supertanker n : the largest class of oil tankers

English

Noun

1. An extremely large tanker ship.

Oil tankers, also known as petroleum tankers, are ships designed for the bulk transport of oil. There are two basic types of oil tanker: the crude tanker and the product tanker. Second only to pipelines in terms of efficiency,]] The technology of oil transportation has evolved alongside the oil industry. Although man's use of oil reaches to prehistory, the first modern commercial exploitation dates back to James Young's manufacture of parafin in 1850. In these early days, oil from Upper Burma was moved in earthenware vessels to the river bank where it was then poured into boat holds. In the 1850s, the Pennsylvania oil fields became a major supplier of oil, and a center of innovation. Also, barrels were leaky, and could only be carried one way. These were followed by the first oil-tank steamer, the Vaderland, which was purchased by Palmers Shipbuilding and Iron Company. Other challenges included allowing for the cargo to expand and contract due to temperature changes, and providing a method to ventilate the tanks.

In 1883, oil tanker design took a large step forward. Working for the Nobel company, Colonel Henry F. Swan designed a set of three Nobel tankers. Instead of one or two large holds, Swan's design used several holds which spanned the width, or beam, of the ship. But this approach of dividing the ship's storage space into smaller tanks virtually eliminated free-surface problems. This same firm soon went on to make much larger oil tankers, such as the Emanuel Nobel and Karl Hagelin, 4,600-ton kerosene tankers with engines.

World War I

| 10,000-60,000

|rowspan="2" valign="center" |$43M |rowspan="2" valign="center" |$42.5M |- | Panamax | 55,000-80,000

|- | Aframax | 80,000-120,000

|rowspan="2" valign="center" |$58M |rowspan="2" valign="center" |$60.7M |- | Suezmax | 120,000-200,000

|- | VLCC | 150,000-300,000

|rowspan="3" valign="center" |$120M |rowspan="3" valign="center" |$116M |- | ULCC | over 300,000 Their size is measured in deadweight tons (DWT). Crude carriers are among the largest, ranging from Panamax-sized vessels to ultra-large crude carriers (ULCCs) of over .

Supertanker is an informal term used to describe the largest tankers. Today it is applied to very-large crude carriers (VLCC) and ULCCs with capacity over . These ships can transport two million barrels of oil.

Because of their great size, supertankers can't generally enter ports fully loaded.

Fleet characteristics

In 2005, oil tankers made up 36.9% of the world's fleet in terms of deadweight tonnage. The world's total oil tankers deadweight tonnage has increased from in 1970 to in 2005.

Cargo movement

In 2005, 2.42 billion metric tons of oil were shipped by tanker. 76.7% of this was crude oil, and the rest consisted of refined petroleum products.

By comparison, in 1970 1.44 billion metric tons of oil were shipped by tanker. This amounted to 34.1% of all seaborne trade for that year. In terms of amount carried and distance carried, oil tankers moved 6,487 billion ton-miles of oil in 1970. In 2005, for each of oil tankers, 6.7 metric tons of cargo was carried. The main discharge ports were located in North America, Europe, and Japan with 537.7, 438.4, and 215.0 million metric tons of cargo discharged in these regions. Panama was the world's largest flag state for oil tankers, with 528 of the vessels in its registry. Of these, 31.6% were under 4 years old and 14.3% were over 20 years old.

In 2005, 475 new oil tankers were built, accounting for . The average size for these new tankers was . Ship-owners and buyers negotiate scrap prices based on factors such as the ship's empty weight (called light ton displacement or LDT) and prices in the scrap metal market. In 1998, almost 700 ships went through the scrapping process at shipbreakers in places like Alang, India and Chittagong, Bangladesh. Between 2000 and 2005, the capacity of oil tankers scrapped each year has ranged between and . In this same timeframe, tankers have accounted for between 56.5 and 90.5 of the world's total scrapped tonnage. In 1985, these vessels would have cost $18M, $22M, and $47M respectively. Some representative prices for that year include $42.5M for a tanker, $60.7M for a , $73M for a , and $116M for tanker. Each tank is split into two or three independent compartments by fore-and-aft bulkheads. Tankers generally have cofferdams forward and aft of the cargo tanks, and sometimes between individual tanks.

A pumproom houses all the pumps connected to a tanker's cargo lines. Most newer tankers are double-hulled, with an extra space between the hull and the storage tanks.

• reduced practice of saltwater ballasting in cargo tanks decreases corrosion,
• increased environmental protection,
• more expensive canal and port expenses,
• cleaning mud from ballast spaces a bigger problem.The safety benefits are less clear on larger vessels and in cases of high speed impact. Fuel oil itself is very difficult to ignite, however its hydrocarbon vapors are explosive when mixed with air in certain concentrations. The purpose of the system is to create an atmosphere inside tanks in which the hydrocarbon oil vapors cannot burn. At the same time it decreases the upper flammable limit or highest concentration at which the vapors can be ignited.

Inert gas systems deliver air with an oxygen concentration of less than 5% by volume. The exception is in cases when the tank must be entered.

Pre-transfer preparation

Prior to any transfer of cargo, the chief officer must develop a transfer plan detailing specifics of the operation such as how much cargo will be moved, which tanks will be cleaned, and how the ship's ballasting will change. The next step before a transfer is the pretransfer conference. The pretransfer conference covers issues such as:

• What products will be moved,
• All connections are secure, The first step in the operation is following the same pretransfer procedures as used in loading. When the transfer begins, it is the ship's cargo pumps that are used to move the product ashore. While pumping, tank levels are carefully watched and key locations, such as the connection at the cargo manifold and the ship's pumproom are constantly monitored.

On most crude-oil tankers, a special crude oil washing (COW) system is part of the cleaning process. This involves blowing fresh air into the tank to force accumulated gasses out. Mucking requires protocols for entry into confined spaces, protective clothing, designated safety observers, and possibly the use of airline respirators. Prior to underway replenishment, naval vessels had to enter a port or anchor to take on fuel. This design was intended to provide flexibility in two ways. Firstly, an OBO would be able the shift between the dry and wet bulk trades based on market conditions.

In practice, the flexibility which the OBO design allows has gone largely unused, as these ships tend to specialize in either the liquid or dry bulk trade. These floating units reduce oil production costs and offer, mobility, large storage capacity, and production versatility. An example of a FSO that used to be an oil tanker is the Knock Nevis. These units are usually moored to the seabed through a spread mooring system.]]

Oil spills have devastating effects on the environment. Crude oil contains polycyclic aromatic hydrocarbons (PAHs) which is very difficult to clean up, and lasts for years in the sediment and marine environment. Marine species constantly exposed to PAHs can exhibit developmental problems, susceptibility to disease, and abnormal reproductive cycles. By the sheer amount of oil carried, modern oil tankers must be considered something of a threat to the environment. As discussed above, a VLCC tanker can carry of crude oil, or 62,000,000 gallons. This is more than six times the amount spilled in the widely known Exxon Valdez incident. In this spill, the ship ran aground and dumped 10.8 million gallons of oil into the ocean in March of 1989. Despite efforts of scientists, managers, and volunteers over 400,000 seabirds, about 1,000 sea otters, and immense numbers of fish were killed. On the other hand, only 5% of the actual spills came from oil tankers, while 51.8% came from other kinds of vessels. |- bgcolor="#CCCCCC" align="center" !Source !Number of spills !% of spill incidents !Spill volume (gallons) !% of spill volume !Average spill size !Median spill size !Maximum spill size |- |TANKSHIP |35 |0.90% |636,834 |45.00% |18,195 |1 |329,678 |- |TANKBARGE |143 |3.70% |215,822 |15.20% |1,509 |3 |151,200 |- |ALL OTHER VESSELS |1527 |39.20% |453,901 |32.00% |297 |3 |335,732 |- |FACILITIES |1099 |28.20% |42,675 |3.00% |39 |1 |2,100 |- |PIPELINES |1 |0.00% |15,000 |1.10% |15,000 |15,000 |- |ALL OTHER NON-VESSEL SOURCES |37 |0.90% |12,781 |0.90% |345 |5 |12,000 |- |UNKNOWN or OTHER |1055 |27.10% |39,700 |2.80% |38 |1 |8,000 |- |YEAR-END STATISTICS |3897 |100.00% |1,416,714 |100.00% |364 |2 |335,732 |} The International Tanker Owners Pollution Federation has tracked 9,351 accidental spills that have occurred since 1974. According to this study, most spills result from routine operations such as loading cargo, discharging cargo, and taking on fuel oil.

See also

• :Category:Tankers
• Aristotle Onassis
• Crude oil washing
• Daniel K. Ludwig
• List of oil spills
• List of replenishment ships of the Royal Fleet Auxiliary
• List of tankers
• List of Type T2 Tanker names
• Marine transfer operations
• MARPOL 73/78
• Prestige oil spill
• Replenishment oiler
• Stavros Niarchos
• T2 tanker
• Tanker (ship)

Notes

References

• American Merchant Seaman's Manual
• Tanker operations: a handbook for the person-in-charge (PIC)
• International Safety Guide for Oil Tankers and Terminals (ISGOTT)
• Double-Hull Tanker Legislation: An Assessment of the Oil Pollution Act of 1990 (1998)
• Sailing ship to supertanker: the hundred-year story of British Esso and its ships
• The Russian Rockefellers: The Saga of the Nobel Family and the Russian Oil Industry
• Review of Maritime Transport, 2006

Further reading

• From T-2 to Supertanker: Development of the Oil Tanker, 1940-2000
• Supertanker!: The Story of the World's Biggest Ships
• Maritime economics

External links

• Bill Willis. Supertankers
• Intertanko - the society of International Tanker Operators
• The International Maritime Organization - Tanker Safety (for double-hulls)
• Largest Ship in the World - Blog covering the largest ships in the world