Supertanker

A supertanker is a certain class of tanker ship built to transport very large quantities of liquids, especially crude oil. The terms VLCC (Very-Large Crude Carrier) and ULCC (Ultra-Large Crude Carrier) are also sometimes used.

Related Topics:
Tanker - Ship - Crude oil

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Tanker ships above 250,000 tonnes deadweight tonnage are generally considered supertankers. They are the largest ships in the world, larger even than aircraft carriers; 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).

Related Topics:
Deadweight tonnage - Aircraft carrier - Knock Nevis - Draft - Tankers - Louisiana Offshore Oil Port

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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 millions of 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 hull is breached. This space is used to carry water ballast when the ship is not carrying an oil cargo.

Related Topics:
Oil spill - Oil

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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.

Related Topics:
Exxon Valdez - United States - Double-hulled - European Union

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