Double-hulled tanker Double-hulled tanker A double-hulled tanker refers to an oil tanker which has a double hull. They reduce the likelihood of leaks occurring than in single-hulled tankers, and their ability to prevent or reduce oil spills led to double hulls being standardized for oil tankers and other types of ships including by the International Convention for the Prevention of Pollution from Ships or MARPOL Convention. After the Exxon Valdez oil spill disaster in Alaska in 1989, the US Government required all new oil tankers built for use between US ports to be equipped with a full double hull. A number of
Oil tanker crude carriers (ULCC) built in the 1970s were over long and had a capacity of . Several factors encouraged this growth. Hostilities in the Middle East which interrupted traffic through the Suez Canal contributed, as did nationalization of Middle East oil refineries. Fierce competition among shipowners also played a part. But apart from these considerations is a simple economic advantage: the larger an oil tanker is, the more cheaply it can move crude oil, and the better it can help meet growing demands for oil. In 1955 the world's largest supertanker was and : SS "Spyros Niarchos" launched that year