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A tanker (or tank ship or tankship) is a
ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep waterways, carrying cargo or passengers, or in support of specialized missions, such as defense, research, and fishing. Ships are generally distinguished ...
designed to transport or store liquids or gases in
bulk Bulk can refer to: Industry * Bulk cargo * Bulk liquids * Bulk mail * Bulk material handling * Bulk pack, packaged bulk materials/products * Bulk purchasing * Baking * Bulk fermentation, the period after mixing when dough is left alone to fer ...
. Major types of tankship include the
oil tanker An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined ...
, the chemical tanker, and
gas carrier A gas carrier, gas tanker, LPG carrier, or LPG tanker is a ship designed to transport LPG, LNG, CNG, or liquefied chemical gases in bulk. Types Fully pressurized gas carrier The seaborne transport of liquefied gases began in 1934 when a m ...
. Tankers also carry commodities such as vegetable oils,
molasses Molasses () is a viscous substance resulting from refining sugarcane or sugar beets into sugar. Molasses varies in the amount of sugar, method of extraction and age of the plant. Sugarcane molasses is primarily used to sweeten and flavour foods ...
and wine. In the
United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
and Military Sealift Command, a tanker used to refuel other ships is called an oiler (or
replenishment oiler A replenishment oiler or replenishment tanker is a naval auxiliary ship with fuel tanks and dry cargo holds which can supply both fuel and dry stores during underway replenishment (UNREP) at sea. Many countries have used replenishment oilers. Th ...
if it can also supply dry stores) but many other navies use the terms tanker and
replenishment tanker A replenishment oiler or replenishment tanker is a naval auxiliary ship with fuel tanks and dry cargo holds which can supply both fuel and dry stores during underway replenishment (UNREP) at sea. Many countries have used replenishment oilers. The ...
. Tankers were first developed in the late 19th century as iron and steel hulls and pumping systems were developed. As of 2005, there were just over 4,000 tankers and supertankers or greater operating worldwide.


Description

Tankers can range in size of capacity from several hundred
tons Tons can refer to: * Tons River, a major river in India * Tamsa River, locally called Tons in its lower parts (Allahabad district, Uttar pradesh, India). * the plural of ton, a unit of mass, force, volume, energy or power :* short ton, 2,000 poun ...
, which includes vessels for servicing small harbours and coastal settlements, to several hundred thousand tons, for long-range haulage. Besides ocean- or seagoing tankers there are also specialized inland-waterway tankers which operate on rivers and canals with an average
cargo Cargo consists of bulk goods conveyed by water, air, or land. In economics, freight is cargo that is transported at a freight rate for commercial gain. ''Cargo'' was originally a shipload but now covers all types of freight, including tra ...
capacity up to some thousand tons. A wide range of products are carried by tankers, including: *
Hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
products such as oil,
liquefied petroleum gas Liquefied petroleum gas (LPG or LP gas) is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, propylene, butylene, isobutane and n-butane. LPG is used as a fuel gas in heating appliances, cookin ...
(LPG), and liquefied natural gas (LNG) * Chemicals, such as
ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...
,
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
, and styrene monomer *
Fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...
*
Wine Wine is an alcoholic drink typically made from Fermentation in winemaking, fermented grapes. Yeast in winemaking, Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different ...
*
Molasses Molasses () is a viscous substance resulting from refining sugarcane or sugar beets into sugar. Molasses varies in the amount of sugar, method of extraction and age of the plant. Sugarcane molasses is primarily used to sweeten and flavour foods ...
*
Citrus juice ''Citrus'' is a genus of flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as oranges, lemons, grapefruits, pomelos, and limes. The genus ''Citrus'' is native to So ...
Tankers are a relatively new concept, dating from the later years of the 19th century. Before this, technology had simply not supported the idea of carrying bulk liquids. The market was also not geared towards transporting or selling cargo in bulk, therefore most ships carried a wide range of different products in different holds and traded outside fixed routes. Liquids were usually loaded in casks—hence the term " tonnage", which refers to the volume of the holds in terms of how many
tun TUN or tun may refer to: Biology * Tun shells, large sea snails of the family '' Tonnidae'' * Tun, a tardigrade in its cryptobiotic state * Tun or Toon, common name for trees of the genus '' Toona'' Places * Tun, Sweden, a locality in Västra ...
s or casks of wine could be carried. Even potable water, vital for the survival of the crew, was stowed in casks. Carrying bulk liquids in earlier ships posed several problems: *The holds: on timber ships the holds were not sufficiently water, oil or air-tight to prevent a liquid cargo from spoiling or leaking. The development of iron and steel hulls solved this problem. *Loading and discharging: Bulk liquids must be pumped - the development of efficient pumps and piping systems was vital to the development of the tanker. Steam engines were developed as prime-movers for early pumping systems. Dedicated cargo handling facilities were now required ashore too - as was a market for receiving a product in that quantity. Casks could be unloaded using ordinary cranes, and the awkward nature of the casks meant that the volume of liquid was always relatively small - therefore keeping the market more stable. * Free surface effect: a large body of liquid carried aboard a ship will affect the ship's stability, particularly when the liquid is flowing around the hold or tank in response to the ship's movements. The effect was negligible in casks, but could cause capsizing if the tank extended the width of the ship; a problem solved by extensive subdivision of the tanks. Tankers were first used by the
oil industry The petroleum industry, also known as the oil industry or the oil patch, includes the global processes of exploration, extraction, refining, transportation (often by oil tankers and pipelines), and marketing of petroleum products. The larges ...
to transfer refined fuel in bulk from refineries to customers. This would then be stored in large tanks ashore, and subdivided for delivery to individual locations. The use of tankers caught on because other liquids were also cheaper to transport in bulk, store in dedicated terminals, then subdivide. Even the Guinness brewery used tankers to transport the stout across the
Irish Sea The Irish Sea or , gv, Y Keayn Yernagh, sco, Erse Sie, gd, Muir Èireann , Ulster-Scots: ''Airish Sea'', cy, Môr Iwerddon . is an extensive body of water that separates the islands of Ireland and Great Britain. It is linked to the C ...
. Different products require different handling and transport, with specialised variants such as " chemical tankers", "
oil tanker An oil tanker, also known as a petroleum tanker, is a ship designed for the bulk transport of oil or its products. There are two basic types of oil tankers: crude tankers and product tankers. Crude tankers move large quantities of unrefined ...
s", and " LNG carriers" developed to handle dangerous chemicals, oil and oil-derived products, and liquefied natural gas respectively. These broad variants may be further differentiated with respect to ability to carry only a single product or simultaneously transport mixed cargoes such as several different chemicals or refined petroleum products. Among oil tankers, supertankers are designed for transporting oil around the
Horn of Africa The Horn of Africa (HoA), also known as the Somali Peninsula, is a large peninsula and geopolitical region in East Africa.Robert Stock, ''Africa South of the Sahara, Second Edition: A Geographical Interpretation'', (The Guilford Press; 2004 ...
from the
Middle East The Middle East ( ar, الشرق الأوسط, ISO 233: ) is a geopolitical region commonly encompassing Arabian Peninsula, Arabia (including the Arabian Peninsula and Bahrain), Anatolia, Asia Minor (Asian part of Turkey except Hatay Pro ...
. The supertanker Seawise Giant, scrapped in 2010, was in length and wide. Supertankers are one of the three preferred methods for transporting large quantities of oil, along with
pipeline transport Pipeline transport is the long-distance transportation of a liquid or gas through a system of Pipe (fluid conveyance), pipes—a pipeline—typically to a market area for consumption. The latest data from 2014 gives a total of slightly less than ...
and rail. Tighter regulation means that tankers now cause fewer environmental disasters resulting from oil spills than in the 1970s. '' Amoco Cadiz'', , '' Erika'', '' Exxon Valdez'', '' Prestige'' and were examples of accidents. Oil spills from tankers amounted to around 1,000 tonnes in 2020 from three incidents (an all-time low), down from 636,000 tonnes from 92 incidents in 1979 - a fall of 99.8%.


Design considerations

Many modern tankers are designed for a specific cargo and a specific route. Draft is typically limited by the depth of water in loading and unloading harbors; and may be limited by the depth of
strait A strait is an oceanic landform connecting two seas or two other large areas of water. The surface water generally flows at the same elevation on both sides and through the strait in either direction. Most commonly, it is a narrow ocean chan ...
s along the preferred shipping route. Cargoes with high
vapor pressure Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed pha ...
at ambient temperatures may require pressurized tanks or vapor recovery systems. Tank heaters may be required to maintain heavy crude oil, residual fuel,
asphalt Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term ...
, wax, or
molasses Molasses () is a viscous substance resulting from refining sugarcane or sugar beets into sugar. Molasses varies in the amount of sugar, method of extraction and age of the plant. Sugarcane molasses is primarily used to sweeten and flavour foods ...
in a fluid state for offloading.


Tanker capacity

Tankers used for liquid fuels are classified according to their capacity. In 1954, Shell Oil developed the average freight rate assessment (AFRA) system, which classifies tankers of different sizes. To make it an independent instrument, Shell consulted the '' London Tanker Brokers’ Panel (LTBP)''. At first, they divided the groups as ''General Purpose'' for tankers under ; ''Medium Range'' for ships between 25,000 and and ''Large Range'' (later Long Range) for the then-enormous ships that were larger than . The ships became larger during the 1970s, and the list was extended, where the tons are metric tonnes: * Under : Extra small tanker *10,000–: Small tanker *25,000–34,999 DWT: Intermediate tanker *35,000–44,999 DWT: Medium Range 1 (MR1) *45,000–: Medium Range 2 (MR2) *55,000–: Long Range 1 (LR1) *80,000–: Long Range 2 (LR2) *160,000–: Very Large Crude Carrier (VLCC) *320,000–: Ultra Large Crude Carrier (ULCC) *550,000-: Hyper Large Crude Carrier (HLCC) *900,000-: Mega Crude Carrier (MCC) * Over : Giga Crude Carrier (GCC) ; Very Large Crude Carrier size range At nearly 380 vessels in the size range to , these are by far the most popular size range among the larger VLCCs. Only seven vessels are larger than this, and approximately 90 between and .


Fleets of the world

; Flag states As of 2005, the United States Maritime Administration's statistics count 4,024 tankers of or greater worldwide. 2,582 of these are double-hulled.
Panama Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es, República de Panamá), is a transcontinental country spanning the southern part of North America and the northern part of South America. It is bordered by Co ...
is the leading flag state of tankers, with 592 registered ships. Five other flag states have more than two hundred registered tankers:
Liberia Liberia (), officially the Republic of Liberia, is a country on the West African coast. It is bordered by Sierra Leone to Liberia–Sierra Leone border, its northwest, Guinea to Guinea–Liberia border, its north, Ivory Coast to Ivory Coast� ...
(520), The Marshall Islands (323),
Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders wi ...
(233),
Singapore Singapore (), officially the Republic of Singapore, is a sovereign island country and city-state in maritime Southeast Asia. It lies about one degree of latitude () north of the equator, off the southern tip of the Malay Peninsula, bor ...
(274) and
The Bahamas The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the a ...
(215). These flag states are also the top six in terms of fleet size in terms of
deadweight tonnage Deadweight tonnage (also known as deadweight; abbreviated to DWT, D.W.T., d.w.t., or dwt) or tons deadweight (DWT) is a measure of how much weight a ship can carry. It is the sum of the weights of cargo, fuel, fresh water, ballast water, pro ...
. ; Largest fleets Greece, Japan, and the United States are the top three owners of tankers (including those owned but registered to other nations), with 733, 394, and 311 vessels respectively. These three nations account for 1,438 vessels or over 36% of the world's fleet. ; Builders Asian companies dominate the construction of tankers. Of the world's 4,024 tankers, 2,822 (over 70%) were built in South Korea, Japan and China.


Further reading

''Petroleum Tables'', a book by William Davies, an early tanker captain, was published in 1903, although Davies had printed earlier versions himself. Including his calculations on the expansion and contraction of bulk oil, and other information for tanker officers, it went into multiple editions, and in 1915 ''The Petroleum World'' commented that it was "the standard book for computations and conversions."''The Petroleum World'', Vol. 12 (1915), p. 146


See also

*
Hydrogen tanker A hydrogen tanker is a tank ship designed for transporting liquefied hydrogen. Research The World Energy Network research program of the Japanese New Sunshine Project was divided into 3 phases during the period 1993 to 2002, its goal was to st ...
*
List of gas carriers This list of gas carrier ships includes LPG carriers and LNG carriers. Ships with multiple names may be listed under each name. A * Al Barrah * Al Dafna * Al Jabirah * Al Oraic * Al Rayyan * Al Thakhira * Ayame * Almarona * Artemis Gas * Alra ...
* List of tankers * T1 tanker *
T2 tanker The T2 tanker, or T2, was a class of oil tanker constructed and produced in large quantities in the United States during World War II. Only the T3 tankers were larger "navy oilers" of the period. Some 533 T2s were built between 1940 and the end o ...
* T3 Tanker


Notes


References

* * * * * * * * * * *


External links


ship-photos.de
Private homepage of categorized ship photos including tankers of all kinds {{DEFAULTSORT:Tanker (Ship) Ship types