A tanker is a ship

Ship

Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...

 designed to transport liquids in bulk. Major types of tankship include the oil tanker

Oil tanker

An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries...

, the chemical tanker

Chemical tanker

A chemical tanker is a type of tanker designed to transport chemicals in bulk.Ocean-going chemical tankers generally range from to in size, which is considerably smaller than the average size of other tanker types due to the specialised nature of their cargoes and the size restrictions of the...

, and the liquefied natural gas carrier.

Background

Tankers can range in size of capacity from several hundred tons

Tonnage

Tonnage is a measure of the size or cargo carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine, and was later used in reference to the weight of a ship's cargo; however, in modern maritime usage, "tonnage" specifically refers to a calculation of the volume...

, 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

Cargo is goods or produce transported, generally for commercial gain, by ship, aircraft, train, van or truck. In modern times, containers are used in most intermodal long-haul cargo transport.-Marine:...

 capacity up to some thousand tons. A wide range of products are carried by tankers, including:

• hydrocarbon
  Hydrocarbon
  In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
  
   products such as oil
  Petroleum
  Petroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
  
  , liquefied petroleum gas (LPG), and liquefied natural gas
  Liquefied natural gas
  Liquefied natural gas or LNG is natural gas that has been converted temporarily to liquid form for ease of storage or transport....
  
   (LNG)
• chemicals
  Chemical substance
  In chemistry, a chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical separation methods, i.e. without breaking chemical bonds. They can be solids, liquids or gases.Chemical substances are...
  
  , such as ammonia
  Ammonia
  Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
  
  , chlorine
  Chlorine
  Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
  
  , and styrene monomer
• fresh water
  Fresh Water
  Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve...
  
  
• wine
  Wine
  Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...
  
  
• molasses
  Molasses
  Molasses is a viscous by-product of the processing of sugar cane, grapes or sugar beets into sugar. The word molasses comes from the Portuguese word melaço, which ultimately comes from mel, the Latin word for "honey". The quality of molasses depends on the maturity of the sugar cane or sugar beet,...
  
  

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

Tonnage

Tonnage is a measure of the size or cargo carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine, and was later used in reference to the weight of a ship's cargo; however, in modern maritime usage, "tonnage" specifically refers to a calculation of the volume...

", which refers to the volume of the holds in terms of how many tun

Tun (unit)

The tun is an old English unit of wine cask volume, holding about 954 litres, almost a cubic metre. Etymologically it is identical to the ton, a unit of mass or weight and constituted approximately 2,048 pints or pounds. Originally, it was a genuine unit of volume and measured 256 gallons ,...

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
  Free Surface Effect
  The free surface effect is one of several mechanisms which can cause a craft to become unstable and roll over . It refers to the tendency of liquids — and of aggregates of small solid objects, like seeds, gravel, or crushed ore which can act as liquids — to slosh about: to move in response to...
  
  : a large body of liquid carried aboard a ship will impact on 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 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 Guiness brewery used tankers to transport the stout across the Irish Sea

Irish Sea

The Irish Sea separates the islands of Ireland and Great Britain. It is connected to the Celtic Sea in the south by St George's Channel, and to the Atlantic Ocean in the north by the North Channel. Anglesey is the largest island within the Irish Sea, followed by the Isle of Man...

.

Different products require different handling and transport, with specialised variants such as "chemical tanker

Chemical tanker

A chemical tanker is a type of tanker designed to transport chemicals in bulk.Ocean-going chemical tankers generally range from to in size, which is considerably smaller than the average size of other tanker types due to the specialised nature of their cargoes and the size restrictions of the...

s", "oil tanker

Oil tanker

An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries...

s", and "LNG carrier

LNG carrier

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

s" developed to handle dangerous chemicals, oil and oil-derived products, and liquefied natural gas

Liquefied natural gas

Liquefied natural gas or LNG is natural gas that has been converted temporarily to liquid form for ease of storage or transport....

 respectively. Among oil tankers, supertankers are designed for transporting oil around the Horn of Africa

Horn of Africa

The Horn of Africa is a peninsula in East Africa that juts hundreds of kilometers into the Arabian Sea and lies along the southern side of the Gulf of Aden. It is the easternmost projection of the African continent...

 from the Middle East

Middle East

The Middle East is a region that encompasses Western Asia and Northern Africa. It is often used as a synonym for Near East, in opposition to Far East...

. The supertanker Seawise Giant, scrapped in 2010, was 458 metres (1,502.6 ft) in length and 69 metres (226.4 ft) wide. Supertankers are one of the three preferred methods for transporting large quantities of oil, along with pipeline transport

Pipeline transport

Pipeline transport is the transportation of goods through a pipe. Most commonly, liquids and gases are sent, but pneumatic tubes that transport solid capsules using compressed air are also used....

 and rail

Rail transport

Rail transport is a means of conveyance of passengers and goods by way of wheeled vehicles running on rail tracks. In contrast to road transport, where vehicles merely run on a prepared surface, rail vehicles are also directionally guided by the tracks they run on...

.

Despite being highly regulated, tankers have been involved in environmental disasters resulting from oil spill

Oil spill

An oil spill is the release of a liquid petroleum hydrocarbon into the environment, especially marine areas, due to human activity, and is a form of pollution. The term is mostly used to describe marine oil spills, where oil is released into the ocean or coastal waters...

s. See Exxon Valdez

Exxon Valdez

Oriental Nicety, formerly Exxon Valdez, Exxon Mediterranean, SeaRiver Mediterranean, S/R Mediterranean, Mediterranean, and Dong Fang Ocean is an oil tanker that gained notoriety after running aground in Prince William Sound spilling hundreds of thousands of barrels of crude oil in Alaska...

, Braer

Braer

The MV Braer was an oil tanker which ran aground off Shetland, Scotland, in January 1993.-Reason for ship's loss:In the ship court after the loss, it was stated that reason for ship's loss was seawater contamination of the diesel oil...

, Prestige oil spill

Prestige oil spill

The Prestige oil spill was an oil spill off the coast of Galicia caused by the sinking of an oil tanker in 2002. The spill polluted thousands of kilometers of coastline and more than one thousand beaches on the Spanish, French and Portuguese coast, as well as causing great harm to the local fishing...

, Torrey Canyon

Torrey Canyon

The Torrey Canyon was a supertanker capable of carrying a cargo of 120,000 tons of crude oil, which was shipwrecked off the western coast of Cornwall, England in March 1967 causing an environmental disaster...

, and Erika

Erika (tanker)

Erika was the name of a tanker built in 1975 and last chartered by Total-Fina-Elf. She sank off the coast of France in 1999, causing a major environmental disaster.- Background :Erika was one of eight sister ships built in Japan...

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 ; Medium Range for ships between 25,000 and and Large 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 long ton

Long ton

Long ton is the name for the unit called the "ton" in the avoirdupois or Imperial system of measurements, as used in the United Kingdom and several other Commonwealth countries. It has been mostly replaced by the tonne, and in the United States by the short ton...

s:

• 10,000–: General Purpose tanker
• 25,000–: Medium Range tanker
• 45,000–: Long Range 1 (LR1)
• 80,000–: Long Range 2 (LR2)
• 160,000–: Very Large Crude Carrier (VLCC)
• 320,000–: Ultra Large Crude Carrier (ULCC)

Petroleum Tankers

Class	Length	Beam Beam (nautical) The beam of a ship is its width at the widest point. Generally speaking, the wider the beam of a ship , the more initial stability it has, at expense of reserve stability in the event of a capsize, where more energy is required to right the vessel from its inverted position...	Draft Draft (hull) The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...	Typical Min DWT	Typical Max DWT
Seawaymax Seawaymax The term Seawaymax refers to vessels which are the maximum size that can fit through the canal locks of the St. Lawrence Seaway.Seawaymax vessels are in length, wide, and have a draft of and a height above the waterline of . A number of lake freighters larger than this size cruise the Great...	226 m (741.5 ft)	24 m (78.7 ft)	7.92 m (26 ft)
Panamax Panamax Panamax and New Panamax are popular terms for the size limits for ships traveling through the Panama Canal. Formally, the limits and requirements are published by the Panama Canal Authority titled "Vessel Requirements"...	228.6 m (750 ft)	32.3 m (106 ft)	12.6 m (41.3 ft)
Aframax Aframax An ' ship is an oil tanker smaller than and with a breadth above 32.31 m. The term is based on the Average Freight Rate Assessment tanker rate system. class tankers are largely used in the basins of the Black Sea, the North Sea, the Caribbean Sea, the China Sea and the Mediterranean...	253 m (830.1 ft)	44.2 m (145 ft)	11.6 m (38.1 ft)
Suezmax Suezmax Suezmax is a naval architecture term for the largest ship measurements capable of transiting the Suez Canal, and is almost exclusively used in reference to tankers. Since the canal has no locks, the only serious limiting factors are draft , and height due to the Suez Canal Bridge...			16 m (52.5 ft)
VLCC (Malaccamax Malaccamax Malaccamax is a naval architecture term for the largest size of ship capable of fitting through the -deep Strait of Malacca. Because the Sunda Strait is even shallower at minimum depth, a post-Malaccamax ship would need to use even longer alternate routes such as:*Lombok Strait, Makassar Strait,... )	470 m (1,542 ft)	60 m (196.9 ft)	20 m (65.6 ft)
ULCC