and causes corrosion, so it should be well
filtered. Oil as a coolant has a lot of advantages. It reduces engine noise, has
purifying and lubrication functions. But oil absorbs less heat than water. Air as a
coolant is free of charge but a great amount of air is needed to cool a small surface.
Кораблестроение, океанотехника и системотехника
объектов морской инфраструктуры» (только для профиля
кораблестроение)
Container Ships
Container ships are cargo ships that carry all cargo in containers, it is called
containerization. Container ships are all purpose-built and are second only to crude
oil tankers as the biggest cargo ships on the oceans. Container ships are designed in
such a way that no space is wasted. Large container ships are built in Demark,
South Korea, Japan.
Their capacity is measured in TEUs (Twenty-foot equivalent units). This is
the number of 20-foot containers that a vessel can carry. The majority of containers
used today are 40 feet in length. Container ships now carry up to 12,000 containers
on a voyage. Container ships mostly do not carry their own loading gear; loading
and unloading can only be done at ports with the necessary cranes.
There is no way to know the contents of each container. There must be as
little vibration of the loaded container as possible. Thus the operator has to be well-
qualified and experienced to operate the crane efficiently.
In open sea, storms can cause the loss of containers. The great value of cargo
on these vessels makes them a target for pirates.
Shipbuilding
Shipbuilding is a construction of ships. It normally takes place in a
specialized facility known as a shipyard.
The profession of a shipbuilder dates back to ancient times. The early
Egyptians knew how to assemble planks of wood into a watertight hull. Their ships
had a single mast with a single square sail. These ships could also be oar propelled.
The Greek ships had much more oars for additional speed; their ships were of a
light construction.
In the 12th century northern European ships began to be built with a rudder.
Later the above water hull for additional stability and techniques for strengthening
the internal frame were developed.
The demand for ships capable of operating safely in the open ocean led to
documentation of design and construction practice. Thus the field of naval
architecture appeared. But construction techniques changed slowly. Iron was
gradually adopted in ships. In the 19th century steel replaced iron, wood continued
to be used for decks. Modern ships have been produced of welded steel with good
properties.
Double Hull
A double hull is a ship hull design and construction method where the
bottom and sides of the ship have two complete layers of watertight hull surface.
One outer layer is a normal hull of the ship and the second inner hull forms an
architectural barrier to sea water in case the outer hull is damaged and leaks.
The space between the two hull layers is often used as storage tanks for fuel
or ballast water. Double hulls are more effective safety measure than the double
bottom. Double hulls are significantly safer than single hulls. In case of grounding
or other underwater damage, the damage is limited to flooding the bottom
compartment and the main occupied areas remain safe.
Double hulls and bottoms are required in all passenger ships, as well as oil
tankers to prevent or reduce oil spill in to the sea. A double hull also strengthens all
the structure of the ship.
But the double hull increases the risk of corrosion in the double hull and it is
very dangerous for the crew to inspect those areas. Besides there can be explosive
accidents in the double hull.
Строительство»
Marine Structures
A port must include convenient and compact means for landing, loading and
discharging of goods and embarkation of passengers. A dock, a wharf or a quay, a
pier or a jetty and many other features are marine structures.
A dock is constructed to handle passengers or general cargo or a
combination of both. It may be required to handle a specific type of cargo,
particularly bulk cargo such as oil, ore, cement, grain, fertilizers. Constructing a
dock it is necessary to take into consideration some factors: whether a temporary or
a permanent installation is required, the size of ships to use a dock, the direction of
waves and wind, soil conditions and others. There are wet docks, artificial basins
for vessels, and dry docks, when the basin is pumped out.
In many locations the ground may be low and marshy and it is necessary to
fill it in. It is done by dredging the adjacent waterway, creating a navigable canal.
A pier or jetty is a dock which projects into water; sometimes it is called a mole.
Piers provide berths on both sides doubling the berthing space for the same length
of a wharf. New quays and wharves should be designed with regard to the nature
of cargo and passenger traffic.
Port Protection
Sea-going ships can use inland waterways but a river has to be widened and
deepened, its banks must be protected so that they do not wash away and block the
river and river ports with mud. It is necessary to maintain the depth of water in the
basins by dredging otherwise the port would become silted.
Seasonal changes of water discharge in rivers make navigation
unpredictable. Insufficient water depths, variability of precipitation and
evaporation cannot support navigation of any significance.
Particular problem for the inland waterway network and ports arises from
floods. Serious bank erosion takes place causing widening of the original section of
rivers and canals and their silting. Floods threaten the stability of the flood banks
and make navigation difficult because of uncertain depths in rivers and canals.
To the banks subjected to wave action traditional of lining is used. It consists
of stone blocks on the slope above water supported by a row of piles at navigation
level and loose stone below water.
Sometimes dams and barriers are constructed to reduce the height of floods
and to control the flow of water in rivers. Earth dams are mostly often used
because they are considered to be permanent and require practically no
maintenance. The type and height of a dam depend on geology and configuration
of the site.
General Cargo Terminals
Bulk shipping terminals, including berths for tankers, vary with the type of
material and machinery and other facilities required for the particular cargo to be
handled.
As for general cargo terminals they are quite conventional and have changed
little over years. Nowadays they are larger and have wider aprons resulted from
usage of various trucks, portal cranes, railroad lanes for cargo handling. Larger
ships of greater tonnage, more capacious storage areas and transit sheds require
longer and wider piers and wharves.
General cargo terminals must be wide enough to accommodate ships of great
size and to provide space for ships’ maneuvering in and out of the inside berth with
the assistance of a tug.
Transit sheds of general cargo terminals provide temporary storage for (1)
goods discharged from vessels and awaiting clearance through customs and
distribution to warehouses on points of destination and (2) goods arriving by land
and awaiting export. Most terminals along the inland waterways have railroad and
highway connections to facilitate the delivery of cargo.