Main article: Merchant ship Commercial crude oil supertanker AbQaiq.

A tanker (or tank ship or tankship) is a ship designed to transport liquids in bulk. Major types of tankship include the oil tanker the chemical tanker and the liquefied natural gas carrier. Contents 1 Background 2 Tanker capacity 3 Fleets of the world 4 See also 5 Notes 6 References 7 External links Background

Tankers can range in size of capacity from several hundred tons 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 capacity up to some thousand tons. A wide range of products are carried by tankers including: hydrocarbon products such as oil liquefied petroleum gas (LPG) and liquefied natural gas (LNG) chemicals such as ammonia chlorine and styrene monomer fresh water wine molasses

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 caskshence the term "tonnage" which refers to the volume of the holds in terms of the amount of tuns of wine (casks) that 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: Describes the effect a large surface area of liquid in a ship will have on the stability of that ship. See Naval Architecture. Liquids in casks posed no problem but one tank across the beam of a ship could pose a stability problem. Extensive sub-division of tanks solved this problem.

In the end the tanker had its beginnings in the oil industry as oil companies sought cheaper ways to transport their refinery product to their customers. The Oil Tanker was born. Today most liquids are cheaper to transport in bulk and dedicated terminals exist for each product. Large storage tanks ashore are used to store the product until it can be subdivided into smaller volumes for delivery to smaller customers.

Even the Guinness brewery company in Dublin had a tanker fleet to export the famous stout to the UK.

Different products require different handling and transport. Thus special types of tankers have been built such as "chemical tankers" and "oil tankers". "LNG carriers" as they are typically known are a relatively rare tanker designed to carry liquefied natural gas.

Among oil tankers supertankers are designed for transporting oil around the Horn of Africa from the Middle East. The supertanker Seawise Giant scrapped in 2010 was 458 meters (1504 feet) in length and 69 m (226 ft) wide.

Supertankers are one of the three preferred methods for transporting large quantities of oil along with pipeline transport and rail. Despite being highly regulated tankers have been involved in environmental disasters resulting from oil spills. See Exxon Valdez Braer Prestige oil spill Torrey Canyon and Erika for examples of coastal accidents. 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 25000  tons deadweight (DWT); Medium Range for ships between 25000 and 45000 DWT and Large Range for the then-enormous ships that were larger than 45000 DWT. The ships became larger during the 1970s and the list was extended where the tons are long tons:1 1000024999 DWT: General Purpose tanker 2500044999 DWT: Medium Range tanker 4500079999 DWT: Large Range 1 (LR1) 80000159999 DWT: Large Range 2 (LR2) 160000319999 DWT: Very Large Crude Carrier (VLCC) 320000549999 DWT: Ultra Large Crude Carrier (ULCC) Petroleum Tankers Class Length Beam Draft Typical Min DWT Typical Max DWT Seawaymax 226 m 24 m 7.92 m 10000 DWT 60000 DWT Panamax 228.6 m 32.3 m 12.6 m 60000 DWT 80000 DWT Aframax 253.0m 44.2m 11.6m 80000 DWT 120000 DWT Suezmax 16 m 120000 DWT 200000 DWT VLCC (Malaccamax) 470 m 60 m 20 m 200000 DWT 315000 DWT ULCC 320000 DWT 550000 DWT At nearly 380 vessels in the size range 279000 DWT to 320000 DWT these are by far the most popular size range among the larger VLCCs. Only seven vessels are larger than this and approximately 90 between 220000 DWT and 279000 DWT.2 Fleets of the world Flag states As of 2005 the United States Maritime Administration's statistics count 4024 tankers of 10000 DWT or greater worldwide.3 2582 of these are double-hulled. Panama is the leading flag state of tankers with 592 registered ships. Five other flag states have more than two hundred registered tankers: Liberia (520) The Marshall Islands (323) Greece (233) Singapore (274) and The Bahamas (215). These flag states are also the top six in terms of fleet size in terms of deadweight tonnage.3 Largest fleets Greece Japan and the United States are the top three owners of tankers with 733 394 and 311 vessels respectively. These three nations account for 1438 vessels or over 36% of the world's fleet.3 Builders Asian companies dominate the construction of tankers. Of the world's 4024 tankers 2822 or over 70% were built in South Korea Japan or China.3 See also Hydrogen tanker List of tankers Notes Evangelista Joe Ed. (Winter 2002). "Scaling the Tanker Market" (PDF). Surveyor (American Bureau of Shipping) (4): 511. Archived from the original on 2007-09-30. http://web.archive.org/web/20070930043604/http://www.eagle.org/NEWS/pubs/pdfs/SurveyorWinter02.pdf. Retrieved 2008-02-27.  Auke Visser (22 February 2007). "Tanker list status 01-01-2007". International Super Tankers. http://supertankers.topcities.com/id295.htm. Retrieved 2008-02-27.  a b c d Office of Data and Economic Analysis (July 2006) (.PDF). World Merchant Fleet 20012005. United States Maritime Administration. pp. 3 5 6. http://www.marad.dot.gov/MARADstatistics/2005%20STATISTICS/World%20Merchant%20Fleet%202005.pdf. Retrieved 2008-02-27.  References Encyclopdia Britannica (1911). "Petroleum". In Chisholm Hugh. Encyclopdia Britannica. 21 (Eleventh ed.). Cambridge: Cambridge University Press. pp. 316322. OCLC 70608430. http://en.wikisource.org/w/index.phptitleUser:TimStarling/ScanSetTIFFdemo&vol21&pageED1A336. Retrieved 2008-02-22.  Encyclopdia Britannica (1911). "Ship". In Chisholm Hugh. Encyclopdia Britannica. 24 (Eleventh ed.). Cambridge: Cambridge University Press. pp. 881889. OCLC 70608430. http://en.wikisource.org/w/index.phptitleUser:TimStarling/ScanSetTIFFdemo&vol24&pageED4A915. Retrieved 2008-02-22.  Hayler William B.; Keever John M. (2003). American Merchant Seaman's Manual. Centerville MD: Cornell Maritime Press. ISBN 0870335499.  Central Intelligence Agency. CIA World Factbook 2008. New York: Skyhorse Publishing. ISBN 1602390800. https://www.cia.gov/library/publications/the-world-factbook/index.html. Retrieved 2008-02-27.  Turpin Edward A.; McEwen William A. (1980). Merchant Marine Officers' Handbook (Fourth ed.). Centreville MD: Cornell Maritime Press. 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