Tanker (ship)

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Commercial crude oil supertanker AbQaiq Supertanker AbQaiq.jpg
Commercial crude oil supertanker AbQaiq

A tanker (or tank ship or tankship) is a ship designed to transport or store liquids or gases in bulk. Major types of tankship include the oil tanker, the chemical tanker, and gas carrier. Tankers also carry commodities such as vegetable oils, molasses and wine. In the United States Navy and Military Sealift Command, a tanker used to refuel other ships is called an oiler (or replenishment oiler if it can also supply dry stores) but many other navies use the terms tanker and replenishment tanker.



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:

The Thomas W. Lawson (1902), converted in 1906 into the world's first sailing tanker. Schooner 'Thomas W. Lawson' 1902-1907a.jpg
The Thomas W. Lawson (1902), converted in 1906 into the world's first sailing tanker.

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 tuns 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:

Tankers were first used by the oil industry 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.

A US Navy T2 tanker in 1943 Type T2-SE-A1 tanker Hat Creek underway at sea on 16 August 1943.jpg
A US Navy T2 tanker in 1943

Different products require different handling and transport, with specialised variants such as "chemical tankers", "oil tankers", 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. [1] 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 (1,503 ft) in length and 69 meters (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. Amoco Cadiz , Braer, Erika , Exxon Valdez , Prestige and Torrey Canyon were examples of coastal accidents.

Primary maritime cargo types

Primary maritime cargo types
Cargo typeCountablePackagingContainerRemarks
Break bulk cargo or general cargo CountableYesNoBreak bulk cargo or general cargo are goods that must be loaded individually, and not in intermodal containers nor in bulk as with oil or grain. Ships that carry this sort of cargo are called general cargo ships. The term break bulk derives from the phrase breaking bulk—the extraction of a portion of the cargo of a ship or the beginning of the unloading process from the ship's holds. These goods may not be in shipping containers. Break bulk cargo is transported in bags, boxes, crates, drums, or barrels. Unit loads of items secured to a pallet or skid are also used. [2]
Bulk cargo (bulk dry cargo)WeighableNoNoBulk cargo is commodity cargo that is transported unpackaged in large quantities. It refers to material in either liquid or granular, particulate form, as a mass of relatively small solids, such as petroleum/crude oil, grain, coal, or gravel. This cargo is usually dropped or poured, with a spout or shovel bucket, into a bulk carrier ship's hold, railroad car/railway wagon, or tanker truck/trailer/semi-trailer body. Smaller quantities (still considered "bulk") can be boxed (or drummed) and palletised. Bulk cargo is classified as liquid or dry.
Bulk liquid cargo WeighableNoNoA tanker (or tank ship or tankship) is a ship designed to transport or store liquids or gases in bulk. Major types of tankship include the oil tanker, the chemical tanker, and gas carrier. Tankers also carry commodities such as vegetable oils, molasses and wine. In the United States Navy and Military Sealift Command, a tanker used to refuel other ships is called an oiler (or replenishment oiler if it can also supply dry stores) but many other navies use the terms tanker and replenishment tanker. A wide range of products are carried by tankers, including:
Container cargo CountableYesYesContainerization is a system of intermodal freight transport using intermodal containers (also called shipping containers and ISO containers). [3] The containers have standardized dimensions. They can be loaded and unloaded, stacked, transported efficiently over long distances, and transferred from one mode of transport to another—container ships, rail transport flatcars, and semi-trailer trucks—without being opened. The handling system is completely mechanized so that all handling is done with cranes [4] and special forklift trucks. All containers are numbered and tracked using computerized systems.
Neo-bulk cargo WeighableYesNoIn the ocean shipping trade, neo-bulk cargo is a type of cargo that is a subcategory of general cargo, alongside the other subcategories of break-bulk cargo and containerized cargo. [5] (Gerhardt Muller, erstwhile professor at the United States Merchant Marine Academy and Manager of Regional Intermodal Planning of the Port Authority of New York and New Jersey, promotes it from a subcategory to being a third major category of cargo in its own right, alongside general and bulk cargo. [6] [7] ) It comprises goods that are prepackaged, counted as they are loaded and unloaded (as opposed to bulk cargo where individual items are not counted), not stored in containers, and transferred as units at port. [5] Types of neo-bulk cargo goods include heavy machinery, lumber, bundled steel, scrap iron, bananas, waste paper, and cars. [5] [8] [7] The category has only become recognized as a distinct cargo category in its own right in recent decades. [6] [7]
Passenger cargo CountableNoNoA passenger ship is a merchant ship whose primary function is to carry passengers on the sea.
Project cargo WeighableYesNoProject cargo is a term used to broadly describe the national or international transportation of large, heavy, high value, or critical (to the project they are intended for) pieces of equipment. Also commonly referred to as heavy lift , this includes shipments made of various components which need disassembly for shipment and reassembly after delivery. [9]
Refrigerated cargo WeighableYesYes / noA reefer ship is a refrigerated cargo ship, typically used to transport perishable commodities which require temperature-controlled transportation, such as fruit, meat, fish, vegetables, dairy products and other foods.
Roll-on/roll-off cargo CountableNoNoRoll-on/roll-off (RORO or ro-ro) ships are vessels designed to carry wheeled cargo, such as cars, trucks, semi-trailer trucks, trailers, and railroad cars, that are driven on and off the ship on their own wheels or using a platform vehicle, such as a self-propelled modular transporter. This is in contrast to lift-on/lift-off (LOLO) vessels, which use a crane to load and unload cargo.

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 straits along the preferred shipping route. Cargoes with high vapor pressure at ambient temperatures may require pressurized tanks or vapor recovery systems. Tank heaters may be required to maintain heavy crude oil, residual fuel, asphalt, wax, or molasses in a fluid state for offloading. [10]

Tanker capacity

Tankers used for liquid fuels are classified according to their capacity.

The small coastal tanker Pegasus on the River Weser Tanker Pegasus.jpg
The small coastal tanker Pegasus on the River Weser
The Very Large Crude Carrier (VLCC) MV Sirius Star in 2008, after her capture by Somali pirates Sirius Star 2008b.jpg
The Very Large Crude Carrier (VLCC) MV Sirius Star in 2008, after her capture by Somali pirates

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 25,000 tons deadweight (DWT); Medium Range for ships between 25,000 and 45,000  DWT and Large Range for the then-enormous ships that were larger than 45,000  DWT. The ships became larger during the 1970s, and the list was extended, where the tons are long tons: [11]

Very Large Crude Carrier size range

At nearly 380 vessels in the size range 279,000 t  DWT to 320,000 t  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 220,000 t  DWT and 279,000 t  DWT. [12]

Distribution of supertanker sizes.png

Fleets of the world

Flag states

As of 2005, the United States Maritime Administration's statistics count 4,024 tankers of 10,000 LT  DWT or greater worldwide. [13] 2,582 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. [13]

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. [13]


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. [13]

Further reading

Petroleum Tables, a book by William Davies, an early tanker captain, was published in 1903, although Davies had printed earlier versions himself. [14] 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." [15]

See also


  1. Morrell, p.1
  2. Notes on Cargo Work by J. F. Kemp and Peter Young, 1971 (3rd edition); page 31. ISBN   0-85309-040-8.
  3. Edmonds, John (2017-03-03). "The Freight Essentials: Getting Your Products Across The Ocean" . Retrieved 2017-09-01.
  4. Lewandowski, Krzysztof (2016). "Growth in the Size of Unit Loads and Shipping Containers from Antique to WWI". Packaging Technology and Science. 29 (8–9): 451–478. doi:10.1002/pts.2231. ISSN   1099-1522.
  5. 1 2 3 CambridgeSystematics 1998, pp. 79.
  6. 1 2 Muller 1998, pp. 90.
  7. 1 2 3 Muller 1995, pp. 3.
  8. Seyoum 2008, pp. 207.
  9. "About Project Cargo Network". Project Cargo Network. Archived from the original on 1 February 2013. Retrieved 6 December 2012.
  10. Morrell, pp.1&8
  11. Evangelista, Joe, Ed. (Winter 2002). "Scaling the Tanker Market" (PDF). Surveyor. American Bureau of Shipping (4): 5–11. Archived from the original (PDF) on 2007-09-30. Retrieved 2008-02-27.
  12. Auke Visser (22 February 2007). "Tanker list, status 01-01-2007". International Super Tankers. Retrieved 2008-02-27.
  13. 1 2 3 4 Office of Data and Economic Analysis (July 2006). "World Merchant Fleet 2001–2005" (PDF). United States Maritime Administration: 3, 5, 6. Archived from the original (.PDF) on 2007-02-21. Retrieved 2008-02-27.Cite journal requires |journal= (help)
  14. William Davies, Petroleum Tables; being some useful Tables used for Ascertaining the Weights and Measures of Petroleum Cargoes, and a Table of Distances (London: Goodman, Burnham, and Company, 1903)
  15. The Petroleum World, Vol. 12 (1915), p. 146

Related Research Articles

Tanker may refer to:

Cargo ship ship or vessel that carries cargo, goods, and materials onboard from one port to another

A cargo ship or freighter is a merchant ship that carries cargo, goods, and materials from one port to another. Thousands of cargo carriers ply the world's seas and oceans each year, handling the bulk of international trade. Cargo ships are usually specially designed for the task, often being equipped with cranes and other mechanisms to load and unload, and come in all sizes. Today, they are almost always built by welded steel, and with some exceptions generally have a life expectancy of 25 to 30 years before being scrapped.

Merchant ship civilian boat or ship that transports cargo or carries passengers for hire

A merchant ship, merchant vessel, trading vessel, or merchantman is a watercraft that transports cargo or carries passengers for hire. This is in contrast to pleasure craft, which are used for personal recreation, and naval ships, which are used for military purposes.

Tank car Type of freight car

A tank car is a type of railroad car or rolling stock designed to transport liquid and gaseous commodities.

Bulk carrier merchant ship specially designed to transport unpackaged bulk cargo

A bulk carrier,bulker is a merchant ship specially designed to transport unpackaged bulk cargo, such as grains, coal, ore, steel coils and cement, in its cargo holds. Since the first specialized bulk carrier was built in 1852, economic forces have led to continued development of these ships, resulting in increased size and sophistication. Today's bulk carriers are specially designed to maximize capacity, safety, efficiency, and durability.

Bulk cargo Commodity cargo transported unpackaged in large quantities

Bulk cargo is commodity cargo that is transported unpackaged in large quantities.

Chemical tanker type of tanker ship designed to transport chemicals in bulk

A chemical tanker is a type of tanker ship designed to transport chemicals in bulk. As defined in MARPOL Annex II, chemical tanker means a 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.

Tank truck motor vehicle designed to carry liquefied loads, dry bulk cargo or gases on roads

A tank truck, gas truck, fuel truck, or tanker truck or tanker, is a motor vehicle designed to carry liquefied loads or gases on roads. The largest such vehicles are similar to railroad tank cars which are also designed to carry liquefied loads. Many variants exist due to the wide variety of liquids that can be transported. Tank trucks tend to be large; they may be insulated or non-insulated; pressurized or non-pressurized; and designed for single or multiple loads. Some are semi-trailer trucks. They are difficult to drive due to their high center of gravity.

Crowley Maritime Diversified transportation and logistics company based in Jacksonville, Florida

Crowley Maritime Corporation, is based in Jacksonville, Florida. Founded in 1892, Crowley is primarily a family- and employee-owned vessel management, owner, and supply chain logistics services company, providing services globally. As of July 2016, Crowley was ranked as the 13th largest private company in Florida, employing approximately 5,300 people worldwide with revenues of $2.2 billion. It provides its services using a fleet of more than 300 vessels, consisting of RO-RO vessels, LO-LO vessels, tankers, Articulated Tug-Barges (ATBs), tugs and barges. Crowley's land-based facilities and equipment include terminals, warehouses, tank farms, and specialized vehicles.

Odfjell SE is a company specializing in the worldwide seaborne transportation and storage of chemicals and other speciality bulk liquids. The Odfjell fleet comprises some 80 ships. The ships transport more than 600 different kinds of liquids, including organic and inorganic bulk liquid chemicals, acids, animal fats, edible oils, portable alcohols and clean petroleum products. Most of Odfjell’s ships are registered in Norway (NIS) and Singapore, and are primarily manned by Norwegian and Filipino mariners.

Malaccamax largest tonnage of ship capable of fitting through the Strait of Malacca

Malaccamax is a naval architecture term for the largest tonnage of ship capable of fitting through the 25-metre-deep (82 ft) Strait of Malacca. Bulk carriers and supertankers have been built to this tonnage, and the term is chosen for very large crude carriers (VLCC). They can transport oil from Arabia to China. A typical Malaccamax tanker can have a maximum length of 333 m (1,093 ft), beam of 60 m (197 ft), draught of 20.5 m (67.3 ft), and tonnage of 300,000 DWT.

Ore-bulk-oil carrier ship type

An ore-bulk-oil carrier, also known as combination carrier or OBO, is a ship designed to be capable of carrying wet or dry cargoes. The idea is to reduce the number of empty (ballast) voyages, in which large ships only carry a cargo one way and return empty for another. These are a feature of the larger bulk trades.

LNG carrier tank ship designed for transporting liquefied natural gas

An LNG carrier is a tank ship designed for transporting liquefied natural gas (LNG). As the LNG market grows rapidly, the fleet of LNG carriers continues to experience tremendous growth.

Heavy-lift ship ship type

A heavy-lift ship is a vessel designed to move very large loads that cannot be handled by normal ships. They are of two types:

Oil tanker Ship designed for the bulk transport of oil

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 crude oil from its point of extraction to refineries. For example, moving crude oil from oil wells in a producing country to refineries in another country. Product tankers, generally much smaller, are designed to move refined products from refineries to points near consuming markets. For example, moving gasoline from refineries in Europe to consumer markets in Nigeria and other West African nations.

History of the oil tanker

The history of the oil tanker is part of the evolution of the technology of oil transportation alongside the oil industry.

The National Iranian Tanker Company (NITC) is a subsidiary of the National Iranian Oil Company, which was privatized in 2009. As of 2011, NITC was owned by funds managing pensions for 5 million Iranians. It is the biggest tanker company in the Middle East. The company transports Iranian crude to export markets and also engages in cross-trading of crude oil cargoes for some 150 oil majors worldwide, including Royal Dutch Shell, Total SA, Saudi Aramco and state-run producers in Kuwait and Abu Dhabi. NITC has a capacity of 11 million tons per year.

BP Shipping is the maritime arm of British headquartered global oil company, BP. The unit covers the marine transport, logistics and insurance requirements of all BP's global activities.

A gas carrier is a ship designed to transport LPG, LNG, CNG, or liquefied chemical gases in bulk.

Today Makes Tomorrow (TMT) is a Taiwanese shipping company that in 2008 directly owned some 60 ships, with many more on order, including dry bulk, crude, cargo, LNG, automobile, and cement carriers.