Supertanker

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A supertanker is an unofficial nickname that applies to a certain class of tanker ship built to transport very large quantities of liquids; in practice this typically refers to crude oil. Supertankers are usually considered to be Very-Large Crude Carriers (VLCC) and Ultra-Large Crude Carriers (ULCC). Among those involved in the shipping industry, it is common practice to refer to supertankers by their size (VLCC, ULCC, Panamax, Suezmax, etc.) since the term "supertanker" tends to be ambigious and open to interpretation.

Tanker ships above 250,000 tonnes deadweight tonnage are generally considered supertankers. They are the largest ships in the world, larger even than supercarriers; the largest of which is the Knock Nevis, weighing in at 647,955 tonnes fully laden. When first introduced, their size and draft prevented them from docking at many existing docks, requiring them to discharge their cargo into smaller tankers offshore. Some ports have developed special deep-water off-loading facilities connected to the land by pipelines (for an example, see Louisiana Offshore Oil Port). Supertankers are also very efficient ships, relying on a single propeller for propulsion, and typically account for only US $0.02 per gallon of gas at the pump. ^{[citation needed]}

Due to their size and mass, supertankers have very poor maneuverability; the stopping distance of a supertanker is typically measured in miles. When operating close to the shoreline they are vulnerable to running aground, whether due to mechanical failure, human error or bad weather. When this happens, oil spills are a significant risk. A typical modern supertanker can carry approximately two million barrels of oil. In "single-hulled" tankers, the hull is also the wall of the oil tanks, and any breach will result in an oil spill. Newer tankers are "double-hulled", with a space between the hull and the storage tanks, to reduce the risk of a spill in the event that the outer hull is breached. This space is used to carry water ballast when the ship is not carrying an oil cargo. In practice the addition of an extra hull to a supertanker should prevent such a ship from suffering a catastophic breach of the hull. The full benefits of a double hull tanker with regard to safety have been proven effective[1].

Following the Exxon Valdez incident, the United States mandated in the Oil Pollution Act of 1990 (OPA-90) that all supertankers entering United States waters be double-hulled by 2015. The European Union has similar legislation requiring all tankers entering their waters to be double-hulled by 2010. By doing this, incidents like the Exxon Valdez oil spill may possibly be avoided.

The largest known double-hulled supertanker in the world is the Hellespont Fairfax. Completed in January 2003, it boasts a deadweight tonnage of 442,470 tonnes.

[edit] See also

• Knock Nevis, the largest ship in the world
• Batillus class supertankers, biggest ships ever constructed
• Hellespont Fairfax, the largest double-hulled supertanker in the world.

[edit] External links

• ship-photos.de: Categorized ship photos.
• Google Maps Satellite Photo of a supertanker off the New York coast.
• Google Maps Satellite Photo and Google Maps Satellite Photo of two supertankers in the Sunda Strait, Indonesia.cs:Supertanker

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