TYPES OF TANKER SHIPS IN WORLD
The
transportation of bulk liquids began in the late 19th century when the discovery
and expedition of oils began. At that time, tankers emerged as the main mode of
transportation to carry bulk liquids from refineries to the global market. As
time passed, different energy products were produced and need for various types
of tankers came into the real picture. Presently, a variety of products such as
crude oil, finished petroleum products, liquefied natural Gas, Chemicals,
Edible oils, wine, juice, molasses etc, are transported through tankers.
Tankers play
a major share of more than 33%.of the world fleet tonnage Tankers, however, are
not restricted to one particular type or variety. There are many types of
tankers in terms of Use, construction and Size. There are two main categories
by which shipping tankers can be classified:
Let’s take a look at the classification of
tankers on the Basis of
1 ] OIL TANKERS : Oil tankers, as their name suggests,
carry oil and its by-products. An Oil Tanker is designed to carry wide variety
of Petroleum products in bulk ranging from Crude oil to refined products. Their
size is measured in DWT (deadweight tonnage) and ranges from 55,000 DWT to
VLCC’s of over 300,000 DWT.Due to their immense size, they have become quite
cheaper to transport petroleum products, it costs around 2-4 cents per Gallon only.
Oil tankers are further sub-divided into two
main types
· PRODUCT TANKERS
· CRUDE TANKERS
PRODUCT
TANKERS are used to transport petroleum based chemicals
they are used to carry refined oil of various grades and are smaller in size as
compared to the Crude oil tankers.
CRUDE TANKERS- These vessels are much larger in
size than the other variants of oil tankers and move a large quantity of
unrefined crude oil to the oil refineries.
2 ]
GAS TANKERS-
They are specially designed to carry different forms of gasses. As per the type
of cargo carried and the requirements these tankers can be classified into five
categories as named below:
· FULLY PRESSURISED SHIPS
· SEMI-PRESSURISED SHIPS
· ETHYLENE SHIPS
· CHEMICAL TANKERS
· LNG CARRIER
A]
FULLY PRESSURISED SHIPS - In these types of Tankers, the cargo is carried in the
ambient temperature. They have “C type” of tanks which are made with Carbon steel.
There are no thermal insulations or other plants. The cargo can be directly
transferred by the pumps or compressor of the ship.
B] SEMI PRESSURIED SHIPS -These are very similar to fully pressurized
ships in term of the tanks construction and structure but they are designed to
carry gas at a maximum working pressure of 5-7 bars. These ships can be used to
transport a wide variety of gas cargo in bulk. Due to its cargo handling flexibility,
semi pressurized gas tankers are most popular among the operators and owners.
C] ETHYLINE SHIPS -This variant of Gas carriers are built
for unambiguous trades but also have arrangements to carry LPG or Chemical Gases.
Their cargo carrying capacity is between 1000-12000 cubic meter.
D] FULLY REFRIGERATED LPG SHIPS - These types of tankers can carry Liquefied gases at
low temperature and atmospheric pressure. They have a prismatic shaped cargo tanks
made up of 3.5% nickel steel, which allows them to carry cargo at a temperature
as low as -48°C.
E] LNG CARRIER - Statistically speaking, there are
around 500 LNG tankers that are currently under operation. LNG is now
considered to be the alternative fuel for ships to comply with IMO 2020. LNG
Carriers are specifically designed to trade a high volume of LNG. These ships
have a cargo carrying capacity of 125000 to 135,000 cubic meter. LNG is carried
at its boiling point, which is -162°C inside a specialized membrane tank.
3] CHEMICAL TANKERS - They range from 5000 to 35000DWT in size.
The size of these vessels is smaller as compared to the Oil tankers due to the
specialized nature of the cargo and the size restriction of the Ports and shore
facilities. They consist of various tanks which are coated with specialized
coatings such as: Phenolic epoxy, stainless steel or zinc paint
4] SLURRY TANKERS - Slurry refers to all those materials that do
not disperse or dissolve in water – and are otherwise regarded as waste materials.
These types of vessels are not ideal for shipping any chemical products other
than slurry itself.
5] HYDROGEN TANKERS - These tankers are specifically
designed to carry Liquifiedhydrogen gas in bulk. Kawasaki heavy industries were
the first company to design a Hydrogen Tanker. As the name suggests, these
tankers were especially designed for the carriage of juices. They either carry
concentrated or fresh orange juice originating from Brazil to other parts of
the world. These tankers have refrigeration, temperature controller and
preservation plants, which helps them to keep the juice fresh at all times.
6] WINE TANKERS - Transporting wine has become quite simpler as sleek
wine tankers are used specifically to carry wine. These tankers are used in
carrying wine from the place of production to different countries.
7] INTEGRATED TUG BARGES - ITBs are prominently used in the
eastern coast of the United States. These tankers are mainly tugs attached to
barges leading to the formation of a single cargo-carrying unit.
CLASSIFICATION OF TANKERS ON THE
BASIS OF SIZE
VLCC tankers have a cargo carrying capacitance of
250,000 tons
ULCC are mega ships and have a cargo
hauling capacity which ranges up to 500,000 tons.
PANAMAX -The type of tanker that can pass
through the Panama Canal is known as Panamax newpanama vessels are those which
can cross the recently made new Panama Canal and have an average capacity of
65,000 DWT .
POST PANAMAX TANKERS - The cargo tankers which cannot be
classified underPanamax category because of their bigger size are known as the
Post-Panamax tankers.
The AFRAMAX cargo tankers are that type of tanker ships
which are mainly used in the Mediterranean Sea, China Sea and the Black Sea.
These tankers have a deadweight tonnage (DWT) between 80,000 and 120,000
tonnes.
SUEZMAX - Panamax tankers are named for vessels
which can navigate through the Panama Canal. Similarly, the Suezmax vessels are
so called because they can pass through the Suez Canal.
Q-MAX - These are the largest LNG carriers
that can docket the LNG terminals in Qatar having a length of approx. 345 meters
and capacity of 266,000 cubic meters it cannot be denied that in the present
day scenario the whole world runs in oil and gas and tanker shipping offers the
best possible transportation efficiency of these products.
What is chemical tanker ? and what does chemical tanker mean ?
A chemical
tanker is a type of tanker ship designed to transport chemicals in bulk as
defined in MARPOL annex to chemical tanker means the ship constructed or
adapted for carrying in bulk any liquid product listed in chapter 17 of the
International bulk chemical code as well as industrial chemicals and clean
petroleum products such ships also often
carry other types of sensitive cargo which require a high standard of tank
cleaning such as palm oil vegetable oils tallow caustic soda and methanol
ocean-going chemical tankers range from 5,000 tones deadweight DWT to 35,000
DWT in size which is smaller than the average size of other tanker types due to
the specialized nature of their cargo and besides restrictions of the port
terminals where they call to load and discharge
Chemical
tankers normally have a series of separate cargo tanks which are coated with
specialized coatings such as phenolic epoxy or zinc paint or made from stainless
steel the coating or cargo tank material determines what types of cargo a
particular tank can carry stainless steel tanks are required for aggressive
acid cargo such as sulfuric and phosphoric acid while easier cargoes such as
vegetable oil can be carried in epoxy coated tanks .
The coating
or tank material also influences how quickly tanks can be cleaned typically
ships with stainless steel tanks can carry a wider range of cargoes and can
clean more quickly between one cargo and another which justifies the additional
cost of their construction
Chemical
tankers often have a system for tank heating in order to maintain the viscosity
of certain cargoes typically by passing pressurized steam through stainless
steel heating coils in the cargo tanks transferring heat into the cargo would
circulate to the tank by convection .
All modern
chemical tankers feature double hull construction and most have one
hydraulically driven submerged cargo pump for each tank with independent piping
which means that each tanks can load a separate cargo without any mixing
consequently many ocean-going chemical tankers may carry numerous different
grades of cargo on the same voyage often loading and discharging these parcels
at different ports or terminals this means that the scheduling stowage planning
and operation of such ships requires a high level of coordination and
specialist knowledge both of sea and onshore tank cleaning after discharging
cargo is a very important aspect of chemical tanker operations
If tanks
which are not properly cleaned of all cargo residue can adversely affect the
purity of the next cargo loaded before tanks are cleaned they must be properly
ventilated and text to be free of potentially explosive gases chemical tankers
usually have transverse stiffeners on deck rather than inside the cargo tanks
in order to make the tank wall smooth and that easier to clean using
permanently fitted tank cleaning machines
Cargo tanks
either empty or filled are normally protected against explosion by inert gas
blankets often nitrogen is the inert gas used supplied either from portable gas
bottles or a nitrogen generator most new chemical tankers are built by
shipbuilders in Japan Korea or China with other builders in Turkey Italy
Germany and Poland Japanese shipbuilders now account for the large majority of
stainless steel chemical tankers built as welding stainless steel to the
accuracy required for cargo tank construction is of skill which is difficult to
acquire notable nature chemical tanker operators include skilled Nielson
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